The anatomic substrate for the sick sinus syndrome in adolescence

Two cases are described, one of cardiac sarcoidosis and another of primary cardiac amyloidosis, in which correlation was made between electrophysiologic and postmortem conduction system studies. In Case 1 the electrocardiogram revealed right bundle branch block with first degree and intermittent third degree atrioventricular (A-V) block and recurrent unifocal paroxysmal ventricular tachycardia. Electrophysiologic studies disclosed normal sinus rhythm with prolonged A-H (175 ms) and H-V (60 ms) intervals and extrastimulus induction of repetitive ventricular firing. Postmortem examination revealed a sarcoid aneurysm of the posterior left ventricle and granulomatous infiltration of the A-V node, His bundle and bundle branches. In Case 2 the electrocardiogram revealed sinus bradycardia, a prolonged S-T interval and recurrent ventricular fibrillation. Electrophysiologic studies demonstrated a prolonged sinus nodal recovery time (6,080 ms) and H-V (85 ms) interval. Postmortem examination revealed marked amyloid infiltration of the sinoatrial node, atria, proximal bundle branches and left and right ventricular myocardium.There was thus excellent correlation between electrophysiologic and pathologic findings. These cases indicate the importance of making a clinical diagnosis of the disease that might in some cases allow specific therapeutic intervention in addition to antiarrhythmic therapy.