CRT in a congenital heart disease patient with interventricular dyssynchrony due to an RV conduction delay.

We encountered a unique pattern of cardiac dyssynchrony in a patient with complex congenital heart disease (heterotaxy syndrome) with a biventricular physiology and systemic left ventricle (LV). On speckle tracking echocardiography, dyssynchrony was not detected within the LV, but was noted in an interventricular fashion between the LV and right ventricle (RV). An electrophysiologic study revealed a conduction delay in the subpulmonary RV. Cardiac resynchronization therapy provided reverse cardiac remodeling and an excellent result in our patient by placing the pacing leads around the dyssynchronous lesion.