Lignocaine prophylaxis in acute myocardial infarction: an evaluation of randomised trials

Although lignocaine has been used in coronary care units for almost two decades, its role in preventing ventricular fibrillation (VF) during acute myocardial infarction (MI) is still debated. Of fifteen randomised trials of lignocaine prophylaxis, most showed no apparent benefit. When the data from all fifteen trials were pooled and a summary relative risk estimate calculated, there was a significant benefit of lignocaine treatment in preventing VF. However, the trials had widely differing treatment schedules, modes of drug administration, and doses of lignocaine; to decrease the clinical heterogenity, minimum criteria for adequacy of treatment were established and the data from six trials which fulfilled these requirements were pooled. The summary relative risk estimate calculated from the pooled data of these six trials also demonstrated a significant prophylactic effect of lignocaine that was even greater when the two trials which treated patients with left ventricular failure and shock were excluded. From these analyses, it is concluded that lignocaine treatment provides prophylaxis against VF in acute MI. The failure of most trials to demonstrate such a prophylactic effect is due to small sample sizes and inadequate treatment protocols.