P-A interval: lack of clinical, electrocardiographic and electrophysiologic correlations

P-A interval is measured from the onset of the P wave to the onset of the low right atrial electrogram during His bundle recording. The significance of this interval was evaluated in 214 patients with intact A-V conduction and bundle branch block. One hundred fifty-eight patients had normal P-A (NPA) 27 +/- 9, mean +/- SD, and 56 had prolonged P-A (PPA). The NPA and PPA patients were similar (P greater than .10) in regard to sex, age, cardiac functional class, and P-R. PPA patients had significantly (P less than .05) greater P duration (mean +/- SEM, PPA vs NPA) 106 +/- 2 msec vs 100 +/- 1 msec), slower heart rates (72 +/- 2 vs 79 +/- 1), and longer sinus recovery times (1104 +/- 44 msec vs 980 +/- 38 msec). A-H was slightly shorter in PPA than in NPA patients suggesting that a systematic error in measruement of PA due to a relatively distal recording site may have been responsible for PA prolongation in some patients. Patients were prospectively followed for 16-56 months (mean 21.9 +/- 0.8 months). PPA was associated with only minor increase in P wave duration and decrease in sinus automaticity. PPA did not predict future occurrence of significant atrial dysrhythmia.