Congenital heart block: Development of late-onset cardiomyopathy, a previously underappreciated sequela

OBJECTIVES We report 16 infants with complete congenital heart block (CHB) who developed late-onset dilated cardiomyopathy despite early institution o f cardiac pacing. BACKGROUND Isolated CHB has an excellent prognosis following pacemaker impl antation. Most early deaths result from delayed initiation of pacing therap y or hemodynamic abnormalities associated with congenital heart defects. METHODS A multi-institutional study was performed to identify common clinic al features and possible risk factors associated with late-onset dilated ca rdiomyopathy in patients born with congenital CHB. RESULTS Congenital heart block was diagnosed in utero in 12 patients and at birth in four patients. Ten of 16 patients had serologic findings consiste nt with neonatal lupus syndrome (NLS). A pericardial effusion was evident o n fetal ultrasound in six patients. In utero determination of left ventricu lar (LV) function was normal in all. Following birth, one infant exhibited a rash consistent with NLS and two had elevated hepatic transaminases and t ransient thrombocytopenia. In the early postnatal period, LV function was n ormal in 15 patients (shortening fraction [SF] = 34 +/- 7%) and was decreas ed in one (SF = 20%). A cardiac pacemaker was implanted during the first tw o weeks of life in 15 patients and at seven months in one patient. Left ven tricular function significantly decreased during follow-up (14 days to 9.3 years, SF = 9% +/- 5%). Twelve of 16 patients developed congestive heart fa ilure before age 24 months. Myocardial biopsy revealed hypertrophy in 11 pa tients, interstitial fibrosis in 11 patients, and myocyte degeneration in t wo patients. Clinical status during follow-up was guarded: four patients di ed from congestive heart failure; seven required cardiac transplantation; o ne was awaiting cardiac transplantation; and four exhibited recovery of SF (31 +/- 2%). CONCLUSIONS Despite early institution of cardiac pacing, some infants with CHB develop LV cardiomyopathy. Patients with CHB require dose follow-up not only of their cardiac rate and rhythm, but also ventricular function. a Am Cell Cardiol 2001;37:238 - 42) (C) 2001 by the American College of Cardiol ogy.