[Effects on high resolution electrocardiogram of coronary angioplasty in acute myocardial infarct].

BACKGROUND

The lower prevalence of ventricular late potentials (LPs) in signal-averaged electrocardiograms (SAECG) observed in patients (pts) treated with systemic thrombolysis, as compared with SAECGs in conventionally treated pts, has been attributed to the patency of the infarct-related artery. Mechanical reperfusion, achieved by means of either primary or rescue percutaneous transluminal coronary angioplasty (PTCA), is associated with higher permeability rates and reduced residual stenosis in the infarct-related artery, when compared to systemic thrombolysis. The aim of this retrospective study was to assess the prevalence of LPs in pts recovering from a first high-risk acute myocardial infarction (AMI) treated with primary or rescue PTCA.

METHODS

Fifty-nine pts (48 pts with clinical signs or electrocardiographic evidence of high-risk AMI or in whom systemic thrombolysis was inadvisable, and 11 pts in whom systemic thrombolysis failed) underwent emergency PTCA within 10 hours of the onset of symptoms. All pts (mean age 61 +/- 9 years, 48 M) were monitored via coronary angiography 9 +/- 4 days after AMI. The SAECG was obtained 10 +/- 4 days after AMI. LPs were defined as the presence of 2 or 3 of the following criteria: filtered duration of the QRS complex > 114 ms, duration of the low amplitude signals > 38 ms and mean square-root voltage of signals in the last 40 ms of the QRS < or = 20 microV.

RESULTS

Primary and rescue PTCA were performed 3 +/- 1.7 and 6.3 +/- 2 hours after AMI, respectively (p = 0.000). Fifty-six pts (95%) had patency (TIMI 3 grade flow) of the infarct-related artery (mean residual stenosis: 18.3 +/- 14.2%) confirmed by control coronary angiography, while the infarct-related artery was occluded in three pts. Sixteen out of 59 pts (27%) had LPs: 14/56 (25%) with TIMI 3 grade flow and 2/3 (67%) with TIMI 0 grade flow. Pts with and without LPs were comparable for age, sex, infarct location, Killip Class, mean peak CK-MB, time to control coronary angiography, time to SAECG, left ventricular ejection fraction, presence of multivessel disease, infarct-related artery and mean residual stenosis in infarct-related artery. LPs were observed more frequently after rescue PTCA than after primary PTCA (64 vs 19%; p = 0.005). Time to treatment was significantly longer in pts with LPs than in those without (4.9 +/- 2.6 vs 3.2 +/- 1.7 hours; p = 0.025). Multivariate analysis indicated that the type of PTCA (primary vs rescue PTCA) was the only independent predictor for the development of LPs.

CONCLUSION

In this study, the prevalence of LPs in pts with patency of the infarct-related artery after primary or rescue PTCA was surprisingly high. Delay to treatment and type of PTCA affected the presence of LPs. The association between infarct-related artery status and prevalence of LPs has not been analyzed, due to the low number of pts with coronary artery occlusion in the control coronary angiography.