Rabea Rashed, Waseem Ahmed, Sohaib Akbar, Uzair Mumtaz, Bilqees Akhtar, Nayyar Riffat.
Frequency of late ventricular potentials as a precursor of complex ventricular arrhythmias in patients with acute myocardial infarction.
J Cardiovascular Dis Jan ;17(1):21-9.

BACKGROUND: Studies on Late Ventricular potentials (LVPs) in subjects of myocardial infarction (MI) were mostly done before the time period when reperfusion techniques were introduced. Controversial results were reported in the studies which were conducted to probe the effects of thrombolysis on Late Ventricular Potentials (LVPs) & incidence of complex ventricular arrhythmias. The predictive significance of late ventricular potentials (LVPs) depends on early thrombolysis so that complete coronary blood flow can be achieved. AIMS & OBJECTIVE: The objective of the study was to determine the frequency of late ventricular potentials as a precursor of complex ventricular arrhythmias in patients with acute myocardial infarction. MATERIAL & METHODS: This comparative prospective study was conducted at Cardiology department of Mayo Hospital, Lahore. Patients who presented with Myocardial Infarction(MI), diagnosed by history, ECG, enzymes were subjected to late potential analysis by Signal Averaged Electrocardiography (SAECG).Patients were divided in to two groups, group-A patients were thrombolysed with Streptokinase (SK+) and group-B patients were not thrombolysed with Streptokinase (SK-). Each group had 66 patients. Patients were followed for a total duration of 6 months. Patients were asked to visit the hospital after specified intervals. The occurrence of LVP was recorded within 1st month (30 days) before any interventional treatment (percutaneous coronary intervention/coronary artery bypass grafting), 90 days and 180 days after acute myocardial infarction. Left ventricular ejection fraction (LVEF) was determined by transthoracic echocardiography within 15 to 20 days after the occurrence of ST elevation myocardial infarction (STEMI). Complex ventricular arrhythmias were detected by 12 lead standard ECG and by 24 hours Holter monitoring after 30 days, 90 days & 180 days of MI. All episodes of fatal or nonfatal arrhythmic events, re-infarction and revascularization procedure were carefully recorded. RESULTS: Late ventricular potentials were seen in 8 (12.12%) patients who were given SK (group A) and in 14(21.21%) patients who were not given SK (group B). Stratification of ejection fraction showed that patients with ejection fraction less than 40% , late ventricular potentials were seen in 2 patients of group A and none of the patients in group B developed late ventricular potentials. However patients whose ejection fraction was more than 40%, late ventricular potentials were seen in 6 patients of group A and in 14 patients of group B. However no statistically significant association was seen between thrombolytic status of patients with late ventricular potentials stratified on the basis of ejection fraction. Although R on T phenomena which can be an initiating factor for development of ventricular arrhythmias was observed in 7 patients (5.3%) out of 132, only 1 patient (0.75 %) was suspected to have sudden cardiac death due to fatal ventricular arrhythmias. This patient had anterior wall MI and was not thrombolysed with streptokinase (group B). His ejection fraction was 42 % and late ventricular potentials were recorded on signal averaged ECG. 4 patients (3.03 %) were observed to have non sustained ventricular tachycardia but no episodes of sustained ventricular arrhythmias or sudden cardiac death were reported in these patients. 3 (75%) out of 4 patients had inferior wall MI who did not received thrombolysis with streptokinase ( group B ) with ejection fraction > 40 % and late ventricular potentials were recorded . 1 ( 25%) out of 4 patient had anterior wall MI, belonged to group B , ejection fraction >40% and late ventricular potentials were present. According to our study patients of group B had high frequency of late ventricular potentials. However patients with ejection fraction >40% from group B showed higher frequency of late ventricular potential as compared to patients of group A. Thrombolysis was main determinant of late ventricular potentials. i.e. Group A : 12.12% vs. Group B:21.21% with p-value=0.161 showing no st rong association between ejection fraction and occurrence of late ventricular potentials. CONCLUSION: Late ventricular potentials were more common in patients who did not receive thrombolytic treatment. KEY WORDS: Late ventricular potentials, signal averaged electrocardiogram, myocardial infarction, ventricular tachycardia.

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