The effect of intravenous amiodarone on heart rate in patients with acute myocardial infarction or ischemia and sinus tachycardia.

The effect of intravenous (IV) amiodarone (300 mg) on heart rate was investigated in 22 patients with acute myocardial infarction (18) or ischemia (4) and sinus tachycardia. There were 11 men and 11 women (age range, 48 to 83 years; mean, 63.5). Amiodarone IV slowed the mean heart rate from 109 +/- 14 beats/min to 94 +/- 15 beats/min (p less than 0.0005). There was a linear correlation between the initial heart rate (preamiodarone) and the final heart rate (postamiodarone), (r = 0.6930, p less than 0.0005). Most of the patients with initial heart rates higher than the mean maintained relatively high heart rates (above the mean), while most patients with lower initial heart rates showed low heart rates (below the mean) after amiodarone administration. Patients in Killip class 1 showed a significant reduction in heart rate after receiving amiodarone, from a mean of 105 +/- 10 to 88 +/- 11 beats/min (p less than 0.01). Patients in Killip class 2 also had reduced heart rates (118 +/- 14 to 81 +/- 39 beats/min), but these changes were not statistically significant. Of the three patients in Killip class 3 to 4, the heart rate slowed by 10 beats/min in one, while in the remaining two no changes were observed. There were no significant side effects from the administration of amiodarone.