title: The paradoxical adverse effect of verapamil for treating clinical paroxysmal supraventricular tachycardia.
abstract: The intravenous administration of verapamil to 2 patients with paroxysmal supraventricular tachycardia (PSVT) resulted in an induction of PSVT during a programmed electrophysiological stimulation study. Each patient had a documented episode of PSVT. Baseline programmed stimulation studies revealed neither induction of PSVT nor an atrial echo; however, PSVT was induced immediately after injecting verapamil (0.15 mg/kg) intravenously in both patients. In 1 patient, the study was repeated 2 days later and similar results were obtained. The serum concentration of verapamil when PSVT was induced was about 80 ng/ml in both cases. Clinicians using verapamil should note that this antiarrhythmic drug may aggravate PSVT, depending on critical changes in AV nodal conduction and refractoriness.
mesh_terms: D000328:Adult; D000368:Aged; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D013617:Tachycardia, Supraventricular / Q000097:blood / Q000139:chemically induced* / Q000188:drug therapy; D013997:Time Factors; D014700:Verapamil / Q000009:adverse effects* / Q000097:blood
chemical_list: D014700:Verapamil