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The components of the Korotkoff sounds
Fundamentals of clinical cardiology
The components
of the Korotkoff
sounds
Simon Rodbard, M.D., Ph.D.* Alan Steven Robbins, B.A.** Duarte, Calif.
T
he series of arterial (Korotkoff) sounds that are heard as a cuff on the arm is deflated offers significant cardiovascular information in addition to the data on the blood pressure level. This additional information is contained in the intensities, durations, and patterns of the components of the arterial sounds. The present study defines these components, their mechanisms of production, and their clinical significance. Method
A blood pressure cuff on the upper arm was inflated to a level higher than systolic arterial pressure and permitted to deflate at about 2 mm. Hg per second. The arterial sounds were auscultated’ and recorded. A microphone in the antecubital fossa transduced the arterial sounds to a 2 channel recording machine on which an electrocardiogram was recorded simultaneously as a reference tracing. The present analysis is based on experience gained in the course of approximately 5,000 recordings on more than 1,200 patients and normal individuals.’ Components
The arterial sounds that are heard over the arterial segment distal to the cuff have From
been shown to be generated during the systolic upstroke of the arterial pressure wave.3 Auscultation usually permits the identification of “tapping” and ‘lrumbling” sounds. The recordings illustrate the following discrete components: opening tap, breakers, rumble, and closing bruit (Fig. 1). Silences were aiso recorded. Opening tap. The opening tap, a highintensity report of brief duration, usually inaugurates the arterial sounds (Figs. 1 and 2). As the pressure wave in the artery under the cuff rises to a value that is sufficient to overcome the collapsing force of the sphygmomanometer cuff, a bolus of blood penetrates into the distal arterial segment which produces the opening tap. Near the systolic cuff pressure, where the slope of the arterial pressure wave is minimal, the amplitude of the tap is small. The amplitude of the tap increases as the cuff pressure falls to pressure levels at which the slope is steeper, (Fig. 2, beats 10 through 20). As the cuff pressure approaches the diastolic value and the slope of the pressure wave decreases, the amplitude of the tap again becomes small (Fig. 2, beats 23 through 27). As the cuff pressure falls, the difference between the pressure in the proximal and distal arterial segments at the instant of
the Department of Cardiology and Cardiac Research, Division of Medicine. City of Hope Medical Center Duarte, Calif. Aided by Grant HE 08721 from the National Heart Institute’ of the United States Public Health Service. Received for pulkation Jan. 26. 1967. *Director, Departnwnt of Cardiology and Cardiac Research, City of Hope Medical Center, Duarte, Calif. 91010. **Medical student at Northwestern University Medical School. Chicago, III.
278
Fig. 1. Arterial sound components. This is an enlargement of beat 11 from Fig. 2. An R wave peak of the electrocardiogram is seen at the left. B is the breaker; T is the opening tap; S is the silence; R is the rumble: C is the closing bruit. This sound was recorded at a crtff pressure of 95 mm. Hg. See the text for full discussion.
vascular opening is reduced. This resEiTs because the pressure in the upstream segment of the artery equais the CUR pressure level at the instant of arterial wall opening, whereas the pressure in the peripheral segment of the artery rises more gradually.3 This reduction in the pressure rlifierence across the cuA is associated with :a dirninution in the intensity of the ta diastoiic pressure level the pressure difference becomes small and the sounds tend to be “muffled” (Fig. 2, beats 25 to 27). The steep slopes of the arteriai pressure upstrokes in aortic regurgitation, in ductus and in generalized artetioarteriosus, scierosis generate very loud opening taps. :n hypertension the tapping sounds tend to be relatively faint, apparect1.J’ because :he low conductance (flow rate, perfusion pressure) of the peripheral vascular bed
Fig. Z. Arterial sound sequence. A continuous record has been cu t into 0 strips which dre &~ow:r .rom above downward. This record was obtained on a 29-year-old man with aortic regurgitation. The beats are numbered adjacent to each R wave of the electrocardiogram or near the vertical marks placed at the peak of each R wave. Pressure le\rels during deflation of the cuff are given. Beat 2 shows the arterial sound at the systohc !evei; rhis consists of an opening tap. Beat 3 shows doubling of the arterial sounds observed when the arterial pressure upstroke is notched. Beat 10 shows a rumble of great intensity and duration. Beat 11 illustrates the silence located between the opening tap and the rumble, as well as the closing bruit. Beat 13 shows the breaker component preceding the opening tap. Beat 27 shows a low intensity opening tap. This is the last arteria? sound of the series, which designates the diastolic blood pressure level.
280
Rodbard and Robbins
results in a high pressure in the arteries beyond the cuff.2 The opening taps are faint when the cardiac output and/or the slopes of the arterial pressure upstroke are reduced. Such faint sounds are elicited in shock, in stenosis of the mitral or aortic valves, and in congestive failure.2 When the vibrational energy of the opening tap is great, the resonances generated by the acoustic impulse persist for relatively long intervals. Thus, the amplitude of the tap determines its apparent duration. By attenuating the lower frequencies of the tap, the apparent duration may be diminished. This was done by using a high band pass filter in the recording system to markedly attenuate frequencies less then 200 cycles per second. Two sets of opening taps have been found in some patients with increased stroke volumes, especially in aortic regurgitation. Such doubling of the sounds is seen clearly (Fig. 2, beats 3 through 6). This phenomenon is usually observed near the systolic level and may be perceived by the well-trained finger as an anacrotic notch or a pulsus bisferiens.4r5 Breakers. Breakers are brief episodes of low-energy noise production which are sometimes recorded immediately preceding the opening tap at a steep portion of the arterial upstroke (Figs. 1 and 2, beats 9 through 20). These noises usually cannot be heard because they are masked by the much louder opening tap sound which follows almost at once. Breakers can be recorded consistently (10 to 30 msec.) before the onset of the tap, in association with the steep arterial upstroke of aortic regurgitation or generalized arteriosclerosis.’ The breakers appear to represent a portion of the energy of the pressure wave upstroke which is transmitted at velocities greater than those of the main portion of the wave. The faster-moving components of each wave arrive at the cuff slightly ahead of t,he main portion of the upstroke. This phenomenon is similar to that observed as the crest of a wave in the sea produces breakers by falling ahead of the foot of the main portion of the wave.6 The front-running portion of the wave appears to have energy barely sufficient to extrude a small volume of fluid at high
Am. Heart J. August, 1967
velocities through the nearly collapsed vessel before the main portion of the wave arrives to produce the much louder opening tap. Rumble. The rumble, a low-pitched, rattling noise, (Fig. 2, beats 8 through 18), is generated in the course of flow through a partially collapsed artery. An enhanced rate of runoff of blood out of the peripheral arteries increases the stream velocity, and lowers the intra-arterial pressure locally in accord with the law of conservation of energy. As the distending pressure in the arterial segment under the cuff falls to the cuff pressure level, the vessel wall collapses, a discrete acoustic impulse is generated, and flow stops. The total energy of the stream then becomes manifest as a distending pressure which reopens the vessel as the stream accelerates, and this causes the pressure to fall again. The resulting recurrent cycle of closing and opening of the arterial segment under the cuff generates a series of discrete acoustic impulses. This murmurlike sound indicates that flow through the arterial segment under the cuff may be intermittent during the rumble phase. The resonances generated by each closure give the impression that the rumble is a continuous sound. An inspection of pressure tracings, in the segment of the artery downstream to the cuff, shows a pattern of discrete impulses. Recordings at the segment of the artery distal to the cuff show pressure oscillations which are related to the recurrent vascular closure.3 The intensity of the rumble varies with the instantaneous pressure difference from the proximal to the distal arterial segments. The intensity is thus affected by the state of vasodilatation (conductance) of the vascular bed of the arm. When the blood runs off rapidly out of the distal arterial segment into the widely opened capillary bed, the rumble is loud. The duration of the rumble also varies with the peripheral vascular conductance. When conductance is maximal, as occurs in hypermetabolic states or after exercise of the muscles of the forearm, the rumble may continue for the entire duration of the pressure wave at the cuff ipressure level.’ In conditions of diminished peripheral
vascular conductance, the opening tap and the rumble may be so faint and of such short duration that they become inaudible. Such faint sounds are usuaiIy associated :vith a subnormal cardiac output, as in severe aortic stenosis, mitral valvular disease, debility, shock, or anesthesia. The estimation of the blood pressure in these circumstances may become indeterminate. The maneuver of closing and opening the fist 1~ times, which increases the vascular conductance of the arm, can restore the intensities and durations of the sounds to levels at which the arterial pressure can be estimated with greater security.‘s8 Closing bruit. A closing bruit is sometimes heard at the end of the rumble, especially \&en the arterial downstroke is steep. This bruit appears to be generated as the descending phase of the arterial pressure wave !alIs to a level at which the arterial segment under the cuff collapses. The closing bruit occurs especially in aortic regurgitation {Fig. l), ductus arteriosus, or arteriosclerosis. If the rate of runoff through the periphera! tissues is high and the pressure in the arterial segment distal to the cuff is low, the pressure drop will generate the highpitched blowing sound characteristic of flow through nearly closed vessels. The rumble may end with a tapping sound at the instant the central arterial pressure falls below the cuff pressure. Silence. SiIence is recorded galvaaometritally as an interval of relative base-line stability (Fig. 1). The silence between the opening tap and the rumble usually cannot be distinguished acousticaily. When a relatively laminar flow passes through a .momentarily widely opened segment of the artery under the cuff, silent intervals may be noted betx%reen the tap and the succeeding rumble. The velocity of the stream in the widely opened vessel increases with the rising arterial pressure wave until laminarity is lost and the silence ends with the onset of a rumhie. Arterial silence is also evident when no cuff is present and the laminar stream moves through the vessel with negligible energy loss. Sounds are also absent when cuff pressure exceeds intravascular pressure and the vessel is collapsed and flow is obstructed.
The
s Qf
t
The phases of the arteridf SOU:;~S ob-= served during indirect blood pressL!re measurements can be evaluated on the basis of the foregoing analysis of the cW.iFonents of the arteriai sounds.9,‘” The sc~rids of Phase I, which designate the s?;s~~Iic blood pressure level, consist of opening Ups. The relatively low intensity of these Laps is due to the reduced slope oi: the arterial pressure near systolic levels. The murmurlike sounds of Phase TI each co~ist of a combination of a tap and a ~x&xlged rumble. The duration and intensit:; oh these rumbles become maximal at about 25 mm. Hg befow the systolic level. “r’hase 111 Zs characterized by loud tapping sofunds followed by a rumble of short du*~ation. In Phase IV, the arterial sounds are mufled in accord with the reduced slope of the first portion of the arterial upstroke. SQU11
art
I
s
The components of the arter:ai sounds offer an instructive approach to the mechanisms of generation of the hear;. sounds and murmurs, The intensity of the heart sound components varies with ehe rate of change of the pressure drop acmss a heart valve at the instant of c!osure ;md, sometimes. at opening. I1 A sma!l rate of pressure change, as occurs in aortic vaIvu;ar stenosis during valve closure, produces 1~relatively iaint tap, while the larger press:!re drop of puimonary arterial hypertertsion produces a booming sound. The arteria! rxrnble bears strong acoustic resemblance w the heart murmurs. In both instances, the bruits are generated by nonlaminar flow which sets adjacen,t specific tissues, into vibration. The durations of the murmurs &tine the intervaIs when a significant pressure gradient. is present at a constricted 0s stenotic segment.;’ The absence of sound indicates that flow is either laminar or sbs:xcted. Since the factors which aKect the genera&n of the Korotkoff sounds can be coritroiied with ease, the hydroacoustic model presenxed here may serve to clarify some of the mechanisms of generation of heart sounds and murmurs.
The arterial sounds include. the fo&~ing components: (1) an opening t2,p gerrcrated
282
Rodbard and Robbim
as the rising intra-arterial pressure overcomes the obstructive force of the compression produced by the cuff; (2) a rumble generated by flow through the partially opened, vibrating arterial wall; (3) a closing bruit produced during the arterial downstroke as intra-arterial pressure falls below the cuff pressure; and (4) breakers which occur prior to the opening tap when the arterial upstroke is steep. (5) Silences represent either laminar flow through a fully opened vessel, or absence of flow. Similarities between the Korotkoff sounds and the heart sounds and murmurs are indicated. 1.
2.
3.
REFERENCES Korotkoff, K. S.: A contribution to the problem of methods for the determination of the blood pressure, Ruskin, A., editor: in Classics in arterial hypertension, Springfield, Ill., 1965, Charles C Thomas, Publisher. Rodbard, S.: The clinical value of timing the arterial sounds (sphygmorecording). Unpublished data. Kodhard. S.. Rubinstein. H. M.. and Rosenblum, S. I Arrival time and calibrated contour of the pulse wave determined indirectly from re-
4.
5.
6.
7. 8.
9. 10.
11.
cordings of arterial compression sounds, .Anc. HEART J. 53:205, 1957. Wood, P.: Diseases of the heart and circulation. Philadelphia, 1959, J. B. Lippincott Company; pp. 28, 572. Rodbard, S., and Ciesielski, J.: Doubling of the arterial sounds in patients with pulsus bisferiens, J. A. M. A. 175:475, 1961. Erlanger, J.: Studies in blood pressure estimations bv indirect method. I. The mechanisms of the os&atory criteria, Am. J. Physiol. 39:401, 1916. Rodbard, S., and Ciesielski, J.: Duration of arterial sounds, Am. J. Cardiol. 8:18, 1961. Rodbard, S. : Mechanisms, significance, and alterations of the Korotkoff sounds, in The theory and practice of auscultation, Segal, B., editor: Philadelphia, 1964, F. A. Davis Company, p. 332. Rodhard. S.: The clinical sienificance of the arterial sounds, Heart Bull. li:41, 1962. Bordley, J., III, Connor, C. A. R., Hamilton, W. F., Kerr, W. K., and Wiggers, C. J.: Recommendations for human blood pressure determinations by sphygmomanometers, Circulation 4:503, 195i. Rodbard, S.: The production and physical qualities of sound in the cardiovascular s>Tstem, iz The theory and practice of auscultation, Segal, B., editor: Philadelphia, 1963, F. A. Davis Company, p. 26.
The components
of the Korotkoff
sounds
Simon Rodbard, M.D., Ph.D.* Alan Steven Robbins, B.A.** Duarte, Calif.
T
he series of arterial (Korotkoff) sounds that are heard as a cuff on the arm is deflated offers significant cardiovascular information in addition to the data on the blood pressure level. This additional information is contained in the intensities, durations, and patterns of the components of the arterial sounds. The present study defines these components, their mechanisms of production, and their clinical significance. Method
A blood pressure cuff on the upper arm was inflated to a level higher than systolic arterial pressure and permitted to deflate at about 2 mm. Hg per second. The arterial sounds were auscultated’ and recorded. A microphone in the antecubital fossa transduced the arterial sounds to a 2 channel recording machine on which an electrocardiogram was recorded simultaneously as a reference tracing. The present analysis is based on experience gained in the course of approximately 5,000 recordings on more than 1,200 patients and normal individuals.’ Components
The arterial sounds that are heard over the arterial segment distal to the cuff have From
been shown to be generated during the systolic upstroke of the arterial pressure wave.3 Auscultation usually permits the identification of “tapping” and ‘lrumbling” sounds. The recordings illustrate the following discrete components: opening tap, breakers, rumble, and closing bruit (Fig. 1). Silences were aiso recorded. Opening tap. The opening tap, a highintensity report of brief duration, usually inaugurates the arterial sounds (Figs. 1 and 2). As the pressure wave in the artery under the cuff rises to a value that is sufficient to overcome the collapsing force of the sphygmomanometer cuff, a bolus of blood penetrates into the distal arterial segment which produces the opening tap. Near the systolic cuff pressure, where the slope of the arterial pressure wave is minimal, the amplitude of the tap is small. The amplitude of the tap increases as the cuff pressure falls to pressure levels at which the slope is steeper, (Fig. 2, beats 10 through 20). As the cuff pressure approaches the diastolic value and the slope of the pressure wave decreases, the amplitude of the tap again becomes small (Fig. 2, beats 23 through 27). As the cuff pressure falls, the difference between the pressure in the proximal and distal arterial segments at the instant of
the Department of Cardiology and Cardiac Research, Division of Medicine. City of Hope Medical Center Duarte, Calif. Aided by Grant HE 08721 from the National Heart Institute’ of the United States Public Health Service. Received for pulkation Jan. 26. 1967. *Director, Departnwnt of Cardiology and Cardiac Research, City of Hope Medical Center, Duarte, Calif. 91010. **Medical student at Northwestern University Medical School. Chicago, III.
278
Fig. 1. Arterial sound components. This is an enlargement of beat 11 from Fig. 2. An R wave peak of the electrocardiogram is seen at the left. B is the breaker; T is the opening tap; S is the silence; R is the rumble: C is the closing bruit. This sound was recorded at a crtff pressure of 95 mm. Hg. See the text for full discussion.
vascular opening is reduced. This resEiTs because the pressure in the upstream segment of the artery equais the CUR pressure level at the instant of arterial wall opening, whereas the pressure in the peripheral segment of the artery rises more gradually.3 This reduction in the pressure rlifierence across the cuA is associated with :a dirninution in the intensity of the ta diastoiic pressure level the pressure difference becomes small and the sounds tend to be “muffled” (Fig. 2, beats 25 to 27). The steep slopes of the arteriai pressure upstrokes in aortic regurgitation, in ductus and in generalized artetioarteriosus, scierosis generate very loud opening taps. :n hypertension the tapping sounds tend to be relatively faint, apparect1.J’ because :he low conductance (flow rate, perfusion pressure) of the peripheral vascular bed
Fig. Z. Arterial sound sequence. A continuous record has been cu t into 0 strips which dre &~ow:r .rom above downward. This record was obtained on a 29-year-old man with aortic regurgitation. The beats are numbered adjacent to each R wave of the electrocardiogram or near the vertical marks placed at the peak of each R wave. Pressure le\rels during deflation of the cuff are given. Beat 2 shows the arterial sound at the systohc !evei; rhis consists of an opening tap. Beat 3 shows doubling of the arterial sounds observed when the arterial pressure upstroke is notched. Beat 10 shows a rumble of great intensity and duration. Beat 11 illustrates the silence located between the opening tap and the rumble, as well as the closing bruit. Beat 13 shows the breaker component preceding the opening tap. Beat 27 shows a low intensity opening tap. This is the last arteria? sound of the series, which designates the diastolic blood pressure level.
280
Rodbard and Robbins
results in a high pressure in the arteries beyond the cuff.2 The opening taps are faint when the cardiac output and/or the slopes of the arterial pressure upstroke are reduced. Such faint sounds are elicited in shock, in stenosis of the mitral or aortic valves, and in congestive failure.2 When the vibrational energy of the opening tap is great, the resonances generated by the acoustic impulse persist for relatively long intervals. Thus, the amplitude of the tap determines its apparent duration. By attenuating the lower frequencies of the tap, the apparent duration may be diminished. This was done by using a high band pass filter in the recording system to markedly attenuate frequencies less then 200 cycles per second. Two sets of opening taps have been found in some patients with increased stroke volumes, especially in aortic regurgitation. Such doubling of the sounds is seen clearly (Fig. 2, beats 3 through 6). This phenomenon is usually observed near the systolic level and may be perceived by the well-trained finger as an anacrotic notch or a pulsus bisferiens.4r5 Breakers. Breakers are brief episodes of low-energy noise production which are sometimes recorded immediately preceding the opening tap at a steep portion of the arterial upstroke (Figs. 1 and 2, beats 9 through 20). These noises usually cannot be heard because they are masked by the much louder opening tap sound which follows almost at once. Breakers can be recorded consistently (10 to 30 msec.) before the onset of the tap, in association with the steep arterial upstroke of aortic regurgitation or generalized arteriosclerosis.’ The breakers appear to represent a portion of the energy of the pressure wave upstroke which is transmitted at velocities greater than those of the main portion of the wave. The faster-moving components of each wave arrive at the cuff slightly ahead of t,he main portion of the upstroke. This phenomenon is similar to that observed as the crest of a wave in the sea produces breakers by falling ahead of the foot of the main portion of the wave.6 The front-running portion of the wave appears to have energy barely sufficient to extrude a small volume of fluid at high
Am. Heart J. August, 1967
velocities through the nearly collapsed vessel before the main portion of the wave arrives to produce the much louder opening tap. Rumble. The rumble, a low-pitched, rattling noise, (Fig. 2, beats 8 through 18), is generated in the course of flow through a partially collapsed artery. An enhanced rate of runoff of blood out of the peripheral arteries increases the stream velocity, and lowers the intra-arterial pressure locally in accord with the law of conservation of energy. As the distending pressure in the arterial segment under the cuff falls to the cuff pressure level, the vessel wall collapses, a discrete acoustic impulse is generated, and flow stops. The total energy of the stream then becomes manifest as a distending pressure which reopens the vessel as the stream accelerates, and this causes the pressure to fall again. The resulting recurrent cycle of closing and opening of the arterial segment under the cuff generates a series of discrete acoustic impulses. This murmurlike sound indicates that flow through the arterial segment under the cuff may be intermittent during the rumble phase. The resonances generated by each closure give the impression that the rumble is a continuous sound. An inspection of pressure tracings, in the segment of the artery downstream to the cuff, shows a pattern of discrete impulses. Recordings at the segment of the artery distal to the cuff show pressure oscillations which are related to the recurrent vascular closure.3 The intensity of the rumble varies with the instantaneous pressure difference from the proximal to the distal arterial segments. The intensity is thus affected by the state of vasodilatation (conductance) of the vascular bed of the arm. When the blood runs off rapidly out of the distal arterial segment into the widely opened capillary bed, the rumble is loud. The duration of the rumble also varies with the peripheral vascular conductance. When conductance is maximal, as occurs in hypermetabolic states or after exercise of the muscles of the forearm, the rumble may continue for the entire duration of the pressure wave at the cuff ipressure level.’ In conditions of diminished peripheral
vascular conductance, the opening tap and the rumble may be so faint and of such short duration that they become inaudible. Such faint sounds are usuaiIy associated :vith a subnormal cardiac output, as in severe aortic stenosis, mitral valvular disease, debility, shock, or anesthesia. The estimation of the blood pressure in these circumstances may become indeterminate. The maneuver of closing and opening the fist 1~ times, which increases the vascular conductance of the arm, can restore the intensities and durations of the sounds to levels at which the arterial pressure can be estimated with greater security.‘s8 Closing bruit. A closing bruit is sometimes heard at the end of the rumble, especially \&en the arterial downstroke is steep. This bruit appears to be generated as the descending phase of the arterial pressure wave !alIs to a level at which the arterial segment under the cuff collapses. The closing bruit occurs especially in aortic regurgitation {Fig. l), ductus arteriosus, or arteriosclerosis. If the rate of runoff through the periphera! tissues is high and the pressure in the arterial segment distal to the cuff is low, the pressure drop will generate the highpitched blowing sound characteristic of flow through nearly closed vessels. The rumble may end with a tapping sound at the instant the central arterial pressure falls below the cuff pressure. Silence. SiIence is recorded galvaaometritally as an interval of relative base-line stability (Fig. 1). The silence between the opening tap and the rumble usually cannot be distinguished acousticaily. When a relatively laminar flow passes through a .momentarily widely opened segment of the artery under the cuff, silent intervals may be noted betx%reen the tap and the succeeding rumble. The velocity of the stream in the widely opened vessel increases with the rising arterial pressure wave until laminarity is lost and the silence ends with the onset of a rumhie. Arterial silence is also evident when no cuff is present and the laminar stream moves through the vessel with negligible energy loss. Sounds are also absent when cuff pressure exceeds intravascular pressure and the vessel is collapsed and flow is obstructed.
The
s Qf
t
The phases of the arteridf SOU:;~S ob-= served during indirect blood pressL!re measurements can be evaluated on the basis of the foregoing analysis of the cW.iFonents of the arteriai sounds.9,‘” The sc~rids of Phase I, which designate the s?;s~~Iic blood pressure level, consist of opening Ups. The relatively low intensity of these Laps is due to the reduced slope oi: the arterial pressure near systolic levels. The murmurlike sounds of Phase TI each co~ist of a combination of a tap and a ~x&xlged rumble. The duration and intensit:; oh these rumbles become maximal at about 25 mm. Hg befow the systolic level. “r’hase 111 Zs characterized by loud tapping sofunds followed by a rumble of short du*~ation. In Phase IV, the arterial sounds are mufled in accord with the reduced slope of the first portion of the arterial upstroke. SQU11
art
I
s
The components of the arter:ai sounds offer an instructive approach to the mechanisms of generation of the hear;. sounds and murmurs, The intensity of the heart sound components varies with ehe rate of change of the pressure drop acmss a heart valve at the instant of c!osure ;md, sometimes. at opening. I1 A sma!l rate of pressure change, as occurs in aortic vaIvu;ar stenosis during valve closure, produces 1~relatively iaint tap, while the larger press:!re drop of puimonary arterial hypertertsion produces a booming sound. The arteria! rxrnble bears strong acoustic resemblance w the heart murmurs. In both instances, the bruits are generated by nonlaminar flow which sets adjacen,t specific tissues, into vibration. The durations of the murmurs &tine the intervaIs when a significant pressure gradient. is present at a constricted 0s stenotic segment.;’ The absence of sound indicates that flow is either laminar or sbs:xcted. Since the factors which aKect the genera&n of the Korotkoff sounds can be coritroiied with ease, the hydroacoustic model presenxed here may serve to clarify some of the mechanisms of generation of heart sounds and murmurs.
The arterial sounds include. the fo&~ing components: (1) an opening t2,p gerrcrated
282
Rodbard and Robbim
as the rising intra-arterial pressure overcomes the obstructive force of the compression produced by the cuff; (2) a rumble generated by flow through the partially opened, vibrating arterial wall; (3) a closing bruit produced during the arterial downstroke as intra-arterial pressure falls below the cuff pressure; and (4) breakers which occur prior to the opening tap when the arterial upstroke is steep. (5) Silences represent either laminar flow through a fully opened vessel, or absence of flow. Similarities between the Korotkoff sounds and the heart sounds and murmurs are indicated. 1.
2.
3.
REFERENCES Korotkoff, K. S.: A contribution to the problem of methods for the determination of the blood pressure, Ruskin, A., editor: in Classics in arterial hypertension, Springfield, Ill., 1965, Charles C Thomas, Publisher. Rodbard, S.: The clinical value of timing the arterial sounds (sphygmorecording). Unpublished data. Kodhard. S.. Rubinstein. H. M.. and Rosenblum, S. I Arrival time and calibrated contour of the pulse wave determined indirectly from re-
4.
5.
6.
7. 8.
9. 10.
11.
cordings of arterial compression sounds, .Anc. HEART J. 53:205, 1957. Wood, P.: Diseases of the heart and circulation. Philadelphia, 1959, J. B. Lippincott Company; pp. 28, 572. Rodbard, S., and Ciesielski, J.: Doubling of the arterial sounds in patients with pulsus bisferiens, J. A. M. A. 175:475, 1961. Erlanger, J.: Studies in blood pressure estimations bv indirect method. I. The mechanisms of the os&atory criteria, Am. J. Physiol. 39:401, 1916. Rodbard, S., and Ciesielski, J.: Duration of arterial sounds, Am. J. Cardiol. 8:18, 1961. Rodbard, S. : Mechanisms, significance, and alterations of the Korotkoff sounds, in The theory and practice of auscultation, Segal, B., editor: Philadelphia, 1964, F. A. Davis Company, p. 332. Rodhard. S.: The clinical sienificance of the arterial sounds, Heart Bull. li:41, 1962. Bordley, J., III, Connor, C. A. R., Hamilton, W. F., Kerr, W. K., and Wiggers, C. J.: Recommendations for human blood pressure determinations by sphygmomanometers, Circulation 4:503, 195i. Rodbard, S.: The production and physical qualities of sound in the cardiovascular s>Tstem, iz The theory and practice of auscultation, Segal, B., editor: Philadelphia, 1963, F. A. Davis Company, p. 26.