PHONOCARDIOGRAPHY 



73 > 



PA 



RV 



R A 



mii^i^^imifitf.-^Hmmf^s^ ^ 



■VSpi|*i 



»N- 



PDA 



PA 



RV 



RA 



FIG. 15. Intracardiac phonocardio- 

 gram, illustrating the use of this tech- 

 nique in the diagnosis of congenital heart 

 disease by sharp intracardiac localiza- 

 tion of murmur production. Each 

 recording was taken as the phono- 

 catheter was pulled back from the 

 pulmonary artery into the right ventricle 

 and then into the right atrium. The 

 upper tracing was taken from a child 

 with a patent ductus arteriosus with a 

 left-to-right shunt. There is a con- 

 tinuous murmur in the pulmonary 

 artery and no significant murmur in 

 either the right ventricle or right 

 atrium. The lower tracing was taken 

 from another child with a ventricular 

 septal defect with a left-to-right shunt. 

 There is a systolic murmur in the 

 pulmonary artery, which is much 

 louder and harsher in the right ven- 

 tricle, and again no murmur in the right 

 atrium. 



(29a). The fact that none may be heard on the chest 

 wall clearly does not mean that they are not present, 

 since, a.s has been previously stated, events may be 

 recorded within the heart that do not reach the 

 chest wall. Certain artifacts can be easily recognized. 

 The flinging of the catheter against the inner wall 

 of the heart or great vessels by cardiac action results 

 in sharp clicking transients that can usually be 

 abolished by changing the position of the transducer. 

 Other possible artifacts are less easih' ruled out. The 

 likelihood that the mere presence of the transducer in 

 a flow stream would change the pattern of flow and 

 thereby cause the production of a murmur has been 

 considered since the introduction of the technique. 

 No rigorous evaluation of this has been carried out, 

 so that no completely satisfactory answer is available. 

 However, certain observations in humans shed some 

 light on this problem. There are many areas in the 

 cardiovascular system in which no murmur is heard. 

 For example, although there is almost always a 

 systolic murmur in the pulmonary artery, most 

 often there is no murmur in the outflow tract of the 

 right ventricle. During systole the volume rate of 

 flow and probably the linear velocity of flow are 

 similar in these two closely adjacent areas, which 

 suggests that the murmur is not produced by the 

 catheter but has something to do with the vascular 

 system itself. The additional observation that the 

 form of the murmur at the pulmonic area on the 

 chest is unchanged by the presence of the catheter 

 in the pulmonary artery, and that the form of the 



murmur within the pulmonarv artery is the same 

 as that on the chest, are in agreement with this 

 conclusion, but, again, are not proof of it. Care must 

 be taken to see that the location of the catheter does 

 not interfere with valvular function and thereby 

 produce a murmur. For example, when the transducer 

 is passed in a retrograde direction against the aortic 

 valve, it appears that \alve closure can be impaired 

 with the consequent production of an artifactual 

 aortic diastolic miu'mur. However, when the catheter 

 is passed through the valve down into the ventricle, 

 disturbance of \alve function does not seem to be 

 produced. For, in this case, withdrawal of the catheter 

 from the ventricle up into the aorta is not associated 

 with a diastolic murmur. 



As more and more interested workers apply the 

 technique of intracardiac phonocardiography to the 

 study of cardiac acoustics, an evaluation of its role 

 in physiological investigations becomes clearer. There 

 is no doubt that it offers, at the present time, the 

 best single approach to the study of the problems of 

 sound and murmin- transmission. Regarding the 

 usefulness of the technique in unraveling problems 

 connected with the genesis of sounds and murmurs, 

 it ofl"ers recordings which do not suffer from possible 

 loss in transmission, and which provide for a varying 

 degree of localization, depending upon the event 

 under investigation. However, concerning answers 

 to questions about the factors responsible for the 

 various events, the problem here resides more with 

 the ability of the investigator to devise unequivocal 



