Comparative hemodynamic and electrocardiographic investigation of antiarrhythmic doses of procainamide and lidocaine was carried out in 19 patients with acute myocardial infarction or with severe left ventricular failure of other etiologies. In 12 patients in whom the standard recommended dosage of these agents was equally effective in abating ventricular tachyarrhythmias, there were no significant adverse hemodynamic and electrical effects or differences (p > 0.05) between relatively small salutary doses of lidocaine and procainamide after their intravenous administration in similar quantity and manner (100 mg in 3 min followed by 2 mg/min for 20 min). Furthermore, larger doses of procainamide (500 mg given 20 mg/min intravenously), which were also therapeutically beneficial in seven additional patients with acute myocardial infarction, caused no significant alteration (p > 0.05) in hemodynamic function. With the 500 mg dose, there was a small difference (p < 0.05) in the directional change of cardiac index which was dependent on the control values: the variable rose slightly in patients with normal indexes whereas it declined slightly in those with low values. Significant Q-T prolongation (p < 0.05) occurred with 500 mg of the agent; otherwise, there were no adverse electrocardiographic or untoward extracardiac effects. Thus, intravenous procainamide is equally effective in acute myocardial infarction and is a relatively safe alternative to lidocaine.
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