Prolongation of the averaged QRS complex: A simple prognostic factor in patients with post-infarction bundle branch block and a history of syncope

Patients with a history of myocardial infarction and complete bundle branch block with syncopal episodes have a high risk of sudden death :the identif ication of the cause of the syncope is therefore essential. The aim of the study was to assess the diagnostic value of non-invasive techniques used in the investigations of syncope: 24 hour Holter recording, high amplificatio n ECG and measurement of left ventricular ejection fraction. The results of these investigations were compared with those of complete electrophysiolog ical investigation evaluating atrioventricular conduction and the inducibil ity of tachycardia. The patient population was 134 patients, 83 with right bundle branch block and 51 with left bundle branch block. Ninety one patien ts had inducible sustained ventricular tachycardia and 24 had atrioventricu lar conduction defects : of these, 14 also had ventricular tachycardia. Dur ing follow-up, there were 12 sudden deaths and 13 deaths from cardiac failu re. Uni- and multivariate analysis showed induction of Ventricular tachycar dia to be a significant risk factor for global mortality and sudden death b ut prolongation of the averaged QRS complex (> 165 msec) was also an indepe ndant risk factor of global cardiac mortality. The authors conclude that simple prolongation of the averaged QRS duration > 160 ms in patients with right bundle branch block and > 170 ms in patient s with left bundle branch block after myocardial infarction and syncope is a significant poor prognostic factor. However, this sign is not predictive of sudden death.