Prognostic Significance of the Lown Grades and Late Potentials in Patients after Myocardial Infarction

ABSTRACT

BACKGROUND AND OBJECTIVES: The aims of this study were to assess the long term overall survival of patients after an acute myocardial infarction (AMI), and to determine the association of survival with the occurrence of ventricular arrhythmia, as recorded by Holter electrocardiography (ECG) and signal-averaged electrocardiography (SAECG). SUBJECTS AND METHODS: One hundred fifty two patients with an AMI were enrolled between January 2000 and August 2006. SAECG and Holter ECG were performed before hospital discharge (at range of 2-10 day). The grading system of Lown was used to evaluate the ventricular premature beats on Holter ECG. Three groups of patients were identified based on the seriousness of the ventricular arrhythmia, as identified by the Holter ECG Lown grade 0, Lown grades 1, 2 and Lown grades 3, 4, 5. SAECG was performed with a high pass frequency of 25 Hz and 40 Hz. The presence of late potentials (LPs) recorded on SAECG was evaluated. The predictors for survival were assessed using Cox's proportional hazard model and Kaplan-Meier analysis. RESULTS: The mean duration of follow-up was 45.8+/-25.5 months. Twenty four patients (15.8%) died during follow-up. The multivariate predictors of all cause death included age [hazard ratio (HR)=1.25, 95% confidence interval (CI)=1.08-1.47, p=0.003] and Lown grades 3, 4 and 5 (HR=19.17, 95% CI=1.25-290.80, p=0.034). Survival analysis did not show a significant relationship between LPs and overall patient survival. The only predictors for overall mortality were age and the Lown grade. CONCLUSION: SAECG did not predict mortality for the patient with AMI. The ventricular arrhythmias recorded by conventional Holter before hospital discharge may be a useful noninvasive prognostic test after an AMI.