PHONOCARDIOGRAPHY 



7'9 



PRESSURES 



FIG. 8. Mitral stenosis : correlation of pressures and acoustics. 

 The relationship between the left heart pressures and the 

 acoustic manifestations of mitral stenosis are shown. The three 

 sets of curves represent from left to right increasing degi'ees of 

 stenosis. The pressures are shown from just before the time of 

 the second sound near the end of systole to just after the time 

 of the first heart sound at the beginning of systole. In each case 

 there is normal sinus rhythm. As the severity of the lesion 

 increases the level of atrial pressure, at the time of the opening 

 of the atrio\entricular vahe, rises with a resultant progressi\e 

 shortening of the interval from second sound component to 

 opening snap (2-OS). Also as the severity of the lesion increases 

 the duration of the diastolic gradient increases with a resultant 

 lengthening of the duration of the diastolic murmur. Finally, 

 as the severity of the lesion increases, the level of atrial pressure 

 at the time it is exceeded by the ventricular pressure rises with 

 a resultant delay in the appearance of the first heart sound 

 component. 



nature of the event. There is no basis for the sug- 

 gestion that since ventricular pressure is rising during 

 the time of the murmur, it is due to flow from the 

 ventricle back into the atrium (75, 97). 



From these considerations and from those on the 

 effect of stenosis on the heart sounds, a complete 

 picture of the acoustics in atrioventricular valve 

 stenosis can be drawn up. (Similar interesting ex- 

 amples could be cited for the other valvular lesions.) 

 If one begins with the point at which the ventricular 

 pressure falls below pressure in the great vessel, there 

 is first a normal second sound component from the 

 side of the lesion. Following this is a short interval 

 until the end of isometric relaxation, when the ven- 

 tricular pressure falls below atrial pressure. There is 

 then the opening snap of the atrioventricular \alve, 

 the distance of which, from the second sound com- 

 ponent, is roughly inversely proportional to the se- 

 verity of the lesion. The opening .snap ushers in the 

 murmur, which because of the nature of the \alve 

 structure is low pitched. The murmur is decrescendo 

 in nature, its duration varying directly with the 

 severity of the lesion. With the onset of atrial me- 

 chanical activity, late in diastole, the murmur be- 

 comes crescendo ending in a late appearing, snapping 



4 



ECG ^-Jl^ ^^■\.J^ _^ L^ 



FIG. 9. Effect of P-R inter\al on presystolic murmur. The 

 pressures are of left ventricle and left atrium in a subject with 

 mitral stenosis. The part of the cycle shown is from near the 

 end of diastole to shortly after the beginning of systole. The 

 part of the acoustic cycle shown is the envelope of the pre- 

 systolic murmur and the first sound. At the bottom is the 

 electrocardiogram (ECG) showing from left to right an in- 

 creasing P-R interval 



first sound, the degree of lateness varying directly with 

 the severity of the lesion. Furthermore, having now 

 considered in detail the relationship between atrial 

 activity and ventricular activity and the effect of 

 exact juxtaposition of these events on the level at 

 which atrial pressure is left at the onset of ventricular 

 contraction, one can see that the lateness of the first 

 sound depends upon this as well as upon the severity 

 of the lesion. This may well account for the poorer 

 correlation between severity and prolongation of the 

 Q-Mi interval than between severity and the A2-OS 

 interval (44, 45, 103). 



On the basis not only of pitch but also of time-course 

 of events a differentiation can be made between dia- 

 stolic murmurs that originate at the semilunar valve 

 and those that originate at the atrioventricular valve. 

 This discussion can be concluded with a consideration 

 of two interesting "functional" diastolic murmurs 

 that occur in the presence of "organic" diastolic 

 miH'murs. 



First, consider the patient known to ha\c an 

 "organic" mitral stenosis with its attendant atrio- 

 ventricular diastolic murmurs. There may be a.ssoci- 

 ated with this a short semilunar diastolic murmur due 

 to one of two reasons. The murmur may be due to 

 aortic valve insufficiency, which is also usually due 

 to rheumatic valvulitis. On the other hand the 

 murmur may be due to pulmonic valve insufficiency. 

 This can arise out of the train of events that start with 

 atrial pressure causing an increase in pulmonary 

 artery pressure which may further rise as pulmonary 

 vascular resistance increases. Finally, the rise in 

 pulmonary artery pressure may then cause dilatation 

 not only of the pulmonary artery but also of the 



