Cardioactive drugs.

Most patients who have taken a large dose of a beta-blocker will demonstrate bradycardia and hypotension. With very large doses there will be coma, convulsions and profound hypotension. A variety of cardiac dysrhythmias and ECG abnormalities are described. The more serious of these can result in cardiorespiratory arrest.2,3 These include: • heart block • intraventricular conduction defects • ST segment elevation • absent P waves, and • ventricular fibrillation or asystole.