PULSATILE BLOOD FLOW 



859 



4) The contour of the time-intensity pattern or 

 "envelope" of a murmur corresponds to the contour 

 of the flow pulse passing through the region at the 

 time of murmur production. 



5) Musical murmurs, that is, murmurs with periodic 

 reproductions in the frequency pattern as opposed to 

 the random vibrations of blowing murmurs, arise 

 from tissue structures, or other coherent material, 

 set into oscillation by blood flow of high velocity. 



Examples of general rule / are found in the con- 

 tinuous aortic murmur of severe degrees of coarcta- 

 tion and the diastolic murmur of minimum aortic re- 

 gurgitation. Examples of general rule 2 are moderate 

 degrees of coarctation, aortic and pulmonary valve 

 stenosis, Korotkoff's sounds, patent ductus arteriosus, 

 and the murmurs of most arteriovenous fistulae. 

 Examples of general rule 3 are mitral stenosis, tri- 

 cuspid stenosis, and occasional right atrial murmur 

 of an interatrial septal defect. Examples of general 

 rule 4 are really found among all murmurs wherever 

 one compares the murmur envelope with the flow 

 pattern as illustrated in section VII on flow in patho- 

 logical conditions. Examples of general rule 5 are the 

 vibrations of a vein wall giving rise to a "venous 

 hum," the "sea gull" murmur arising from vibration 

 of aortic valve cusps in aortic regurgitation, and the 

 "moaning" systolic murmur of retroverted mitral 

 cusps, or arising from vegetation on the mitral cusps 

 giving rise to a systolic low-frequency periodic 

 murmur in mitral regurgitation. In addition, musical 

 qualities may be heard in arteriovenous fistulas which 

 are presumably due to the vibration of the vascular 

 wall, and are usually superimposed, like most musical 

 murmurs, upon blowing or random noise vibrations. 



VII. NORMAL AND PATHOLOGICAL FLOW 

 PULSES IN HUMANS 



The normal human flow pulses closely resemble in 

 pattern those which have been found in the cor- 

 responding vessels of the dog and sheep. Most records 

 of human flow pulses have been made at the time of 

 a surgical procedure indicated because of some 

 pathological condition. The pulses in this section 

 presented as "normal" tracings are so called because 

 there was no physiological reason to doubt their 

 normalcy and second, because they correspond to 

 those found in the experimental animal. 



Flow in the Ascending Aorta 



Normal blood-flow patterns are shown in figure 

 26. As in the dog, they show a rapid acceleration 

 phase, a slower deceleration phase with a high- 

 frequency (40-60 cps) backflow coincident with aortic 

 valve closure. The volume of the flow pulse has little 

 effect on these contour features (fig. 26) except from 

 hypodynamic ventricles and severe degrees of exercise. 

 Diastole is relatively uneventful with the resonant 

 wave not appearing. The ejection pattern of the left 

 ventricle in the presence of aortic valve stenosis is 

 shown in figure 28. The principal deviations from 

 normal contour seen here are a more flattened and 

 delayed peak, with flow vibrations superimposed. 

 In addition, there is less prominence of the valve 

 closure backflow wave. The backflow wave incident 



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fig. 28. Aortic valve stenosis of rheumatic origin without 

 regurgitation in a 1 4-year-old boy. Measurements were made 

 during thoracotomy prior to repair. Flow pulse shows the 

 rounded irregular top of turbulent blood flow, corresponding to 

 a diamond-shaped murmur and a pressure gradient between the 

 left ventricle and ascending aorta which follows the contour rule 



