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Ultrasound Cardiography in Clinical Practice
Symposium on Changing Concepts of Disease
U Itra-sound Cardiography in Clinical Practice William K. Smith, Jr., MD.,* William S. Frankl, M.D.**
The term ultrasound refers to sound waves having frequencies above the range of human hearing, that is, greater than 20,000 cycles per second. 21 • 24 At frequencies above 20,000 cycles per second, the passage of ultrasonic waves through air is progressively attenuated, so that the practical application of ultrasound is essentially confined to its use in solid or liquid media. The first such application by man was the development of "sonar" for the detection of enemy submarines by Langevin during World War 1.21 With this technique a transmitting transducer attached to the ship's hull generates a short pulse of ultrasound waves directed toward the bottom of the sea beneath the ship. When the pulse strikes the bottom, some of the ultrasound is reflected back toward the ship and is picked up by a receiving transducer. If the transit time from emission of the pulse to reception of the echo is measured, and if the velocity of sound transmission in salt water is known, then the distance to the bottom can be calculated. With the development of radar during World War II it became possible to measure very short time intervals accurately with electronic circuits. Using such circuits, Firestone in 1945 developed an instrument for ultrasonic testing of material in industry, using sonar techniques. 14 The principle of this ultrasonic reflectoscope is shown in Figure 1. A piezoelectric crystal serves as the ultrasonic transducer, converting electrical impulses into short pulses of ultrasound. The ultrasound pulses are beamed through the material, and during the intervals between pulses the same transducer acts as a receiver, reconverting any returning echoes into electrical energy. Echoes are produced when the ultrasound waves reach interfaces between materials of differing densities, such as solid-gas, solid-liquid, or gas-liquid interfaces. These "accoustical interfaces" reflect ultrasound in much the same way that light is reflected, so that when the ultrasound beam is perpendicular to the interface the • Associate Professor of Medicine and Director, Cardiac Graphics Laboratory, Cardiology Division, Medical College of Pennsylvania; Attending PhYSiCian, Veterans Administration Hospital, Philadelphia, Pennsylvania "Professor of Medicine and Director, Cardiology Division, Medical College of Pennsylvania; Consultant, Veterans Administration Hospital, Philadelphia, Pennsylvania
Medical Clinics of North America- Vol. 57, No. 4, July 1973
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SIGNAL FROM
I
TRANSDUCER _¥'/DEFECT SIGNAL FROM S I G N A L _ I - - - + - - - - - - - - i - E N D OF MATERIAL
i
.----_...J
TRANSDUCE:J1L_ _ _-tt_ _ _ _ DEFECT
t
MATERIAL TESTED
Figure 1. Industrial use of ultrasound for testing solid materiaL Lower half of the diagram shows the ultrasound transducer applied to one side of the sample, so that short pulses of ultrasound energy can be beamed through the material. Display of the echo signals as they appear on the cathode ray tube oscilloscope is shown above. On the right is an echo "spike" representing the ultrasound pulse as it originates from the transducer; the echoes from the acoustic interfaces produced by the defect and the opposite side of the material are also shown. The height of these signals corresponds to the intensity of the reflected echoes, and thus gives an indication of the magnitude or density of the interfaces. Their location on the x axis of the oscilloscope display corresponds to the depth of the interface in the material, so that the display can be calibrated and the location of the flaw measured from the ultrasonogram.
reflected ultrasound returns toward its source. The opposite side of the material represents a strong accoustical interface because of the marked change in density from solid to air, and any faults or flaws in the material also act as interfaces and produce echoes. These are displayed on the cathode ray tube, with the location of the echo on the x axis corresponding to the distance of the flaw from the transducer. The x axis can be calibrated for depth, so that the exact location of the flaw can be accurately determined without damage to the material. 24 The ultrasonic reflectoscope was applied to medical diagnosis by Edler and Hertz in 1954 when they demonstrated motion of the mitral valve in man with this nonsurgical, noninvasive techniqueY The pulses are generated by piezoelectric crystal transducers, coupled to the chest wall with water ora semisolid gel, so that the ultrasound waves are not attenuated by pockets of air between the transducer and the chest wall. The same transducer which is used to generate the ultrasound pulse also acts as a receiving transducer to convert the returning echoes to electrical energy. Crystals with resonant frequencies in the range of 2 to 2.5 MHz (2 to 2.5 megacycles per second) are used. The crystals are activated by short electrical impulses which generate 5 to 10 microsecond pulses of ultrasound waves, at repetition rates of 200 to 2000 times per second. The periods between pulses last 0.5 to 5 milliseconds (depending on the repetition rate) and during these periods the crystal transducer acts as a receiver and "listens" for echoes from the ultrasound pulse. Returning echoes are converted into electrical energy by the crystal, and these small electrical signals are amplified for display on the oscilloscope screen. The display is accomplished by having the electron beam of the cathode ray tube begin to move from left to right on the x axis across the screen at the same time that the pulse is generated. It moves at a constant rate and, as
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returning echoes are received, the beam is momentarily deflected upward on the screen to produce a "spike," the height of which is proportional to the intensity of the echo, and thus to the "density" of the accoustical interface which produced the echo. Thus, the oscilloscope shows the depth of the various interfaces and their intensity. This is known as the "A mode" display, and an example of intracardiac structures shown in this mode is seen in Figure 2. In "B mode" display the echoes are represented by dots along the x axis, rather than spikes, and the intervening spaces between dots are left blank. Brightness or intensity of the dot represents intensity of the echo (and therefore intensity of the accoustic interface producing the echo) and distance from the left side of the screen represents depth. Because of the rapid repetition rate of the ultrasound pulses, the dots persist on the screen as stationary echoes, or, if an interface is moving in the path of the ultrasound beam, then the dot representing its echo is seen to move back and forth along the x axis on the screen. To permanently record this movement of the echoes, the "M mode" (time-motion mode) was developed. In this modality the display of echoes along the x axis is slowly
Jy
T CW
1
AW
14cm
vs
MV
r r
PW
L
Figure 2. "A mode" presentation of echoes from the various cardiac structures in a normal young man. The height of the echo "spikes" represents intensity of the reflected ultrasound from the interfaces. Tissue depth marked in centimeters from left to right. T = transducer signal. CW = chest wall echoes. AW = anterior wall of the right ventricle. VS = ventricular septum. MV = anterior leaflet of the mitral valve. PW = posterior wall of the left ventricle. L = lung echoes.
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moved upward on the screen (in the direction of the y axis). The moving dots then describe waves during their vertical travel, while the stationary dots describe vertical straight lines. An oscilloscope camera photographs this sweep with a time exposure and thus records the motion of the interfaces which were in the path of the ultrasound beam. As photographed from the display, the x axis represents distance of the interface from the transducer on the chest wall, and the y axis represents time, but for convenience of analysis (and to correspond with the other graphic records) the photograph is turned on its side (rotated 90°) so that the axes are reversed, and the x (horizontal) axis becomes time and the y (vertical) axis becomes depth from the chest wall. Figure 3 shows the movement of cardiac structures recorded in M mode. It can be readily appreciated that the M mode is most useful in echocardiography, for not only do characteristic motions identify the various structures in the heart, but an analysis
EKG
CW AW---i.
IVS---
MV
----t.
PW---t. P---L - -__
_-.... ...
Figure 3. M Mode echocardiogram (or Moving "B mode" echocardiogram) showing motion of the various cardiac structures lying in the path of the ultrasonic beam. The patient had a large anterior and posterior pericardial effusion. The transducer is located parasternally in the fourth left intercostal space, pointing directly posterioriy. Anterior or posterior motion of the interfaces in the path of the ultrasonic beam is recorded as an upward or downward movement of the various traces. Time is represented horizontally, so that the location of an interface at any given point in the cardiac cycle can be obtained by comparison with the simultaneously recorded electrocardiogram. Time dots are one second apart horizontally, and the same dots represent tissue depth in centimeters vertically. EKG = electrocardiogram. CW = stationary echoes from the chest wall. AW = anterior right ventricular wall motion, separated by the pericardial effusion from the chest wall echoes. IVS = ventricular septal motion. MV = motion of the anterior leaflet of the mitral valve. PW = posterior left ventricular wall motion, separated from the pericardium by the pericardial effusion. P = posterior parietal pericardium. L = echoes from the lung.
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of the motion of intracardiac structures becomes available, without invading the heart.
ULTRASOUND TECHNIQUES IN CARDIOLOGY The cardiac examination is begun by placing the crystal transducer parasternally in the left fourth intercostal space and directing the ultrasound beam posteriorly and slightly medial or cephalad, looking for the characteristic motion of the anterior leaflet of the mitral valve.1O, 53 This motion is illustrated in Figure 4, which shows the slow anterior movement of the anterior leaflet in systole CC to D), and two anterior opening movements in diastole CD to E and F to A). The systolic anterior movement CC to D), occurring while the valve is in its closed position, represents the anterior projection of systolic movement of the base of the heart toward its apex during left ventricular contraction. 6 • 52. 53 The first diastolic anterior movement CD to E) represents initial opening of the valve as left ventricular pressure falls below left atrial pressure and early dia-
Figure 4. Normal anterior leaflet mitral valve motion. Total amplitude of motion (CE amplitude) is 28 mm. Amplitude of motion during diastole (DE amplitude) is 20 mm. Opening movement slope (DE slope) is 290 mm/sec. Early diastolic closure (EF slope) is 93 mm/sec. EKG = electrocardiogram. IVS = region of ventricular septal echoes. MV = anterior leaflet mitral valve movement. PW = posterior ventricular wall motion. Syst = systole. Diast = diastole. 1 cm = one centimeter of tissue depth. Time dots are one second apart horizontally, and the same dots represent tissue depth in centimeters vertically.
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stolic filling begins. Immediately after the first rush of blood into the ventricle, the valve leaflet drifts back to its closed position (E to F). With atrial systole the valve again opens (anterior leaflet F to A movement) followed by closure of the valve with ventricular systole (A to C movement). In the presence of atrial fibrillation the A wave is, of course, absent. Point C coincides with the second component (mitral closure component) of the first heart sound, and point D occurs 10 to 50 milliseconds after the aortic component of the second heart sound. 10 Point E represents the point of maximum opening of the valve and coincides with the time of the opening snap in mitral stenosis. 16 When present, the third heart sound occurs during the mid portion of the E to F movement; it may follow the inscription of an early slower portion of the E to F slope. lO (When the E to F slope is divided into an early slow portion and a fast late portion, the point of change is labeled Fo.53 Fourth heart sounds coincide with the A point, the peak of the A movement of the valve. 10 The total amplitude of motion of the anterior leaflet, that is the vertical distance from point C to point E (CE amplitude) measures 20 to 33 mm. in normal subjects. lO The amplitude of diastolic movement of the valve (DE amplitude) may measure up to 5 mm. less than the CE amplitude, and the magnitude of this excursion has been related to valve leaflet mobility.47.53 The slope of the D to E movement is measured as millimeters of excursion per second of movement and the normal range is 250 to 500 mm. per second. 10 The slope of the E to F movement (EF slope) or E to Fo movement (EFo slope) is normally 80 to 190 mm. per second measured as vertical excursion per second of movement. lO • 41 Echocardiograms showing the greatest amplitude of anterior mitral leaflet excursion with definite E and A waves are best for analysis, and in practice can usually be recorded parasternally in the fourth left intercostal space. In patients with cardiomegaly the valve echo may be located 1 to 5 cm. away from the parasternal position or in the third or fifth interspaces, and in patients with gross chamber enlargement or anatomic distortion of the heart the mitral valve echo may be'recorded from some other area of the precordium. In order to obtain satisfactory tracings a water-soluble gel is applied to the transducer so that direct contact is made with the chest wall, excluding any air pockets which would markedly attenuate the ultrasound beam. The transducer must be in an intercostal space, between the ribs, to prevent the loss of ultrasound energy which would occur if one attempted to send the beam through a rib. Echoes from the anterior part of the heart are much stronger than those from the posterior cardiac structures (i.e., the left ventricle, the left atrium, etc.), and the machine has near and far intensity or gain controls. Familiarity with these intensity adjustments, as well as the contrast controls, must be acquired if one is to obtain distinct and continuous signals from some of the "weaker" reflecting interfaces in the heart. Finally, very slight changes in angulation or location of the transducer can be responsible for change in angle of the beam with respect to the interfaces, and consequent remarkable change in the quality of the echo ob-
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tained from a given structure. Some patience is required in learning the technique, but experience can be rapidly acquired, and tracings of high quality can be routinely obtained by technicians.
CARDIAC ANATOMY AND IDENTIFICATION OF INTRACARDIAC ECHOES Casual positioning of the transducer on the precordium can produce a confusing array of moving interfaces, defying identification or analysis. Similarly, random searching for a specific interface is time consuming, and there is no proof that the resulting final record truly represents the interface sought. Therefore, the importance of a systematic approach cannot be overemphasized: it is the key to finding and understanding the motions of the various intracardiac structures.9 • 20. 36 The method begins with identification of the characteristic anterior mitral valve leaflet motion, usually readily found; then, without moving the transducer, locating other structures by changing the instrument gain or by slightly angling the transducer beam toward adjacent areas of the heart. In this way ventricular septum, aortic valve and root, left atrial and left ventricular posterior walls, and the posterior pericardial space can be studied without changing the location of the transducer on the chest wall. Threedimensional relationships can be inferred by comparing depth with the direction in which the beam was angulated, and characteristic patterns of motion of each structure can be recorded in sequence. Figure 5 shows a schematic, two dimensional representation of the structures through which the echo beam passes with only slight change of angulation either medially and cephalad, or laterally and inferiorly. Tricuspid valve motion may also be recorded (although with difficulty in normals) by angling the transducer medially and inferiorly or by moving its location down one interspace from the mitral valve location. 20 • 28 Pulmonary valve motion has recently been studied by Gramiak et aI., using a technique for locating the valve leaflets with a 60 per cent success rate in patients under 14 years of age. 1S To complete the examination, motion of the mitral valve ring toward the apex can usually be recorded by placing the transducer at the cardiac apex and pointing toward the base of the heart. 6 • 52 Mitral ring movement represents the systolic movement of the base of the heart toward the apex along its major axis, and provides an indication of major axis shortening during systole. The ability to record the echocardiogram of the ventricular cavities, septum, and posterior left ventricular wall enables one to diagnose pericardial effusion; to estimate left ventricular cavity size and wall thickness; to estimate left ventricular stroke volume; to evaluate heart muscle performance; and to detect abnormalities of the ventricular septum or septal motion. Figure 6 shows the left ventricular cavity with ventricular septal motion above and left ventricular posterior wall motion below, and from tracings such as this estimates of left ventricular function and stroke volume can be made.
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2
3
MEDIASTINUM. VERTEBRAE
~~~~------~~----------tJr---7 B
Figure 5. Two dimensional schematic representation of various paths of the echo beam which can be obtained by slightly changing the angle of the transducer on the chest wall (labeled 1 through 8). The transducer is in the location in which the anterior mitral valve leaflet motion is recorded, usually in the fourth left intercostal space parasternally. Angling the transducer slightly medially or cephalad (directions 1, 2, or 3) allows recording of the motion of the aortic root and the left atrium immediately behind the aortic root. The anterior mitral valve leaflet motion can be recorded with the beam pointing in directions number 4, 5, or 6, with anyone of a number of structures recorded deep to the anterior leaflet, including the posterior left atrial wall, posterior mitral ring, posterior mitral valve leaflet, or posterior left ventricular wall. Pointing the beam in directions 7 or 8 allows one to record motion of the muscular ventricular septum and posterior left ventricular wall. Mediastinal structures or vertebrae produce strong echoes which may be mistaken for pericardium, but this confusion can be avoided by directing the beam laterally off the free edge of the anterior leaflet of the mitral valve, in directions 7 and 8. A = aorta. Aor. R = aortic ring. LA = left atrium. LV = left ventricle. Memb. S = membranous septum. ML = mitral leaflets (Ant. = anterior leaflet, Post. = posterior leaflet). Musc. S. = muscular septum. MR = mitral valve ring. NC = non-coronary cusp of the aortic valve. P A = pulmonary artery. Pul. R = pulmonary valve ring. RC = right coronary cusp of the aortic valve. RV = right ventricle.
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EKG-
vs-
pw-
Figure 6. Motion of ~the ventricular septum and posterior left ventricular wall. VS = motion of the ventricular septum, recorded at the interface between the left side of the ventricular septum and the left ventricular cavity. PW = motion of the posterior ventricular wall. As the sweep progressed (from left to right across the illustration), the instrument gain was increased, so that more intense echoes were recorded from both interfaces, and finally echoes from the blood in the ventricular cavity began to appear (on the right hand side of the photograph). It should be noted that the ventricular septum and the posterior wall approach each other as the ventricle contracts in systole, and move apart as the ventricle fills in diastole. EKG = electrocardiogram. VS = ventricular septum. PW = posterior left ventricular wall motion.
DIAGNOSTIC USES OF ECHOCARDIOGRAPHY Echocardiography has become in our opinion the most useful technique for the diagnosis of pericardial effusion. It is of great assistance in confirming the severity of mitral stenosis and establishing (or excluding) this diagnosis in patients with combined valvular disease, poorly heard murmurs, etc. lO , 12,22,53 Finally, its application has been explored in a growing number of other conditions, a partial listing of which includes: acute aortic regurgitation,37, 38 systolic prolapse of the mitral valve,7, 15, 19,29,42 tricuspid stenosis,t2, 28 prosthetic mitral valve function,26, 34,45,49 obstructive cardiomyopathy (idiopathic hypertrophic subaortic stenosis),35, 39, 43 atrial myxoma,a0' 33, 51 left atrial enlargement,23 Ebstein's anomaly,5,31 congenital cardiac lesions,2,3,32 Austin Flint murmur,4,38 arrhythmias,t7 and myocardial infarction. 25 ,48 We will briefly discuss echocardiography in pericardial effusion and mitral valve disease, since these are the most widely used clinical applications.
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Pericardial Effusion In the space of a decade the echocardiogram has become one of the most reliable methods for the diagnosis of pericardial effusion. The area of posterior left ventricular wall distant from the mediastinum is located, so that mediastinal echoes will not be mistaken for pericardium. 1 • 13 With appropriate adjustment of gain controls a space can be seen between the normally moving posterior wall echo and a strong pericardium-lung interface, and this echo-free space represents the effusion (Fig. 7). Gain control must be carefully adjusted since the space can be obscured by echoes from the fluid itself if too great intensity of ultrasound is used. It is also helpful to turn down the gain control until the posterior wall echo disappears, and the reflection from the stronger pericardium-lung interface is identified. Anterior pericardial effusion frequently accompanies posterior effusion, but should not be diagnosed in the absence of posterior fluid accumulation. 19 Estimation of the volume of the effusion is an approximation at best, but the finding of synchronous movement of anterior and posterior walls, the so-called "swinging heart," indicates a large effusion which may frequently be neoplastic in originP Pleural fluid may also be recognized behind the heart, and must be differentiated from pericardial effusion; occasionally both effusions are seen together. 1
-
E KG---=
-
. .
....... ~
CW PE-~
AW-....·
PW--4I:
PE p---'L. l -__ Figure 7. Large hemopericardium in 17 year old boy, following blunt chest trauma. CW = stationary chest wall echoes. AW = anterior right ventricular epicardial motion. PE = space representing the pericardial effusion. PW = posterior left ventricular epicardial motion. P = reflection from the posterior parietal pericardium. L = lung. This large collection of blood, measuring in excess of 650 cc. had collected slowly in a nine day period following an automobile accident, and was accompanied by increasing signs of pericardial tamponade.
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Mitral Valve Disease MITRAL STENOSIS. Decrease in EF slope (or EFo slope) occurs when the anterior leaflet of the mitral valve is kept open in diastole by a persistent atrioventricular pressure gradient of mitral stenosis, and the diminution in EF slope corresponds to the severity of the stenosis. lo • 12. 22 Mild stenosis is associated with EF slopes greater than 35 mm. per second, slopes of 15 to 35 mm. per second are seen in severe stenosis. lO Amplitude of anterior leaflet motion correlates with mobility of the valve leaflet; CE amplitudes below 15 mm. (or DE amplitudes below 12 mm.) represent rigid valves.lO In the presence of a rigid valve with severe calcification or with amplitude of motion less than 10 mm., the EF slope does not reliably indicate the degree of stenosis, and predominant mitral regurgitation can be present even though the EF slope is in the stenotic range. lO . 47 Increased intensity of the anterior leaflet echoes or multiple parallel echoes suggest thickening, fibrosis, or calcification of the valve. 27 Figure 8 shows the anterior leaflet echo in severe mitral stenosis. After a successful valvotomy the wave form returns toward normal, although persistence of some decrease in EF slope and amplitude of motion is usually noted, especially in those patients having calcified valves.lO. 12.22.47 Patients having diastolic murmurs due to increased flow (flow murmurs or "flow rumbles") or the Austin Flint rumble, do not show a decreased EF slope. aB Tricuspid stenosis can be differentiated from mitral
EKG
MV
Figure 8. Severe advanced mitral stenosis in 67 year old woman having a heavily calci· fied rigid valve. Note the marked reduction in excursion of the valve, reduced speed of early diastolic opening, and markedly reduced EF slope, as the valve remains in a fixed "open" position throughout diastole. CE amplitude 12 mm. DE slope 130 mm/sec. EF slope 10 mm/sec. EKG = electrocardiogram. MV = mitral valve echoes.
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stenosis by demonstrating a normal mitral EF slope with decreased tricuspid EF slope. 2s Other conditions can produce a decreased EF slope and falsely suggest the diagnosis of mitral stenosis. These include tachycardiap, 53 left atrial myxoma,30, 33, 51 idiopathic hypertrophic subaortic stenosis (lHSS),39,43 aortic stenosis,s aortic regurgitation,t9 and reduced left ventricular compliance due to left ventricular hypertrophy, especially in patients having an atrial gallop.44 Therefore, Feigenbaum proposes four additional criteria to be satisfied before diagnosis of mitral stenosis is made by echocardiography; First, that the closure of the valve in mid diastole not be present (i.e., that Fo-F movement not be present); second, that a characteristic motion of the posterior mitral leaflet anteriorly in diastole be seen beneath the anterior leaflet echo; third, that the diagnosis not be made in tracings showing tachycardia; and fourth, that adequate amplitude of leaflet motion (DE amplitude) be present.S,53 MITRAL REGURGITATION (Fig. 9). It has been suggested that anterior mitral leaflet motion is increased in amplitude and has an abnormally rapid diastolic closure (DE slope greater than 150 mm. per second) in mi-
EKG
MV
LAW Figure 9. Mitral regurgitation, showing increased anterior leaflet excursion which measures 48 mm. Diastolic opening movement (DE slope) is normal at 275 mm/sec.; and early diastolic closure (EF slope) is normal at 80 mm/sec. EKG = electrocardiogram. MV = anterior leaflet mitral valve motion. LAW = posterior left atrial wall motion.
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tral regurgitation. 41 Possibly this pattern indicates a flail anterior leaflet as might be found in stretching or rupture of the chordae tendineae or other dysfunction of the mitral valve supporting structures. 46 In patients with proven rupture of a chordae tendineae, a prolapsing mitral leaflet may be seen within the left atrium in systole. On the other hand, Winters and co-workers found restriction of anterior leaflet motion (EF slopes of 16 to 56 mm. per second) commonly present in patients with rheumatic mitral regurgitation, especially when there was valvular calcification, and they concluded that an abnormally slow diastolic slope may be due to high grade mitral regurgitation with minimal or mild mitral stenosis.50 COMBINED MITRAL STENOSIS AND REGURGITATION (Fig. la). The combined lesion may result in variable echo patterns. Segal et al. have described a characteristic pattern showing an initially rapid EF slope followed by a plateau. 4o If the initial component is less than 45 to 50 mm. per second, then dominant stenosis is predicted, and if it is greater than 60 mm. per second, then dominant regurgitation is expected. 40 , 47 MITRAL VALVE PROLAPSE. A mid systolic prolapse of one or both mi-
EKG
MV
Figure 10. Combined mitral stenosis and insuffiCiency. Diastolic anterior leaflet excursion (DE amplitude) measures 16 mm, and is normal or slightly reduced. Rate of diastolic opening (DE slope) is normal, measuring 230 mm/sec. Early diastolic closure (EF slope) is slightly reduced, measuring 45-50 mm/sec. This pattern of normal early diastolic closure with abrupt termination in mid-diastole, has been attributed to dominant mitral regurgitation with a lesser degree of mitral stenosis. EKG = electrocardiogram (atrial fibrillation is present). MV = anterior leaflet mitral valve motion.
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EKG
MV
PW
Figure 11. Posterior motion of the anterior mitral valve leaflet echo during late systole, suggesting prolapse of the anterior leaflet of the mitral valve. Arrows indicate point of prolapse. CE amplitude = 31 mm. DE slope = 269 mm/sec. EF slope = 136 mm/sec. EKG = electrocardiogram. MV = anterior mitral valve leaflet motion. PW = posterior wall echo.
tral leaflets has been demonstrated angiographically in the "systolic click-late systolic murmur syndrome," and is attributed to failure of the mitral valve supporting structures to hold the leaflets as the ventricular pressure rises in systole. In these patients posterior prolapse of the anterior or posterior leaflets can be seen echocardiographically during systole, followed by the click and murmur. 7 , 15, 19,29,42 Since the degree of mitral regurgitation is mild and the condition benign, its diagnosis by echocardiography should be helpful. Figure 11 shows such a mid systolic prolapse of the anterior leaflet.
SUMMARY Ultrasound has proved to be a valuable tool in cardiac diagnosis, especially in detection of mitral stenosis, pericardial effusion, and mitral valve prolapse. It is an easy technique to master, without inconvenience to the patient, and it may prove to be a valuable method for diagnosis and for evaluation of cardiac function.
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REFERENCES 1. Casarella, W. J., and Schneider, B. 0.: Pitfalls in the ultrasonic diagnosis of pericardial effusion. Amer. J. Roentgen. 110:760, 1970. 2. Chester, E., Joffe, H. S., Beck, W., et al.: Echocardiographic recognition of mitralsemilunar valve discontinuity. An aid to the diagnosis of origin of both great vessels from the right ventricle. Circulation, 43:725,1971. 3. Chester, E., Joffe, H. S., Beck, W., et al.: Echocardiography in the diagnosis of congenital heart disease. Pediat. Clin. N. Amer., 18:1163,1971. 4. Craige, E., and Fortuin, N. J.: Studies of mitral valve motion with the Austin Flint murmur (AFM). (Abstract). Circulation, 44:11-33, 1971. 5. Crews, T. L., Pridie, R, Benham, R, et al.: Auscultatory and phonocardiographic findings in Ebstein's anomaly. Correlation of the first heart sound with ultrasonic records of tricuspid valve movement. (Abstract). Circulation, 42:111-113, 1970. 6. Dayem, M. K A., Oakley, C. M., Preger, L., et al.: Movements of the mitral valve annulus. Cardiovasc. Res., 1 :116,1967. 7. Dillon, J. C., Haine, C. L., Chang, S., et al.: Use of echocardiography in patients with prolapsed mitral valve. Circulation, 43:503, 1971. 8. Duchak, J. M., Jr., Chang, S., and Feigenbaum, H.: The posterior mitral valve echo and the echocardiographic diagnosis of mitral stenosis. Amer. J. CardioL, 29:628, 1972. 9. Edler, I.: Cardiac studies by ultrasound. In Luisada, A. A., ed.: Cardiology, an Encyclopedia of the Cardiovascular System. SuppL I, Part 4. New York, McGraw-Hill Book Co., 1962, pp. 410-424. 10. Edler, I.: Ultrasoundcardiography in mitral valve stenosis. Amer. J. CardioL, 19:18, 1967. 11. Edler, I., and Herz, C. H.: Use of ultrasonic reflectoscope for continuous recording of movements of heart walls. KungL Fysiogr. Sallsk. Lund. ForhandL, 24:40, 1954. 12. Effert, S.: Pre- and postoperative evaluation of mitral stenosis by ultrasound. Amer. J. CardioL, 19:59, 1967. 13. Feigenbaum, H.: Echocardiographic diagnosis of pericardial effusion. Amer. J. CardioL, 26:475, 1970. 14. Firestone, F. A.: Supersonic reflectoscope, an instrument for inspecting the interior of solid parts by means of sound waves. J. Accoust. Soc. Amer., 17:287, 1946. 15. Frankl, W. S., MacMillan, R, and Smith, W. K, Jr.: Differential echocardiographic patterns in mitral regurgitation. Angiology, 23 :642, 1972. 16. Friedman, N. J.: Echocardiographic studies of mitral valve motion. Genesis of the opening snap in mitral stenosis. Amer. Heart J., 80: 1 77, 1970. 17. Gabor, G. E., and Winsberg, F.: Motion of mitral valves in cardiac arrhythmias. Ultrasonic cardiographic study. Invest. RadioL, 5:355,1970. 18. Gramiak, R, Nanda, N. C., and Shah, P. M.: Echocardiographic detection of the pulmonary valve. Radiology, 102:153, 1972. 19. Gramiak, R, and Shah, P. M.: Cardiac ultrasonography. A review of current applications. RadioL Clin. N. Amer., 9:469, 1971. 20. Gramiak, R, Shah, P. M., and Kramer, D. H.: Ultrasoundcardiography: Contrast studies in anatomy and function. Radiology, 92:939, 1969. 21. Gordon, D., ed.: Ultrasound as a Diagnostic and Surgical TooL Baltimore, Williams and Wilkins Co., 1964. 22. Gustafson, A.: Correlation between ultrasoundcardiography, hemodynamics and surgical findings in mitral stenosis. Amer. J. CardioL, 19:32, 1967. 23. Hirata, T., Wolfe, S. B., Popp, R L., et al.: Estimation of the left atrial size using ultrasound. Amer. Heart J., 78:43, 1969. 24. Hertz, C. H.: Ultrasonic engineering in heart diagnosis. Amer. J. CardioL, 19:6,1967. 25. Inoue, K, Smulyan, H., Mookherjee, S., et al.: Ultrasonic measurements of left ventricular wall motion in acute myocardial infarction. Circulation, 43:778, 1971. 26. Johnson, M. L., Paton, B. C., and Holmes, J. H.: Ultrasonic evaluation of prosthetic valve motion. (Abstract). Circulation, 41-42:II-3, 1970. 27. Joyner, C. R: Experience with ultrasound in the study of heart disease and the production of intracardiac sound. In Kelly, E., ed.: Diagnostic Ultrasound. New York, Plenum Press, 1966. 28. Joyner, C. R, Hey, E. B., Johnson, J., et al.: Reflected ultrasound in the diagnosis of tricuspid stenosis. Amer. J. CardioL, 19:66,1967. 29. Kerber, RD., Isaeff, D. M., and Hancock, E. W.: Echocardiographic patterns in patients with the syndrome of systolic click and late systolic murmur. New Eng. J. Med., 284:691, 1971. 30. Kostis, J. B., and Moghadam, A. N.: Echocardiographic diagnosis of left atrial myxoma. Chest, 58:550, 1970. 31. Kotler, M., and Tabatznik, B.: Recognition of Ebstein's anomaly by ultra-sound technique (abstract). Circulation, 43-44:11-34, 1971.
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32. Lundstrom, N. R., and Edler, 1.: Ultrasoundcardiography in infants and children. Acta Paediatr. Scand., 60:117,1971. 33. Nasser, W. K., Davis, R. H., Dillon, J. C., et al.: Atrial myxoma. 11. Phonocardiographic, echocardiographic, hemodynamic, and angiographic features in nine cases. Amer. Heart J.,83:810, 1972. 34. Popp, R. L., and Carmichael, B. M.: Cardiac echography in the diagnosis of prosthetic valve malfunction. (Abstract). Circulation, 43-44:11-33, 1971. 35. Popp, R. L., and Harrison, D. C.: Ultrasound in the diagnosis and evaluation of therapy in idiopathic hypertrophic subaortic stenosis. Circulation, 40:905, 1969. 36. Popp, R. L., Wolfe, S. B., Hirara, T., et al.: Estimation of right and left ventricular size by ultrasound. A study of echoes from the interventricular septum. Amer. J. Cardiol., 24:523, 1969. 37. Pridie, R. B., Benham, R., and Oakley, C. M.: Recognition of aortic regurgitation of recent onset by ultrasound technique (abstract). Amer. J. Cardiol., 26:654, 1970. 38. Pridie, R. B., Benham, R., and Oakley, C. M.: Echocardiography of the mitral valve in aortic valve disease. Brit. Heart J., 33:296, 1971. 39. Pridie, R. B., and Oakley, C. M.: Mechanism of mitral regurgitation in hypertrophic obstructive cardiomyopathy. Brit. Heart J., 32:302, 1970. 40. Segal, B. L., Likoff, W., and Kingsley, B.: Echocardiography. Clinical application in combined mitral stenosis and mitral regurgitation. Amer. J. Cardiol., 19:42, 1967. 41. Segal, B. L., Likoff, W., and Kingsley, B.: Echocardiography. Clinical application in mitral regurgitation. Amer. J. Cardiol., 19:50,1967. 42. Shah, P. M., and Gramiak, R.: Echocardiographic recognition of mitral valve prolapse (abstract). Circulation, 42:111-45, 1970. 43. Shah, P. M., Grarniak, R., and Kramer, D. H.: Ultrasound localization of left ventricular outflow obstruction in hypertrophic obstructive cardiomyopathy. Circulation, 40:3, 1969. 44. Shah, P. M., Gramiak, R., Kramer, D. H., et al.: Determinants of atrial (S,) and ventricular (S3) gallop sounds in primary myocardial disease. N. Eng. J. Med., 278:753,1968. 45. Siggers, D. C., Srivongse, S. A., and Deuchar, D.: Analysis of dynamics of mitral StarrEdwards valve prosthesis using reflected ultrasound. Brit. Heart J., 23:401, 1971. 46. Wharton, C. F. P.: Reflected ultrasound patterns in mitral valve disease. Guy's Hospital Rep., 118:187,1969. 47. Wharton, C. F. P., and Lopez-Bescos, L.: Mitral valve movement: A study using an ultrasound technique. Brit. Heart J., 32:344, 1970. 48. Wharton, C. F. P., Smithen, C. S., and Sowton, E.: Changes in left ventricular wall movement after acute myocardial infarction measured by reflected ultrasound. Brit. Med. J., 4:75, 1971. 49. Winters, W. L., Jr., Gimenez, J., and Soloff, L. A.: Clinical application of ultrasound in the analysis of prosthetic ball valve motion. Amer. J. Cardiol., 19:97, 1967. 50. Winters, W. L., Jr., Hafer, J., Jr., and Soloff, L. A.: Abnormal mitral valve motion as demonstrated by the ultrasound technique in apparent pure mitral insufficiency. Amer. Heart J., 77:196,1969. 51. Wolfe, S. B., Popp, R. L., and Feigenbaum, H.: Diagnosis of atrial tumors by ultrasound. Circulation, 39:615, 1969. 52. Zaky, A., Grabhorn, L., and Feigenbaum, H.: Movement of the mitral ring: A study in ultrasoundcardiography. Cardiovasc. Res., 1 :121,1967. 53. Zaky, A., Nasser, W. K., and Feigenbaum, H.: A study of mitral valve action recorded by reflected ultrasound and its application in the study of mitral stenosis. Circulation, 37:789, 1968. Medical College of Pennsylvania Philadelphia, Pennsylvania 19129 (Dr. Frankl)
U Itra-sound Cardiography in Clinical Practice William K. Smith, Jr., MD.,* William S. Frankl, M.D.**
The term ultrasound refers to sound waves having frequencies above the range of human hearing, that is, greater than 20,000 cycles per second. 21 • 24 At frequencies above 20,000 cycles per second, the passage of ultrasonic waves through air is progressively attenuated, so that the practical application of ultrasound is essentially confined to its use in solid or liquid media. The first such application by man was the development of "sonar" for the detection of enemy submarines by Langevin during World War 1.21 With this technique a transmitting transducer attached to the ship's hull generates a short pulse of ultrasound waves directed toward the bottom of the sea beneath the ship. When the pulse strikes the bottom, some of the ultrasound is reflected back toward the ship and is picked up by a receiving transducer. If the transit time from emission of the pulse to reception of the echo is measured, and if the velocity of sound transmission in salt water is known, then the distance to the bottom can be calculated. With the development of radar during World War II it became possible to measure very short time intervals accurately with electronic circuits. Using such circuits, Firestone in 1945 developed an instrument for ultrasonic testing of material in industry, using sonar techniques. 14 The principle of this ultrasonic reflectoscope is shown in Figure 1. A piezoelectric crystal serves as the ultrasonic transducer, converting electrical impulses into short pulses of ultrasound. The ultrasound pulses are beamed through the material, and during the intervals between pulses the same transducer acts as a receiver, reconverting any returning echoes into electrical energy. Echoes are produced when the ultrasound waves reach interfaces between materials of differing densities, such as solid-gas, solid-liquid, or gas-liquid interfaces. These "accoustical interfaces" reflect ultrasound in much the same way that light is reflected, so that when the ultrasound beam is perpendicular to the interface the • Associate Professor of Medicine and Director, Cardiac Graphics Laboratory, Cardiology Division, Medical College of Pennsylvania; Attending PhYSiCian, Veterans Administration Hospital, Philadelphia, Pennsylvania "Professor of Medicine and Director, Cardiology Division, Medical College of Pennsylvania; Consultant, Veterans Administration Hospital, Philadelphia, Pennsylvania
Medical Clinics of North America- Vol. 57, No. 4, July 1973
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SIGNAL FROM
I
TRANSDUCER _¥'/DEFECT SIGNAL FROM S I G N A L _ I - - - + - - - - - - - - i - E N D OF MATERIAL
i
.----_...J
TRANSDUCE:J1L_ _ _-tt_ _ _ _ DEFECT
t
MATERIAL TESTED
Figure 1. Industrial use of ultrasound for testing solid materiaL Lower half of the diagram shows the ultrasound transducer applied to one side of the sample, so that short pulses of ultrasound energy can be beamed through the material. Display of the echo signals as they appear on the cathode ray tube oscilloscope is shown above. On the right is an echo "spike" representing the ultrasound pulse as it originates from the transducer; the echoes from the acoustic interfaces produced by the defect and the opposite side of the material are also shown. The height of these signals corresponds to the intensity of the reflected echoes, and thus gives an indication of the magnitude or density of the interfaces. Their location on the x axis of the oscilloscope display corresponds to the depth of the interface in the material, so that the display can be calibrated and the location of the flaw measured from the ultrasonogram.
reflected ultrasound returns toward its source. The opposite side of the material represents a strong accoustical interface because of the marked change in density from solid to air, and any faults or flaws in the material also act as interfaces and produce echoes. These are displayed on the cathode ray tube, with the location of the echo on the x axis corresponding to the distance of the flaw from the transducer. The x axis can be calibrated for depth, so that the exact location of the flaw can be accurately determined without damage to the material. 24 The ultrasonic reflectoscope was applied to medical diagnosis by Edler and Hertz in 1954 when they demonstrated motion of the mitral valve in man with this nonsurgical, noninvasive techniqueY The pulses are generated by piezoelectric crystal transducers, coupled to the chest wall with water ora semisolid gel, so that the ultrasound waves are not attenuated by pockets of air between the transducer and the chest wall. The same transducer which is used to generate the ultrasound pulse also acts as a receiving transducer to convert the returning echoes to electrical energy. Crystals with resonant frequencies in the range of 2 to 2.5 MHz (2 to 2.5 megacycles per second) are used. The crystals are activated by short electrical impulses which generate 5 to 10 microsecond pulses of ultrasound waves, at repetition rates of 200 to 2000 times per second. The periods between pulses last 0.5 to 5 milliseconds (depending on the repetition rate) and during these periods the crystal transducer acts as a receiver and "listens" for echoes from the ultrasound pulse. Returning echoes are converted into electrical energy by the crystal, and these small electrical signals are amplified for display on the oscilloscope screen. The display is accomplished by having the electron beam of the cathode ray tube begin to move from left to right on the x axis across the screen at the same time that the pulse is generated. It moves at a constant rate and, as
961
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returning echoes are received, the beam is momentarily deflected upward on the screen to produce a "spike," the height of which is proportional to the intensity of the echo, and thus to the "density" of the accoustical interface which produced the echo. Thus, the oscilloscope shows the depth of the various interfaces and their intensity. This is known as the "A mode" display, and an example of intracardiac structures shown in this mode is seen in Figure 2. In "B mode" display the echoes are represented by dots along the x axis, rather than spikes, and the intervening spaces between dots are left blank. Brightness or intensity of the dot represents intensity of the echo (and therefore intensity of the accoustic interface producing the echo) and distance from the left side of the screen represents depth. Because of the rapid repetition rate of the ultrasound pulses, the dots persist on the screen as stationary echoes, or, if an interface is moving in the path of the ultrasound beam, then the dot representing its echo is seen to move back and forth along the x axis on the screen. To permanently record this movement of the echoes, the "M mode" (time-motion mode) was developed. In this modality the display of echoes along the x axis is slowly
Jy
T CW
1
AW
14cm
vs
MV
r r
PW
L
Figure 2. "A mode" presentation of echoes from the various cardiac structures in a normal young man. The height of the echo "spikes" represents intensity of the reflected ultrasound from the interfaces. Tissue depth marked in centimeters from left to right. T = transducer signal. CW = chest wall echoes. AW = anterior wall of the right ventricle. VS = ventricular septum. MV = anterior leaflet of the mitral valve. PW = posterior wall of the left ventricle. L = lung echoes.
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moved upward on the screen (in the direction of the y axis). The moving dots then describe waves during their vertical travel, while the stationary dots describe vertical straight lines. An oscilloscope camera photographs this sweep with a time exposure and thus records the motion of the interfaces which were in the path of the ultrasound beam. As photographed from the display, the x axis represents distance of the interface from the transducer on the chest wall, and the y axis represents time, but for convenience of analysis (and to correspond with the other graphic records) the photograph is turned on its side (rotated 90°) so that the axes are reversed, and the x (horizontal) axis becomes time and the y (vertical) axis becomes depth from the chest wall. Figure 3 shows the movement of cardiac structures recorded in M mode. It can be readily appreciated that the M mode is most useful in echocardiography, for not only do characteristic motions identify the various structures in the heart, but an analysis
EKG
CW AW---i.
IVS---
MV
----t.
PW---t. P---L - -__
_-.... ...
Figure 3. M Mode echocardiogram (or Moving "B mode" echocardiogram) showing motion of the various cardiac structures lying in the path of the ultrasonic beam. The patient had a large anterior and posterior pericardial effusion. The transducer is located parasternally in the fourth left intercostal space, pointing directly posterioriy. Anterior or posterior motion of the interfaces in the path of the ultrasonic beam is recorded as an upward or downward movement of the various traces. Time is represented horizontally, so that the location of an interface at any given point in the cardiac cycle can be obtained by comparison with the simultaneously recorded electrocardiogram. Time dots are one second apart horizontally, and the same dots represent tissue depth in centimeters vertically. EKG = electrocardiogram. CW = stationary echoes from the chest wall. AW = anterior right ventricular wall motion, separated by the pericardial effusion from the chest wall echoes. IVS = ventricular septal motion. MV = motion of the anterior leaflet of the mitral valve. PW = posterior left ventricular wall motion, separated from the pericardium by the pericardial effusion. P = posterior parietal pericardium. L = echoes from the lung.
ULTRASOUND CARDIOGRAPHY
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of the motion of intracardiac structures becomes available, without invading the heart.
ULTRASOUND TECHNIQUES IN CARDIOLOGY The cardiac examination is begun by placing the crystal transducer parasternally in the left fourth intercostal space and directing the ultrasound beam posteriorly and slightly medial or cephalad, looking for the characteristic motion of the anterior leaflet of the mitral valve.1O, 53 This motion is illustrated in Figure 4, which shows the slow anterior movement of the anterior leaflet in systole CC to D), and two anterior opening movements in diastole CD to E and F to A). The systolic anterior movement CC to D), occurring while the valve is in its closed position, represents the anterior projection of systolic movement of the base of the heart toward its apex during left ventricular contraction. 6 • 52. 53 The first diastolic anterior movement CD to E) represents initial opening of the valve as left ventricular pressure falls below left atrial pressure and early dia-
Figure 4. Normal anterior leaflet mitral valve motion. Total amplitude of motion (CE amplitude) is 28 mm. Amplitude of motion during diastole (DE amplitude) is 20 mm. Opening movement slope (DE slope) is 290 mm/sec. Early diastolic closure (EF slope) is 93 mm/sec. EKG = electrocardiogram. IVS = region of ventricular septal echoes. MV = anterior leaflet mitral valve movement. PW = posterior ventricular wall motion. Syst = systole. Diast = diastole. 1 cm = one centimeter of tissue depth. Time dots are one second apart horizontally, and the same dots represent tissue depth in centimeters vertically.
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stolic filling begins. Immediately after the first rush of blood into the ventricle, the valve leaflet drifts back to its closed position (E to F). With atrial systole the valve again opens (anterior leaflet F to A movement) followed by closure of the valve with ventricular systole (A to C movement). In the presence of atrial fibrillation the A wave is, of course, absent. Point C coincides with the second component (mitral closure component) of the first heart sound, and point D occurs 10 to 50 milliseconds after the aortic component of the second heart sound. 10 Point E represents the point of maximum opening of the valve and coincides with the time of the opening snap in mitral stenosis. 16 When present, the third heart sound occurs during the mid portion of the E to F movement; it may follow the inscription of an early slower portion of the E to F slope. lO (When the E to F slope is divided into an early slow portion and a fast late portion, the point of change is labeled Fo.53 Fourth heart sounds coincide with the A point, the peak of the A movement of the valve. 10 The total amplitude of motion of the anterior leaflet, that is the vertical distance from point C to point E (CE amplitude) measures 20 to 33 mm. in normal subjects. lO The amplitude of diastolic movement of the valve (DE amplitude) may measure up to 5 mm. less than the CE amplitude, and the magnitude of this excursion has been related to valve leaflet mobility.47.53 The slope of the D to E movement is measured as millimeters of excursion per second of movement and the normal range is 250 to 500 mm. per second. 10 The slope of the E to F movement (EF slope) or E to Fo movement (EFo slope) is normally 80 to 190 mm. per second measured as vertical excursion per second of movement. lO • 41 Echocardiograms showing the greatest amplitude of anterior mitral leaflet excursion with definite E and A waves are best for analysis, and in practice can usually be recorded parasternally in the fourth left intercostal space. In patients with cardiomegaly the valve echo may be located 1 to 5 cm. away from the parasternal position or in the third or fifth interspaces, and in patients with gross chamber enlargement or anatomic distortion of the heart the mitral valve echo may be'recorded from some other area of the precordium. In order to obtain satisfactory tracings a water-soluble gel is applied to the transducer so that direct contact is made with the chest wall, excluding any air pockets which would markedly attenuate the ultrasound beam. The transducer must be in an intercostal space, between the ribs, to prevent the loss of ultrasound energy which would occur if one attempted to send the beam through a rib. Echoes from the anterior part of the heart are much stronger than those from the posterior cardiac structures (i.e., the left ventricle, the left atrium, etc.), and the machine has near and far intensity or gain controls. Familiarity with these intensity adjustments, as well as the contrast controls, must be acquired if one is to obtain distinct and continuous signals from some of the "weaker" reflecting interfaces in the heart. Finally, very slight changes in angulation or location of the transducer can be responsible for change in angle of the beam with respect to the interfaces, and consequent remarkable change in the quality of the echo ob-
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tained from a given structure. Some patience is required in learning the technique, but experience can be rapidly acquired, and tracings of high quality can be routinely obtained by technicians.
CARDIAC ANATOMY AND IDENTIFICATION OF INTRACARDIAC ECHOES Casual positioning of the transducer on the precordium can produce a confusing array of moving interfaces, defying identification or analysis. Similarly, random searching for a specific interface is time consuming, and there is no proof that the resulting final record truly represents the interface sought. Therefore, the importance of a systematic approach cannot be overemphasized: it is the key to finding and understanding the motions of the various intracardiac structures.9 • 20. 36 The method begins with identification of the characteristic anterior mitral valve leaflet motion, usually readily found; then, without moving the transducer, locating other structures by changing the instrument gain or by slightly angling the transducer beam toward adjacent areas of the heart. In this way ventricular septum, aortic valve and root, left atrial and left ventricular posterior walls, and the posterior pericardial space can be studied without changing the location of the transducer on the chest wall. Threedimensional relationships can be inferred by comparing depth with the direction in which the beam was angulated, and characteristic patterns of motion of each structure can be recorded in sequence. Figure 5 shows a schematic, two dimensional representation of the structures through which the echo beam passes with only slight change of angulation either medially and cephalad, or laterally and inferiorly. Tricuspid valve motion may also be recorded (although with difficulty in normals) by angling the transducer medially and inferiorly or by moving its location down one interspace from the mitral valve location. 20 • 28 Pulmonary valve motion has recently been studied by Gramiak et aI., using a technique for locating the valve leaflets with a 60 per cent success rate in patients under 14 years of age. 1S To complete the examination, motion of the mitral valve ring toward the apex can usually be recorded by placing the transducer at the cardiac apex and pointing toward the base of the heart. 6 • 52 Mitral ring movement represents the systolic movement of the base of the heart toward the apex along its major axis, and provides an indication of major axis shortening during systole. The ability to record the echocardiogram of the ventricular cavities, septum, and posterior left ventricular wall enables one to diagnose pericardial effusion; to estimate left ventricular cavity size and wall thickness; to estimate left ventricular stroke volume; to evaluate heart muscle performance; and to detect abnormalities of the ventricular septum or septal motion. Figure 6 shows the left ventricular cavity with ventricular septal motion above and left ventricular posterior wall motion below, and from tracings such as this estimates of left ventricular function and stroke volume can be made.
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2
3
MEDIASTINUM. VERTEBRAE
~~~~------~~----------tJr---7 B
Figure 5. Two dimensional schematic representation of various paths of the echo beam which can be obtained by slightly changing the angle of the transducer on the chest wall (labeled 1 through 8). The transducer is in the location in which the anterior mitral valve leaflet motion is recorded, usually in the fourth left intercostal space parasternally. Angling the transducer slightly medially or cephalad (directions 1, 2, or 3) allows recording of the motion of the aortic root and the left atrium immediately behind the aortic root. The anterior mitral valve leaflet motion can be recorded with the beam pointing in directions number 4, 5, or 6, with anyone of a number of structures recorded deep to the anterior leaflet, including the posterior left atrial wall, posterior mitral ring, posterior mitral valve leaflet, or posterior left ventricular wall. Pointing the beam in directions 7 or 8 allows one to record motion of the muscular ventricular septum and posterior left ventricular wall. Mediastinal structures or vertebrae produce strong echoes which may be mistaken for pericardium, but this confusion can be avoided by directing the beam laterally off the free edge of the anterior leaflet of the mitral valve, in directions 7 and 8. A = aorta. Aor. R = aortic ring. LA = left atrium. LV = left ventricle. Memb. S = membranous septum. ML = mitral leaflets (Ant. = anterior leaflet, Post. = posterior leaflet). Musc. S. = muscular septum. MR = mitral valve ring. NC = non-coronary cusp of the aortic valve. P A = pulmonary artery. Pul. R = pulmonary valve ring. RC = right coronary cusp of the aortic valve. RV = right ventricle.
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EKG-
vs-
pw-
Figure 6. Motion of ~the ventricular septum and posterior left ventricular wall. VS = motion of the ventricular septum, recorded at the interface between the left side of the ventricular septum and the left ventricular cavity. PW = motion of the posterior ventricular wall. As the sweep progressed (from left to right across the illustration), the instrument gain was increased, so that more intense echoes were recorded from both interfaces, and finally echoes from the blood in the ventricular cavity began to appear (on the right hand side of the photograph). It should be noted that the ventricular septum and the posterior wall approach each other as the ventricle contracts in systole, and move apart as the ventricle fills in diastole. EKG = electrocardiogram. VS = ventricular septum. PW = posterior left ventricular wall motion.
DIAGNOSTIC USES OF ECHOCARDIOGRAPHY Echocardiography has become in our opinion the most useful technique for the diagnosis of pericardial effusion. It is of great assistance in confirming the severity of mitral stenosis and establishing (or excluding) this diagnosis in patients with combined valvular disease, poorly heard murmurs, etc. lO , 12,22,53 Finally, its application has been explored in a growing number of other conditions, a partial listing of which includes: acute aortic regurgitation,37, 38 systolic prolapse of the mitral valve,7, 15, 19,29,42 tricuspid stenosis,t2, 28 prosthetic mitral valve function,26, 34,45,49 obstructive cardiomyopathy (idiopathic hypertrophic subaortic stenosis),35, 39, 43 atrial myxoma,a0' 33, 51 left atrial enlargement,23 Ebstein's anomaly,5,31 congenital cardiac lesions,2,3,32 Austin Flint murmur,4,38 arrhythmias,t7 and myocardial infarction. 25 ,48 We will briefly discuss echocardiography in pericardial effusion and mitral valve disease, since these are the most widely used clinical applications.
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Pericardial Effusion In the space of a decade the echocardiogram has become one of the most reliable methods for the diagnosis of pericardial effusion. The area of posterior left ventricular wall distant from the mediastinum is located, so that mediastinal echoes will not be mistaken for pericardium. 1 • 13 With appropriate adjustment of gain controls a space can be seen between the normally moving posterior wall echo and a strong pericardium-lung interface, and this echo-free space represents the effusion (Fig. 7). Gain control must be carefully adjusted since the space can be obscured by echoes from the fluid itself if too great intensity of ultrasound is used. It is also helpful to turn down the gain control until the posterior wall echo disappears, and the reflection from the stronger pericardium-lung interface is identified. Anterior pericardial effusion frequently accompanies posterior effusion, but should not be diagnosed in the absence of posterior fluid accumulation. 19 Estimation of the volume of the effusion is an approximation at best, but the finding of synchronous movement of anterior and posterior walls, the so-called "swinging heart," indicates a large effusion which may frequently be neoplastic in originP Pleural fluid may also be recognized behind the heart, and must be differentiated from pericardial effusion; occasionally both effusions are seen together. 1
-
E KG---=
-
. .
....... ~
CW PE-~
AW-....·
PW--4I:
PE p---'L. l -__ Figure 7. Large hemopericardium in 17 year old boy, following blunt chest trauma. CW = stationary chest wall echoes. AW = anterior right ventricular epicardial motion. PE = space representing the pericardial effusion. PW = posterior left ventricular epicardial motion. P = reflection from the posterior parietal pericardium. L = lung. This large collection of blood, measuring in excess of 650 cc. had collected slowly in a nine day period following an automobile accident, and was accompanied by increasing signs of pericardial tamponade.
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Mitral Valve Disease MITRAL STENOSIS. Decrease in EF slope (or EFo slope) occurs when the anterior leaflet of the mitral valve is kept open in diastole by a persistent atrioventricular pressure gradient of mitral stenosis, and the diminution in EF slope corresponds to the severity of the stenosis. lo • 12. 22 Mild stenosis is associated with EF slopes greater than 35 mm. per second, slopes of 15 to 35 mm. per second are seen in severe stenosis. lO Amplitude of anterior leaflet motion correlates with mobility of the valve leaflet; CE amplitudes below 15 mm. (or DE amplitudes below 12 mm.) represent rigid valves.lO In the presence of a rigid valve with severe calcification or with amplitude of motion less than 10 mm., the EF slope does not reliably indicate the degree of stenosis, and predominant mitral regurgitation can be present even though the EF slope is in the stenotic range. lO . 47 Increased intensity of the anterior leaflet echoes or multiple parallel echoes suggest thickening, fibrosis, or calcification of the valve. 27 Figure 8 shows the anterior leaflet echo in severe mitral stenosis. After a successful valvotomy the wave form returns toward normal, although persistence of some decrease in EF slope and amplitude of motion is usually noted, especially in those patients having calcified valves.lO. 12.22.47 Patients having diastolic murmurs due to increased flow (flow murmurs or "flow rumbles") or the Austin Flint rumble, do not show a decreased EF slope. aB Tricuspid stenosis can be differentiated from mitral
EKG
MV
Figure 8. Severe advanced mitral stenosis in 67 year old woman having a heavily calci· fied rigid valve. Note the marked reduction in excursion of the valve, reduced speed of early diastolic opening, and markedly reduced EF slope, as the valve remains in a fixed "open" position throughout diastole. CE amplitude 12 mm. DE slope 130 mm/sec. EF slope 10 mm/sec. EKG = electrocardiogram. MV = mitral valve echoes.
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stenosis by demonstrating a normal mitral EF slope with decreased tricuspid EF slope. 2s Other conditions can produce a decreased EF slope and falsely suggest the diagnosis of mitral stenosis. These include tachycardiap, 53 left atrial myxoma,30, 33, 51 idiopathic hypertrophic subaortic stenosis (lHSS),39,43 aortic stenosis,s aortic regurgitation,t9 and reduced left ventricular compliance due to left ventricular hypertrophy, especially in patients having an atrial gallop.44 Therefore, Feigenbaum proposes four additional criteria to be satisfied before diagnosis of mitral stenosis is made by echocardiography; First, that the closure of the valve in mid diastole not be present (i.e., that Fo-F movement not be present); second, that a characteristic motion of the posterior mitral leaflet anteriorly in diastole be seen beneath the anterior leaflet echo; third, that the diagnosis not be made in tracings showing tachycardia; and fourth, that adequate amplitude of leaflet motion (DE amplitude) be present.S,53 MITRAL REGURGITATION (Fig. 9). It has been suggested that anterior mitral leaflet motion is increased in amplitude and has an abnormally rapid diastolic closure (DE slope greater than 150 mm. per second) in mi-
EKG
MV
LAW Figure 9. Mitral regurgitation, showing increased anterior leaflet excursion which measures 48 mm. Diastolic opening movement (DE slope) is normal at 275 mm/sec.; and early diastolic closure (EF slope) is normal at 80 mm/sec. EKG = electrocardiogram. MV = anterior leaflet mitral valve motion. LAW = posterior left atrial wall motion.
ULTRASOUND CARDIOGRAPHY
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tral regurgitation. 41 Possibly this pattern indicates a flail anterior leaflet as might be found in stretching or rupture of the chordae tendineae or other dysfunction of the mitral valve supporting structures. 46 In patients with proven rupture of a chordae tendineae, a prolapsing mitral leaflet may be seen within the left atrium in systole. On the other hand, Winters and co-workers found restriction of anterior leaflet motion (EF slopes of 16 to 56 mm. per second) commonly present in patients with rheumatic mitral regurgitation, especially when there was valvular calcification, and they concluded that an abnormally slow diastolic slope may be due to high grade mitral regurgitation with minimal or mild mitral stenosis.50 COMBINED MITRAL STENOSIS AND REGURGITATION (Fig. la). The combined lesion may result in variable echo patterns. Segal et al. have described a characteristic pattern showing an initially rapid EF slope followed by a plateau. 4o If the initial component is less than 45 to 50 mm. per second, then dominant stenosis is predicted, and if it is greater than 60 mm. per second, then dominant regurgitation is expected. 40 , 47 MITRAL VALVE PROLAPSE. A mid systolic prolapse of one or both mi-
EKG
MV
Figure 10. Combined mitral stenosis and insuffiCiency. Diastolic anterior leaflet excursion (DE amplitude) measures 16 mm, and is normal or slightly reduced. Rate of diastolic opening (DE slope) is normal, measuring 230 mm/sec. Early diastolic closure (EF slope) is slightly reduced, measuring 45-50 mm/sec. This pattern of normal early diastolic closure with abrupt termination in mid-diastole, has been attributed to dominant mitral regurgitation with a lesser degree of mitral stenosis. EKG = electrocardiogram (atrial fibrillation is present). MV = anterior leaflet mitral valve motion.
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FRANKL
EKG
MV
PW
Figure 11. Posterior motion of the anterior mitral valve leaflet echo during late systole, suggesting prolapse of the anterior leaflet of the mitral valve. Arrows indicate point of prolapse. CE amplitude = 31 mm. DE slope = 269 mm/sec. EF slope = 136 mm/sec. EKG = electrocardiogram. MV = anterior mitral valve leaflet motion. PW = posterior wall echo.
tral leaflets has been demonstrated angiographically in the "systolic click-late systolic murmur syndrome," and is attributed to failure of the mitral valve supporting structures to hold the leaflets as the ventricular pressure rises in systole. In these patients posterior prolapse of the anterior or posterior leaflets can be seen echocardiographically during systole, followed by the click and murmur. 7 , 15, 19,29,42 Since the degree of mitral regurgitation is mild and the condition benign, its diagnosis by echocardiography should be helpful. Figure 11 shows such a mid systolic prolapse of the anterior leaflet.
SUMMARY Ultrasound has proved to be a valuable tool in cardiac diagnosis, especially in detection of mitral stenosis, pericardial effusion, and mitral valve prolapse. It is an easy technique to master, without inconvenience to the patient, and it may prove to be a valuable method for diagnosis and for evaluation of cardiac function.
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REFERENCES 1. Casarella, W. J., and Schneider, B. 0.: Pitfalls in the ultrasonic diagnosis of pericardial effusion. Amer. J. Roentgen. 110:760, 1970. 2. Chester, E., Joffe, H. S., Beck, W., et al.: Echocardiographic recognition of mitralsemilunar valve discontinuity. An aid to the diagnosis of origin of both great vessels from the right ventricle. Circulation, 43:725,1971. 3. Chester, E., Joffe, H. S., Beck, W., et al.: Echocardiography in the diagnosis of congenital heart disease. Pediat. Clin. N. Amer., 18:1163,1971. 4. Craige, E., and Fortuin, N. J.: Studies of mitral valve motion with the Austin Flint murmur (AFM). (Abstract). Circulation, 44:11-33, 1971. 5. Crews, T. L., Pridie, R, Benham, R, et al.: Auscultatory and phonocardiographic findings in Ebstein's anomaly. Correlation of the first heart sound with ultrasonic records of tricuspid valve movement. (Abstract). Circulation, 42:111-113, 1970. 6. Dayem, M. K A., Oakley, C. M., Preger, L., et al.: Movements of the mitral valve annulus. Cardiovasc. Res., 1 :116,1967. 7. Dillon, J. C., Haine, C. L., Chang, S., et al.: Use of echocardiography in patients with prolapsed mitral valve. Circulation, 43:503, 1971. 8. Duchak, J. M., Jr., Chang, S., and Feigenbaum, H.: The posterior mitral valve echo and the echocardiographic diagnosis of mitral stenosis. Amer. J. CardioL, 29:628, 1972. 9. Edler, I.: Cardiac studies by ultrasound. In Luisada, A. A., ed.: Cardiology, an Encyclopedia of the Cardiovascular System. SuppL I, Part 4. New York, McGraw-Hill Book Co., 1962, pp. 410-424. 10. Edler, I.: Ultrasoundcardiography in mitral valve stenosis. Amer. J. CardioL, 19:18, 1967. 11. Edler, I., and Herz, C. H.: Use of ultrasonic reflectoscope for continuous recording of movements of heart walls. KungL Fysiogr. Sallsk. Lund. ForhandL, 24:40, 1954. 12. Effert, S.: Pre- and postoperative evaluation of mitral stenosis by ultrasound. Amer. J. CardioL, 19:59, 1967. 13. Feigenbaum, H.: Echocardiographic diagnosis of pericardial effusion. Amer. J. CardioL, 26:475, 1970. 14. Firestone, F. A.: Supersonic reflectoscope, an instrument for inspecting the interior of solid parts by means of sound waves. J. Accoust. Soc. Amer., 17:287, 1946. 15. Frankl, W. S., MacMillan, R, and Smith, W. K, Jr.: Differential echocardiographic patterns in mitral regurgitation. Angiology, 23 :642, 1972. 16. Friedman, N. J.: Echocardiographic studies of mitral valve motion. Genesis of the opening snap in mitral stenosis. Amer. Heart J., 80: 1 77, 1970. 17. Gabor, G. E., and Winsberg, F.: Motion of mitral valves in cardiac arrhythmias. Ultrasonic cardiographic study. Invest. RadioL, 5:355,1970. 18. Gramiak, R, Nanda, N. C., and Shah, P. M.: Echocardiographic detection of the pulmonary valve. Radiology, 102:153, 1972. 19. Gramiak, R, and Shah, P. M.: Cardiac ultrasonography. A review of current applications. RadioL Clin. N. Amer., 9:469, 1971. 20. Gramiak, R, Shah, P. M., and Kramer, D. H.: Ultrasoundcardiography: Contrast studies in anatomy and function. Radiology, 92:939, 1969. 21. Gordon, D., ed.: Ultrasound as a Diagnostic and Surgical TooL Baltimore, Williams and Wilkins Co., 1964. 22. Gustafson, A.: Correlation between ultrasoundcardiography, hemodynamics and surgical findings in mitral stenosis. Amer. J. CardioL, 19:32, 1967. 23. Hirata, T., Wolfe, S. B., Popp, R L., et al.: Estimation of the left atrial size using ultrasound. Amer. Heart J., 78:43, 1969. 24. Hertz, C. H.: Ultrasonic engineering in heart diagnosis. Amer. J. CardioL, 19:6,1967. 25. Inoue, K, Smulyan, H., Mookherjee, S., et al.: Ultrasonic measurements of left ventricular wall motion in acute myocardial infarction. Circulation, 43:778, 1971. 26. Johnson, M. L., Paton, B. C., and Holmes, J. H.: Ultrasonic evaluation of prosthetic valve motion. (Abstract). Circulation, 41-42:II-3, 1970. 27. Joyner, C. R: Experience with ultrasound in the study of heart disease and the production of intracardiac sound. In Kelly, E., ed.: Diagnostic Ultrasound. New York, Plenum Press, 1966. 28. Joyner, C. R, Hey, E. B., Johnson, J., et al.: Reflected ultrasound in the diagnosis of tricuspid stenosis. Amer. J. CardioL, 19:66,1967. 29. Kerber, RD., Isaeff, D. M., and Hancock, E. W.: Echocardiographic patterns in patients with the syndrome of systolic click and late systolic murmur. New Eng. J. Med., 284:691, 1971. 30. Kostis, J. B., and Moghadam, A. N.: Echocardiographic diagnosis of left atrial myxoma. Chest, 58:550, 1970. 31. Kotler, M., and Tabatznik, B.: Recognition of Ebstein's anomaly by ultra-sound technique (abstract). Circulation, 43-44:11-34, 1971.
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32. Lundstrom, N. R., and Edler, 1.: Ultrasoundcardiography in infants and children. Acta Paediatr. Scand., 60:117,1971. 33. Nasser, W. K., Davis, R. H., Dillon, J. C., et al.: Atrial myxoma. 11. Phonocardiographic, echocardiographic, hemodynamic, and angiographic features in nine cases. Amer. Heart J.,83:810, 1972. 34. Popp, R. L., and Carmichael, B. M.: Cardiac echography in the diagnosis of prosthetic valve malfunction. (Abstract). Circulation, 43-44:11-33, 1971. 35. Popp, R. L., and Harrison, D. C.: Ultrasound in the diagnosis and evaluation of therapy in idiopathic hypertrophic subaortic stenosis. Circulation, 40:905, 1969. 36. Popp, R. L., Wolfe, S. B., Hirara, T., et al.: Estimation of right and left ventricular size by ultrasound. A study of echoes from the interventricular septum. Amer. J. Cardiol., 24:523, 1969. 37. Pridie, R. B., Benham, R., and Oakley, C. M.: Recognition of aortic regurgitation of recent onset by ultrasound technique (abstract). Amer. J. Cardiol., 26:654, 1970. 38. Pridie, R. B., Benham, R., and Oakley, C. M.: Echocardiography of the mitral valve in aortic valve disease. Brit. Heart J., 33:296, 1971. 39. Pridie, R. B., and Oakley, C. M.: Mechanism of mitral regurgitation in hypertrophic obstructive cardiomyopathy. Brit. Heart J., 32:302, 1970. 40. Segal, B. L., Likoff, W., and Kingsley, B.: Echocardiography. Clinical application in combined mitral stenosis and mitral regurgitation. Amer. J. Cardiol., 19:42, 1967. 41. Segal, B. L., Likoff, W., and Kingsley, B.: Echocardiography. Clinical application in mitral regurgitation. Amer. J. Cardiol., 19:50,1967. 42. Shah, P. M., and Gramiak, R.: Echocardiographic recognition of mitral valve prolapse (abstract). Circulation, 42:111-45, 1970. 43. Shah, P. M., Grarniak, R., and Kramer, D. H.: Ultrasound localization of left ventricular outflow obstruction in hypertrophic obstructive cardiomyopathy. Circulation, 40:3, 1969. 44. Shah, P. M., Gramiak, R., Kramer, D. H., et al.: Determinants of atrial (S,) and ventricular (S3) gallop sounds in primary myocardial disease. N. Eng. J. Med., 278:753,1968. 45. Siggers, D. C., Srivongse, S. A., and Deuchar, D.: Analysis of dynamics of mitral StarrEdwards valve prosthesis using reflected ultrasound. Brit. Heart J., 23:401, 1971. 46. Wharton, C. F. P.: Reflected ultrasound patterns in mitral valve disease. Guy's Hospital Rep., 118:187,1969. 47. Wharton, C. F. P., and Lopez-Bescos, L.: Mitral valve movement: A study using an ultrasound technique. Brit. Heart J., 32:344, 1970. 48. Wharton, C. F. P., Smithen, C. S., and Sowton, E.: Changes in left ventricular wall movement after acute myocardial infarction measured by reflected ultrasound. Brit. Med. J., 4:75, 1971. 49. Winters, W. L., Jr., Gimenez, J., and Soloff, L. A.: Clinical application of ultrasound in the analysis of prosthetic ball valve motion. Amer. J. Cardiol., 19:97, 1967. 50. Winters, W. L., Jr., Hafer, J., Jr., and Soloff, L. A.: Abnormal mitral valve motion as demonstrated by the ultrasound technique in apparent pure mitral insufficiency. Amer. Heart J., 77:196,1969. 51. Wolfe, S. B., Popp, R. L., and Feigenbaum, H.: Diagnosis of atrial tumors by ultrasound. Circulation, 39:615, 1969. 52. Zaky, A., Grabhorn, L., and Feigenbaum, H.: Movement of the mitral ring: A study in ultrasoundcardiography. Cardiovasc. Res., 1 :121,1967. 53. Zaky, A., Nasser, W. K., and Feigenbaum, H.: A study of mitral valve action recorded by reflected ultrasound and its application in the study of mitral stenosis. Circulation, 37:789, 1968. Medical College of Pennsylvania Philadelphia, Pennsylvania 19129 (Dr. Frankl)