Figure 78-15 Adverse response to verapamil. Tachycardia thought to be atrial flutter was present initially (A). After the injection of 5 mg verapamil, the rate accelerated and the patient became unresponsive, necessitating cardioversion (B). The first rhythm was ventricular tachycardia. Cardiovascular collapse is a potential complication of verapamil injection when the tachycardia is ventricular in origin.