Antiarrhythmic efficacy and side- effects of lidocaine given in the prehospital phase of acute myocardial infarction

One hundred and fifty-one patients with suspected AMI received 300 mg lidocaine i.m. or a placebo, double-blind and at random before being transported to hospital by a mobile coronary care unit. Patients with second-degree or complete AV block and sinus bradycardia (<50 beats/min) were excluded. Fifty-four patients developed myocardial infarction, while 96 had other diagnoses. The patients were kept under clinical observation, with continuous ECG registration, from the time of receiving the injection for 3 h. The lidocaine injection significantly reduced the incidence of ventricular tachyarrhythmias in patients with myocardial infarction during the period 30–90 min after injection. No serious haemodynamic side-effects were observed. A V conduction disturbances possibly due to lidocaine were observed in three patients. No serious side-effects of lidocaine occurred in the patients who did not develop myocardial infarction. It is concluded that patients with suspected AMI may be given 300 mg lidocaine i.m. before transport to hospital with a low risk of serious side-effects, provided the contraindications are observed.