SUPERNORMAL ATRIAL CONDUCTION AND ITS RELATION TO ATRIAL VULNERABILITY AND ATRIAL-FIBRILLATION IN PATIENTS WITH SICK SINUS SYNDROME AND PAROXYSMAL ATRIAL-FIBRILLATION

The purpose of this study was to evaluate prospectively the relationsh ip between supernormal atrial conduction (SNC) and the atrial vulnerab ility to fibrillation in patients with sick sinus syndrome (SSS) and p aroxysmal atrial fibrillation (PAF). Programmed atrial stimulation was performed in 32 age-matched control patients (group I), 26 with SSS b ut without tachyarrhythmias (group II), and 24 with both SSS and PAF ( group III) to assess some determinants of atrial vulnerability, SNC, a nd atrial fibrillation inducibility. Supernormal atrial conduction was observed in 20 (63%) patients of group I, 12(46%) patients of group I I, and 5 (21%) patients of group III (group I vs group III; p < 0.002) . The SNC zone was 46 +/- 44 msec in group I, 36 +/- 42 msec in group II, and 12 +/- 24 msec in group III. (group I vs group III; p < 0.001) . The absence of SNC showed a specificity of 89% and a positive predic tive accuracy of 79% in predicting inducibility of atrial fibrillation . The sensitivity was 33% and the negative predictive accuracy was 52% . The SNC zone showed a significant inverse correlation with P wave du ration (r = -0.32; p < 0.003), intraatrial conduction time (r = -0.28; p < 0.02), and maximum conduction delay (r = -0.23; p < 0.05). The ma ximum decrease in conduction time during supernormal conduction showed a significant inverse correlation with P wave duration (r = -0.27; p < 0.02), intraatrial conduction time (r = -0.26; p < 0.02), and with t he maximum conduction delay (r = -0.27; p < 0.02). We conclude that th e greater the atrial vulnerability and the greater the atrial conducti on defects, the lower the occurrence of supernormal atrial conduction in the SSS. The absence of supernormal atrial conduction associated wi th atrial conduction defects may play an important role in the develop ment of atrial fibrillation in patients with sick sinus syndrome and p aroxysmal atrial fibrillation.