Prevention of primary ventricular fibrillation in acute myocardial infarction with prophylactic lidocaine.

Primary ventricular fibrillation (VF) during an acute myocardial infarction (AMI) occurs with a high incidence and mortality rate with or without thrombolysis. The incidence varies from 2% to 19% depending on the definition of "primary." Primary VF in this study refers to fibrillation occurring in the absence of shock or pulmonary edema. Mortality rate, when primary VF occurs, is 2 to 4 times greater than when it does not. Prevention of VF has been impeded by the publication of the 1996 recommendations of the American Heart Association and American College of Cardiology against the use of prophylactic lidocaine based on meta-analysis studies implying toxicity. This observational study of 4,254 patients with AMI reports the incidence and mortality rates of primary VF over 32 years. Of the 4,254 patients, 4,150 received prophylactic lidocaine, and 104 patients did not receive prophylactic lidocaine due to the 1996 guidelines, after which administration of prophylactic lidocaine was governed by physician choice. The incidence of primary VF was 0.5% among the 4,150 who received prophylactic lidocaine and 10% among the 104 who did not (p <0.0001). Among the 4,150 receiving prophylactic lidocaine, sinoatrial block occurred in 0.5% and complete infranodal atrial ventricular block occurred in 0.2%, all secondary to the site of infarction (concurrent serum lidocaine levels were < 4 microg/ml). Asystole was an agonal rhythm in 4%; these patients had been off lidocaine for 48 hours. Mortality rates were 10.5% in patients without primary VF and 25% in patients with VF (p <0.001). Thus, prophylactic lidocaine markedly decreased the incidence of VF in 4,150 patients with AMI to 0.5% compared with trials before and after thrombolysis (2% to 19%) and with the 104 patients in this study who did not receive prophylactic lidocaine (10%). No lidocaine-induced sinoatrial or atrial ventricular block or asystole occurred.