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The clinical significance of the fourth heart sound in aortic stenosis
The Clinical Significance of the Fourth Heart Sound in Aortic Stenosis
WALTER
H. CAULFIELD,
ANTONIO
C. deLEON,
JOSEPH
K. PERLOFF,
R.
BARRETT
Washington,
MD
Jr., MD,
STEELMAN,
MD,
FACC
FACC MD
D. C.
From the Department of Medicine, Georgetown University School of Medicine, Division of Cardiology, Georgetown University Hospital, Washington, D. C. This study was supported in part by U. S. Public Health Service Career Program Award HE-14,099 and by U. S. Public Health Service Grants HE-3319 and HE-S433 from the National Institutes of Health, Bethesda, Md. Address for reprints: Antonio C. deleon, Jr., MD, Division of Cardiology, Georgetown University Hospital, 3800 Reservoir Rd., N.W., Washington, D. C. 20007.
VOLUME 28. AUGUST 1971
It has previously been proposed that the presence of a fourth heart sound in an adult with discrete aortic stenosis predicts a peak systolic gradient of 75 mm Hg or more. A number of exceptions led us to reinvestigate this concept. Accordingly, 124 patients were studied in order to examine the significance of the fourth heart sound in the clinical assessment of severity in discrete obstruction to left ventricular outflow. Since both age and aortic stenosis are independent variables in the production of the fourth heart sound, the data were reviewed in this light. The results indicate that: (1) over age 40 years, the fourth heart sound is not a reliable index of severity in discrete aortic stenosis; (2) under age 40 years, a fourth heart sound is good evidence of a peak systolic gradient of 75 mm Hg or more: (3) absence of a fourth heart sound in any adult subject suggests that the peak gradient is less than 75 mm Hg and probably less than 60 mm Hg, provided that factors hindering detection of a fourth heart sound (such as very short P-R interval, emphysema or obesity) are taken into account. The essence of the problem can be concisely stated as follows: In severe aortic stenosis a fourth heart sound is almost always present, but the presence of a fourth heart sound in adults with aortic stenosis implies severity of disease only in subjects under 40 years of age.
Discrete obstruction to left ventricular outflow is readily diagnosed, but clinical assessment of ,severity remains a problem. Criteria for severity abound and include dyspnea, syncope and angina ; a slow rising, broad, peaked arterial pulse ; a sustained left ventricular impulse ; a loud, long mid-systolic murmur ; paradoxical or reverse splitting of the second heart sound; electrocardiographic evidence of left ventricular hypertrophy ; radiologic evidence of left ventricular and left atria1 enlargement, as well as calcification of the aortic valve. Despite this impressive list, inconsistencies are common, more so in older subjects than in children. In addition to the standards oiled, the force of left atria1 contraction and the presystolic condition of the left ventricle have been considered in clinical estimates of severity in aortic stenosis. An increased force of left atria1 contraction may significantly augment left ventricular filling pressure just before ventricular contraction, and a fourth heart sound may accompany this increase in presystolic pressure. Potain’ recognized this tendency in left ventricular hypertrophy when he wrote that the wall of the ventricle “. . . is placed under tension precisely at the moment that this [the added sound] occurs.” It has been reasoned that as obstruction to left ventricular outflow increases, the ventricle must contract more forcibly ; an increase in end-diastolic fiber
179
CAULFIELD ET AL.
TABLE I Incidence
of Fourth Heart Sound in Aortic Stenosis
no. of cases With a fourth heart sound (80 heard and recorded, 8 recorded but not heard) Without a fourth heart sound
of obstruction.”
124 88
36
Subjects with an associated aortic in-
competence of minor degree were considered for all practical purposes as having “pure” aortic stenosis. Phonocardiograms with appropriate reference tracings, utilizing a Sanborn 4-channel photographic recorder, were obtained from all patients, and all patients
Figure 1. A, tracings from a 51 year old man with a peak aortic gradient of 20 mm Hg. The phonocardiogram from the second right intercostal space (2 its) (filter 100 Hz) shows a relatively short mid-systolic murmur (SM) and a soft early diastolic murmur (DM). A prominent fourth heart sound (S,) is recorded at the apex (filter 100 Hz). B, tracings from a 56 year old man with a peak aortic gradient of 92 mm Hg. The phonocardiogram from the second right intercostal space (filter 100 Hz) shows a relatively long mid-systolic murmur (SM). A fourth heart sound (S,) was recorded at the apex (filter 50 Hzfsec).
length (presystolic distension) permits that chamber to achieve the required increase in contractile force. Accordingly, the presence of a fourth heart sound-which is the auscultatory counterpart of presystolic distension-has been used in assessing severity of obstruction in adults with discrete aortic ,stenosis.2 Goldblatt et a1.2 concluded that a fourth heart sound predicted a peak systolic gradient of at least 75 mm Hg. However, because we have encountered an appreciable number of exceptions to this finding, we investigated the problem in 124 postpuberal patients with isolated, discrete aortic stenosis.
Materials and Methods One or more of us personally assessed the history, physical signs, electrocardiogram and cardiac radiograms of each patient. Stable sinus rhythm was obligatory for inclusion in the study, but subjects with P-R intervals exceeding 0.20 second were eliminated. Since an audible fourth heart sound sometimes occurs in normal children, patients less than 12 years old were excluded.2 Patients with idiopathic hypertrophic subaortic stenosis were also excluded because a fourth heart sound in this disorder is unrelated to the degree 180
underwent either transseptal or retrograde catheterization of the left heart chambers or percutaneous left ventricular puncture, or both. A fourth heart sound was considered present only when it was clearly identified on the phonocardiogram as a low frequency presystolic vibration occurring at least 0.07 second after the P wave but before the QRS interval of the electrocardiogram (Fig. 1). This timing corresponds with the second or “audible” component of the fourth heart sound. Peak systolic ventriculoaortic gradients were averaged through at least 1 respiratory cycle; cardiac output was determined after left ventricular injection of indocyanine green dye, and the size of the aortic valve orifice was calculated from Gorlin’s formula. One subject showed no gradient in the control tracing but an abnormal gradient (15 mm Hg) after inhalation of amyl nitrite.
Results A fourth heart sound was recorded in 83 of the 124 patients; the sound was also heard with a stethoscope in 80 ‘of the 88. In the remaining 36 subjects, a fourth heart sound was neither heard nor recorded (Table I). Phonocardiographic and hemodynamic data are shown in Table II. Peak systolic gradient : The 88 patients with I documented fourth heart sound (Groups I to III Table II) were analyzed according to peak systolic gradient (Table III) : Group I: 48 had a peak aortic gradient of a least 75 mm Hg (range 75 to 160, average 103). Group II : 15 had a peak aortic gradient of 60 tm 70 mm Hg (average 66). Group III : 25 had a peak aortic gradient of les than 60 mm Hg (range 0 to 55, average 25). The 36 patients without a fourth heart soun (Groups IV to VI, Table II) were analyzed accord ing to peak systolic gradient (Table IV) : Group IV: 5 had a gradient of at least 75 mr Hg (range 76 to 107, average 90). Group V: 5 had a gradient of 60 to 72 mm H (average 67). Group VI : 26 had a gradient of less than 60 nn Hg (range 14 to 55, average 39). Age and peak systolic. gradient: The 88 PZ tients with a documented fourth heart soun (Groups I to III, Table II) were then analyzed a( The American Journal of CARDIOLOC
FOURTH
TABLE
HEART SOUND
IN AORTIC STENOSIS
II
Phonocerdiographlc
and Hemodynqmic
Data in 124 Cases Average
no. of Cases Group I (gradient Group II (gradient Group III (gradient Group IV (gradient Group V (gradient Group VI (gradient
Age (vr)
49 275
mm
+ (17?4)
Hg) 15
60-75
mm
+
Hg)
(4rz4) 25
<60
mm
SC
Average Peak Gradient (mm Hg)
Average LA Average Aortic A Wave (mm Hg) Valve Orifice (cmz)
103 (75-M) 66
$5)
w-70)
(124)
+ (124)
Hg)
(CT5)
(&)
5 275
mm
(l&3)
Hg)
-
(7&?07)
(12%)
(6J2)
$7) 20 (7-32)
(16%
(l&595)
$5)
5 60-75
mm
Hg)
0.52 (0.2-1.1) 0.61 (0.3-0.9) 1.03 (0.4-2.5) 0.42 (0.3-0.6) 0.62 (0.5-0.9) (O.E4)
Average LV Z Point (mm Hg)
(k480) $6) $3) (3!iO) $3)
26 <60 mm
Hg)
Figures in parentheses indicate range. + = present; - = absent. LA = left atrial; LV = left ventricular; SC = fourth
heart
(2!:1)
sound.
cording to both age and peak systolic gradient (Table IV) : 1. Of 88 patients, 76 were aged 40 years or more, and 37 of them had a gradient of less than 75 mm Hg. In Group I, 39 of 48 patients were aged 40 years or more (range 40 to 74, average 56) ; in Group II, all 15 patients were aged 40 years or more (range 40 to 74, average 54) ; in Group III, 22 of 25 patients were aged 40 years or more (range 40 to 64, average 51). 2. Of the 88 patients, 12 were aged 13 to 40 years, and 2 of them had a gradient of less than 75 mm Hg. These 2 patients were aged 13 and 15 years, respectively.
Discussion In 1875, Pierre-Carl Potain’ wrote the following description of what is now recognized as the atria1 or fourth heart sound. “We distinguish here three sounds, namely: the two normal sounds and an additional sound. . . . As to the abnormal sound, it is placed immediately before [the first heart sound] preceding it sometimes by a very short time. . . . The sound is dull, much more so than the normal sound.” Weitzman4 showed that the audible component of the fourth heart sound originates within the cavity of the recipient ventricle as that
chamber receives blood following atria1 contraction. Potain proposed this mechanism, stating, “This sound results from the abruptness with which dilatation takes place during the presystolic period which corresponds to the contraction of the auricle.“’ This mechanism was confirmed by Muiesan et al.5 in experimental animals. To appreciate Geilesis of fourth heart sound: the clinical significance of the fourth heart sound in aortic stenosis it is necessary to understand the factors upon which the genesis of the sound depends, namely: (1) effective atria1 contraction; (2) unimpeded ventricular filling (absence of atrioventricular valve obstruction) ; and (3) diminished ventricular distensibility (compliance) .” Ventricular hypertrophy sets the stage for the presence of all 3 factors. The compliance of a hypertrophied ventricle is reduced, and its atrium contracts with greater force across an unobstructed atrioventricular valve. Accordingly, fourth heart sounds originating in the left ventricle are auscultatory features of aortic stenosis, systemic hyperTABLE IV Distribution of 124 Cases According Systolic Gradient
~-.
no. of Cases
Average Age (yr) __.._
A. 36 Cases
Without
to Age and Peak
_-
a Fourth
Gradient (mm Hg) -. -.. --
-
Heart Sound
TABLE III Distribution of the 88 Cases with a Fourth Heart Sound According to Peak Systolic Gradients Gradient (mm Hg)
no. of Cases 46 40
275 74 to 60
15 25
VOLUME
28. AUGUST
<60
1971
275 72 to 60 <60
43 34 30
5 5 26 B. 88 Cases
With
76
>40
12
<40
a Fourth Heart _ _ -
Sound -.. 37 gradients <75 2 gradients <75
---
--
181
CAULFIELD
ET AL.
tension and other causes of left ventricular hypertrophy; fourth heart sounds originating in the right ventricle are accompaniments of pulmonary stenosis or pulmonary hypertension. In addition, ischemic heart disease may result in a decrease of left ventricular compliant in the face of effective atria1 contraction, and fourth heart sounds are common in this context.7 Finally, there appears to be a decrease in left ventricular distensibility associated with advancing age, even in subjects without clinical evidence of heart disease. The corollary of this observation is that the incidence of fourth heart sounds has an independent tendency to increase with age per se. Accordingly, the prevalence of a fourth heart sound in aortic stenosis must be examined in the light of both the degree of obstruction and the patient’s age. The possibility that coexisting degenerative heart disease might result in a fourth heart sound in aortic stenosis was recognized in early reports.2 Correlation of aortic gradient and fourth sound: Three questions can now be posed. First, how accurately does an aortic gradient above a certain level predict the pre.sence of a fourth heart sound? Second, how accurately does the presence of a fourth heart sound predict an aortic gradient above a certain level ? Third, if a discrepancy exists in the conclusions based upon these 2 questions, how can this discrepancy be resolved? In answer to the first question, the data show that a gradient of ‘75 mm Hg or more is associated with a 90 percent incidence of a fourth heart sound (Table II). Fifty-three patients had such a gradient, and 48 of them had a fourth heart sound. In fact, the correlation is about as good with gradients of 60 mm Hg or more ; 73 patients had such a gradient, and 63 of them had a fourth heart sound, an incidence of 86 percent (Table II). In answer to the second question, the results show that in patients with aortic stenosis and a fourth heart sound, 45 percent (40 of 88) had a gradient of less than 75 mm Hg and 28 percent (25 of 88) had a gradient of less than 60 mm Hg. In answer to the third question, Effect of age: the inaccuracy of predicting the gradient from the presence of a fourth heart sound as opposed to predicting the fourth heart sound from the gradient
can be resolved by introducing age as a variable. Seventy-six of our patients with fourth heart sounds were aged 40 years or over, and half of them (37 of 76) had gradients of less than 75 mm Hg (Table WE!). Twenty-nine percent (22 of 76) had a gradient of less than 60 mm Hg. A relatively small number of our patients (12) were under 40 years of age, and 2 of them (aged 13 and 15 years) had a fourth heart sound with a gradient of less than 75 mm Hg. Goldblatt and co-workers2 found that 29 of 30 relatively young (average age 32 years) adults with aortic stenosis and a fourth heart sound had a gradient of 75 mm Hg or more. The exception was a man aged 53 years. In older subjects 2 factors-age and aortic stenosis-contribute to the presence of a fourth heart sound, whereas in young adults there is essentially only 1 contributing factor-aortic stenosis. It is, therefore, understandable that in older adults with aortic stenosis the presence of a fourth heart sound is an unreliable sign of severity. The issue is compounded by the observation that aortic stenosis is predominantly a disease of men,8 and degenerative heart disease is more common in men than in women. Conversely, in young adults with aortic stenosis, the presence of a fourth heart sound is likely to indicate a peak gradient of at least 75 mm Hg. Group IV in Table II calls attention to the occasional patient who has severe aortic stenosis but no fourth heart sound. There may be a number of reasons for this discrepancy, namely, a very short P-R interval or factors that hinder auscultation, such as emphysema or obesity. Correlation of fourth sound and A wave: The left atria1 A wave and left ventricular end-diastolic pressure (Z point) tended to be increased (average 17 to 18 mm Hg) in subjects with a gradient over 60 mm Hg and close to normal (average 11 to 13 mm Hg) in subjects with a gradient of less than 60 mm Hg (Table II). However, an occasional fourth heart sound was present in patients with a normal left atria1 A wave, and absent in patients with a large A wave. Both the force of left atria1 contraction and the presystolic condition of the left ventricle appear to be determinants of the fourth heart sound in aortic stenosis.
References Potain P-C: Concerning the cardiac rhythm called gallop rhythm. Bull Sot Med Hop Paris 12:137, 1876. Cited in, Major RH: Classic Descriptions of Disease. Springfield, Ill, Charles C Thomas, 1948, p 388 Goldblatt A, Aygen MM, Rraunwald E: Hemodynamic phonocardiographic correlations of the fourth heart sound in aortic stenosis. Circulation 26:92-98, 1962 Braunwald W, Morrow AG, Cornell WP, et al: Idiopathic hypertrophic subaortic stenosis: clinical, hemodynamic and angiographic manifestations. Amer J Med 29:924945, 1960 The mechanism and significance of the Weftzman D:
182
auricular
sound. Brit Heart J 17:70-78,
1955
Hemo5. Muiesan 6, MacCan6n DM, Nufiez-Dey D, et al: dynamic correlates of the fourth heart sound. Amer J Physiol 201:95-98, 1961 6. O’Rourke RA: Clinical Ann DC 39:95-97,197O
significance
of atrial
sound.
7. Hill IC, O’Rourke RA. Lewis RP, et al: The value of the atrial gallop in acute myocardial Amer Heart J 78:194-201.1969 8.
Anatomically isolated Roberts WC: ease. Amer J bled 49:151-159, 1970
The
Amwian
aortic
Med
diagnostic infarction.
valvular
dis-
Joumol of CARDIOLOQY
WALTER
H. CAULFIELD,
ANTONIO
C. deLEON,
JOSEPH
K. PERLOFF,
R.
BARRETT
Washington,
MD
Jr., MD,
STEELMAN,
MD,
FACC
FACC MD
D. C.
From the Department of Medicine, Georgetown University School of Medicine, Division of Cardiology, Georgetown University Hospital, Washington, D. C. This study was supported in part by U. S. Public Health Service Career Program Award HE-14,099 and by U. S. Public Health Service Grants HE-3319 and HE-S433 from the National Institutes of Health, Bethesda, Md. Address for reprints: Antonio C. deleon, Jr., MD, Division of Cardiology, Georgetown University Hospital, 3800 Reservoir Rd., N.W., Washington, D. C. 20007.
VOLUME 28. AUGUST 1971
It has previously been proposed that the presence of a fourth heart sound in an adult with discrete aortic stenosis predicts a peak systolic gradient of 75 mm Hg or more. A number of exceptions led us to reinvestigate this concept. Accordingly, 124 patients were studied in order to examine the significance of the fourth heart sound in the clinical assessment of severity in discrete obstruction to left ventricular outflow. Since both age and aortic stenosis are independent variables in the production of the fourth heart sound, the data were reviewed in this light. The results indicate that: (1) over age 40 years, the fourth heart sound is not a reliable index of severity in discrete aortic stenosis; (2) under age 40 years, a fourth heart sound is good evidence of a peak systolic gradient of 75 mm Hg or more: (3) absence of a fourth heart sound in any adult subject suggests that the peak gradient is less than 75 mm Hg and probably less than 60 mm Hg, provided that factors hindering detection of a fourth heart sound (such as very short P-R interval, emphysema or obesity) are taken into account. The essence of the problem can be concisely stated as follows: In severe aortic stenosis a fourth heart sound is almost always present, but the presence of a fourth heart sound in adults with aortic stenosis implies severity of disease only in subjects under 40 years of age.
Discrete obstruction to left ventricular outflow is readily diagnosed, but clinical assessment of ,severity remains a problem. Criteria for severity abound and include dyspnea, syncope and angina ; a slow rising, broad, peaked arterial pulse ; a sustained left ventricular impulse ; a loud, long mid-systolic murmur ; paradoxical or reverse splitting of the second heart sound; electrocardiographic evidence of left ventricular hypertrophy ; radiologic evidence of left ventricular and left atria1 enlargement, as well as calcification of the aortic valve. Despite this impressive list, inconsistencies are common, more so in older subjects than in children. In addition to the standards oiled, the force of left atria1 contraction and the presystolic condition of the left ventricle have been considered in clinical estimates of severity in aortic stenosis. An increased force of left atria1 contraction may significantly augment left ventricular filling pressure just before ventricular contraction, and a fourth heart sound may accompany this increase in presystolic pressure. Potain’ recognized this tendency in left ventricular hypertrophy when he wrote that the wall of the ventricle “. . . is placed under tension precisely at the moment that this [the added sound] occurs.” It has been reasoned that as obstruction to left ventricular outflow increases, the ventricle must contract more forcibly ; an increase in end-diastolic fiber
179
CAULFIELD ET AL.
TABLE I Incidence
of Fourth Heart Sound in Aortic Stenosis
no. of cases With a fourth heart sound (80 heard and recorded, 8 recorded but not heard) Without a fourth heart sound
of obstruction.”
124 88
36
Subjects with an associated aortic in-
competence of minor degree were considered for all practical purposes as having “pure” aortic stenosis. Phonocardiograms with appropriate reference tracings, utilizing a Sanborn 4-channel photographic recorder, were obtained from all patients, and all patients
Figure 1. A, tracings from a 51 year old man with a peak aortic gradient of 20 mm Hg. The phonocardiogram from the second right intercostal space (2 its) (filter 100 Hz) shows a relatively short mid-systolic murmur (SM) and a soft early diastolic murmur (DM). A prominent fourth heart sound (S,) is recorded at the apex (filter 100 Hz). B, tracings from a 56 year old man with a peak aortic gradient of 92 mm Hg. The phonocardiogram from the second right intercostal space (filter 100 Hz) shows a relatively long mid-systolic murmur (SM). A fourth heart sound (S,) was recorded at the apex (filter 50 Hzfsec).
length (presystolic distension) permits that chamber to achieve the required increase in contractile force. Accordingly, the presence of a fourth heart sound-which is the auscultatory counterpart of presystolic distension-has been used in assessing severity of obstruction in adults with discrete aortic ,stenosis.2 Goldblatt et a1.2 concluded that a fourth heart sound predicted a peak systolic gradient of at least 75 mm Hg. However, because we have encountered an appreciable number of exceptions to this finding, we investigated the problem in 124 postpuberal patients with isolated, discrete aortic stenosis.
Materials and Methods One or more of us personally assessed the history, physical signs, electrocardiogram and cardiac radiograms of each patient. Stable sinus rhythm was obligatory for inclusion in the study, but subjects with P-R intervals exceeding 0.20 second were eliminated. Since an audible fourth heart sound sometimes occurs in normal children, patients less than 12 years old were excluded.2 Patients with idiopathic hypertrophic subaortic stenosis were also excluded because a fourth heart sound in this disorder is unrelated to the degree 180
underwent either transseptal or retrograde catheterization of the left heart chambers or percutaneous left ventricular puncture, or both. A fourth heart sound was considered present only when it was clearly identified on the phonocardiogram as a low frequency presystolic vibration occurring at least 0.07 second after the P wave but before the QRS interval of the electrocardiogram (Fig. 1). This timing corresponds with the second or “audible” component of the fourth heart sound. Peak systolic ventriculoaortic gradients were averaged through at least 1 respiratory cycle; cardiac output was determined after left ventricular injection of indocyanine green dye, and the size of the aortic valve orifice was calculated from Gorlin’s formula. One subject showed no gradient in the control tracing but an abnormal gradient (15 mm Hg) after inhalation of amyl nitrite.
Results A fourth heart sound was recorded in 83 of the 124 patients; the sound was also heard with a stethoscope in 80 ‘of the 88. In the remaining 36 subjects, a fourth heart sound was neither heard nor recorded (Table I). Phonocardiographic and hemodynamic data are shown in Table II. Peak systolic gradient : The 88 patients with I documented fourth heart sound (Groups I to III Table II) were analyzed according to peak systolic gradient (Table III) : Group I: 48 had a peak aortic gradient of a least 75 mm Hg (range 75 to 160, average 103). Group II : 15 had a peak aortic gradient of 60 tm 70 mm Hg (average 66). Group III : 25 had a peak aortic gradient of les than 60 mm Hg (range 0 to 55, average 25). The 36 patients without a fourth heart soun (Groups IV to VI, Table II) were analyzed accord ing to peak systolic gradient (Table IV) : Group IV: 5 had a gradient of at least 75 mr Hg (range 76 to 107, average 90). Group V: 5 had a gradient of 60 to 72 mm H (average 67). Group VI : 26 had a gradient of less than 60 nn Hg (range 14 to 55, average 39). Age and peak systolic. gradient: The 88 PZ tients with a documented fourth heart soun (Groups I to III, Table II) were then analyzed a( The American Journal of CARDIOLOC
FOURTH
TABLE
HEART SOUND
IN AORTIC STENOSIS
II
Phonocerdiographlc
and Hemodynqmic
Data in 124 Cases Average
no. of Cases Group I (gradient Group II (gradient Group III (gradient Group IV (gradient Group V (gradient Group VI (gradient
Age (vr)
49 275
mm
+ (17?4)
Hg) 15
60-75
mm
+
Hg)
(4rz4) 25
<60
mm
SC
Average Peak Gradient (mm Hg)
Average LA Average Aortic A Wave (mm Hg) Valve Orifice (cmz)
103 (75-M) 66
$5)
w-70)
(124)
+ (124)
Hg)
(CT5)
(&)
5 275
mm
(l&3)
Hg)
-
(7&?07)
(12%)
(6J2)
$7) 20 (7-32)
(16%
(l&595)
$5)
5 60-75
mm
Hg)
0.52 (0.2-1.1) 0.61 (0.3-0.9) 1.03 (0.4-2.5) 0.42 (0.3-0.6) 0.62 (0.5-0.9) (O.E4)
Average LV Z Point (mm Hg)
(k480) $6) $3) (3!iO) $3)
26 <60 mm
Hg)
Figures in parentheses indicate range. + = present; - = absent. LA = left atrial; LV = left ventricular; SC = fourth
heart
(2!:1)
sound.
cording to both age and peak systolic gradient (Table IV) : 1. Of 88 patients, 76 were aged 40 years or more, and 37 of them had a gradient of less than 75 mm Hg. In Group I, 39 of 48 patients were aged 40 years or more (range 40 to 74, average 56) ; in Group II, all 15 patients were aged 40 years or more (range 40 to 74, average 54) ; in Group III, 22 of 25 patients were aged 40 years or more (range 40 to 64, average 51). 2. Of the 88 patients, 12 were aged 13 to 40 years, and 2 of them had a gradient of less than 75 mm Hg. These 2 patients were aged 13 and 15 years, respectively.
Discussion In 1875, Pierre-Carl Potain’ wrote the following description of what is now recognized as the atria1 or fourth heart sound. “We distinguish here three sounds, namely: the two normal sounds and an additional sound. . . . As to the abnormal sound, it is placed immediately before [the first heart sound] preceding it sometimes by a very short time. . . . The sound is dull, much more so than the normal sound.” Weitzman4 showed that the audible component of the fourth heart sound originates within the cavity of the recipient ventricle as that
chamber receives blood following atria1 contraction. Potain proposed this mechanism, stating, “This sound results from the abruptness with which dilatation takes place during the presystolic period which corresponds to the contraction of the auricle.“’ This mechanism was confirmed by Muiesan et al.5 in experimental animals. To appreciate Geilesis of fourth heart sound: the clinical significance of the fourth heart sound in aortic stenosis it is necessary to understand the factors upon which the genesis of the sound depends, namely: (1) effective atria1 contraction; (2) unimpeded ventricular filling (absence of atrioventricular valve obstruction) ; and (3) diminished ventricular distensibility (compliance) .” Ventricular hypertrophy sets the stage for the presence of all 3 factors. The compliance of a hypertrophied ventricle is reduced, and its atrium contracts with greater force across an unobstructed atrioventricular valve. Accordingly, fourth heart sounds originating in the left ventricle are auscultatory features of aortic stenosis, systemic hyperTABLE IV Distribution of 124 Cases According Systolic Gradient
~-.
no. of Cases
Average Age (yr) __.._
A. 36 Cases
Without
to Age and Peak
_-
a Fourth
Gradient (mm Hg) -. -.. --
-
Heart Sound
TABLE III Distribution of the 88 Cases with a Fourth Heart Sound According to Peak Systolic Gradients Gradient (mm Hg)
no. of Cases 46 40
275 74 to 60
15 25
VOLUME
28. AUGUST
<60
1971
275 72 to 60 <60
43 34 30
5 5 26 B. 88 Cases
With
76
>40
12
<40
a Fourth Heart _ _ -
Sound -.. 37 gradients <75 2 gradients <75
---
--
181
CAULFIELD
ET AL.
tension and other causes of left ventricular hypertrophy; fourth heart sounds originating in the right ventricle are accompaniments of pulmonary stenosis or pulmonary hypertension. In addition, ischemic heart disease may result in a decrease of left ventricular compliant in the face of effective atria1 contraction, and fourth heart sounds are common in this context.7 Finally, there appears to be a decrease in left ventricular distensibility associated with advancing age, even in subjects without clinical evidence of heart disease. The corollary of this observation is that the incidence of fourth heart sounds has an independent tendency to increase with age per se. Accordingly, the prevalence of a fourth heart sound in aortic stenosis must be examined in the light of both the degree of obstruction and the patient’s age. The possibility that coexisting degenerative heart disease might result in a fourth heart sound in aortic stenosis was recognized in early reports.2 Correlation of aortic gradient and fourth sound: Three questions can now be posed. First, how accurately does an aortic gradient above a certain level predict the pre.sence of a fourth heart sound? Second, how accurately does the presence of a fourth heart sound predict an aortic gradient above a certain level ? Third, if a discrepancy exists in the conclusions based upon these 2 questions, how can this discrepancy be resolved? In answer to the first question, the data show that a gradient of ‘75 mm Hg or more is associated with a 90 percent incidence of a fourth heart sound (Table II). Fifty-three patients had such a gradient, and 48 of them had a fourth heart sound. In fact, the correlation is about as good with gradients of 60 mm Hg or more ; 73 patients had such a gradient, and 63 of them had a fourth heart sound, an incidence of 86 percent (Table II). In answer to the second question, the results show that in patients with aortic stenosis and a fourth heart sound, 45 percent (40 of 88) had a gradient of less than 75 mm Hg and 28 percent (25 of 88) had a gradient of less than 60 mm Hg. In answer to the third question, Effect of age: the inaccuracy of predicting the gradient from the presence of a fourth heart sound as opposed to predicting the fourth heart sound from the gradient
can be resolved by introducing age as a variable. Seventy-six of our patients with fourth heart sounds were aged 40 years or over, and half of them (37 of 76) had gradients of less than 75 mm Hg (Table WE!). Twenty-nine percent (22 of 76) had a gradient of less than 60 mm Hg. A relatively small number of our patients (12) were under 40 years of age, and 2 of them (aged 13 and 15 years) had a fourth heart sound with a gradient of less than 75 mm Hg. Goldblatt and co-workers2 found that 29 of 30 relatively young (average age 32 years) adults with aortic stenosis and a fourth heart sound had a gradient of 75 mm Hg or more. The exception was a man aged 53 years. In older subjects 2 factors-age and aortic stenosis-contribute to the presence of a fourth heart sound, whereas in young adults there is essentially only 1 contributing factor-aortic stenosis. It is, therefore, understandable that in older adults with aortic stenosis the presence of a fourth heart sound is an unreliable sign of severity. The issue is compounded by the observation that aortic stenosis is predominantly a disease of men,8 and degenerative heart disease is more common in men than in women. Conversely, in young adults with aortic stenosis, the presence of a fourth heart sound is likely to indicate a peak gradient of at least 75 mm Hg. Group IV in Table II calls attention to the occasional patient who has severe aortic stenosis but no fourth heart sound. There may be a number of reasons for this discrepancy, namely, a very short P-R interval or factors that hinder auscultation, such as emphysema or obesity. Correlation of fourth sound and A wave: The left atria1 A wave and left ventricular end-diastolic pressure (Z point) tended to be increased (average 17 to 18 mm Hg) in subjects with a gradient over 60 mm Hg and close to normal (average 11 to 13 mm Hg) in subjects with a gradient of less than 60 mm Hg (Table II). However, an occasional fourth heart sound was present in patients with a normal left atria1 A wave, and absent in patients with a large A wave. Both the force of left atria1 contraction and the presystolic condition of the left ventricle appear to be determinants of the fourth heart sound in aortic stenosis.
References Potain P-C: Concerning the cardiac rhythm called gallop rhythm. Bull Sot Med Hop Paris 12:137, 1876. Cited in, Major RH: Classic Descriptions of Disease. Springfield, Ill, Charles C Thomas, 1948, p 388 Goldblatt A, Aygen MM, Rraunwald E: Hemodynamic phonocardiographic correlations of the fourth heart sound in aortic stenosis. Circulation 26:92-98, 1962 Braunwald W, Morrow AG, Cornell WP, et al: Idiopathic hypertrophic subaortic stenosis: clinical, hemodynamic and angiographic manifestations. Amer J Med 29:924945, 1960 The mechanism and significance of the Weftzman D:
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