RELATIONSHIP BETWEEN ATRIAL CONDUCTION DEFECTS AND FRACTIONATED ATRIAL ENDOCARDIAL ELECTROGRAMS IN PATIENTS WITH SICK SINUS SYNDROME

The relationship between abnormal atrial electrograms (AAE) recorded d uring sinus rhythm by endocardial catheter mapping of the right atrium and the atrial conduction defects of sinus impulses or single atrial extrastimuli was investigated in 44 patients with sick sinus syndrome. The patients were divided into two groups on the basis of the presenc e (n = 29) or absence (n = 15) of AAE recorded during sinus rhythm. Th e P wave duration in the AAE (+) Group patients was 137 +/- 14 msec, a nd 125 +/- 15 msec in the AAE (-) Group; P < 0.02. The intraatrial con duction time of sinus impulses in the AAE (+) Group was 54 +/- 12 msec , and 39 +/-9 msec in the AAE (-) Group; P < 0.001. The interatrial co nduction time in the AAE (+) Group was 101 +/- 14 msec, and 78 +/- 16 msec in the AAE (-) Group; P < 0.001. In the AAE (+) Group, 11 (38%) p atients had a sinus node recovery time > 4 seconds, whereas in the AAE (-) Group there was only one (6%) patient; P < 0.03. AAE showed a spe cificity of 93% and a positive predictive accuracy of 91% in predictin g inducibility of atrial fibrillation. The sensitivity was 35% and the negative predictive accuracy was 42%. Sustained atrial fibrillation w as induced in ten (35%) patients of the AAE (+) Group, and in one (7%) patient of the AAE (-) Group; P < 0.05. These data suggest that in pa tients with sick sinus syndrome who possess abnormal endocardial elect rograms in sinus rhythm within the right atrium have: (1) a significan tly longer P wave duration; (2) a significantly longer intraatrial and interatrial conduction time of sinus impulses; and (3) a significantl y greater sinus node dysfunction and higher incidence of induction of sustained atrial fibrillation. It is concluded that there are signific antly greater atrial conduction defects in patients with sick sinus sy ndrome who possess AAE within the right atrium during sinus rhythm.