QUANTITATIVE-ANALYSIS OF SIGNAL-AVERAGED P-WAVES IN IDIOPATHIC PAROXYSMAL ATRIAL-FIBRILLATION

Detailed analysis of the QRS complex can identify patients at risk from ventricular arrhythmias, but similar techniques applied to the atria have been disappointing. This study attempts to quantitate differences in the fine morphology of P waves in a group of 9 patients with paroxysmal atrial fibrillation (AF) versus 15 control subjects. Atrial triggered signal-averaging was combined with a detailed investigation of P-wave duration, high-frequency spatial voltage and spatial velocity. Signal-averaged P-wave duration was significantly increased in patients with paroxysmal AF (135 +/- 8 vs 126 +/- 4 ms, p < 0.05). The root-mean-square voltage at frequencies > 35 Hz in these patients was also significantly greater (16 +/- 3 vs 12 +/- 1-mu-V, p < 0.05). Similar observations were made at frequencies > 40 Hz (10 +/- 3 vs 7 +/- 1-mu-V, p < 0.05). These differences appeared to be confined to the third quarter of the P wave (third quarter root-mean-square voltage at > 40 Hz expressed as a ratio of total P-wave root-mean-square voltage, 1.4 +/- 0.1 vs 1.2 +/- 0.1, p = 0.005). Spatial velocity was also increased in the paroxysmal AF group (peak spatial velocity 6.4 +/- 1.8 vs 4.6 +/- 0.5 mV/s, p < 0.05). These observations support previous intracardiac data that implicate delay and fragmentation of intraatrial conduction in the pathogenesis of paroxysmal AF.