Conduction disturbances in acute myocardial infarction: A clinical study and brief review of the literature

Introduction: Heart blocks may occur as complications of acute myocardial infarction (AMI) and are accompanied by increased in-hospital mortality. The objective of this investigation was to study heart blocks in patients with AMI and to assess their association with clinical features and therapeutic measures. Methods: Four hundred consecutive patients (263 men, 137 women, mean age 59.6 ± 8.4 years) who were admitted with the diagnosis of AMI were assessed. The initial ECG, recorded immediately after the patient's admission to the emergency department, was considered as baseline. Any heart blocks occurring over the following days were noted by comparing the relevant ECGs with this baseline ECG. Results: The overall prevalence of heart blocks was 15.8%. There was no significant statistical correlation between the incidence of heart blocks and the patients' age and sex. Although the prevalence of cigarette smoking, hypertension, hypercholesterolaemia and diabetes mellitus in patients with heart block was greater than in patients without, the differences were not statistically significant. The development of heart blocks was more common among those patients treated with thrombolytic therapy (21.1% vs. 12%, p=0.01). Also, the development of heart blocks was associated with a significantly lower left ventricular ejection fraction. It was found that 25% of patients who died following AMI had experienced heart blocks, compared with only 13.6% of those who survived (p<0.01). Conclusions: Development of heart blocks has important prognostic significance. The higher prevalence of heart blocks in anterior wall or Q-wave infarctions indicates that the increased mortality following heart block development is probably not related solely to the conduction disturbance itself, but also to the relatively larger infarcted area.