Lidocaine and the quarternary ammonium compound QX-572 in acute myocardial infarction. A comparative study.

Patients with suspected or proven acute myocardial infarction complicated by ventricular arrhythmias not corrected by lidocaine therapy (bolus dose 100 mg followed by infusion 2 mg/min) were treated either with an increased dose of lidocaine (bolus dose 50 mg followed by infusion 3 mg/min) or with 600 mg N,N-bis dimethylammonium chloride (QX-572, Astra, Sweden) as an i.v. infusion during 30 min (3 patients) or 60 min (13 patients). In the lidocaine group the arrhythmias were controlled in 6 out of 15 patients, in the QZ-572 group in 12 out of 16, a difference that is not statistically significant. However, the frequency of side-effects was significantly higher (p less than 0.001) in the QX-572 group (15 out of 16 patients). They were also more severe, including pronounced tachycardia and hypertension. It is concluded that despite the high antiarrhythmic effect of QX-572, an increase of the lidocaine dose would be safer and preferable in the clinical situation studied.