Atrial transport and aortic insufficiency.

The study of patients with aortic insufficiency has revealed that many demonstrate a first degree The possible advantages of this P-R prolongation have only recently been described (Herbert, 1967). It appears that such a mechanism enables the left atrium to contract earlier (relative to ventricular systole) and thus deliver its volume contribution to forward flow before the premature closure of the mitral valve left atrium, and thus the right heart as well, to function at a normal or nearly normal pressure level. In short, atrial transport (whose major components are the early rapid filling phase and atrial systole) occupies an abbreviated diastolic period due to the aortic reflux which prematurely closes the mitral valve. It is the purpose of this paper to describe further, (a) the components of the prolonged P-R interval in aortic insufficiency, and (b) the manner in which atrial transport is affected. SUBJECTS AND METHODS Twenty-two patients were submitted to right and left heart catheterization with cine-angiocardiography. The diagnosis of aortic insufficiency in 12 patients was based on angiographic demonstration of a grossly incompetent aortic valve. The other 10 patients were referred for evaluation of either an unusual murmur or a possible cardiac aberration suggested by routine chest films. Following a normal right and left heart catheteri-zation these patients were adjudged to have no heart disease. Lead II was selected for the electrocardiographic measurements as it proved to reflect in almost every instance the true P wave and P-R interval duration Two of the patients with aortic insufficiency were recei vinga digitalis preparation. Neither was considered to be digitalis toxic. Early records in one of these patients (Case 5, see Table II), before any drug therapy, also demonstrated the high degree of A-V block. The heart rates varied from 48 to 93 beats a minute, and were considered to be within a range which would not significantly affect the P-R interval (Schlamowitz, 1946; Macruz et al., 1958). RESULTS The electrocardiographic data of the 10 normal patients appear in Table I. The mean P wave duration is 0 094 sec., conforming to that reported by Macruz et al. (1958) of 009 sec. The mean P-R interval is 0 153 sec. and does not vary significantly from the 0 143 value reported by Schlamo-witz (1946). The comparable data of the aortic insufficiency group appear in Table II. The P-R intervals and P waves are both considerably longer than in …