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Posterior wall velocity: An unreliable index of total left ventricular performance in patients with coronary artery disease
Posterior Wall Velocity: An Unreliable Index of Total Left Ventricular Performance in Patients with Coronary Artery Disease
PHILIP LUDBROOK, MRCP JOEL
S. KARLINER,
ARNOLD KIRK
MB,
BS,
MRACP,
(UK) LONDON,
MD,
FACC
BA
L. PETERSON,
GEORGE
R. LEOPOLD,
ROBERT
A.
MD
O’ROURKE,
MD MD,
FACC
San Diego, California
From the Cardiovascular Division, Department of Medicine, and the Department of Radiology, University of California, San Diego, La Jolla, Calif. This study was supported by U. S. Public Health Service Graduate Training-Grant 5 TO i HE 05846, U. S. Public Health Service Undergraduate Training Grant 5 TO 2 HE 05888 and the National Heart Foundation of Australia (Dr. Ludbrook). Manuscript accepted August 9, 1973. Address for reorints: Robert A. O’Rourke. MD, University Hospital of San Diego County: 225 West Dickinson St., San Diego, Calif. 92103.
Posterior wall velocity determined by use of echocardiography has been proposed as an index of total lefl ventricular performance in patients with ischemic heart disease. Accordingly, in g normal subjects and 39 patients with angiographically documented coronary artery disease, we compared mean endocardial posterior wall velocity determined by echocardiography with echocardiographic and biplane cineangiographic calculations of ejection fraction and the mean rate of circumferential fiber shortening (mean VcF), and wlth externally recorded systolic time intervals. All studies were performed on the same day in each patient. Mean endocardial posterior wall velocity averaged 4.6 cm/set (range kg to 6.7) and correlated poorly with echocardiographic ejection fraction (r = 0.47), cineangiographic ejection fraction (r = 0.26), cineangiographic mean VcF (r = 0.47), the ratio of preejection period to left ventricular ejection time (r = -0.35) and the preejection period corrected for heart rate (r = -0.30). Substitution of maximal for mean endocardial posterior wall velocity did not improve the separation of normal from depressed left ventricular performance. Epicardial posterior wall velocity, a mbasurement more easily obtalnable than endocardial posterior wall velocity, also did not correlate well with systolic time intervals or with ejection fraction or mean Vcp derived from the echocardiogram and cineangiogram. Both endocardial and epicardial posterior wall velocity values were poorly reproducible on a day to day or a beat to beat basis. We conclude that neither endocardial nor epicardial posterior wall velocity, whether derived as a mean or a maximum, provides an accurate measure of total left ventricular performance in patients wtth coronary artery disease.
There has been considerable recent interest in the noninvasive estimation of left ventricular performance in man. Both echocardiography14 and externally recorded systolic time intervals5 have been proposed as methods suitable for serial atraumatic assessment of myocardial function. It has been suggested that echocardiographic measurement of left ventricular posterior wall velocity might provide a simple reproducible method for serial evaluation of total cardiac performance.6-8 Accordingly, we compared echocardiographic estimates of posterior wall velocity with other echocardiographic indexes of left ventricular function and with externally recorded systolic time intervals and indexes of myocardial performance derived from cineangiocardiograms in patients with and without coronary artery disease.
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ECG
FIGURE 1. Echocardiogram showing the left ventricular (L.V.) endocardiil surface of the interventricular (I.V.) septum and the left ventricular posterior (post.) wall endocardium. Careful visualization of the posterior chordae insured both accurate definition of the lefl ventricular endocardium and consistent lbcalizatlon of the ultrasound beam. Automatically incorporated into the display are the simultaneous electraca’rdiiram and timedistance markers. Distance is plotted on the ordinate and time on the abscissa. The left ventricular internal enddiistolic dimension (LVIW) between endocardial surfaces was measured along a vertical line drawn through the QRS complex. The left ventricular internal end-systolic dimension (LVIDs) was defined as the smallest distance separating the endocardial surfaces of the septum and the left ventricular posterior wall. Ejection time (ET) was taken as the length of time from the peak of the QRS complex to the maximal excursion of the left ventricularposterior wall. less 50 msec for the preejection period when no appreciable fiber shortening occurs.’ ‘.I2 In each instance, posterior wall velocity was derived from the same cycles used to calculate ejection fraction and mean Vc,. In the case illustrated, a sinus arrhythmia was present.
I.V. Sqdum
L.V. Endocwdial swfaae
Post ChorfJaE
Post. L.V. Wall EdOWdid
Methods
+- 1 set +
FIGURE 2. Two methods for calculating left ventricular posterior wall velocity are shown. A, the mean posterior wall velocity is equal to posterior wall excursion (PWE) measured from points C to D, divided by the ejectlon time (ET), as defined. B, maximal posterior wall velocity is calculated by constructing a tangent (TG) to the steepest part ‘of the left ventricular posterior wall and expressing the slope in centimeters per second.
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In 48 patients admitted for diagnostic cardiac catheterization and coronary angiography, echocardiographic estimates of posterior wall velocity and left ventricular dimensions were performed by one observer within 24 hours of catheterization. Thirty-nine of these patients had coronary artery disease; the remaining nine had no evident cardiac disease. Ten additional patients were studied daily by echocardiography for an average of 6 days in the coronary care unit; seven of these patients had documented acute myocardial infarction, and the other three had angina pectoris without overt infarction. Another nine normal subjects were also examined daily by echocardiography for an average of 3 days. All echocardiographic studies were performed with subjects in the basal fasting state, in either the supine or left lateral decubitus position. Methods of ultrasound echocardiography have previously been described in detai1.3,gJ0 A commercially available ultrasonoscope (Ekoline 20, Mark II, Smith-Kline) was used with a 2.25 megaHerz, 0.75 inch transducer that had a repetition rate of 1,000 impulses/set. Polaroid photographs of the “time-motion” echocardiographic display were made directly from the oscilloscope (Fig. 1). Careful visualization of the “x” line representing echoes from the supporting apparatus of the mitral valve ensured both accurate definition of the left ventricular endocardium and consistent localization of the ultrasound beam. In all 48 patients a complete echocardiographic left ventricular dimensional analysis was performed using methods previously described for determination of end-diastolic and end-systolic volumes and ejection fraction, mean velocity of circumferential fiber shortening, and posterior wall velocity.3 For the latter measure, two types of determinations were made. A mean value
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FffiURE 3. Mean endocardial posterior wall velocity (PWV) determined by echocardiography plotted against ejection fraction determined by echocardiiraphy (M) and cineangiography (rlghl). The crossed lines represent the lower limits of normal for each measurement (25 mm/set for mean posterior wall velocity and 0.52 for ejection fraction).
for posterior wall velocity (mean PWV [cm/set]) was calculated from the value for posterior wall excursion divided by the ejection time (less 50 msec for isovolumetric contraction, when little significant fiber shortening occursll [Fig. 21). Mean posterior wall velocity was derived at both the endocardial and epicardial surfaces. To validate the method of calculating ejection time, we compared our technique with the alternative method of measuring the duration of systole directly from the echocardiogram. For 40 of the 48 patients the correlation between results of the two techniques was excellent (r = 0.987, P <10e6). The average difference between the two determinations was 6.3 msec (range 0 to 15 msec). Neither method yielded a value consistently larger or smaller than that of the other. In the remaining eight patients, the ejection time could not be accurately determined directly from the ultrasound recording because of the initial slurring of the upstroke associated with isovolumetric systole. The left ventricular ejection time derived from the externally recorded carotid pulse tracing averaged 260.5 f 5.0 (standard error) msec (range 178 to 338), and that obtained by the ultrasound method described averaged 259 f 4.8 msec (range 170 to 340). There was a highly significant correlation between the two measures (r = 0.870, P <10p6). As with the previous comparison, neither method yielded a value consistently larger or smaller than that of the other. Maximal pkterior wall velocity (PWVmax [cm/set]), calculated at both the endocardial and the epicardial surfaces, was determined from the slope of a tangent drawn to the steepest position of the anterior movement of the posterior wall echo (Fig. 2). For each determination of ejection fraction, mean velocity of basal circumferential fiber shortening (mean VCF) and posterior wall velocity, five satisfactorily recorded beats were averaged. Thus, the beats from which the echocardiographic ejection fraction and mean VCF were derived were from the same cycles used to calculate posterior wall velocity, thereby eliminating any bias in the comparisons among these determinations.
In the 10 patients who were studied in the coronary care unit, echocardiographic recordings were made of epicardial posterior wall movement only, since we sought to test the validity and reproducibility of the epicardial posterior wall velocity alone as an index of left ventricular performance. Recordings of the epicardial surface, which can be obtained rapidly and with minimal discomfort to the patient, were thought to be most suited to patients with documented or suspected acute myocardial infarction. Cardiac catheterization was performed with patients in the fasting state after premeditation with 100 mg of sodium pentobarbital. Left ventricular catheterization was performed by the retrograde arterial technique, and left ventricular cineangiograms were recorded at 75 frames/set after intraventricular injection of 40 to 50 ml of 75 percent Hypaquee over 2 to 3 seconds. End-systolic and end-diastolic left ventricular volumes were estimated using the area-length method for biplane ventriculograms,13 and the ejection fraction was calculated from these measurements.14 Mean VCF was derived from the lateral projection of the left ventriculogram by calculating the shortening of a chord drawn perpendicular to the long axis of the ventricle at one third of the distance from the midpoint of the mitral valve plane to the cardiac apex.3J2 This chord was selected for comparison since it corresponds most closely to the plane of the ultrasound beam.3 Systolic time interuals were measured from simultaneous recordings of a high frequency phonocardiogram, indirect carotid arterial pulse and electrocardiogram on a multichannel recorder (Elena-Schonander Minograf) at a paper speed of 100 mm/set, immediately after the echocardiogram. Calculations of mean intervals were derived from measurements of 10 optimally recorded cardiac cycles. Observed intervals were corrected for heart rate and sex according to the regression equations of Weissler and coworkers,5 and expressed as indexes. The ratio of preejection period (PEP) to left ventricular ejection time (LVET) was obtained by dividing the observed PEP by the uncor-
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100
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lMAN WF &he)_ckuku MEAN Wr @ho)-&u&c FIGURE 4. Mean endocardiil posterior wall velocity (PWV) plotted against the mean rate of basal circumferential fiber shortening (mean Vcr) determined by echocardiiraphy (left) and by cineangiography (rlght). The cressed lines represent the lower limits of normal for each measurement (25 mmkec for mean posterior wall velocity, 1.05 circumferenceskec for mean Vcr by echocardffgraphy and 1.20 circumferenceskec for mean Vcr by cineangiography).
rected LVET, since it has previously been shown that this ratio is independent of heart rate.‘” Echocardiograms satisfactory for volume estimation and for calculation of posterior wall velocity were obtained in all 48 patients studied in the catheterization laboratory. In 20 of these patients left ventricular cineangiograms were suitable for volume and mean VCF determinations; that is, there was adequate opacification of normally conducted
beats that did not follow one or more premature contractions. The 10 patients studied in the coronary care unit and the 9 normal control subjects also had satisfactory echocardiograms for analysis of posterior wall velocity. In 6 patients 16 echocardiographic dimensional analyses and determinations of systolic time intervals were performed to test observer and technique reproducibility. The average variation for echocardiographic determinations .in
. . . . . . . .
N: 48
N= 48
I = -0.30
I = -0.35
p<.Ol
p <.05 I
0.42
1 I.0
I
144
1
200
PEP1 - msec PEP/ LVET 6tGURE 5. Mean endocardial posterior wall velocity (PWV) plotted against the ratio of the preejection period to the left ventricular ejection time (PEPILVET) (kft), and against the preejection period (PEP) corrected for heart rate (PEPI) (rfght). The creased ffnes depict the lower limit of normal for posterior wall velocity (25 mmkec), and the upper limit of normal for PEPILVET (0.420) and for preejectiin period corrected for heart rate (144 msec).
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the same patient was 3 percent for ejection fraction and 6.5 percent for mean Vex; the average variation for PEP/ LVET was 9 percent. These figures are in accord with previous data from our laboratory showing that mean Vex was reproducible within 6 percent when determined by echocardiography3 and cineventriculography.12
Results In the 48 patients, mean endocardial posterior wall velocity averaged 3.8 cmfsec (range 2.0 to 7.4) and correlated closely with maximal endocardial posterior wall velocity (average 4.6 cm/set; range 2.9 to 8.7). In nine patients considered to have normal left ventricular function on the basis of hemodynamic studies, mean endocardial posterior wall velocity averaged 4.2 cm/set (range 3.0 to 4.4) and maximal endocardial posterior wall velocity averaged 5.1 cm/set (range 3.7 to 5.6). In the 39 patients with coronary artery disease, mean posterior wall velocity averaged 3.6 cm/ set (range 2.0 to 7.4) and the average maximal posterior wall velocity was 4.3 cm/set (range 2.1 to 7.5). Neither mean nor maximal posterior wall velocity separated normal from impaired left ventricular performance.
Posterior wall velocity vs. ejection fraction:
Figure 3 shows the poor correlation between mean endocardial posterior wall velocity and ejection fraction determined by echocardiogram and cineangiocardiogram. In 7 patients with a reduced ejection fraction by echocardiogram (<0.52), mean endocardial posterior wall velocity exceeded our lower limit of normal for mean posterior wall velocity (2.5 cm/ set, a value that is 2 standard deviations below the mean value derived from 24 normal subjects in our laboratory). Similarly, in five patients with a depressed ejection fraction by cineangiogram, mean endocardial posterior wall velocity was within the normal range. Use of maximal endocardial posterior wall velocity did not improve the separation of normal from abnormal left ventricular performance. Posterior wall velocity vs. VCF: Figure 4 shows the correlation between mean endocardial posterior wall velocity and mean VCF determined by echocardiogram and cineangiocardiogram. Of 25 patients with a reduced mean VCF (X1.05 circumferences/set) by echocardiogram, only 3 had a depressed mean endocardial posterior wall velocity (Fig. 4, left panel). Similarly, of 12 patients whose mean VCF by cineangiogram was reduced (Cl.2 circumferences/sec),12 only 2 had an abnormal value for mean posterior wall velocity (Fig. 4, right panel). Substitution of maximal for mean endocardial posterior wall velocity did not improve the separation. Posterior wall velocity vs. PEP/LVET: Equally poor results were obtained when mean endocardial posterior wall velocity was plotted against the ratio of preejection period (PEP) to left ventricular ejection time (LVET) (Fig. 5, left panel), and the preejection period was corrected for heart rate (PEPI, Fig 5, right panel). Of 23 patients with an abnormal PEP/ LVET ratio (>0.420), 21 had a normal value for mean posterior wall velocity. In five patients PEP1 was ab-
Ii
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ZjL?;; 100
50 MEAN
Pwv
(Epicardial)-
mm/set
Day2 FIGURE 6. Mean posterior wall velocity (PWV) at the epicardial surface obtained on one day (Day 1) is plotted against mean epicardial posterior wall velocity measured on the next day (Day 2). Seven patients with myocardiil infarction and three patients with angina pectoris (doeed circles) and nine normal subjects (open circles) were studied. The solid line represents the line of identity.
normal (> 144 msec), but mean posterior wall velocity was within the normal range, whereas the converse was true in three patients. Maximal epicardial posterior wall velocity (average 2.3 cmlsec, range 1.1 to 4.1) also failed to distinguish patients with normal left ventricular function (average 2.5 cm/set, range 1.9 to 3.0) from those with reduced performance (average 2.2 cm/set, range 1.1 to 4.1). This measure also failed to show significant correlation with mean endocardial posterior wall velocity, maximal endocardial posterior wall velocity, echocardiographic ejection fraction, echocardiographic mean VCF, PEP/LVET, PEPI, cineangiographic ejection fraction, cineangiographic mean VCF or heart rate.
Posterior wall velocity in acute myocardial infarction: Estimations of mean epicardial posterior wall velocity performed in 10 patients with acute myocardial infarction or angina pectoris studied in the coronary care unit also failed to distinguish patients from normal control subjects. Thus, mean epicardial posterior wall velocity averaged 2.27 cm/set (range 0.5 to 4.4) in these patients, and 2.2 cm/set (range 0.5 to 3.0) in nine normal control subjects. Furthermore, despite careful attention to consistent localization of the ultrasound beam, daily estimations of epicardial posterior wall velocity in individual subjects showed wide variation. Figure 6 depicts mean epicardial posterior wall velocity as measured on two successive days in the 10 patients hospitalized in the coronary care unit and in 9 normal control subjects. There is a disappointing correlation be-
April 1974
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POSTERKWI WALL VELOClTY AND LEFT VENTRGULAR
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<
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Thus echocardiographic ejection fraction (mean 0.61, range 0.21 to 0.83) correlated well with cineangiographic ejection fraction (mean 0.54, range 0.19 to 0.73; r = 0.83, P
.
.
5
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N=48 I =0.5
Discussion
p <.oo/
0 0
I 50
I 100
MAXIMAL Pwv (Endocardiol) - mm/set FIGURE 7. .Maximal posteriorwall velocity (PWV) at the epicardial surface is plotted against maximal posterior wall velocity at the endocardial surface in all 48 patients studied. The sold line represents the line of identity. In each instance, the endocardial velocity exceeds the epicardial velocity. Such a disparity is to be expected, since the posterior wall myocardium not only moves anteriorly, but also thickens during systole.
tween the paired measurements in each patient, indicating that the measurement of mean epicardial posterior wall velocity is poorly reproducible from day to day. Similarly, endocardial posterior wall velocity is also a poorly reproducible measure. For example, in six patients, four of whom had normal left ventricular function, mean endocardial posterior wall velocity determined on 16 occasions varied by an average of 20.5 percent (range 6 to 52 percent) and maximal endocardial posterior wall velocity by an average of 15.8 percent (range 7.5 to 27 percent). Further, despite the use of only strictly satisfactorily recorded beats for calculation, there was a beat. to beat variation in maximal endocardial posterior wall velocity averaging 42 percent (range 6.0 to 143 percent). These variations in endocardial posterior wall velocity occurred despite careful attention to visualization of the mitral valve supporting apparatus (“x”-line) as a landmark (Fig. 1). Since epicardial posterior wall velocity is rapidly and easily obtainable by echocardiography, we compared this measure with endocardial posterior wall velocity, which is difficult and time-consuming to obtain, in all 48 patients. The results, shown in Figure 7, indicate a poor correlation between the two measures of posterior wall velocity. Echographic and ventriculographic ejection fraction and VCF: Highly significant correlations were obtained by comparing echocardiographic and ventriculographic estimations of ejection fraction. These values also correlated well with systolic time intervals, particularly the PEP/LVET ratio and the preejection period corrected for heart rate (PEPI).
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Noninvasive techniques, such as ultrasound echocardiography and measurement of systolic time intervals, recently have been utilized to quantitate left ventricular function in man. Thus, echocardiographic determinations of both ejection fraction’ and mean velocity of basal circumferential fiber shortening (mean VCF~) previously have been reported to correlate well with standard cineangiographic estimates of these measures, and thereby to provide reliable estimates of left ventricular performance in the basal state. It has also been shown that the ratio of preejection period to left ventricular ejection time (PEP/ LVET) correlates highly with cineangiographic determinations of ejection fraction16 and that the preejection period corrected for heart rate (PEPI) reflects the contractile state of the ventricle during isovolumetric systole. l7 Systolic time intervals have also been reported to be of use in routine follow-up studies of patients who have had coronary bypass surgery, particularly in the documentation of early changes in left ventricular function before clinical deterioration occurs.18 However, ultrasound determinations of ejection fraction and mean VCF require an operator highly experienced in the performance of echocardiography, considerable time and a cooperative, supine patient. These requirements may be difficult to meet in sick patients, especially those with acute myocardial infarction. Because the velocity of the posterior left ventricular epicardial surface is among the simplest of ultrasound measurements to obtain, it has been suggested that calculation of posterior wall velocity might provide a suitable alternative to more complex echocardiographic measurements of left ventricular function. Posterior wall velocity has been reported to reflect the velocity of circumferential fiber shortening6 and to correspond to changes in left ventricular performance induced by physiologic and pharmacologic interventions,6y7 and by acute myocardial infarction.8 Reliability and reproducibility of posterior wall velocity determinations: Our results indicated that measurement of posterior wall velocity did not correlate satisfactorily with either echocardiographic
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or standard cineangiographic measurements of ejection fraction and mean VCF. Equally poor results were obtained when posterior wall velocity was compared with measurement of systolic time intervals. Disappointing correlations were obtained whether posterior wall endocardium or epicardium was examined, or mean or maximal velocity calculated. The closest correlation observed was between mean endocardial posterior wall velocity and echocardiographic mean VCF (F = 0.70), presumably because calculation of posterior wall excursion is part of the calculation of mean VCF by this method. However, in 16 patients with wall motion abnormalities documented by cineangiography, mean endocardial posterior wall velocity was normal in 13 and echocardiographic mean VCF was depressed in 15. Our serial studies in 10 patients with acute myocardial infarction or angina pectoris who were hospitalized in the coronary care unit showed that both endocardial and epicardial posterior wall velocity vary widely from day to day, and from beat to beat in individual patients, despite careful efforts to achieve a consistent ultrasound beam plane by careful visualization of the mitral valve apparatus. Therefore, these measures appeared to be unreliable for assessment of basal left ventricular performance or changes in myocardial function produced by interventions. In searching for a noninvasive measure of cardiac function that could be obtained rapidly and easily in the coronary care unit, we examined the velocity of movement of left ventricular posterior wall epicardium, since consistent definition of posterior wall endocardium is usually more difficult and time consuming. However, as indicated, this measure also did not distinguish normal from abnormal left ventricular performance, correlate significantly with other indexes examined, or demonstrate adequate reproducibility’ from beat to beat or day to day. Thus, we were unable to confirm the observation that abnormalities in the contour of the left ventricular posterior wall epicardial echo could be utilized to predict alterations in myocardial function.6 Reasons for unreliability of posterior wall velocity as an index of myocardial performance: In
comparison with. other measures of myocardial performance, the values for posterior wall velocity generally tended to overestimate left ventricular function. Furthermore, despite the inability of posterior wall velocity to provide accurate information on total left ventricular performance in patients with coronary heart disease, ultrasound estimates of other ejection phase indexes of myocardial function, particularly mean Vcp, remain highly comparable to cineangiographic measurements. lg Why posterior wall velocity is unreliable and mean VCF accurate may be ex-
AND LEFT MNTFICLHAR
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plained as follows: (1) Despite accurate localization and consistent examination of one area of the posterior left ventricular wall, and despite use of the same cycles for determination of both mean VCF and posterior wall velocity, it is probable that in patients with coronary artery disease such an area is unrepresentative of the left ventricular myocardium as a whole. This is so because the posterior wall is an uncommon site for the localization of ischemic damage in comparison with the anterior, lateral, inferior or apical segments of the left ventricle, and the motion of these segments is entirely ignored in the determination of posterior wall velocity. (2) It has been our observation that when excursion of one of the ventricular walls is reduced because of ischemia or fibrosis, some compensation frequently is provided by increased excursion of the opposing wall, so that any error introduced by measurement of movement of one wall tends to be canceled by that of the other. McDonald et al.20 have recently described the influence on the echocardiogram of the anterior motion of the whole heart during systole. This systolic anterior motion diminishes the recorded posterior excursion of the interventricular septum and, conversely, increases the recorded anterior movement of the posterior left ventricular wall. This effect of the anterior motion of the whole heart during systole tends to be nullified when both septal and posterior wall movement are measured in the echocardiographic estimation of left ventricular dimensions, but it may lead to exaggeration of calculated posterior wall velocity. The results of our study are in agreement with the recent observations of Fogelman et al.,zl who found no consistent abnormalities in the rate of systolic motion of the posterior left ventricular wall during exercise-induced angina pectoris. They also reported that early diastolic motion of the posterior wall was reduced only during stress-induced angina.21 In our study we did not examine patients with valvular heart disease or nonischemic cardiomyopathy. Although the possibility remains that in such patients estimation of posterior wall velocity might provide useful information on total left ventricular perforthat mance, Belenkie et al.22 recently demonstrated mean posterior wall velocity correlated poorly with other ultrasound and cineangiographic measures of left ventricular performance in 20 patients with valvular heart disease and in 3 subjects with nonischemit cardiomyopathy. We conclude that despite its ease and speed of performance, calculation of posterior wall endocardial or epicardial velocity, whether derived as a mean or maximum, is unreliable for basal or serial assessment of total left ventricular performance in patients with ischemic heart disease.
References 1. Pombo JR, Troy BL, Russell RO Jr: Left ventricular volumes and ejection fraction by echocardiography. Circulation 43: 460-490, 197 1 2. Felgenbeum H, Zaky A, Nasser WK: Use of ultrasound to mea-
sure left ventricular stroke volume. Circulation 35: 1092- 1099, 1967 3. Cooper RH, O’Rourke RA, Karllner JS, et al: A comparison of ultrasound and cineangiographic measurements of the mean
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5. 6. 7.
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rate of circumferential fiber shortening in man. Circulation 46: 914-923,1972 Paraekoe JA, Grossman W, Saltz S, et al: A non-invasive technique for the determination of velocity of circumferential fiber shortening in man. Circ Res 29:610-615, 1971 Welesler AM. Garrard CL Jr: Systolic time intervals in cardiac disease. ModConcepts Cardiovasc Dis 40:1-6, 1971 Kraunz RF, Kennedy JW: Ultrasonic determination of left ventricular wall motion in normal man. Am Heart J 79:36-43, 1970 Kraunz RF, Ryan TJ: Ultrasound measurements of ventricular wall motion following administration of vasoactive drugs. Am J Cardiil27:464-473, 1971 lneue K, Smulyan H, Mookherjee S, et al: Ultrasonic measurement of left ventricular wall motion in acute myocardial infarction. Circulation 431778-785, 1971 i%pp RL, Wolfe SB, Hlrata T, et al: Estimation of right and left ventricular size by ultrasound. Am J Cardiol 24523-530. 1969 Felgenbaum H, Stone JM, Lee DA, et al: Identification of ultrasound echoes from the left ventricle by use of intracardiac injections of indocyanine green. Circulation 41:615-621, 1970 Karllner JS, Bouchard RJ, Gault JH: Dimensional changes of the human left ventricle prior to aortic valve opening. Circulation 44~312-322, 1971 Karllner JS, Gault JH, Eckberg D, et al: Mean velocity of fiber shortening: a simplified measure of left ventricular myocardial contractility. Circulation 44:323-333, 197 1 D@e HT, Sandler H, Ballew DW, et al: The use of biplane angiocardiography for the measurement of left ventricular volume in man. Am Heart J 60~762-776, 1960
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14. Dodge HT, Sandler H, Baxley WA, et al: Usefulness and limitations of radiographic methods for determining left ventricular volume. Am J Cardiol 16:10-24, 1966 15. Welfielef AM, Harrle WS, Schoenfeld CD: Bedside technics for the evaluation of ventricular function in man. Am J Cardiol 23: 577-583, 1969 16. Garrard CL Jr, Weleeter AM, Dodge HT: The relationship of alterations in systolic time intervals to ejection fraction in patients with cardiac disease. Circulation 42:455-462. 1970 17. Metzger CC, Cheen BC, Kroetz FW, et al: True isovolumic contraction time. Its correlation with two external indices of ventricular performance. Am J Cardiol 25:434-442. 1970 ia. Johnson AD. D’Rourke RA. Karllner JS, et al: Effect of myocardial revasculariiation on systolic time intervals in patients with left ventricular dysfunction. Circulation 45:suppl 1:1-91-l-96, 1972 19. Ludbrook P. Karllner JS, Peterson K, et al: Comparison of ultrasound and cineangiographic measurements of left ventricular performance in patients with and without wall motion abnormalities. Br Heart J 35:1026-1032, 1973 20. McDonald IO, Felgenbaum H, Chang S: Analysis of left ventricular wall motion by reflected ultrasound. Circulation 46:14-25, 1972 21. Fogelman AL, Abrasl AS, Pearce ML, et al: Echocardiographic study of the abnormal motion of the posterior left ventricular wall during angina pectoris. Circulation 46:905-913, 1972 22. Befenkle I, Nutter Do, Clark DW, et al: Assessment of left ventricular dimensions and function by echocardiography. Am J Cardiol3 1:755-762. 1973
PHILIP LUDBROOK, MRCP JOEL
S. KARLINER,
ARNOLD KIRK
MB,
BS,
MRACP,
(UK) LONDON,
MD,
FACC
BA
L. PETERSON,
GEORGE
R. LEOPOLD,
ROBERT
A.
MD
O’ROURKE,
MD MD,
FACC
San Diego, California
From the Cardiovascular Division, Department of Medicine, and the Department of Radiology, University of California, San Diego, La Jolla, Calif. This study was supported by U. S. Public Health Service Graduate Training-Grant 5 TO i HE 05846, U. S. Public Health Service Undergraduate Training Grant 5 TO 2 HE 05888 and the National Heart Foundation of Australia (Dr. Ludbrook). Manuscript accepted August 9, 1973. Address for reorints: Robert A. O’Rourke. MD, University Hospital of San Diego County: 225 West Dickinson St., San Diego, Calif. 92103.
Posterior wall velocity determined by use of echocardiography has been proposed as an index of total lefl ventricular performance in patients with ischemic heart disease. Accordingly, in g normal subjects and 39 patients with angiographically documented coronary artery disease, we compared mean endocardial posterior wall velocity determined by echocardiography with echocardiographic and biplane cineangiographic calculations of ejection fraction and the mean rate of circumferential fiber shortening (mean VcF), and wlth externally recorded systolic time intervals. All studies were performed on the same day in each patient. Mean endocardial posterior wall velocity averaged 4.6 cm/set (range kg to 6.7) and correlated poorly with echocardiographic ejection fraction (r = 0.47), cineangiographic ejection fraction (r = 0.26), cineangiographic mean VcF (r = 0.47), the ratio of preejection period to left ventricular ejection time (r = -0.35) and the preejection period corrected for heart rate (r = -0.30). Substitution of maximal for mean endocardial posterior wall velocity did not improve the separation of normal from depressed left ventricular performance. Epicardial posterior wall velocity, a mbasurement more easily obtalnable than endocardial posterior wall velocity, also did not correlate well with systolic time intervals or with ejection fraction or mean Vcp derived from the echocardiogram and cineangiogram. Both endocardial and epicardial posterior wall velocity values were poorly reproducible on a day to day or a beat to beat basis. We conclude that neither endocardial nor epicardial posterior wall velocity, whether derived as a mean or a maximum, provides an accurate measure of total left ventricular performance in patients wtth coronary artery disease.
There has been considerable recent interest in the noninvasive estimation of left ventricular performance in man. Both echocardiography14 and externally recorded systolic time intervals5 have been proposed as methods suitable for serial atraumatic assessment of myocardial function. It has been suggested that echocardiographic measurement of left ventricular posterior wall velocity might provide a simple reproducible method for serial evaluation of total cardiac performance.6-8 Accordingly, we compared echocardiographic estimates of posterior wall velocity with other echocardiographic indexes of left ventricular function and with externally recorded systolic time intervals and indexes of myocardial performance derived from cineangiocardiograms in patients with and without coronary artery disease.
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ECG
FIGURE 1. Echocardiogram showing the left ventricular (L.V.) endocardiil surface of the interventricular (I.V.) septum and the left ventricular posterior (post.) wall endocardium. Careful visualization of the posterior chordae insured both accurate definition of the lefl ventricular endocardium and consistent lbcalizatlon of the ultrasound beam. Automatically incorporated into the display are the simultaneous electraca’rdiiram and timedistance markers. Distance is plotted on the ordinate and time on the abscissa. The left ventricular internal enddiistolic dimension (LVIW) between endocardial surfaces was measured along a vertical line drawn through the QRS complex. The left ventricular internal end-systolic dimension (LVIDs) was defined as the smallest distance separating the endocardial surfaces of the septum and the left ventricular posterior wall. Ejection time (ET) was taken as the length of time from the peak of the QRS complex to the maximal excursion of the left ventricularposterior wall. less 50 msec for the preejection period when no appreciable fiber shortening occurs.’ ‘.I2 In each instance, posterior wall velocity was derived from the same cycles used to calculate ejection fraction and mean Vc,. In the case illustrated, a sinus arrhythmia was present.
I.V. Sqdum
L.V. Endocwdial swfaae
Post ChorfJaE
Post. L.V. Wall EdOWdid
Methods
+- 1 set +
FIGURE 2. Two methods for calculating left ventricular posterior wall velocity are shown. A, the mean posterior wall velocity is equal to posterior wall excursion (PWE) measured from points C to D, divided by the ejectlon time (ET), as defined. B, maximal posterior wall velocity is calculated by constructing a tangent (TG) to the steepest part ‘of the left ventricular posterior wall and expressing the slope in centimeters per second.
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In 48 patients admitted for diagnostic cardiac catheterization and coronary angiography, echocardiographic estimates of posterior wall velocity and left ventricular dimensions were performed by one observer within 24 hours of catheterization. Thirty-nine of these patients had coronary artery disease; the remaining nine had no evident cardiac disease. Ten additional patients were studied daily by echocardiography for an average of 6 days in the coronary care unit; seven of these patients had documented acute myocardial infarction, and the other three had angina pectoris without overt infarction. Another nine normal subjects were also examined daily by echocardiography for an average of 3 days. All echocardiographic studies were performed with subjects in the basal fasting state, in either the supine or left lateral decubitus position. Methods of ultrasound echocardiography have previously been described in detai1.3,gJ0 A commercially available ultrasonoscope (Ekoline 20, Mark II, Smith-Kline) was used with a 2.25 megaHerz, 0.75 inch transducer that had a repetition rate of 1,000 impulses/set. Polaroid photographs of the “time-motion” echocardiographic display were made directly from the oscilloscope (Fig. 1). Careful visualization of the “x” line representing echoes from the supporting apparatus of the mitral valve ensured both accurate definition of the left ventricular endocardium and consistent localization of the ultrasound beam. In all 48 patients a complete echocardiographic left ventricular dimensional analysis was performed using methods previously described for determination of end-diastolic and end-systolic volumes and ejection fraction, mean velocity of circumferential fiber shortening, and posterior wall velocity.3 For the latter measure, two types of determinations were made. A mean value
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FffiURE 3. Mean endocardial posterior wall velocity (PWV) determined by echocardiography plotted against ejection fraction determined by echocardiiraphy (M) and cineangiography (rlghl). The crossed lines represent the lower limits of normal for each measurement (25 mm/set for mean posterior wall velocity and 0.52 for ejection fraction).
for posterior wall velocity (mean PWV [cm/set]) was calculated from the value for posterior wall excursion divided by the ejection time (less 50 msec for isovolumetric contraction, when little significant fiber shortening occursll [Fig. 21). Mean posterior wall velocity was derived at both the endocardial and epicardial surfaces. To validate the method of calculating ejection time, we compared our technique with the alternative method of measuring the duration of systole directly from the echocardiogram. For 40 of the 48 patients the correlation between results of the two techniques was excellent (r = 0.987, P <10e6). The average difference between the two determinations was 6.3 msec (range 0 to 15 msec). Neither method yielded a value consistently larger or smaller than that of the other. In the remaining eight patients, the ejection time could not be accurately determined directly from the ultrasound recording because of the initial slurring of the upstroke associated with isovolumetric systole. The left ventricular ejection time derived from the externally recorded carotid pulse tracing averaged 260.5 f 5.0 (standard error) msec (range 178 to 338), and that obtained by the ultrasound method described averaged 259 f 4.8 msec (range 170 to 340). There was a highly significant correlation between the two measures (r = 0.870, P <10p6). As with the previous comparison, neither method yielded a value consistently larger or smaller than that of the other. Maximal pkterior wall velocity (PWVmax [cm/set]), calculated at both the endocardial and the epicardial surfaces, was determined from the slope of a tangent drawn to the steepest position of the anterior movement of the posterior wall echo (Fig. 2). For each determination of ejection fraction, mean velocity of basal circumferential fiber shortening (mean VCF) and posterior wall velocity, five satisfactorily recorded beats were averaged. Thus, the beats from which the echocardiographic ejection fraction and mean VCF were derived were from the same cycles used to calculate posterior wall velocity, thereby eliminating any bias in the comparisons among these determinations.
In the 10 patients who were studied in the coronary care unit, echocardiographic recordings were made of epicardial posterior wall movement only, since we sought to test the validity and reproducibility of the epicardial posterior wall velocity alone as an index of left ventricular performance. Recordings of the epicardial surface, which can be obtained rapidly and with minimal discomfort to the patient, were thought to be most suited to patients with documented or suspected acute myocardial infarction. Cardiac catheterization was performed with patients in the fasting state after premeditation with 100 mg of sodium pentobarbital. Left ventricular catheterization was performed by the retrograde arterial technique, and left ventricular cineangiograms were recorded at 75 frames/set after intraventricular injection of 40 to 50 ml of 75 percent Hypaquee over 2 to 3 seconds. End-systolic and end-diastolic left ventricular volumes were estimated using the area-length method for biplane ventriculograms,13 and the ejection fraction was calculated from these measurements.14 Mean VCF was derived from the lateral projection of the left ventriculogram by calculating the shortening of a chord drawn perpendicular to the long axis of the ventricle at one third of the distance from the midpoint of the mitral valve plane to the cardiac apex.3J2 This chord was selected for comparison since it corresponds most closely to the plane of the ultrasound beam.3 Systolic time interuals were measured from simultaneous recordings of a high frequency phonocardiogram, indirect carotid arterial pulse and electrocardiogram on a multichannel recorder (Elena-Schonander Minograf) at a paper speed of 100 mm/set, immediately after the echocardiogram. Calculations of mean intervals were derived from measurements of 10 optimally recorded cardiac cycles. Observed intervals were corrected for heart rate and sex according to the regression equations of Weissler and coworkers,5 and expressed as indexes. The ratio of preejection period (PEP) to left ventricular ejection time (LVET) was obtained by dividing the observed PEP by the uncor-
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100
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rected LVET, since it has previously been shown that this ratio is independent of heart rate.‘” Echocardiograms satisfactory for volume estimation and for calculation of posterior wall velocity were obtained in all 48 patients studied in the catheterization laboratory. In 20 of these patients left ventricular cineangiograms were suitable for volume and mean VCF determinations; that is, there was adequate opacification of normally conducted
beats that did not follow one or more premature contractions. The 10 patients studied in the coronary care unit and the 9 normal control subjects also had satisfactory echocardiograms for analysis of posterior wall velocity. In 6 patients 16 echocardiographic dimensional analyses and determinations of systolic time intervals were performed to test observer and technique reproducibility. The average variation for echocardiographic determinations .in
. . . . . . . .
N: 48
N= 48
I = -0.30
I = -0.35
p<.Ol
p <.05 I
0.42
1 I.0
I
144
1
200
PEP1 - msec PEP/ LVET 6tGURE 5. Mean endocardial posterior wall velocity (PWV) plotted against the ratio of the preejection period to the left ventricular ejection time (PEPILVET) (kft), and against the preejection period (PEP) corrected for heart rate (PEPI) (rfght). The creased ffnes depict the lower limit of normal for posterior wall velocity (25 mmkec), and the upper limit of normal for PEPILVET (0.420) and for preejectiin period corrected for heart rate (144 msec).
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the same patient was 3 percent for ejection fraction and 6.5 percent for mean Vex; the average variation for PEP/ LVET was 9 percent. These figures are in accord with previous data from our laboratory showing that mean Vex was reproducible within 6 percent when determined by echocardiography3 and cineventriculography.12
Results In the 48 patients, mean endocardial posterior wall velocity averaged 3.8 cmfsec (range 2.0 to 7.4) and correlated closely with maximal endocardial posterior wall velocity (average 4.6 cm/set; range 2.9 to 8.7). In nine patients considered to have normal left ventricular function on the basis of hemodynamic studies, mean endocardial posterior wall velocity averaged 4.2 cm/set (range 3.0 to 4.4) and maximal endocardial posterior wall velocity averaged 5.1 cm/set (range 3.7 to 5.6). In the 39 patients with coronary artery disease, mean posterior wall velocity averaged 3.6 cm/ set (range 2.0 to 7.4) and the average maximal posterior wall velocity was 4.3 cm/set (range 2.1 to 7.5). Neither mean nor maximal posterior wall velocity separated normal from impaired left ventricular performance.
Posterior wall velocity vs. ejection fraction:
Figure 3 shows the poor correlation between mean endocardial posterior wall velocity and ejection fraction determined by echocardiogram and cineangiocardiogram. In 7 patients with a reduced ejection fraction by echocardiogram (<0.52), mean endocardial posterior wall velocity exceeded our lower limit of normal for mean posterior wall velocity (2.5 cm/ set, a value that is 2 standard deviations below the mean value derived from 24 normal subjects in our laboratory). Similarly, in five patients with a depressed ejection fraction by cineangiogram, mean endocardial posterior wall velocity was within the normal range. Use of maximal endocardial posterior wall velocity did not improve the separation of normal from abnormal left ventricular performance. Posterior wall velocity vs. VCF: Figure 4 shows the correlation between mean endocardial posterior wall velocity and mean VCF determined by echocardiogram and cineangiocardiogram. Of 25 patients with a reduced mean VCF (X1.05 circumferences/set) by echocardiogram, only 3 had a depressed mean endocardial posterior wall velocity (Fig. 4, left panel). Similarly, of 12 patients whose mean VCF by cineangiogram was reduced (Cl.2 circumferences/sec),12 only 2 had an abnormal value for mean posterior wall velocity (Fig. 4, right panel). Substitution of maximal for mean endocardial posterior wall velocity did not improve the separation. Posterior wall velocity vs. PEP/LVET: Equally poor results were obtained when mean endocardial posterior wall velocity was plotted against the ratio of preejection period (PEP) to left ventricular ejection time (LVET) (Fig. 5, left panel), and the preejection period was corrected for heart rate (PEPI, Fig 5, right panel). Of 23 patients with an abnormal PEP/ LVET ratio (>0.420), 21 had a normal value for mean posterior wall velocity. In five patients PEP1 was ab-
Ii
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50 MEAN
Pwv
(Epicardial)-
mm/set
Day2 FIGURE 6. Mean posterior wall velocity (PWV) at the epicardial surface obtained on one day (Day 1) is plotted against mean epicardial posterior wall velocity measured on the next day (Day 2). Seven patients with myocardiil infarction and three patients with angina pectoris (doeed circles) and nine normal subjects (open circles) were studied. The solid line represents the line of identity.
normal (> 144 msec), but mean posterior wall velocity was within the normal range, whereas the converse was true in three patients. Maximal epicardial posterior wall velocity (average 2.3 cmlsec, range 1.1 to 4.1) also failed to distinguish patients with normal left ventricular function (average 2.5 cm/set, range 1.9 to 3.0) from those with reduced performance (average 2.2 cm/set, range 1.1 to 4.1). This measure also failed to show significant correlation with mean endocardial posterior wall velocity, maximal endocardial posterior wall velocity, echocardiographic ejection fraction, echocardiographic mean VCF, PEP/LVET, PEPI, cineangiographic ejection fraction, cineangiographic mean VCF or heart rate.
Posterior wall velocity in acute myocardial infarction: Estimations of mean epicardial posterior wall velocity performed in 10 patients with acute myocardial infarction or angina pectoris studied in the coronary care unit also failed to distinguish patients from normal control subjects. Thus, mean epicardial posterior wall velocity averaged 2.27 cm/set (range 0.5 to 4.4) in these patients, and 2.2 cm/set (range 0.5 to 3.0) in nine normal control subjects. Furthermore, despite careful attention to consistent localization of the ultrasound beam, daily estimations of epicardial posterior wall velocity in individual subjects showed wide variation. Figure 6 depicts mean epicardial posterior wall velocity as measured on two successive days in the 10 patients hospitalized in the coronary care unit and in 9 normal control subjects. There is a disappointing correlation be-
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POSTERKWI WALL VELOClTY AND LEFT VENTRGULAR
l
<
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Thus echocardiographic ejection fraction (mean 0.61, range 0.21 to 0.83) correlated well with cineangiographic ejection fraction (mean 0.54, range 0.19 to 0.73; r = 0.83, P
.
.
5
x
3
N=48 I =0.5
Discussion
p <.oo/
0 0
I 50
I 100
MAXIMAL Pwv (Endocardiol) - mm/set FIGURE 7. .Maximal posteriorwall velocity (PWV) at the epicardial surface is plotted against maximal posterior wall velocity at the endocardial surface in all 48 patients studied. The sold line represents the line of identity. In each instance, the endocardial velocity exceeds the epicardial velocity. Such a disparity is to be expected, since the posterior wall myocardium not only moves anteriorly, but also thickens during systole.
tween the paired measurements in each patient, indicating that the measurement of mean epicardial posterior wall velocity is poorly reproducible from day to day. Similarly, endocardial posterior wall velocity is also a poorly reproducible measure. For example, in six patients, four of whom had normal left ventricular function, mean endocardial posterior wall velocity determined on 16 occasions varied by an average of 20.5 percent (range 6 to 52 percent) and maximal endocardial posterior wall velocity by an average of 15.8 percent (range 7.5 to 27 percent). Further, despite the use of only strictly satisfactorily recorded beats for calculation, there was a beat. to beat variation in maximal endocardial posterior wall velocity averaging 42 percent (range 6.0 to 143 percent). These variations in endocardial posterior wall velocity occurred despite careful attention to visualization of the mitral valve supporting apparatus (“x”-line) as a landmark (Fig. 1). Since epicardial posterior wall velocity is rapidly and easily obtainable by echocardiography, we compared this measure with endocardial posterior wall velocity, which is difficult and time-consuming to obtain, in all 48 patients. The results, shown in Figure 7, indicate a poor correlation between the two measures of posterior wall velocity. Echographic and ventriculographic ejection fraction and VCF: Highly significant correlations were obtained by comparing echocardiographic and ventriculographic estimations of ejection fraction. These values also correlated well with systolic time intervals, particularly the PEP/LVET ratio and the preejection period corrected for heart rate (PEPI).
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Noninvasive techniques, such as ultrasound echocardiography and measurement of systolic time intervals, recently have been utilized to quantitate left ventricular function in man. Thus, echocardiographic determinations of both ejection fraction’ and mean velocity of basal circumferential fiber shortening (mean VCF~) previously have been reported to correlate well with standard cineangiographic estimates of these measures, and thereby to provide reliable estimates of left ventricular performance in the basal state. It has also been shown that the ratio of preejection period to left ventricular ejection time (PEP/ LVET) correlates highly with cineangiographic determinations of ejection fraction16 and that the preejection period corrected for heart rate (PEPI) reflects the contractile state of the ventricle during isovolumetric systole. l7 Systolic time intervals have also been reported to be of use in routine follow-up studies of patients who have had coronary bypass surgery, particularly in the documentation of early changes in left ventricular function before clinical deterioration occurs.18 However, ultrasound determinations of ejection fraction and mean VCF require an operator highly experienced in the performance of echocardiography, considerable time and a cooperative, supine patient. These requirements may be difficult to meet in sick patients, especially those with acute myocardial infarction. Because the velocity of the posterior left ventricular epicardial surface is among the simplest of ultrasound measurements to obtain, it has been suggested that calculation of posterior wall velocity might provide a suitable alternative to more complex echocardiographic measurements of left ventricular function. Posterior wall velocity has been reported to reflect the velocity of circumferential fiber shortening6 and to correspond to changes in left ventricular performance induced by physiologic and pharmacologic interventions,6y7 and by acute myocardial infarction.8 Reliability and reproducibility of posterior wall velocity determinations: Our results indicated that measurement of posterior wall velocity did not correlate satisfactorily with either echocardiographic
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or standard cineangiographic measurements of ejection fraction and mean VCF. Equally poor results were obtained when posterior wall velocity was compared with measurement of systolic time intervals. Disappointing correlations were obtained whether posterior wall endocardium or epicardium was examined, or mean or maximal velocity calculated. The closest correlation observed was between mean endocardial posterior wall velocity and echocardiographic mean VCF (F = 0.70), presumably because calculation of posterior wall excursion is part of the calculation of mean VCF by this method. However, in 16 patients with wall motion abnormalities documented by cineangiography, mean endocardial posterior wall velocity was normal in 13 and echocardiographic mean VCF was depressed in 15. Our serial studies in 10 patients with acute myocardial infarction or angina pectoris who were hospitalized in the coronary care unit showed that both endocardial and epicardial posterior wall velocity vary widely from day to day, and from beat to beat in individual patients, despite careful efforts to achieve a consistent ultrasound beam plane by careful visualization of the mitral valve apparatus. Therefore, these measures appeared to be unreliable for assessment of basal left ventricular performance or changes in myocardial function produced by interventions. In searching for a noninvasive measure of cardiac function that could be obtained rapidly and easily in the coronary care unit, we examined the velocity of movement of left ventricular posterior wall epicardium, since consistent definition of posterior wall endocardium is usually more difficult and time consuming. However, as indicated, this measure also did not distinguish normal from abnormal left ventricular performance, correlate significantly with other indexes examined, or demonstrate adequate reproducibility’ from beat to beat or day to day. Thus, we were unable to confirm the observation that abnormalities in the contour of the left ventricular posterior wall epicardial echo could be utilized to predict alterations in myocardial function.6 Reasons for unreliability of posterior wall velocity as an index of myocardial performance: In
comparison with. other measures of myocardial performance, the values for posterior wall velocity generally tended to overestimate left ventricular function. Furthermore, despite the inability of posterior wall velocity to provide accurate information on total left ventricular performance in patients with coronary heart disease, ultrasound estimates of other ejection phase indexes of myocardial function, particularly mean Vcp, remain highly comparable to cineangiographic measurements. lg Why posterior wall velocity is unreliable and mean VCF accurate may be ex-
AND LEFT MNTFICLHAR
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plained as follows: (1) Despite accurate localization and consistent examination of one area of the posterior left ventricular wall, and despite use of the same cycles for determination of both mean VCF and posterior wall velocity, it is probable that in patients with coronary artery disease such an area is unrepresentative of the left ventricular myocardium as a whole. This is so because the posterior wall is an uncommon site for the localization of ischemic damage in comparison with the anterior, lateral, inferior or apical segments of the left ventricle, and the motion of these segments is entirely ignored in the determination of posterior wall velocity. (2) It has been our observation that when excursion of one of the ventricular walls is reduced because of ischemia or fibrosis, some compensation frequently is provided by increased excursion of the opposing wall, so that any error introduced by measurement of movement of one wall tends to be canceled by that of the other. McDonald et al.20 have recently described the influence on the echocardiogram of the anterior motion of the whole heart during systole. This systolic anterior motion diminishes the recorded posterior excursion of the interventricular septum and, conversely, increases the recorded anterior movement of the posterior left ventricular wall. This effect of the anterior motion of the whole heart during systole tends to be nullified when both septal and posterior wall movement are measured in the echocardiographic estimation of left ventricular dimensions, but it may lead to exaggeration of calculated posterior wall velocity. The results of our study are in agreement with the recent observations of Fogelman et al.,zl who found no consistent abnormalities in the rate of systolic motion of the posterior left ventricular wall during exercise-induced angina pectoris. They also reported that early diastolic motion of the posterior wall was reduced only during stress-induced angina.21 In our study we did not examine patients with valvular heart disease or nonischemic cardiomyopathy. Although the possibility remains that in such patients estimation of posterior wall velocity might provide useful information on total left ventricular perforthat mance, Belenkie et al.22 recently demonstrated mean posterior wall velocity correlated poorly with other ultrasound and cineangiographic measures of left ventricular performance in 20 patients with valvular heart disease and in 3 subjects with nonischemit cardiomyopathy. We conclude that despite its ease and speed of performance, calculation of posterior wall endocardial or epicardial velocity, whether derived as a mean or maximum, is unreliable for basal or serial assessment of total left ventricular performance in patients with ischemic heart disease.
References 1. Pombo JR, Troy BL, Russell RO Jr: Left ventricular volumes and ejection fraction by echocardiography. Circulation 43: 460-490, 197 1 2. Felgenbeum H, Zaky A, Nasser WK: Use of ultrasound to mea-
sure left ventricular stroke volume. Circulation 35: 1092- 1099, 1967 3. Cooper RH, O’Rourke RA, Karllner JS, et al: A comparison of ultrasound and cineangiographic measurements of the mean
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5. 6. 7.
6.
9. 10.
11.
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13.
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rate of circumferential fiber shortening in man. Circulation 46: 914-923,1972 Paraekoe JA, Grossman W, Saltz S, et al: A non-invasive technique for the determination of velocity of circumferential fiber shortening in man. Circ Res 29:610-615, 1971 Welesler AM. Garrard CL Jr: Systolic time intervals in cardiac disease. ModConcepts Cardiovasc Dis 40:1-6, 1971 Kraunz RF, Kennedy JW: Ultrasonic determination of left ventricular wall motion in normal man. Am Heart J 79:36-43, 1970 Kraunz RF, Ryan TJ: Ultrasound measurements of ventricular wall motion following administration of vasoactive drugs. Am J Cardiil27:464-473, 1971 lneue K, Smulyan H, Mookherjee S, et al: Ultrasonic measurement of left ventricular wall motion in acute myocardial infarction. Circulation 431778-785, 1971 i%pp RL, Wolfe SB, Hlrata T, et al: Estimation of right and left ventricular size by ultrasound. Am J Cardiol 24523-530. 1969 Felgenbaum H, Stone JM, Lee DA, et al: Identification of ultrasound echoes from the left ventricle by use of intracardiac injections of indocyanine green. Circulation 41:615-621, 1970 Karllner JS, Bouchard RJ, Gault JH: Dimensional changes of the human left ventricle prior to aortic valve opening. Circulation 44~312-322, 1971 Karllner JS, Gault JH, Eckberg D, et al: Mean velocity of fiber shortening: a simplified measure of left ventricular myocardial contractility. Circulation 44:323-333, 197 1 D@e HT, Sandler H, Ballew DW, et al: The use of biplane angiocardiography for the measurement of left ventricular volume in man. Am Heart J 60~762-776, 1960
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14. Dodge HT, Sandler H, Baxley WA, et al: Usefulness and limitations of radiographic methods for determining left ventricular volume. Am J Cardiol 16:10-24, 1966 15. Welfielef AM, Harrle WS, Schoenfeld CD: Bedside technics for the evaluation of ventricular function in man. Am J Cardiol 23: 577-583, 1969 16. Garrard CL Jr, Weleeter AM, Dodge HT: The relationship of alterations in systolic time intervals to ejection fraction in patients with cardiac disease. Circulation 42:455-462. 1970 17. Metzger CC, Cheen BC, Kroetz FW, et al: True isovolumic contraction time. Its correlation with two external indices of ventricular performance. Am J Cardiol 25:434-442. 1970 ia. Johnson AD. D’Rourke RA. Karllner JS, et al: Effect of myocardial revasculariiation on systolic time intervals in patients with left ventricular dysfunction. Circulation 45:suppl 1:1-91-l-96, 1972 19. Ludbrook P. Karllner JS, Peterson K, et al: Comparison of ultrasound and cineangiographic measurements of left ventricular performance in patients with and without wall motion abnormalities. Br Heart J 35:1026-1032, 1973 20. McDonald IO, Felgenbaum H, Chang S: Analysis of left ventricular wall motion by reflected ultrasound. Circulation 46:14-25, 1972 21. Fogelman AL, Abrasl AS, Pearce ML, et al: Echocardiographic study of the abnormal motion of the posterior left ventricular wall during angina pectoris. Circulation 46:905-913, 1972 22. Befenkle I, Nutter Do, Clark DW, et al: Assessment of left ventricular dimensions and function by echocardiography. Am J Cardiol3 1:755-762. 1973