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HANDBOOK OF PHYSIOLOGY 



CIRCULATION I 



(for any given flow value) is an index of the severity 

 of the obstruction. The usual type of compensation 

 for this lesion is an increase in the amplitude of the 

 ventricular pressure, often with alterations in the rate 

 of rise and decline. The level of the great vessel 

 pressure may be unchanged (or lower) but the shape 

 of the pressure curve is greatly altered. It rises much 

 more slowly than in the normal, and reaches its peak 

 later. The gradient of pressure increases from the 

 time of valve opening to a point near the middle of 

 systole and then declines so that there is little or no 

 gradient just before valve closure. If one meikes a 

 first approximation assumption that the intensity of 

 the murmur is related to the pressure gradient, then 

 the time-course of the acoustics can be deduced. 

 There will be no murmur from the time of the atrio- 

 ventricular valve closure component of the first heart 

 sound until the end of isometric contraction. This will 

 be followed by the onset of the murmur with an 

 increase in intensity to mid-systole, followed by a 

 decline in intensity with disappearance shortly before 

 the second sound component. The form of the murmur 

 is crescendo-decrescendo, and its envelope is diamond- 

 shaped. The three characteristics which define this 

 murmur are: /) it begins not with the first sound but 

 shortly thereafter, 2) it is crescendo-decrescendo 

 (diamond-shaped), and j) it ends before the second 

 sound. The last point needs some clarification, since, 

 when the whole of cardiac acoustics (both sides of 

 the heart) is considered, the murmur may not appear 

 in this fashion. Assuming that only one semilunar 

 valve is stenosed, then the change in dynamics will 

 occur and the murmur will arise from only one side 

 of the heart. The other is unaffected. On the un- 

 affected side the duration of systole and the time of 

 appearance and intensity of the second sound com- 

 ponent are normal. On the affected side, systole is 

 prolonged and the intensity of the second sound 

 component, as discussed previously, is reduced. In 

 such a situation, although the murmur ends before 

 its own second sound component, it may not end 

 before the other. It has also been stated that as the 

 severity of the stenosis increases the point of ma.xi- 

 mum intensity of the murmur (peak of the diamond) 

 occurs later in systole. This appears not to be in 

 agreement with the statement presented here that 

 the maximum intensity occurs at or near midsystole. 

 This seeming discrepancy is resolved by die fact 

 that, in the former statement, the end of systole is 

 being taken as the time of occurrence of the second 

 sound component on the unaffected side, whereas the 



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i) VVAW 



FIG. 6. Ejection-type systolic murmur due to semilunar 

 stenosis. The pressure curves are of great vessel, ventricle, and 

 atrium, for a subject with semilunar valvular stenosis. Below 

 is shown the ejection-type systolic murmur. The various sounds 

 have also been added. Compare with fig. i (normal) and fig. 7 

 (atrioventricular insufficiency). 



FIG. 7. Regurgitant-type systolic inurmur due to atrioven- 

 tricular insufficiency. Similar to fig. 6, but for a subject with 

 atrioventricular valvular insufficiency. Below are shown the 

 regurgitant-type systolic murmur, and the sounds. Compare 

 with fig. I (normal) and fig. 6 (semilunar stenosis). 



latter statement considers only the affected side. 

 Therefore, both considerations are true. 



This type of systolic murmur, the internal character- 

 istics of which identify it, regardless of location on the 

 thorax, as a murmur originating at the semilunar 

 valve, has been named by Leatham (51), who first 

 called attention to it, an ejection murmur (fig. 6). It 

 should be remembered that whereas murmurs due to 

 semilunar stenosis are ejection murmurs, not all 

 ejection murmurs are due to pathological obstruction 

 to flow. Regardless of etiology, systolic murmurs that 

 originate at the semilunar valve are ejection in type. 

 For the diagnosis of stenosis, as the term is used here, 

 one might expect not only the murmur but also in- 

 crease in the duration of mechanical systole with 

 delay and diminution of the second sound component. 

 Unfortunately, to complicate matters still further, 

 these criteria may not always be present (83). In 

 addition to these criteria we have felt, as others have, 

 that an additional distinguishing feature between so- 

 called "functional"' ejection murmurs and "organic" 

 ejection murmurs is that the organic murmurs have 

 higher frequency components (60). 



