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Tape-recorded heart sounds: A comparison with mediate auscultation
1150
T h e ]ournal o[ P E D I A T R I C S
Tape-recorded heart sounds: A comparison with mediate auscultation An attempt has been made to evaluate the relative el~iciency o[ utilizing tape-recorded heart sounds [or the detection (screening) o[ children who may have significant cardiac disease and who thus would require more extensive and precise studies to identify their cardiac status. The results #om such a method are compared with those obtained by mediate auscultation.
Lowell W. Perry, M.D.,* Sidney Abraham, Martin E. Levy, M.D., and Cesar A. Caceres, M.D.** WASHINGTON,
D. C.
T H ~ P U R P O S E of this paper is to evaluate a method for the detection (screening) of heart disease. The need for a method to screen for heart disease is illustrated by observations such as those of Friedman and Wells? They found that of 1,572 children who were listed as having an innocent murmur on their school health record, only 1.6 per cent had organic heart disease as determined by re-examination. On the other hand, they found that of 1,464 children examined because their school records indicated the presence of heart disease, only 25.9 per cent actually had organic heart disease. This observation suggests that school children should be evaluated not only to detect previously unknown heart disease but also to correct misdiagnoses of heart disease, and thus eliminate needless fears and inapproFrom the Heart Disease Control Program, Division o[ Chronic Diseases, U. S. Department o[ Health, Education and Wel[are. Address, Department o] Pediatrics, George Washington University School o] Medicine, 725 23rd Street, N.W., Room 101, Washington, D. C. 20037. **Department o[ Medicine, George Washington University School ot Medicine.
priately imposed physical limitations. A community, however, may find it difficult to initiate a program to screen its school population for heart disease, often owing to a lack of available physicians. Even when medical personnel are available, the time required for adequate continuation of the project may be such that relatively few physicians can participate. These facts have stimulated attempts to develop screening techniques for the detection of heart disease which requires as little expenditure of the physician's time as is consistent with accuracy and efficiency. One of these screening techniques utilizes tape-recorded heart sounds. 2-~ Tape recordings permit rapid screening examinations of heart sounds of a large group of subjects and conserve the time and energy of medical personnel. Do the interpretations of tape recordings of heart sounds agree with the findings by mediate (stethoscopic) auscultation? This paper describes a study in which the interpretations of tape-recorded heart sounds are compared with those of mediate auscultation.
Volume 67 Number 6
Tape-recorded heart sounds
METHOD AND MATERIALS Four hundred and twenty-six children between the ages of 4 and 17 years (the total population of a local welfare home) were examined by mediate auscultation and had tape recordings made of their heart sounds. The same areas of the chest (third intercostal space at the left sternal border and the apex) were selected for the tape recordings and for auscultation. All examinations were performed with the child sitting and leaning forward. The position of the child and the two areas of the chest examined were those which have been used in several similar studies?' 8, 7 In order to describe the heart sounds and establish a basis with which to compare the tape recordings, two physicians, one trained in pediatric and the other in adult cardiology, independently examined each child. They were instructed to examine only the 2 areas of the chest mentioned above. They then compared their auscultatory findings. When their findings differed, they immediately reexamined the child and resolved their interpretations of the heart sounds. Tape recordings were made with the Heart Disease Control Program's portable equipment for recording heart sounds. 4 Recordings of each subject were made for 11 and 28 seconds, respectively, on two separate recorders in order to assess the relationship of length of recording to the efficiency of detecting heart sounds.
1 15 1
The tape recordings were listened to independently by 4 physicians, each of whom had previous experience in listening to tape-recorded heart sounds. The auscultators and the tape listeners were instructed to classify the heart sounds of each child into one of 3 groups as follows: Group I, no murmur, normal heart sounds; Group II, innocent murmur, normal heart sounds; and Group III, murmur or other heart sound abnormality suggestive of an organic lesion which should require further examination for adequate evaluation.
RESULTS Interpretation of heart sounds by mediate auscultation. The interpretations of examination by mediate auscultation were as follows: Group I (no murmur), 329 children; Group II (innocent murmur), 87 children; Group III (possible organic lesion), 10 children. Of the 10 children in Group III, 3 had Grade 1-2 basal systolic murmurs with associated second sound abnormalities. Three had Grade 2 basal systolic murmurs with tone characteristics suggestive of associated pathology, but with normal second sounds. In addition, one child had a Grade 2 apical systolic murmur suggestive of mitral insufficiency. Two had, respectively, a Grade 3 and a Grade 4 systolic murmur suggestive of pulmonic stenosis. The single diastolic murmur encountered was of Grade 1 intensity and was thought to represent insufficiency of a semilunar valve.
Table I. A comparison of the classifications of heart sounds from tape recordings with those by mediate auscultation*
correctly
% o[ children with heart sounds suggestive o[ organic disease (Group II1) identified correctly
A
82.6 ( 2 7 2 / 3 2 9 )
42.5 ( 3 7 / 8 7 )
40.0 ( 4 / 1 0 )
B C D Mean
89.2 (273/306) 88.9 (289/325) 91.2 (289/317) 87.9
8.0 (7/87) 15.3 (13/85) 19.3 (16/83) 21.3
20.0 (2/10) 50.0 (5/10) 44.0 (4/9) 38.5
% of children with innocent Tape
listener
~G;foChilld)rendeWlti~e~~
murmur (Group II) identified
*Recordings which were considered to be technically unsatisfactory for interpretation were eliminated from the statistical analysis of the physician who considered the recording unsatisfactory. This accounts for the variations in the denominator used to calculate the percentage of the groups detected. Each listener designated about 2 per cent of the recordings as technically unsatisfactory.
1152
December 1965
Perry et al.
Eight of the 10 abnormalities identified by mediate auscultation were murmurs of Grade 2 intensity or less. Interpretation of heart sounds from tape recordings. For reasons explained in the discussion, only the data obtained from the 11 second recordings are used in this paper. A comparison of the classifications of heart sounds from the tape recordings with the interpretations from mediate auscultation is shown in Table I. Of the children who were classified as Group I (no murmur) on mediate auscultation, 83 to 91 per cent were identified correctly by the individual tape listeners. Of the children classified as Group II (innocent murmur) on mediate auscultation, 8 to 43 per cent were identified correctly by the individual tape listeners. From 20 to 50 per cent of the children in Group III (possible organic lesion) were identified correctly by the individual tape listeners. These data suggest that it is inefficient to have a single listener interpret tape recordings to detect heart sound abnormalities. It is possible to arrange the results to make the method appear to be more efficient: first, by looking at the data as it has been handled in studies which employ this methodology s' 6 and, second, by examining a statistical method which will help the methodology yield the most cases of potential heart disease. This purposeful manipulation of the data illustrates further the capabilities and limitations of the methodology. It has been the practice in the communities which employ the methodology used in this study to have two physicians independently interpret the recorded heart sounds, s, 6 By using the findings of two independent listeners, more heart sound abnormalities will be detected than when the results of a single interpretor are used? In Table II the findings of the 4 physicians who listened to the tape recordings of the children in our study are arranged by pairs. This reveals that from 91 to 95 per cent of the children who were classified as Groups I and II on mediate auscultation were identified correctly as having normal heart sounds
Table II. A comparison of the classifications of heart sounds from tape recordings with those by mediate auscultation-results of individual tape listeners are paired* % of children with % of children with heart sounds sugno murmur or inno- gestive of organic cent murmur [ disease (Group Tape (Groups I and II) I I I ) identified as listeners identified as normal abnormal
A and B A and C A and D B and C B and D CandD Mean
94.1 91.7 94.8 91.3 93.3 91.2 93.0
(370/393) (376/410) (379/400) (355/389) (361/379) (361/396)
40.0 70.0 44.4 60.0 44.4 66.6 544
(4/10) (7/10) (4/9) (6/10) (4/9) (6/9)
*It has been assumed, 2, s probably incorrectly, that physiciaas listening to tape recordings can distinguish an innocent murmur from a murmur which may be associated with an organic lesion. On this basis, children w h o are classified as Group I or Group I I by the tape listeners are considered to he normal and given no farther examination; only children who are classified as Group I l l by the tape listeners are considered tn be abnormal and are referred for complete cardiologic evaluation.
by one or both of the pair of tape listeners. Of the children in Group III on mediate auscultation, from 40 to 70 per cent were identified as having abnormal heart sounds when the interpretations of the tape listeners were paired. Evaluation of the data as illustrated in Table II also indicates that the tape listeners experienced difficulty in detecting innocent murmurs and in distinguishing innocent murmurs from those which may be associated with organic lesions. These differences are illustrated in Table III which lists the interpretations of the 4 tape listeners of the recordings of the subjects in Group III. Of the 10 subjects who were suspected of having an organic lesion by mediate auscultation, 7 were identified as Group I I I when the results of all 4 tape listeners were considered. It will be noted, however, that some of these subjects were considered to have an innocent murmur by the tape listeners. Also, there was considerable variation among the observers. There was agreement between all the tape listeners and the mediate auscultators in only the one instance in which the murmur was quite loud.
Volume 67
Number 6
T a p e - r e c o r d e d heart sounds
115 3
Table I I I . T h e interpretations from mediate auscultation and those from the tape recordings of the 10 children in Group I I I Auscultators' description o[ heart sounds Subject
Murmur
110 143 166
Grade 1-2 basal systolic Grade 1 basal systolic Grade 1 basal systolic
174 208 252 334 358
Grade Grade Grade Grade Grade
421 428
Grade 3 basal systolic Grade 1 basal diastolic
2 basal systolic 2 basal systolic 2 basal systolic 2 apical systolic 4 basal systolic
I
Valve sounds
Second sound split + fixed Second sound split + fixed Second sound single + accentuated Normal Normal Normal Normal Pulmonic component diminished Normal Normal
Tape listeners A
I
B
I
C I D
+
_
.4-
D
+
--
--
U
+
-
+
+
4-_
+.
+
+_
+
-
+
-
+
+
+
+
+
+_
+
+
+
+
--
+
- , G r o u p I, no m u r m u r . +, Group I I , innocent m u r m u r . +, G r o u p I I I , m u r m u r or other abnormalities. U , Technically unsatisfactory; recordings which were considered to be not suitable for interpretation. These were eliminated from the statistical consideration for the physician who listed them as technically unsatisfactory.
T h e data in Table I I I indicate that it may be unreasonable to request a physician to attempt to differentiate between an innocent m u r m u r and a m u r m u r which may be associated with an organic lesion by listening to recorded heart sounds. T h e 4 physicians noted a m u r m u r in the recordings of 9 of the 10 subjects in Group I I I . N o m u r m u r was noted on the 11 second tape of subject 334, but a m u r m u r was identified by one of the readers of the 28 second tape. W h e n oscillographic phonocardiograms were made, a m u r m u r was seen on the recording of each of the 10 subjects in Group I I I . Table I I I also suggests that tape listeners were unable to identify abnormalities of the valve sounds. T h e data in Tables I V and V demonstrate that if the physician were not required to differentiate between an innocent m u r m u r and one which may be associated with an organic lesion, a greater percentage of those placed in Group I I I on mediate auscultation would be detected. For individual listeners 40 to 80 per cent of those with abnormal heart sounds would be identified. Pairing the results of the tape listeners would lead to the detection of 56 to 90 per cent of those with abnormal heart sounds. Increasing the efficiency of the identification of those with abnormal heart sounds, however, would be accompanied by a decrease in the efficiency with which those with normal heart sounds
Table IV. Agreement between interpretation of tape recordings and mediate auscultation when all m u r m u r s noted on tape are considered abnormal
Tape listener
A B C D Mean
% of children with % o[ children with heart sounds sugno murmur or inno- gestive o[ organic cent murmur disease (Group (Groups I and II) I I I ) identified as identified as normal abnormal
76.2 89.8 84.6 87.8 84.5
(317/416) (353/393) (347/410) (351/400)
80.0 40.0 70.0 55.6 61.5
(8/10) (4/10) (7/10) (5/9)
Table V. Agreement between interpretation of tape recordings and mediate auscultation when all murmurs noted on tape are considered abnormal and results of individual tape listeners are paired
Tape listeners
A and B A and D C A and B and C B andD C and D Mean
% o[ children with % o[ children with heart sounds sugno murmur or inno- gestive o[ organic cent murmur [ disease (Group (Groups I and II) l l I ) identified as identified as normal abnormal
68.2 71.0 73.0 75.6 81.0 78.0 74.4
(268/393) (291/410) (292/400) (294/389) (307/379) (309/396)
80.0 90.0 77.8 80.0 55.6
(8/10) (9/10) (7/9) (8/10) (5/9)
88.9
(8/9)
78.9
1 1 54
Perry et al.
are identified correctly. For example, if the results of listeners A and B, as shown in Table V were used, 80 per cent of those with heart sound abnormalities would be detected, but to accomplish this, approximately 32 per cent of the children with normal heart sounds would also require examination by a cardiologist. DISCUSSION
In this study, tape recordings of heart sounds were recorded by a technician from two areas of the chest at the rate of 950 to 300 children per day. Subsequently, a physician listened to the tape recordings at a rate of 100 to 120 per hour. The recorded heart sounds were characterized by the physician: (1) as normal with no evidence of a murmur; (2) as including an innocent murmur; and (3) as being suggestive of organic heart disease. Those children who were found to have murmurs or other heart sound abnormalities, such as a widely split second sound, suggestive of organic disease, were to be referred for further medical evaluation. The use of tape recordings allows the physician to evaluate, within a period of 2 to 3 hours, the heart sounds obtained during a full working day by a technician. This would appear to be an efficient way to conserve about 75 per cent of the physician's time required for primary screening for heart disease. When two physicians listen to each tape, as has been the practice in most screening studies of this type, z, 3, 6, 7 4 to 6 hours (i.e., 2 to 3 hours per physician) are required to interpret the sounds obtained by a technician within a period of 8 hours. This plan would conserve 25 to 50 per cent of the physician's time. Our results show that there is a significant difference in the interpretation of heart sounds by mediate auscultation and by listening to tape recordings. Dobrow and associates 5 demonstrated that, although abnormal heart sounds are recorded on magnetic tape, a large percentage of low intensity murmurs will not be detected by the human interpretor listening to the tape. It would appear that the majority of murmurs of Grade 3
December 1965
intensity and above will be detected. Miller and associates 3 also demonstrated that a great percentage of loud murmurs will be detected with this technique. In our study, most innocent murmurs, which are generally of low intensity, were not detected by physicians listening to magnetic tape recordings. Originally, the decision to use 11 seconds of tape-recorded heart sounds to detect abnormalities was an arbitrary one. In this study a longer duration (28 seconds) also was used to see if results would be improved. The fatigue, boredom, and soporific effects involved in listening to tape-recorded heart sounds probably account for the fact that the efficiency of the technique was not improved with the longer recording time. Indeed, our listeners found it difficult to concentrate, even on the 11 second recordings, for longer than an hour at a time. Tape recordings will be useful in the detection of heart disease only when there is a murmur or other abnormality of the heart sounds, and only if these are present at the recording sites. Our study demonstrates that many of these abnormalities may be undetected by physician listeners even when the sounds are actually recorded on tile tape. This observation supports the recommendation that if tape recordings are to be used for the detection of heart disease, the recording techniques should be part of a multiphasic screening program? Furthermore, it is evident that the results of heart disease screening studies which utilize only tape recordings cannot be acceptable as reliable indicators of the incidence and prevalence of heart disease. It would appear that utilization of taperecorded heart sounds provides a potential technique for the detection of heart disease when large populations must be examined. It is our inability to extract the information contained on the tapes that seems to be one of the major weaknesses of the method. The development of transducers that bring out the maximum amount of clinically significant data in heart sounds will be helpful. Recording apparatus with the highest possible signalto-noise ratio may also improve the efficiency
Volume 67 Number 6
of the method. A promising potential source of improvement lies in the new techniques for display and analysis of heart sounds, especially the utilization of computer analysis of the sounds, which are being developed. Until such time as these improvements are perfected, it would be unwise to recommend the use of tape-recorded heart sounds as a routine procedure in mass screening for heart disease. SUMMARY
Screening for heart disease with tape-recorded heart sounds has been evaluated by comparing the interpretations of tape recordings with the interpretations of mediate auscultation when both examinations were from the same area of the chest. T h e results suggest that by listening to tape recordings a physician can easily detect loud murmurs. There is, however, a substantial difference between the interpretations of mediate auscultation and of tape recordings when low intensity murmurs or subtle heart sound abnormalities are present. T a p e listeners frequently m a y fail to detect low intensity murmurs. This was reflected in the failure to identify low intensity murmurs which m a y be associated with an organic lesion and innocent murmurs. T h e results also indicate that it is unreasonable to expect a physician to differentiate between an innocent m u r m u r and other low intensity murmurs by listening to tape recordings. Modifications which are underway m a y increase the efficiency of the use of tape-recorded heart sounds in screening for heart
Tape-recorded heart sounds
1155
disease in large groups of persons. Until these improvements are completed, however, it would be wise to consider the method as an experimental technique. The authors wish to thank the following for their help with the project: Drs. Juan B. Calatayud, D. Jackson Coleman, Robert J. Dobrow, Stuart W. Rosner; Messrs. Morton Gilbert, Morton Robins, David Winer, William Stevens, Robert Warren, John Saunders, Emmett Pope, Jerome Wiener; Misses Lillian Dick, Jean Galijas, and Sondra Swinehart; and Mines. Margaret McAllister, Eleanor Wise, and Joyce Teague. REFERENCES
1. Friedman, S., and Wells, C. R. E.: Experience in secondary screening of cardiac suspects of school age, J. P~DIAT. 49: 410, 1956. 2. Abrams, I.: Evaluation of tape recording of heart sounds on a mass scale in school children, J. School Health 33: 62, 1963. 3. Miller, R. A., Smith, J., Stamler, J., Hahnemann, B., Paul, M. H., Abrams, I., Halt, G., Edelman, J., Willard, J., and Stevens, W.: The detection of heart disease in children. Results of a mass field trial with use of tape-recorded heart sounds, Circulation 25: 85, 1962. 4. Coleman, D. J., Dobrow, R. J., Whiteman, J. R., Calatayud, J. B., and Caceres, C. A.: A new portable heart sound recording system, Am. J. M. Electronics 3: 192, 1964. 5. Dobrow, R. J., Galatayud, J. B., Abraham, S., and Caceres, C. A.: The study of physician variation of heart sound interpretation, M. Ann. District of Columbia 33: 305, 1964. 6. Morton, W., and Huhn, L.: Evaluation of tape-recorded heart sounds as a heart disease screening method. Results from students in grades 9-12. Unpublished data. 7. Naiman, R. A., and Barrow, J. G.: Heart disease screening in school children: A comparison between clinical screening and heart sound recording, Circulation 29: 708, 1964.
T h e ]ournal o[ P E D I A T R I C S
Tape-recorded heart sounds: A comparison with mediate auscultation An attempt has been made to evaluate the relative el~iciency o[ utilizing tape-recorded heart sounds [or the detection (screening) o[ children who may have significant cardiac disease and who thus would require more extensive and precise studies to identify their cardiac status. The results #om such a method are compared with those obtained by mediate auscultation.
Lowell W. Perry, M.D.,* Sidney Abraham, Martin E. Levy, M.D., and Cesar A. Caceres, M.D.** WASHINGTON,
D. C.
T H ~ P U R P O S E of this paper is to evaluate a method for the detection (screening) of heart disease. The need for a method to screen for heart disease is illustrated by observations such as those of Friedman and Wells? They found that of 1,572 children who were listed as having an innocent murmur on their school health record, only 1.6 per cent had organic heart disease as determined by re-examination. On the other hand, they found that of 1,464 children examined because their school records indicated the presence of heart disease, only 25.9 per cent actually had organic heart disease. This observation suggests that school children should be evaluated not only to detect previously unknown heart disease but also to correct misdiagnoses of heart disease, and thus eliminate needless fears and inapproFrom the Heart Disease Control Program, Division o[ Chronic Diseases, U. S. Department o[ Health, Education and Wel[are. Address, Department o] Pediatrics, George Washington University School o] Medicine, 725 23rd Street, N.W., Room 101, Washington, D. C. 20037. **Department o[ Medicine, George Washington University School ot Medicine.
priately imposed physical limitations. A community, however, may find it difficult to initiate a program to screen its school population for heart disease, often owing to a lack of available physicians. Even when medical personnel are available, the time required for adequate continuation of the project may be such that relatively few physicians can participate. These facts have stimulated attempts to develop screening techniques for the detection of heart disease which requires as little expenditure of the physician's time as is consistent with accuracy and efficiency. One of these screening techniques utilizes tape-recorded heart sounds. 2-~ Tape recordings permit rapid screening examinations of heart sounds of a large group of subjects and conserve the time and energy of medical personnel. Do the interpretations of tape recordings of heart sounds agree with the findings by mediate (stethoscopic) auscultation? This paper describes a study in which the interpretations of tape-recorded heart sounds are compared with those of mediate auscultation.
Volume 67 Number 6
Tape-recorded heart sounds
METHOD AND MATERIALS Four hundred and twenty-six children between the ages of 4 and 17 years (the total population of a local welfare home) were examined by mediate auscultation and had tape recordings made of their heart sounds. The same areas of the chest (third intercostal space at the left sternal border and the apex) were selected for the tape recordings and for auscultation. All examinations were performed with the child sitting and leaning forward. The position of the child and the two areas of the chest examined were those which have been used in several similar studies?' 8, 7 In order to describe the heart sounds and establish a basis with which to compare the tape recordings, two physicians, one trained in pediatric and the other in adult cardiology, independently examined each child. They were instructed to examine only the 2 areas of the chest mentioned above. They then compared their auscultatory findings. When their findings differed, they immediately reexamined the child and resolved their interpretations of the heart sounds. Tape recordings were made with the Heart Disease Control Program's portable equipment for recording heart sounds. 4 Recordings of each subject were made for 11 and 28 seconds, respectively, on two separate recorders in order to assess the relationship of length of recording to the efficiency of detecting heart sounds.
1 15 1
The tape recordings were listened to independently by 4 physicians, each of whom had previous experience in listening to tape-recorded heart sounds. The auscultators and the tape listeners were instructed to classify the heart sounds of each child into one of 3 groups as follows: Group I, no murmur, normal heart sounds; Group II, innocent murmur, normal heart sounds; and Group III, murmur or other heart sound abnormality suggestive of an organic lesion which should require further examination for adequate evaluation.
RESULTS Interpretation of heart sounds by mediate auscultation. The interpretations of examination by mediate auscultation were as follows: Group I (no murmur), 329 children; Group II (innocent murmur), 87 children; Group III (possible organic lesion), 10 children. Of the 10 children in Group III, 3 had Grade 1-2 basal systolic murmurs with associated second sound abnormalities. Three had Grade 2 basal systolic murmurs with tone characteristics suggestive of associated pathology, but with normal second sounds. In addition, one child had a Grade 2 apical systolic murmur suggestive of mitral insufficiency. Two had, respectively, a Grade 3 and a Grade 4 systolic murmur suggestive of pulmonic stenosis. The single diastolic murmur encountered was of Grade 1 intensity and was thought to represent insufficiency of a semilunar valve.
Table I. A comparison of the classifications of heart sounds from tape recordings with those by mediate auscultation*
correctly
% o[ children with heart sounds suggestive o[ organic disease (Group II1) identified correctly
A
82.6 ( 2 7 2 / 3 2 9 )
42.5 ( 3 7 / 8 7 )
40.0 ( 4 / 1 0 )
B C D Mean
89.2 (273/306) 88.9 (289/325) 91.2 (289/317) 87.9
8.0 (7/87) 15.3 (13/85) 19.3 (16/83) 21.3
20.0 (2/10) 50.0 (5/10) 44.0 (4/9) 38.5
% of children with innocent Tape
listener
~G;foChilld)rendeWlti~e~~
murmur (Group II) identified
*Recordings which were considered to be technically unsatisfactory for interpretation were eliminated from the statistical analysis of the physician who considered the recording unsatisfactory. This accounts for the variations in the denominator used to calculate the percentage of the groups detected. Each listener designated about 2 per cent of the recordings as technically unsatisfactory.
1152
December 1965
Perry et al.
Eight of the 10 abnormalities identified by mediate auscultation were murmurs of Grade 2 intensity or less. Interpretation of heart sounds from tape recordings. For reasons explained in the discussion, only the data obtained from the 11 second recordings are used in this paper. A comparison of the classifications of heart sounds from the tape recordings with the interpretations from mediate auscultation is shown in Table I. Of the children who were classified as Group I (no murmur) on mediate auscultation, 83 to 91 per cent were identified correctly by the individual tape listeners. Of the children classified as Group II (innocent murmur) on mediate auscultation, 8 to 43 per cent were identified correctly by the individual tape listeners. From 20 to 50 per cent of the children in Group III (possible organic lesion) were identified correctly by the individual tape listeners. These data suggest that it is inefficient to have a single listener interpret tape recordings to detect heart sound abnormalities. It is possible to arrange the results to make the method appear to be more efficient: first, by looking at the data as it has been handled in studies which employ this methodology s' 6 and, second, by examining a statistical method which will help the methodology yield the most cases of potential heart disease. This purposeful manipulation of the data illustrates further the capabilities and limitations of the methodology. It has been the practice in the communities which employ the methodology used in this study to have two physicians independently interpret the recorded heart sounds, s, 6 By using the findings of two independent listeners, more heart sound abnormalities will be detected than when the results of a single interpretor are used? In Table II the findings of the 4 physicians who listened to the tape recordings of the children in our study are arranged by pairs. This reveals that from 91 to 95 per cent of the children who were classified as Groups I and II on mediate auscultation were identified correctly as having normal heart sounds
Table II. A comparison of the classifications of heart sounds from tape recordings with those by mediate auscultation-results of individual tape listeners are paired* % of children with % of children with heart sounds sugno murmur or inno- gestive of organic cent murmur [ disease (Group Tape (Groups I and II) I I I ) identified as listeners identified as normal abnormal
A and B A and C A and D B and C B and D CandD Mean
94.1 91.7 94.8 91.3 93.3 91.2 93.0
(370/393) (376/410) (379/400) (355/389) (361/379) (361/396)
40.0 70.0 44.4 60.0 44.4 66.6 544
(4/10) (7/10) (4/9) (6/10) (4/9) (6/9)
*It has been assumed, 2, s probably incorrectly, that physiciaas listening to tape recordings can distinguish an innocent murmur from a murmur which may be associated with an organic lesion. On this basis, children w h o are classified as Group I or Group I I by the tape listeners are considered to he normal and given no farther examination; only children who are classified as Group I l l by the tape listeners are considered tn be abnormal and are referred for complete cardiologic evaluation.
by one or both of the pair of tape listeners. Of the children in Group III on mediate auscultation, from 40 to 70 per cent were identified as having abnormal heart sounds when the interpretations of the tape listeners were paired. Evaluation of the data as illustrated in Table II also indicates that the tape listeners experienced difficulty in detecting innocent murmurs and in distinguishing innocent murmurs from those which may be associated with organic lesions. These differences are illustrated in Table III which lists the interpretations of the 4 tape listeners of the recordings of the subjects in Group III. Of the 10 subjects who were suspected of having an organic lesion by mediate auscultation, 7 were identified as Group I I I when the results of all 4 tape listeners were considered. It will be noted, however, that some of these subjects were considered to have an innocent murmur by the tape listeners. Also, there was considerable variation among the observers. There was agreement between all the tape listeners and the mediate auscultators in only the one instance in which the murmur was quite loud.
Volume 67
Number 6
T a p e - r e c o r d e d heart sounds
115 3
Table I I I . T h e interpretations from mediate auscultation and those from the tape recordings of the 10 children in Group I I I Auscultators' description o[ heart sounds Subject
Murmur
110 143 166
Grade 1-2 basal systolic Grade 1 basal systolic Grade 1 basal systolic
174 208 252 334 358
Grade Grade Grade Grade Grade
421 428
Grade 3 basal systolic Grade 1 basal diastolic
2 basal systolic 2 basal systolic 2 basal systolic 2 apical systolic 4 basal systolic
I
Valve sounds
Second sound split + fixed Second sound split + fixed Second sound single + accentuated Normal Normal Normal Normal Pulmonic component diminished Normal Normal
Tape listeners A
I
B
I
C I D
+
_
.4-
D
+
--
--
U
+
-
+
+
4-_
+.
+
+_
+
-
+
-
+
+
+
+
+
+_
+
+
+
+
--
+
- , G r o u p I, no m u r m u r . +, Group I I , innocent m u r m u r . +, G r o u p I I I , m u r m u r or other abnormalities. U , Technically unsatisfactory; recordings which were considered to be not suitable for interpretation. These were eliminated from the statistical consideration for the physician who listed them as technically unsatisfactory.
T h e data in Table I I I indicate that it may be unreasonable to request a physician to attempt to differentiate between an innocent m u r m u r and a m u r m u r which may be associated with an organic lesion by listening to recorded heart sounds. T h e 4 physicians noted a m u r m u r in the recordings of 9 of the 10 subjects in Group I I I . N o m u r m u r was noted on the 11 second tape of subject 334, but a m u r m u r was identified by one of the readers of the 28 second tape. W h e n oscillographic phonocardiograms were made, a m u r m u r was seen on the recording of each of the 10 subjects in Group I I I . Table I I I also suggests that tape listeners were unable to identify abnormalities of the valve sounds. T h e data in Tables I V and V demonstrate that if the physician were not required to differentiate between an innocent m u r m u r and one which may be associated with an organic lesion, a greater percentage of those placed in Group I I I on mediate auscultation would be detected. For individual listeners 40 to 80 per cent of those with abnormal heart sounds would be identified. Pairing the results of the tape listeners would lead to the detection of 56 to 90 per cent of those with abnormal heart sounds. Increasing the efficiency of the identification of those with abnormal heart sounds, however, would be accompanied by a decrease in the efficiency with which those with normal heart sounds
Table IV. Agreement between interpretation of tape recordings and mediate auscultation when all m u r m u r s noted on tape are considered abnormal
Tape listener
A B C D Mean
% of children with % o[ children with heart sounds sugno murmur or inno- gestive o[ organic cent murmur disease (Group (Groups I and II) I I I ) identified as identified as normal abnormal
76.2 89.8 84.6 87.8 84.5
(317/416) (353/393) (347/410) (351/400)
80.0 40.0 70.0 55.6 61.5
(8/10) (4/10) (7/10) (5/9)
Table V. Agreement between interpretation of tape recordings and mediate auscultation when all murmurs noted on tape are considered abnormal and results of individual tape listeners are paired
Tape listeners
A and B A and D C A and B and C B andD C and D Mean
% o[ children with % o[ children with heart sounds sugno murmur or inno- gestive o[ organic cent murmur [ disease (Group (Groups I and II) l l I ) identified as identified as normal abnormal
68.2 71.0 73.0 75.6 81.0 78.0 74.4
(268/393) (291/410) (292/400) (294/389) (307/379) (309/396)
80.0 90.0 77.8 80.0 55.6
(8/10) (9/10) (7/9) (8/10) (5/9)
88.9
(8/9)
78.9
1 1 54
Perry et al.
are identified correctly. For example, if the results of listeners A and B, as shown in Table V were used, 80 per cent of those with heart sound abnormalities would be detected, but to accomplish this, approximately 32 per cent of the children with normal heart sounds would also require examination by a cardiologist. DISCUSSION
In this study, tape recordings of heart sounds were recorded by a technician from two areas of the chest at the rate of 950 to 300 children per day. Subsequently, a physician listened to the tape recordings at a rate of 100 to 120 per hour. The recorded heart sounds were characterized by the physician: (1) as normal with no evidence of a murmur; (2) as including an innocent murmur; and (3) as being suggestive of organic heart disease. Those children who were found to have murmurs or other heart sound abnormalities, such as a widely split second sound, suggestive of organic disease, were to be referred for further medical evaluation. The use of tape recordings allows the physician to evaluate, within a period of 2 to 3 hours, the heart sounds obtained during a full working day by a technician. This would appear to be an efficient way to conserve about 75 per cent of the physician's time required for primary screening for heart disease. When two physicians listen to each tape, as has been the practice in most screening studies of this type, z, 3, 6, 7 4 to 6 hours (i.e., 2 to 3 hours per physician) are required to interpret the sounds obtained by a technician within a period of 8 hours. This plan would conserve 25 to 50 per cent of the physician's time. Our results show that there is a significant difference in the interpretation of heart sounds by mediate auscultation and by listening to tape recordings. Dobrow and associates 5 demonstrated that, although abnormal heart sounds are recorded on magnetic tape, a large percentage of low intensity murmurs will not be detected by the human interpretor listening to the tape. It would appear that the majority of murmurs of Grade 3
December 1965
intensity and above will be detected. Miller and associates 3 also demonstrated that a great percentage of loud murmurs will be detected with this technique. In our study, most innocent murmurs, which are generally of low intensity, were not detected by physicians listening to magnetic tape recordings. Originally, the decision to use 11 seconds of tape-recorded heart sounds to detect abnormalities was an arbitrary one. In this study a longer duration (28 seconds) also was used to see if results would be improved. The fatigue, boredom, and soporific effects involved in listening to tape-recorded heart sounds probably account for the fact that the efficiency of the technique was not improved with the longer recording time. Indeed, our listeners found it difficult to concentrate, even on the 11 second recordings, for longer than an hour at a time. Tape recordings will be useful in the detection of heart disease only when there is a murmur or other abnormality of the heart sounds, and only if these are present at the recording sites. Our study demonstrates that many of these abnormalities may be undetected by physician listeners even when the sounds are actually recorded on tile tape. This observation supports the recommendation that if tape recordings are to be used for the detection of heart disease, the recording techniques should be part of a multiphasic screening program? Furthermore, it is evident that the results of heart disease screening studies which utilize only tape recordings cannot be acceptable as reliable indicators of the incidence and prevalence of heart disease. It would appear that utilization of taperecorded heart sounds provides a potential technique for the detection of heart disease when large populations must be examined. It is our inability to extract the information contained on the tapes that seems to be one of the major weaknesses of the method. The development of transducers that bring out the maximum amount of clinically significant data in heart sounds will be helpful. Recording apparatus with the highest possible signalto-noise ratio may also improve the efficiency
Volume 67 Number 6
of the method. A promising potential source of improvement lies in the new techniques for display and analysis of heart sounds, especially the utilization of computer analysis of the sounds, which are being developed. Until such time as these improvements are perfected, it would be unwise to recommend the use of tape-recorded heart sounds as a routine procedure in mass screening for heart disease. SUMMARY
Screening for heart disease with tape-recorded heart sounds has been evaluated by comparing the interpretations of tape recordings with the interpretations of mediate auscultation when both examinations were from the same area of the chest. T h e results suggest that by listening to tape recordings a physician can easily detect loud murmurs. There is, however, a substantial difference between the interpretations of mediate auscultation and of tape recordings when low intensity murmurs or subtle heart sound abnormalities are present. T a p e listeners frequently m a y fail to detect low intensity murmurs. This was reflected in the failure to identify low intensity murmurs which m a y be associated with an organic lesion and innocent murmurs. T h e results also indicate that it is unreasonable to expect a physician to differentiate between an innocent m u r m u r and other low intensity murmurs by listening to tape recordings. Modifications which are underway m a y increase the efficiency of the use of tape-recorded heart sounds in screening for heart
Tape-recorded heart sounds
1155
disease in large groups of persons. Until these improvements are completed, however, it would be wise to consider the method as an experimental technique. The authors wish to thank the following for their help with the project: Drs. Juan B. Calatayud, D. Jackson Coleman, Robert J. Dobrow, Stuart W. Rosner; Messrs. Morton Gilbert, Morton Robins, David Winer, William Stevens, Robert Warren, John Saunders, Emmett Pope, Jerome Wiener; Misses Lillian Dick, Jean Galijas, and Sondra Swinehart; and Mines. Margaret McAllister, Eleanor Wise, and Joyce Teague. REFERENCES
1. Friedman, S., and Wells, C. R. E.: Experience in secondary screening of cardiac suspects of school age, J. P~DIAT. 49: 410, 1956. 2. Abrams, I.: Evaluation of tape recording of heart sounds on a mass scale in school children, J. School Health 33: 62, 1963. 3. Miller, R. A., Smith, J., Stamler, J., Hahnemann, B., Paul, M. H., Abrams, I., Halt, G., Edelman, J., Willard, J., and Stevens, W.: The detection of heart disease in children. Results of a mass field trial with use of tape-recorded heart sounds, Circulation 25: 85, 1962. 4. Coleman, D. J., Dobrow, R. J., Whiteman, J. R., Calatayud, J. B., and Caceres, C. A.: A new portable heart sound recording system, Am. J. M. Electronics 3: 192, 1964. 5. Dobrow, R. J., Galatayud, J. B., Abraham, S., and Caceres, C. A.: The study of physician variation of heart sound interpretation, M. Ann. District of Columbia 33: 305, 1964. 6. Morton, W., and Huhn, L.: Evaluation of tape-recorded heart sounds as a heart disease screening method. Results from students in grades 9-12. Unpublished data. 7. Naiman, R. A., and Barrow, J. G.: Heart disease screening in school children: A comparison between clinical screening and heart sound recording, Circulation 29: 708, 1964.