SIGNIFICANCE OF SIGNAL-AVERAGED P-WAVE CHANGES DURING EXERCISE IN PATIENTS WITH CORONARY-ARTERY DISEASE AND CORRELATION WITH ANGIOGRAPHIC FINDINGS

The maximal P-wave duration in all time-aligned leads, and the maximal P-wave amplitude in leads V5 and V6 were measured on a 12-lead, signal-averaged electrocardiogram during the recovery period of an exercise stress test (EST). The study group consisted of 75 patients with coronary artery disease (CAD) documented by greater-than-or-equal-to 50% diameter stenosis in 1 or more arteries and a control group of 47 subjects, 15 of them young volunteers and 32 with no or minimal coronary atherosclerosis disease and normal left ventricular function. All subject underwent a symptom limited EST, with use of the Ellestad protocol. Signal-averaged P waves recorded before exercise, and for the first 6 minutes in recovery were measured using a 5 X magnifier. The mean P duration before exercise in the control group was 107 +/- 16 ms (+/- 1 standard deviation) and 111 +/- 15 ms at the third minute of recovery, (p < 0.001). In patients with CAD it was 112 +/- 12 and 129 +/- 19 ms (+/- 1 standard deviation), p <0.001, respectively. Differences in P-wave duration were found to be statistically significant (p < 0.001) throughout recovery in the group with CAD when compared with control and maximal values at the third minute. The increase in P-wave duration (greater-than-or-equal-to 20 ms) was used as an additional parameter to exercise-induced ST-segment depression, ST elevation, or anginal pain for the test interpretation. The sensitivity increased from 57 to 75% and the specificity decreased from 85 to 77%. It is concluded that the measurement of the P-wave duration during recovery adds diagnostic power during EST.