Prevalence of late potentials after myocardial infarction treated with systemic thrombolysis or primary percutaneous transluminal coronary angioplasty.

BACKGROUND: The presence of late potentials (LP) after myocardial infarction (MI) is related to an occluded infarct-related coronary artery (IRA). However, the effects of the signal-averaged electrocardiogram (SAECG) of systemic thrombolysis are contradicting. Reperfusion in the IRA is more frequently observed after primary percutaneous transluminal coronary angioplasty (PTCA) than after systemic thrombolysis. The aim of this prospective study was to compare the prevalence of LP in survivors of acute MI treated with either systemic thrombolysis or primary PTCA.

METHODS: Between October 1994 and January 1997, 134 patients (pts) with acute MI were treated with reperfusion therapy within 12 hours of the onset of symptoms: seventy-four pts received systemic thrombolysis and 60 underwent primary PTCA. All pts (mean age 61 +/- 10 years, 120 males) had a control coronary angiography 9 +/- 5 and 10 +/- 4 days after acute MI, respectively. The recorded signals were amplified, averaged and filtered with bi-directional Butterworth filtering (band-pass filter range of 40-250 Hz). LPs were defined as the presence of 2 or 3 of the following criteria: filtered duration of the QRS complex > 114 ms, root mean square voltage of signals in the last 40 ms of the QRS < or = 20 mV and duration of the low amplitude signals > 38 ms.

RESULTS: The two groups of pts did not differ significantly with respect to age, gender, presence of either diabetes or hypertension, site of MI, previous MI, Killip class, time to treatment, peak CK-MB level, incidence of reinfarction, extent of coronary artery disease and left ventricular ejection fraction. One hundred pts (75%) had patency (TIMI 3 grade flow) of the IRA at control coronary angiography. Twenty-seven pts (20%) had LP: 16 pts (22%) among those treated with systemic thrombolysis and 11 pts (18%) among those treated with primary PTCA (p = ns). Pts treated with primary PTCA had higher patency rates [95% (57/60) vs 58% (43/74); p = 0.00002] and less severe residual stenosis (19 +/- 15% vs 72 +/- 18%; p = 0.0001) in the IRA. LP were found in 15 pts (15%) with TIMI 3 grade flow and in 12 pts (35%) with TIMI 0-2 grade flow (p = 0.017). By multivariate analysis, including 18 clinical and electrocardiographic variables, an occluded IRA was the only independent predictor of the development of LP (Wald chi 2: 6.1453; p = 0.0132).

CONCLUSION: Results of this prospective study suggest that primary PTCA alone does not reduce the prevalence of LP when compared to systemic thrombolysis. Only the patency of the IRA, as determined before the hospital discharge, affected the development of LP after acute MI.