Effects of low dose transdermal scopolamine on heart rate variability in acute myocardial infarction

Objectives. We hypothesized that by enhancing parasympathetic activity, low dose transdermal scopolamine would increase heart rate variability after myocardial infarction. Background. Low heart rate variability is associated with increased mortality after acute myocardial infarction. Methods. Conventional time domain heart rate variability was measured from 24-h Holter recordings of 61 consecutive male patients (mean age 58 ± 10 years, left ventricular ejection fraction 44.7 ± 15,5%) 6 days (median) after acute myocardial infarction. Patients were then randomly assigned to wear one patch of transdermal scopolamine or a matching placebo patch for 24 h, during which their 24-h heart rate variability was remeasured. Results. Compared with placebo, transdermal scopolamine caused a significant increase in time domain measures of 24-h heart rate variability by 26% to 35% above baseline. Transdermal scopolamine was well tolerated. Conclusions. Low dose transdermal scopolamine safely increases cardiac parasympthetic activity and short-term heart rate variability after acute myocardial infarction. Whether the effect of transdermal scopolamine on heart rate variability is a reasonable surrogate for improvement of long-term morbidity and mortality requires an appropriately designed investigation.