Analysis of the signal-averaged P-wave duration in patients with percutaneous coronary angioplasty-induced myocardial ischemia

To assess the impact of angioplasty-induced myocardial ischemia on the duration of the surface P wave, patients undergoing elective angioplasty of isolated lesion in the left anterior descending, circumflex or right coronary arteries were monitored with a 3-channel electrocardiographic Holter system. The leads used were modified bipolar chest leads V 5, aVF and V 2 (CM-V 5, CS-aVF and CMV 2). After electrocardiographic signal-averaging, the earliest onset and the latest offset of the P wave were identified in all of the above timealigned signal-averaged leads, and the composite maximal P duration was measured under 10 X magnification. The maximal ST-segment shift during balloon inflation was also measured in all of the above leads at 60 ms after the J point. In the study group comprising 47 patients, the mean signal-averaged P-wave duration was 125.0 ± 16 ms at baseline versus 130.0 ± 15 ms during balloon inflation, p < 0.005. In the left anterior descending coronary artery group (n = 23), the mean signalaveraged P-wave duration was 122.4 ± 17 ms and 131.3 ± 16 ms during balloon inflation, p < 0.005. In the group with a right coronary artery lesion (n = 18), the values were 127.3 ± 14 ms and 128.4 ± 13 ms respectively (p = not significant). Significant increases in the P-wave duration were found to occur in groups both with (n = 34) and without (n = 13) ST-segment shift ≥1 mm (both p < 0.05). Thus, the duration of the signalaveraged surface P wave is prolonged during angioplasty-induced ischemia, but significantly so only in the group with left anterior descending coronary artery occlusion.