Study
of Respiratory Influence on the Intensity of Heart Sound in Normal Subjects
Kyozo Ishikawa, M.D., F.I.C.A.,
and Takeshi Tamura, M.D.
TOKYO, JAPAN
Abstract
The amplitudes of the first and second heart sounds were recorded during quiet natural breathing in 31 normal subjects. A total of 3,656 and 3,016 heart beats were available at the apex and pulmonic areas respectively. The intensities of the first and second heart sounds were found to be increased during expiration. This respiratory tendency in the heart sounds was less prominent during the transitional phase between expiration and inspiration. Therefore we suggest that respiratory changes in heart sounds should be evaluated with a heart beat located at or close to the center of each inspiration and expiration. Respiratory alteration in the intensity of heart sounds is one of the commonest auscultatory pitfalls. Auscultatory evaluation of the intensity of heart sounds should thus be performed carefully, with the respiratory changes kept in mind. Introduction It is generally accepted that the intensity of the cardiac sounds provides useful information about a variety of cardiac conditions. The intensity of the cardiac sounds is known to be influenced by numerous factors such as the force of cardiac valve closure, the presence or absence of valvular insufficiency, the valve positions at the onset of their closure, and the mobility of the valves. Interest has focused principally on the mechanism of the genesis of heart sounds,’-’ and little attention has been given to respiratory changes in the intensity of heart sounds. A review of the literature in English shows that Heinzen is the only investigator who has made extensive studies on the respiratory changes in cardiac sounds.’ He pointed out that the first and second sounds tended to increase toward the peak of inspiration and that they tended to decrease toward expiration. In the course of a phonocardiographic study giving special emphasis to respiratory changes in cardiac sounds, we developed the strong impression that the cardiac sounds tended to increase during expiration and to decrease during inspiration. This finding was quite contrary to the observations of Heinzen.
From
Kyorin University,
School of Medicine,
Tokyo, Japan,
and Yamato
Prefecture, Japan.
750
Downloaded from ang.sagepub.com at UNIVERSITY OF ALBERTA LIBRARY on June 28, 2015
City Hospital, Kanagawa
751 The
present research was therefore undertaken
extensive study of respiratory changes in the cardiac sounds of normal subjects. The results are essential to the proper clinical evaluation of heart sounds in a variety of clinical as an
settings. Materials and Methods
Thirty-one normal subjects comprised the study group. There were 23 men and 8 women whose ages ranged from 13 to 47 with a mean of 29 years. A crystal microphone was used to record phonocardiograms (PCGs) with all subjects because of its sensitivity and practical convenience. The microphone was firmly affixed to the anterior chest at the apex and at the pulmonic area with specially designed adhesive tape. The subjects were made to lie supine on a bed in a soundproof room. They were instructed to breathe normally and to avoid yawning or excessive thoracic excursions. The frequency response of the filter of our recording system comprised a cutoff frequency of 160 Hz and a maximum gradient of 24 db/Oct. The recording speed was 100 mm/sec. All PCGs were taken with a Sanei Heart Sound preamplifier and recorded on a photographic recorder, together with a simultaneously recording electrocardiographic lead and respiratory curve. An electrocardiographic lead showing distinct Q and P waves was selected. The respiratory tracing was maintained throughout the PCG recording with a strain-gauge transducer connected to a rubber belt around the boundary between the chest and abdomen. All 31 subjects had normal electrocardiograms, in which the PR interval was between 0.12 and 0.20 sec and was virtually constant in each subject throughout the PCG recording. Premature beats and marked sinus arrhythmia were not observed in any subject. PCGs were recorded during more than 10 consecutive respiratory cycles. Longer tracings were necessary in subjects with a less uniform respiratory pattern. The amplitudes of the first heart sound, S(I), and the aortic component, S(IIA), and pulmonic component, S(IIP), of the second heart sound were measured. All these heart sounds were divided into those during inspiration (Ins) and those during expiration (Exp) on the basis of the respiratory curve. The respiratory effect on the intensity of heart sounds was analyzed by using a single beat located at or close to the center of each Ins and Exp. Amplification of the recording system was adjusted for each subject in order to ensure the proper amplitudes of the heart sounds. In each subj ect the statistical significance of the difference in intensity of the heart sounds between Ins and Exp was tested by the student’s t test. Results All pertinent data are presented in Table 1. At the apex, S(I) and S(IIA) were identified sufficiently clearly for precise analysis to be made in 30 of the 311
Downloaded from ang.sagepub.com at UNIVERSITY OF ALBERTA LIBRARY on June 28, 2015
752 TABLE 1
Respiratory Changes
in the
Intensity of Heart Sounds in 31 Normal Subjects
Exp: expiration; Ins: inspiration; I: first heart sound; IIA: aortic component of second heart sound; 0: tensity of heart sound in Exp > that in Ins; 0: intensity of heart circle sound in Exp that in Ins.
in-
=
subjects (97%), while S(IIP) was identified in 19 of the 31 (61%). At the pulmonic area, S(I) and S(IIP) were both identified in 23 of the 31 subjects (74%), and S(IIA) was noted in 26 of the 31 (84%). Table 2 summarizes the respiratory effects on the intensity of the heart sounds. 1. At the apex: Twenty-six of 30 subjects (87%), 21 of 30 (70%), and 13 of 19 (68%) showed expiratory increases in the intensity of S(I) and S(IIA), and 6 of
Downloaded from ang.sagepub.com at UNIVERSITY OF ALBERTA LIBRARY on June 28, 2015
753 Comparison of Magnitude of
*
Based
on a
TABLE 2 Heart Sounds Between
Expiration and Inspiration
*
single heart beat located at or near the center of each expiration and inspiration.
19
(32%) showed no respiratory change in the intensity of S(I), S(IIA), and S(IIP). Four of 30 subjects (13%), 9 of 30 (30%), and 6 of 19 (32%) showed no respiratory change in the intensity of S(I), S(IIA), and S(IIP) respectively. No
subject
revealed
an
inspiratory
increase in the
intensity
of any of the cardiac
sounds.
representative example in which we observed expiratory increases in the amplitude of S(I) and S(IIA), and a slight inspiratory increase in the amplitude of S(IIP). 2. At the pulmonic area: Nineteen of 23 subjects (83%), 25 of 26 (96%), and 20 of 23 (87%) showed expiratory increases in the intensity of S(I), S(IIA), and S(IIP) respectively. Four of 23 subjects (17%), 1 of 26 (4%), and 3 of 23 (13%) revealed no respiratory changes in the intensity of S(I), S(IIA), and S(IIP) reFigure
I is
a
FIG. 1. A representative PCG tracing recorded in a 19-year-old man (Case 5). Note the expiratory inin the amplitude of S(I) and S(IIA), and the inspiratory increase in the amplitude of S(IIP). As a whole, the intensities of S(I), S(IIA), and S(IIP) were statistically increased in Exp compared to those in Ins (see Table 1). creases
Downloaded from ang.sagepub.com at UNIVERSITY OF ALBERTA LIBRARY on June 28, 2015
754
spectively. No subject revealed an inspiratory increase in the intensity of any of the cardiac sounds. Discussion
great amount of diagnostic information can be obtained from heart sounds. However, auscultation is essentially a subjective matter. The phy-
Clearly,
a
sician usually estimates the intensity of the heart sounds and murmurs solely from personal experience, taking the respiratory effect on cardiac phenomena into consideration. It is generally known that the PR interval and RR interval on electrocardiograms show a close relationship to the intensities of heart sounds. In this study, however, no remarkable change in these intervals was observed throughout the PCG recordings for each subject. The data obtained in this study indicate that, in 31 normal subjects, the amplitudes of S(I), S(IIA), and S(IIP) tended to increase during Exp. This observation is in sharp contrast with the report of Heinzen,’ who indicated that S(I), S(IIA), and S(IIP) tended to increase toward the peak of Ins and tended to decrease toward the peak of Exp. The reason for the discrepancy in results between the two studies is unclear. In some subjects it was rather difficult to draw a clear line between Ins and Exp. The fact that inspiration causes more noises in PCG tracings than expiration was of some help in marking a more precise separation between Ins and Exp. A carryover effect of Ins on Exp and vice versa can reasonably be expected. This carryover effect may render it difficult to investigate the independent influences of inspiration and expiration on heart sounds. Bearing this in mind, we selected single beats at or close to the center of both Ins and Exp for further analysis. This analysis accentuated the basic finding that the heart sound tended to increase during Exp and to decrease during Ins. We found that the respiratory change in the intensity of S(I) was more consistent than that of S(IIA) or S(IIP), although the reason for this remains undetermined. The inspiratory decrease in the intensity of the heart sounds may arise mainly from the insulating effect of the inflated lung on the transmission of heart sounds to the body surface, although other factors must be considered. Hemodynamic differences between Ins and Exp could be involved in the genesis of such respiratory changes. Virtually no quantitative approach has been devised for the analysis of heart sounds and murmurs because of the considerable difficulties involved in calibrating such sounds and murmurs. Indeed, the fact that no truly reliable calibration is available in PCG analysis represents an enormous barrier to further progress in the field of clinical PCG. In the daily clinical situation, it is not infrequent to encounter problems in judging the intensity of heart sounds. Respiratory alteration in the intensity of
Downloaded from ang.sagepub.com at UNIVERSITY OF ALBERTA LIBRARY on June 28, 2015
755
heart sounds is one of the commonest auscultatory pitfalls. Auscultatory evaluation of the intensity of heart sounds should thus be performed carefully, with the respiratory changes always in mind. On the basis of this study it should also be emphasized that the intensity of the heart sounds is considerably influenced even by quiet natural breathing. Kyozo Ishikawa, M. D., F.I.C.A.
of Medicine Kyorin University School 6-20
Shinkawa, Mitaka City
Tokyo, Japan References 1.
Shah, P. M., Mori, M., MacCanon, D. M.,
et
correlates of the various components of the first heart sound. Circ. Res., 12: 386, 1962. 2. Mori, M., Shah, P. M., MacCanon, D. M., et al.: Hemodynamic correlates of the various components of the second heart sound. Caral.:
3.
Hemodynamic
diologia, 44: 5, 1964. Bagaert, A.: New concept
the mechanism of the first heart sound. Am. J. Cardiol., 18: 253, 1966. on
4. Sakamoto, T., Kusukawa, R., MacCanon, D. M., et al.: Hemodynamic determinants of
the
amplitude
of the first heart sound. Circ.
Res., 16: 45, 1965. 5. Piemme, T. E., Barnete, G. O., Dexter, L.:
Relationship of heart sounds to accelaration of blood flow. Circ. Res., 18: 303, 1966. 6. Harris, A., Sutton, G.: Second heart sound in normal subjects. Br. Heart J., 30: 739, 1968. 7. Kardalinos, A.: The second heart sound. Am. Heart J., 64: 610, 1962. 8. Heinzen, P.: Quantitative Phonokardiographie. Stuttgart, Georg Thieme Verlag, 1960.
Downloaded from ang.sagepub.com at UNIVERSITY OF ALBERTA LIBRARY on June 28, 2015
of Respiratory Influence on the Intensity of Heart Sound in Normal Subjects
Kyozo Ishikawa, M.D., F.I.C.A.,
and Takeshi Tamura, M.D.
TOKYO, JAPAN
Abstract
The amplitudes of the first and second heart sounds were recorded during quiet natural breathing in 31 normal subjects. A total of 3,656 and 3,016 heart beats were available at the apex and pulmonic areas respectively. The intensities of the first and second heart sounds were found to be increased during expiration. This respiratory tendency in the heart sounds was less prominent during the transitional phase between expiration and inspiration. Therefore we suggest that respiratory changes in heart sounds should be evaluated with a heart beat located at or close to the center of each inspiration and expiration. Respiratory alteration in the intensity of heart sounds is one of the commonest auscultatory pitfalls. Auscultatory evaluation of the intensity of heart sounds should thus be performed carefully, with the respiratory changes kept in mind. Introduction It is generally accepted that the intensity of the cardiac sounds provides useful information about a variety of cardiac conditions. The intensity of the cardiac sounds is known to be influenced by numerous factors such as the force of cardiac valve closure, the presence or absence of valvular insufficiency, the valve positions at the onset of their closure, and the mobility of the valves. Interest has focused principally on the mechanism of the genesis of heart sounds,’-’ and little attention has been given to respiratory changes in the intensity of heart sounds. A review of the literature in English shows that Heinzen is the only investigator who has made extensive studies on the respiratory changes in cardiac sounds.’ He pointed out that the first and second sounds tended to increase toward the peak of inspiration and that they tended to decrease toward expiration. In the course of a phonocardiographic study giving special emphasis to respiratory changes in cardiac sounds, we developed the strong impression that the cardiac sounds tended to increase during expiration and to decrease during inspiration. This finding was quite contrary to the observations of Heinzen.
From
Kyorin University,
School of Medicine,
Tokyo, Japan,
and Yamato
Prefecture, Japan.
750
Downloaded from ang.sagepub.com at UNIVERSITY OF ALBERTA LIBRARY on June 28, 2015
City Hospital, Kanagawa
751 The
present research was therefore undertaken
extensive study of respiratory changes in the cardiac sounds of normal subjects. The results are essential to the proper clinical evaluation of heart sounds in a variety of clinical as an
settings. Materials and Methods
Thirty-one normal subjects comprised the study group. There were 23 men and 8 women whose ages ranged from 13 to 47 with a mean of 29 years. A crystal microphone was used to record phonocardiograms (PCGs) with all subjects because of its sensitivity and practical convenience. The microphone was firmly affixed to the anterior chest at the apex and at the pulmonic area with specially designed adhesive tape. The subjects were made to lie supine on a bed in a soundproof room. They were instructed to breathe normally and to avoid yawning or excessive thoracic excursions. The frequency response of the filter of our recording system comprised a cutoff frequency of 160 Hz and a maximum gradient of 24 db/Oct. The recording speed was 100 mm/sec. All PCGs were taken with a Sanei Heart Sound preamplifier and recorded on a photographic recorder, together with a simultaneously recording electrocardiographic lead and respiratory curve. An electrocardiographic lead showing distinct Q and P waves was selected. The respiratory tracing was maintained throughout the PCG recording with a strain-gauge transducer connected to a rubber belt around the boundary between the chest and abdomen. All 31 subjects had normal electrocardiograms, in which the PR interval was between 0.12 and 0.20 sec and was virtually constant in each subject throughout the PCG recording. Premature beats and marked sinus arrhythmia were not observed in any subject. PCGs were recorded during more than 10 consecutive respiratory cycles. Longer tracings were necessary in subjects with a less uniform respiratory pattern. The amplitudes of the first heart sound, S(I), and the aortic component, S(IIA), and pulmonic component, S(IIP), of the second heart sound were measured. All these heart sounds were divided into those during inspiration (Ins) and those during expiration (Exp) on the basis of the respiratory curve. The respiratory effect on the intensity of heart sounds was analyzed by using a single beat located at or close to the center of each Ins and Exp. Amplification of the recording system was adjusted for each subject in order to ensure the proper amplitudes of the heart sounds. In each subj ect the statistical significance of the difference in intensity of the heart sounds between Ins and Exp was tested by the student’s t test. Results All pertinent data are presented in Table 1. At the apex, S(I) and S(IIA) were identified sufficiently clearly for precise analysis to be made in 30 of the 311
Downloaded from ang.sagepub.com at UNIVERSITY OF ALBERTA LIBRARY on June 28, 2015
752 TABLE 1
Respiratory Changes
in the
Intensity of Heart Sounds in 31 Normal Subjects
Exp: expiration; Ins: inspiration; I: first heart sound; IIA: aortic component of second heart sound; 0: tensity of heart sound in Exp > that in Ins; 0: intensity of heart circle sound in Exp that in Ins.
in-
=
subjects (97%), while S(IIP) was identified in 19 of the 31 (61%). At the pulmonic area, S(I) and S(IIP) were both identified in 23 of the 31 subjects (74%), and S(IIA) was noted in 26 of the 31 (84%). Table 2 summarizes the respiratory effects on the intensity of the heart sounds. 1. At the apex: Twenty-six of 30 subjects (87%), 21 of 30 (70%), and 13 of 19 (68%) showed expiratory increases in the intensity of S(I) and S(IIA), and 6 of
Downloaded from ang.sagepub.com at UNIVERSITY OF ALBERTA LIBRARY on June 28, 2015
753 Comparison of Magnitude of
*
Based
on a
TABLE 2 Heart Sounds Between
Expiration and Inspiration
*
single heart beat located at or near the center of each expiration and inspiration.
19
(32%) showed no respiratory change in the intensity of S(I), S(IIA), and S(IIP). Four of 30 subjects (13%), 9 of 30 (30%), and 6 of 19 (32%) showed no respiratory change in the intensity of S(I), S(IIA), and S(IIP) respectively. No
subject
revealed
an
inspiratory
increase in the
intensity
of any of the cardiac
sounds.
representative example in which we observed expiratory increases in the amplitude of S(I) and S(IIA), and a slight inspiratory increase in the amplitude of S(IIP). 2. At the pulmonic area: Nineteen of 23 subjects (83%), 25 of 26 (96%), and 20 of 23 (87%) showed expiratory increases in the intensity of S(I), S(IIA), and S(IIP) respectively. Four of 23 subjects (17%), 1 of 26 (4%), and 3 of 23 (13%) revealed no respiratory changes in the intensity of S(I), S(IIA), and S(IIP) reFigure
I is
a
FIG. 1. A representative PCG tracing recorded in a 19-year-old man (Case 5). Note the expiratory inin the amplitude of S(I) and S(IIA), and the inspiratory increase in the amplitude of S(IIP). As a whole, the intensities of S(I), S(IIA), and S(IIP) were statistically increased in Exp compared to those in Ins (see Table 1). creases
Downloaded from ang.sagepub.com at UNIVERSITY OF ALBERTA LIBRARY on June 28, 2015
754
spectively. No subject revealed an inspiratory increase in the intensity of any of the cardiac sounds. Discussion
great amount of diagnostic information can be obtained from heart sounds. However, auscultation is essentially a subjective matter. The phy-
Clearly,
a
sician usually estimates the intensity of the heart sounds and murmurs solely from personal experience, taking the respiratory effect on cardiac phenomena into consideration. It is generally known that the PR interval and RR interval on electrocardiograms show a close relationship to the intensities of heart sounds. In this study, however, no remarkable change in these intervals was observed throughout the PCG recordings for each subject. The data obtained in this study indicate that, in 31 normal subjects, the amplitudes of S(I), S(IIA), and S(IIP) tended to increase during Exp. This observation is in sharp contrast with the report of Heinzen,’ who indicated that S(I), S(IIA), and S(IIP) tended to increase toward the peak of Ins and tended to decrease toward the peak of Exp. The reason for the discrepancy in results between the two studies is unclear. In some subjects it was rather difficult to draw a clear line between Ins and Exp. The fact that inspiration causes more noises in PCG tracings than expiration was of some help in marking a more precise separation between Ins and Exp. A carryover effect of Ins on Exp and vice versa can reasonably be expected. This carryover effect may render it difficult to investigate the independent influences of inspiration and expiration on heart sounds. Bearing this in mind, we selected single beats at or close to the center of both Ins and Exp for further analysis. This analysis accentuated the basic finding that the heart sound tended to increase during Exp and to decrease during Ins. We found that the respiratory change in the intensity of S(I) was more consistent than that of S(IIA) or S(IIP), although the reason for this remains undetermined. The inspiratory decrease in the intensity of the heart sounds may arise mainly from the insulating effect of the inflated lung on the transmission of heart sounds to the body surface, although other factors must be considered. Hemodynamic differences between Ins and Exp could be involved in the genesis of such respiratory changes. Virtually no quantitative approach has been devised for the analysis of heart sounds and murmurs because of the considerable difficulties involved in calibrating such sounds and murmurs. Indeed, the fact that no truly reliable calibration is available in PCG analysis represents an enormous barrier to further progress in the field of clinical PCG. In the daily clinical situation, it is not infrequent to encounter problems in judging the intensity of heart sounds. Respiratory alteration in the intensity of
Downloaded from ang.sagepub.com at UNIVERSITY OF ALBERTA LIBRARY on June 28, 2015
755
heart sounds is one of the commonest auscultatory pitfalls. Auscultatory evaluation of the intensity of heart sounds should thus be performed carefully, with the respiratory changes always in mind. On the basis of this study it should also be emphasized that the intensity of the heart sounds is considerably influenced even by quiet natural breathing. Kyozo Ishikawa, M. D., F.I.C.A.
of Medicine Kyorin University School 6-20
Shinkawa, Mitaka City
Tokyo, Japan References 1.
Shah, P. M., Mori, M., MacCanon, D. M.,
et
correlates of the various components of the first heart sound. Circ. Res., 12: 386, 1962. 2. Mori, M., Shah, P. M., MacCanon, D. M., et al.: Hemodynamic correlates of the various components of the second heart sound. Caral.:
3.
Hemodynamic
diologia, 44: 5, 1964. Bagaert, A.: New concept
the mechanism of the first heart sound. Am. J. Cardiol., 18: 253, 1966. on
4. Sakamoto, T., Kusukawa, R., MacCanon, D. M., et al.: Hemodynamic determinants of
the
amplitude
of the first heart sound. Circ.
Res., 16: 45, 1965. 5. Piemme, T. E., Barnete, G. O., Dexter, L.:
Relationship of heart sounds to accelaration of blood flow. Circ. Res., 18: 303, 1966. 6. Harris, A., Sutton, G.: Second heart sound in normal subjects. Br. Heart J., 30: 739, 1968. 7. Kardalinos, A.: The second heart sound. Am. Heart J., 64: 610, 1962. 8. Heinzen, P.: Quantitative Phonokardiographie. Stuttgart, Georg Thieme Verlag, 1960.
Downloaded from ang.sagepub.com at UNIVERSITY OF ALBERTA LIBRARY on June 28, 2015
