Histopathologic and electrophysiologic correlations in idiopathic dilated cardiomyopathy and sustained ventricular tachyarrhythmia

Idiopathic dilated cardiomyopathy is associated with a high incidence of serious ventricular arrhythmias, which carry a significant risk of sudden death.¹ In contrast to patients with coronary artery disease, in whom ventricular tachycardia arises as a result of reentrant circuits that form during the healing of an infarct,^2-4 the histologic substrate for ventricular arrhythmias in dilated cardiomyopathy has not been identified. Using various semiquantitative scoring methods, several groups have attempted to correlate histopathology with hemodynamic data as well as prognosis in patients with idiopathic dilated cardiomyopathy.^5-8 Myocarditis has been reported in patients with dilated cardiomyopathy and unexplained ventricular arrhythmias.⁹ However, a possible correlation between the inducibility of sustained ventricular tachycardia during electrophysiologic study and histopathology has not been systematically examined. A preliminary report from Stanford University suggested that a semiquantitative histologic score may be useful in predicting response to β blockers in patients with dilated cardiomyopathy.¹⁰ To determine if an identifiable histologic correlate for inducible sustained ventricular tachycardia exists in patients with idiopathic dilated cardiomyopathy presenting with sustained ventricular tachyarrhythmia, we analyzed histologic and electrophysiologic data from 25 such patients using the same scoring system.