Arrhythmic Complications After Parasympatholytic Treatment of Bradyarrhythmias in a Coronary Care Unit

Parasympatholytic treatment of bradyarrhythmias is part of the policy in coronary care units (CCU). Because of psychotic central nervous reactions following repeated i.v. doses of atropine, this drug was replaced by methyl scopolamine, and no such reactions have occurred since then. During a period of continuous ECG‐recording in a CCU, 27 patients with bradyarrhythmias were given at least one dose of 0.12‐0.5 mg methyl scopolamine. Its maximal effect as measured by the peak QRS‐rate occurred after about 10 min. Within this time atrial fibrillation appeared for the first time in 2 patients, and ventricular tachycardia and ventricular fibrillation in another subject. During the following 2 hours no further major arrhythmias were observed. All of these arrhythmias occurred in the 16 patients with AMI and none in the 11 subjects with other diagnoses. The possibility of a causal relationship between treatment with methyl scopolamine and appearance of tachyarrhythmias is discussed. The arrhythmic complications described in this study have made us reduce the initial i.v. dose of methyl scopolamine from 0.5 to 0.06‐0.12 mg, which often is satisfactory.