OBJECTIVE: To investigate whether transdermal scopolamine increased cardiac vagal activity in patients during the acute phase of myocardial infarction. METHODS: 30 patients with a first acute myocardial infarction and preserved sinus rhythm who were on no drug that could influence the sinus node were randomly assigned to either treatment group or placebo group. Measures of heart rate variability (HRV) in patients given drug or placebo were obtained by digital 24 hour Holter recording before and after treatment. Baroreflex sensitivity was performed using the phenylephrine method. RESULTS: No significant differences was found in the indices of the time domain and the frequency domain in both groups before treatment. Patients with transdermal scopolamine showed a significant increase in the standard deviation of normal RR intervals (SDNN), standard deviation of all five min mean normal RR intervals (SDANN), root mean square of differences of successive normal RR intervals (rMSSD), total power (TP, 0.000. - 0.40 Hz), low frequency peak (LF, 0.040 - 0.15 Hz), high frequency peak (HF, 0.15 - 0.40 Hz), and Baroreflex sensitivity after treatment (P
