Does late revascularization alter the evolution of the signal-averaged electrocardiogram in patients with a recent transmural myocardial infarction?
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Signal-averaged electrocardiogram
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Signal-averaged electrocardiogram
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This editorial refers to ‘Reduced prognostic power of ventricular late potentials in post-infarction patients of the reperfusion era’† by A. Bauer et al. , on page 755
Signal-averaged electrocardiogram (SAECG) reveals presence of late potentials that are low-amplitude high-frequency waveforms within the terminal portion of the QRS complex. Late potentials reflect the presence of slow conduction within the ventricular myocardium that may serve as a substrate for arrhythmogenesis. The underlying histology is hypothesized to be areas of fibrosis interspersed among areas of viable myocardium. Early studies showed that the presence of late potentials predicted inducibility of ventricular arrhythmias during programmed electrical stimulation in patients with remote myocardial infarction. Although the presence of late potentials was not a highly sensitive or specific marker for sudden death, it was regarded as having a good negative predictive value for arrhythmic events in post-infarction patients in the 1980s.
Currently, it is well established that beta-blockers and successful thrombolysis/revascularization reduce the prevalence of late potentials after acute myocardial infarction.1 However, less data were published on the effect of reperfusion and/or beta-blocker therapy on the prognostic value of SAECG in post-infarct risk stratification. In the Cardiac Arrhythmia Suppression Trial Substudy …
*Corresponding author. Tel: +852 28554244; fax: +852 28551143. E-mail address : cplau{at}hkucc.hku.hk
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Signal-averaged electrocardiogram
Reperfusion Therapy
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Coronary arteries
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Signal-averaged electrocardiogram
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Background Recent evidence suggests that late reperfusion of an occluded infarct-related artery after an acute myocardial infarction may reduce the frequency of subsequent arrhythmic events. Late mechanical reperfusion by percutaneous transluminal coronary angioplasty (PTCA) under these circumstances has a high success rate. The present study was performed to test the hypothesis that the late mechanical restoration of anterograde flow in an occluded infarct artery after an acute myocardial infarction causes a resolution of late potentials. Methods Twenty subjects (10 men, one woman; aged 32–77 years) suffering a first acute myocardial infarction, with signal-averaged electrocardiographic (ECG) recordings and a severely occluded infarct-related artery, were prospectively identified. Results Eighteen patients underwent successful PTCA of the occluded artery 6–32 days after a first acute myocardial infarction. Late potentials were observed in 14 patients 5–22 days after the infarction. A follow-up signal-averaged ECG was performed 1–8 days later. In the subgroup of 12 patients with successful reperfusion and an abnormal signal-averaged ECG before PTCA, seven (58.3%) showed resolution of the late potentials at follow-up; in these patients the filtered QRS duration showed a significant reduction (112.1 ±;14.2 to 96.7±;12.7ms, P=0.02), the root-mean-square voltage increased (9.8±;6.5 to 33.1 ±;15.5μV, P=0.017), and the duration of low-amplitude signals <40μV decreased after angioplasty (46.3 ±;11.0 to 28.5 ±; 6.5ms, P< 0.022). In contrast, two patients with late potentials before PTCA and unsuccessful reperfusion had no significant changes in signal-averaged ECG. Conclusions In some patients with an acute myocardial infarction, late mechanical reperfusion of the culprit vessel may reduce the incidence of abnormalities on the signal-averaged ECG. Whether this will improve long-term survival has yet to be confirmed in a large trial.
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