Effect of successful coronary angioplasty on the signal-averaged electrocardiogram

The effect of successful coronary artery angioplasty on the signal-averaged electrocardiogram (SAECG) was examined in 50 patients (41 men, 9 women, aged 55 +/- 8 years) with stable (26 patients) or unstable angina (24 patients) and good overall left ventricular function (ejection fraction = 55% +/- 8%). The SAECG was recorded before and within 24-48 hours after the angioplasty and was filtered at 40-250 Hz, with 250 beats averaged. The noise level averaged 0.57 +/- 0.15 microV before and 0.56 +/- 0.17 microV after the procedure. There was no overall significant difference between pre- and postangioplasty SAECGs. Subgroup analysis showed that 14 patients had a significant increase of the root mean square voltage of the last 40 msec of the filtered QRS that was independent of noise level changes, previous myocardial infarction, stable or unstable angina status, positive or negative baseline SAECG, or vessel being dilated. Eleven patients (22%) had late potentials at baseline, of whom four (36%) lost them after angioplasty, while one patient developed them after the procedure, all due to root mean square voltage changes. Thus, successful angioplasty exerted no significant overall effect on the SAECG, suggesting that the substrate of late potentials was not grossly altered by the procedure in our patients. However, there appear to be some patients, constituting approximately one third of this study population, who derive a favorable influence on the SAECG from angioplasty, a subgroup that needs to be further defined in future studies.