PHONOCARDIOGRAPHY 



703 



pulmonic valve closure component of the second heart 

 sound, 9) the opening of the tricuspid valve, 10) the 

 opening of the mitral valve, //) the right ventricular 

 third heart sound, and finally 12) the left ventricular 

 third heart sound. This order must be considered 

 tentative and in need of further documentation. 



Relalionslup Between Acoustic Events and 

 Other Physiological Parameters 



Although it is clear that the closest physiological 

 parameter, that is readily measurable at the present 

 time, is the intravascular pressure, it is not always 

 practicable nor desirable to carry out such a com- 

 parison. In such circumstances other phenomena may 

 be used to substitute for certain of the wished-for me- 

 chanical correlates. Rather than obtaining the corre- 

 late from within the heart, phenomena seen "on the 

 surface" of the body are used, in inuch the same way 

 that the heart sounds "on the surface"" of the body are 

 used in lieu of information from the source. 



ELECTROCARDIOGRAM. This parameter is certainly the 

 most venerable and although it has clear-cut benefits, 

 its limitations must be recognized. First in its favor is 

 the ea.se with which technically satisfactory record- 

 ings can be obtained. Second, it is the least liable of 

 all the '"surface"' phenomena to deceive one in differ- 

 entiating systole from diastole. However, since precise 

 electrico-acoustical correlation has not yet been es- 

 tablished and since this may well vary under differing 

 circumstances, the differentiation of systole from 

 diastole, by this method, is less exact than when 

 mechanico-acoustical correlation is used. That is to 

 say, that although the electrocardiogram can be used 

 to establish the onset, duration, and end of both elec- 

 trical systole and diastole, it can only approximate 

 these findings for mechanical systole and diastole. Its 

 greatest \alue appears to lie in its ability to place .sets 

 of acoustic \ibrations into certain classes of events and 

 ruling out their placement in other sets. The basis 

 upon which this can be done is the well-known fact 

 that electrical events always precede mechanical 

 events of the same order. So that, for example, a set 

 of vibrations postulated to represent the fourth heart 

 sound must succeed the P wave of the electrocardio- 

 gram. If they precede this electrical event the sug- 

 gested identification is then known to be false. Simi- 

 larly, the first sound must follow the onset of the QRS 

 complex. Having established that the vibrations fol- 

 low their electrical counterpart, there are rough 

 guides as to the minimum and maximum allowable 



intervals, but, as stated pre\'iously, precise quantita- 

 tion has not been established, and indeed may be 

 physiologically impossible. What physiological knowl- 

 edge is to be gained from the elucidation of this 

 parameter remains to be established. There is clearly 

 no consistent relationship between the second sound 

 and the T wave of the electrocardiogram, though a 

 possible relationship with the U wave exists, which 

 deserves further investigation. The electrico-acoustical 

 relationships for the atrioventricular valve openings 

 and third sounds are not known. 



JUGULAR VENOUS PULSE. Since, in the human, there are 

 no valves between the right atrium and the jugular 

 vein, pressure phenomena in the former are well re- 

 flected in the latter. The jugular venous pulse can 

 therefore be used as a "surface'" phenomenon reflect- 

 ing the mechanical events within the right atrium, 

 i.e., from the "'source."' A number of workers have 

 studied the time delay between right atrium and 

 jugular vein, and reached different conclusions (28, 

 38, 46, 49, 107, p. 164). The problem appears to lie 

 in the different techniques used, and any laboratory 

 attempting correlation between acoustic events and 

 jugular venous pulse should certainly establish its own 

 figures. The recording obtained from the neck resem- 

 bles the source not only in time-course of events but 

 also in the shape and magnitude. In this way informa- 

 tion can be obtained about the three positive and two 

 negative deflections. Concerning the deflections, one 

 technical problem presents itself. This is the extent to 

 which the pulsations of the carotid artery may inter- 

 fere with bona fide \enous pulsations. Depending upon 

 the technique and the presence of abnormally in- 

 creased systolic expansion of the artery, the c wave 

 mav represent in part or in full a carotid artery event. 

 For this reason few workers ha\e confidence in their 

 conclusions regarding this particular wave in the 

 venous pulse. A rigorous solution to this problem, 

 however, has not been carried out. It must be remem- 

 bered that the data reflect only right atrial events 

 which can safely be correlated, if desired, with right 

 ventricular events. The jugular pulse does not and 

 cannot reflect the time-course, magnitude, or the 

 shape of the deflections in the left atrium, and there- 

 fore cannot safely be correlated with left ventricular 

 events. It is only in the special circumstance, in which 

 a defect in the atrial septum of size sufficient to render 

 the two atria into one hemodynamic chamber, that 

 the jugular pulse wave would bear any relation to 

 left atrial activity. 



.Since there is a reliable correlation between right 



