The electrocardiogram during sinus rhythm and tachycardia in patients with Mahaim fibers. The importance of an “rS” pattern in lead III

Abstract

To describe the clinical experience of patients with polymorphic ventricular tachycardia (PMVT) in a hospital setting.A 2-year prospective, observational study of patients with symptomatic and asymptomatic PMVT admitted to the coronary care unit of a community medical center. Electrocardiograms were reviewed for a pattern diagnostic of PMVT, and the QTc interval of the baseline ECG was determined. Etiologic factors, management, and clinical outcomes were also analyzed.The study included 27 patients (13 men) with a mean age of 66.6 ± 10 years. Fourteen patients had a prolonged QTc interval ≥520 ms (group A), and 10 patients had a normal QTc interval ≤440 ms (group B). Acute hypokalemia (n = 7) in the setting of underlying heart disease was the principal cause of the acquired QT syndrome; other causally related factors included severe bradycardia and the proarrhythmic effect of drugs. Acute myocardial infarction (n = 6) was the principal cause of PMVT associated with a normal QTc interval; other causal factors included right ventricular cardiomyopathy and the proarrhythmic effect of electrical cardioversion. Eight patients (group C) had brief runs of asymptomatic nonsustained PMVT, which recurred in 5 patients as symptomatic sustained PMVT despite appropriate treatment. Cardiac arrest (63%) requiring emergency defibrillation was the predominant clinical presentation irrespective of the QT interval. Four patients (15%) died, but only 2 owing to refractory PMVT/VF.PMVT with or without QTc prolongation is a sporadic tachyarrhythmia that has frequent malignant potential for cardiac arrest. Successful management mandates emergency defibrillation for cardiac arrest and other appropriate measures for suppression of PMVT. The prognosis of PMVT is improved when the cause is correctly identified and promptly treated.