PHONOCARDIOGRAPHY 



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lesions produce similar hemodynamic changes, the 

 murmur becomes less characteristic. 



When a lesion produces a change in hemodynamics 

 or in flow pattern at a distance from the lesion, 

 murmurs, if produced, are characteristic not neces- 

 sarily of the lesion but rather of the flow pattern 

 changes at the site where these occur. Finally, both 

 types of murmurs may be produced by a lesion, one 

 due to the change in flow pattern at the lesion and 

 one at a distance. This information is essential to 

 understand the current problems in devising a satis- 

 factor\- classification of murmurs. The traditional 

 classification of differentiating between so-called or- 

 ganic and functional murmurs is less than ideal. In 

 the sense that all murmurs are produced by changes 

 in blood flow, they can be said to be "functional." 

 Furthermore, changes in blood flow at a distance 

 from a lesion are often indistinguishable from changes 

 produced by physiological alterations in the circu- 

 lation (i.e., not associated with heart disease or any 

 given lesion), and from this will often come indis- 

 guishable murmurs. For example, an increased car- 

 diac output, such as seen in anemia, will increase flow 

 in the pulmonary artery and may produce a murmur 

 which is indistinguishable from the murmur produced 

 by increased pulmonary artery flow secondary to the 

 left-to-right shunt of an atrial septal defect. The 

 problem is further complicated by the attempts to 

 classify separately changes in the flow pattern pro- 

 duced at a valve area by increases in flow across a 

 normal orifice, from those produced by normal or 

 reduced flow across a reduced valve area. Addition- 

 ally, problems arise in classification and differentiation 

 of murmurs at valve areas caused by regurgitation due 

 to structural changes in the leaflets from those pro- 

 duced by dilatation of the valve ring. There appears 

 to be no ready answer to the problem of classification. 

 At present, one way of handling it is first to recognize 

 certain murmurs which bear a close enough relation- 

 ship to the anatomical lesion that they may be called 

 organic. The murmur is caused by flow through the 

 lesion itself. Second, there is a group of murmurs 

 clearly unassociated with clinically significant cardiac 

 lesions and they may be called functional or unas- 

 sociated with heart disease. And third, there is a 

 group of murmurs which may or may not be associ- 

 ated with cardiac lesions, and the differentiation is 

 made by reference to other information. Until such 

 time as a more precise identification of all of the 

 factors involved in murmur production and trans- 

 mission are known, any classification will remain in- 

 adequate. 



MURMURS OF v.\LVULAR ORIGIN. Disorders in valve 

 function, both stenosis and insufficiency, have the 

 capacity of producing changes in blood flow that 

 yield murmurs. Since there are four valves and since 

 each valve can be diseased in two ways, there are 

 eight possible murmurs of valvular origin. To identify 

 precisely the site of origin of the murmur, criteria are 

 needed to separate these eight possibilities. The first 

 important criterion is the phase of the cardiac cycle in 

 which the murmur occurs. The eight can in this way 

 be divided into two groups of four murmurs each. 

 The systolic murmurs are those of mitral insufficiency, 

 tricuspid insufficiency, aortic stenosis, and pulmonic 

 stenosis. The diastolic murmurs are those of mitral 

 stenosis, tricuspid stenosis, aortic insufficiency, and 

 pulmonic insufficiency. In the case of valvular stenosis 

 the flow pattern is altered by the obstruction to 

 forward flow. Since the forward flow across the semi- 

 lunar valves occurs in systole, these murmurs are 

 systolic, and since forward flow across the atrio- 

 ventricular valves occurs in diastole, these are dia- 

 stolic murmurs. In the case of valvular insufficiency 

 the valve allows blood to flow backward into the next 

 most proximal chamber during the period of time 

 when the valve is normally closed. Since the semi- 

 lunar valves are normally closed in diastole, in- 

 sufficiency produces a diastolic murmur, and since 

 the atrioventricular valves are normally closed in 

 systole, here insufficiency produces a systolic murmur. 



Consider first the systolic murmurs. Traditionally, 

 the most important acoustic criterion for identifi- 

 cation has been the area on the thorax to which the 

 murmur shows preferential transmission. In most cases 

 this criterion holds true due undoubtedly to the fact 

 that from patient to patient not only is the heart in 

 about the same place in the thorax but the nature of 

 transmission is probably nearly the same. However, 

 exceptions do occur and, in order to validate the first 

 criterion and provide rigorous support for identifi- 

 cation, recourse must be had to the physiological 

 basis of murmur production. In order to understand 

 these criteria, basic information must be at hand on 

 the nature of the hemodynamic changes produced by 

 the various valvular lesions. 



In the presence of stenosis of the semilunar valve 

 the relationship between the ventricular pressure and 

 the pressure in the great vessel is changed. In the 

 normal, these two pressures are virtually identical 

 during systole, but because of the obstruction to flow 

 imposed by the diseased valve there is a loss of energy 

 across the valve. This manifests itself as a difference 

 in the pressures, and the amount of this difference 



