CAP were diagnosed by TEAP using RPE intervals in 55 cases of paroxysmal supraventricular tachycardia (PSVT). There were no obvious CAP manifestations of ECG in those cases, the mean RPE interval during tachycardia was 140 +/- 29 ms, and the lower limit of x +/- 2 s was 82 ms. Among them, the VA intervals were measured by electrocardiophysiological examination in 21 cases. The mean value was 130 +/- 25 ms, and the lower limit of x +/- 2 s was 80 ms. The results suggest that RPE over 82 ms may be an important diagnostic threshold cut off point of atrioventricular reciprocation.