Dilated cardiomyopathy in isolated congenital complete atrioventricular block: early and long-term risk in children

OBJECTIVES We sought to identify the risk factors predicting the development of dilated cardiomyopathy (DCM) in patients with isolated congenital complete atrioventricular block (CCAVB). BACKGROUND Recently evidence has emerged that a subset of patients with CCAVB develop DCM. METHODS This was a retrospective study of 149 patients with CCAVB who had heart size and left ventricular (LV) function assessed by echocardiography and chest radiography over a follow-up period of 10 ± 7 years. RESULTS Nine patients developed DCM at the age of 6.5 ± 5 years. No definite cause could be identified. In these nine patients, CCAVB was diagnosed in eight at 23 ± 2.3 weeks gestation and in one at birth. Maternal SSA/SSB antibodies were confirmed in seven of the nine patients. Pacemakers were implanted in eight patients in the first month and in one patient at five years of age. The initial left ventricular end-diastolic dimension (LVEDD) was in the 96th ± 2.6 percentile and the cardiothoracic (CT) ratio was 64 ± 3.8% in the nine patients who developed DCM, and differed significantly in patients with CCAVB (p < 0.005) who did not develop DCM. The LVEDD and CT ratio did not decrease in the patients with CCAVB and DCM, but decreased significantly in the patients with CCAVB without DCM (p < 0.001) once pacing was initiated. Two patients with DCM died within two months of diagnosis; one patient is neurologically compromised; two patients received a heart transplant; and four patients are listed for heart transplantation. CONCLUSIONS Isolated CCAVB is associated with a long-term risk for the development of DCM. Risk factors may be SSA/SSB antibodies, increased heart size at initial evaluation and the absence of pacemaker-associated improvement.