Abnormal Conduction-Induced Cardiomyopathy: JACC Review Topic of the Week.

Nonischemic cardiomyopathies are a frequent occurrence. The understanding of the mechanism(s) and triggers of these cardiomyopathies have led to improvement and even recovery of left ventricular function. Although chronic right ventricular pacing-induced cardiomyopathy has been recognized for many years, left bundle branch block and pre-excitation have been recently identified as potential reversible causes of cardiomyopathy. These cardiomyopathies share a similar abnormal ventricular propagation that can be recognized by a wide QRS duration with left bundle branch block pattern; thus, we coined the term abnormal conduction-induced cardiomyopathies. Such abnormal propagation results in an abnormal contractility that can only be recognized by cardiac imaging as ventricular dyssynchrony. Appropriate diagnosis and treatment will not only lead to improved left ventricular ejection fraction and functional class, but may also reduce morbidity and mortality. This review presents an update of the mechanisms, prevalence, incidence, and risk factors, as well as their diagnosis and management, while highlighting current gaps of knowledge. [Display omitted] • Abnormal conduction-induced CM refers to LV systolic dysfunction caused by RVP, LBBB, or pre-excitation. In each case, ventricular dysfunction is reversible if properly treated. • Abnormal conduction-induced cardiomyopathies share a similar pattern of abnormal ventricular activation that can be recognized by a wide QRS duration and LBBB pattern resulting in abnormal contractility identified by cardiac imaging as ventricular dyssynchrony. • Appropriate diagnosis and treatment of these cardiomyopathies will not only improve LVEF and functional capacity but may also reduce mortality. [ABSTRACT FROM AUTHOR]