Effective Atrial Synchronized Single-Site Left Ventricular Pacing Prevents Heart Transplantation in Congenital Left Bundle Branch Block and Dilated Cardiomyopathy in Infants

Cardiac resynchronization is recommended by current guidelines for the treatment of heart failure in patients with dilated cardiomyopathy and mechanical dyssynchrony. We report the benefit of CRT by means of atrial synchronized single-site ventricular pacing in two infants with normal atrioventricular conduction and postnatal left bundle branch block and dilated cardiomyopathy. One infant was referred to us for transplantation at the age of 3 months (a), and the other one at the age of 5 weeks (b). Both were suffering from end-stage heart failure due to dilatative cardiomyopathy (a: LVEDD 42 mm [Z-score: +14], EF 13%; b: LVEDD 42 mm [Z-score: +11], EF 16%) and left bundle branch block. At the age of 3.5 months (a)/6 weeks (b), both infants underwent heart surgery with placing of atrial and ventricular epicardial leads. In both infants, the ventricular leads were placed on the posterolateral wall of the left ventricle. The appropriate AV delay was determined by echocardiographic measurements. It was optimized when AV-VTI and LV-EF were the largest, reference E and A peaks were separated and ECG QRS duration was the narrowest. After 8 weeks (a)/2.5 weeks (b), both infants showed significant reverse remodeling of the left ventricular size (a: LVEDD 29 mm [Z-score: +2.4]; b: LVEDD 33 mm [Z-score: +5]) and could be discharged. After follow-up time of 9 months (a) and 9 years (b), both children show normal left ventricular function (a: FS 35%; b: FS 36%) and left ventricular sizes (a: LVEDD 25 mm [Z-score: +0.41]; b: LVEDD 44mm [Z-score: +1.08]. They still have left bundle branch block without ventricular pacing.

In conclusion, we assume that a congenital form of left bundle branch block may cause cardiomyopathy and adequate resynchronization therapy may induce reverse remodeling of the left ventricle.