The Effect of Intravenous Amiodarone on Heart Rate in Patients with Acute Myocardial Infarction or Ischemia and Sinus Tachycardia: Clinical Implication

The Effect of Intravenous Amiodarone on Heart Rate in Patients with Acute Myocardial Infarction or Ischemia and Sinus Tachycardia: Clinical ImplicationAmiodarone in Acute Myocardial Ischemia-Infarction
There are few data regarding the effect of amiodarone on heart rate in patients with acute myocardial infarction or ischemia. Moreover, in no clinical studies to our knowledge was amiodarone given specifically for the treatment of sinus tachycardia. Temam gave IV amiodarone to 50 patients with acute myocardial ischemia-infarction. He found a mean decrease of 15 percent in the heart rate in one hour without significant fall in blood pressure. Lotto et al reported their experience with 12 patients with acute myocardial infarction in whom (3-blockers were contraindicated. Heart rate decreased in all but one patient (111 ±14 to 99 ±11.8 beats/min). This effect was more marked in patients with high initial heart rates and was almost absent when the initial heart rate was below 80 beats/ min. There was a linear correlation between the reduction in heart rate caused by amiodarone and the initial heart rate (r = 0.917).

Our results, which agree with those of Temam and Lotto et al, show that IV amiodarone significantly slows heart rates in patients with sinus tachycardia during acute myocardial ischemia or infarction (Fig 1). We found a linear correlation between the preamio-darone and the postamiodarone heart rates (r = 0.6930) (Fig 2), however, with a relatively similar reduction in almost all of the patients. Patients with a relatively high initial heart rate maintained a relatively high heart rate after amiodarone administration, as seen in the right upper quadrant of Figure 2. Patients with low initial heart rates demonstrated a heart rate lower than the mean after drug administration. This similar relative reduction in heart rate after amiodarone is also demonstrated in almost all of the patients in Figure 1. We observed a marked effect on heart rate in patients in Killip classes 1 and 2, whereas this negative chronotropic effect was absent in two of the three patients in Killip class 3 to 4. This observation is probably related to the different degree of sympathetic (catecholamine) stimulation seen in both groups.
Clinical Implication
Sinus tachycardia is a common arrhythmia that sometimes appears in the first days of an acute myocardial infarction, particularly in patients with anterior myocardial infarction. In addition, sinus tachycardia may worsen myocardial ischemia by an adrenergic-dependent mechanism. The treatment of choice for this condition is usually (3-blockers. However, there are certain conditions where the administration of (3-blockers is either contraindicated (bronchial asthma, chronic obstructive pulmonary disease, congestive heart failure) or partially contraindicated (severe peripheral vascular disease or mild congestive heart failure). In these cases, IV amiodarone may be the substitute of choice for the treatment of sinus tachycardia, if clinically indicated.