TC Yung, VF Puddy, MP Leung, KT Chau

Background Congenital complete heart block (CCHB) is an uncommon congenital bradyarrhythmia that can be lethal. Knowledge on its clinical course would throw light on the management of this disease.

Method We retrospectively reviewed the hospital records of 25 patients diagnosed as CCHB who were admitted into our unit between 1981 - 1995. The patients were divided into those without (n = 19) and with (n = 6) intracardiac anomalies, and their outcomes were compared between groups. Clinical variables of age of diagnosis, ventricular rate at rest, QRS duration, corrected QT interval (QTc) and cardiothoracic (CT) ratio were also compared between symptomatic and asymptomatic patients of the isolated CCHB group. Chi square, Student's t and Fisher's Exact tests were utilized where appropriate.

Results The patients were aged between 7 days - 17 years (mean = 7.3 years) when they were last seen. Of the patients with isolated CCHB, 9 developed symptoms including heart failure (6), Stokes Adams attack (2) and limited exercise tolerance (1). Six had and 4 are awaiting pacemaker insertion. Symptomatic patients had a larger CT ratio >= 60% (p = 0.07) when compared to the asymptomatic patients. Diagnosis at an early age and other electrocardiographic measurements did not differentiate between symptomatic and asymptomatic patients. One each of symptomatic and asymptomatic patient died of sepsis and without an obvious cause respectively. Of the 6 patients with intracardiac lesions, 3 had neonatal death related to heart failure and 1 died of sepsis at 2 years of age. The mortality for patients with structural heart lesions were significantly higher than those without (4/6 vs 2/19, p < 0.05).

Conclusion Amongst patients with isolated CCHB, a large CT ratio (>= 60%) may predict the development of symptoms. The presence of associated structural heart disease carries a poorer prognosis.