A unique and complex pattern of intra-$ ventricular trifascicular block was documented electrocardiographically, for the first time, in a newborn infant with a history of transient intrauterine bradycardia. The clinical course was progressive, leading to a high-degree atrioventricular block, accompanied by severe Adams-Stokes attacks and congestive heart failure. Pacemaker therapy had to be instituted at the age of 3 months.
Congenital intraventricular trifascicularblock differs from the usual form of congenital heart block. It deserves close observation and early therapeutic intervention.Rosenbaum et al1 first introduced the concept of "intraventricular trifascicular block" in 1969, when they described four adult patients with right bundle-branch block and intermittent left anterior and poste¬ rior hemiblock. The very existence of three main terminal fascicles (the right bundle branch and the two di¬ visions of the left) of the intraven¬ tricular conduction system has been proved by postmortem microdissec¬ tion,1 2 and by animal experiments.3 Rosenbaum et al4 reviewed the litera¬ ture and collected retrospectively a total of 20 cases demonstrating one form or another of trifascicular block. From those cases they proposed a log¬ ical electrocardiographic classifica¬ tion of trifascicular blocks into eight spatiotemporal possibilities (PI to P8), depending on the constant or in¬ termittent nature of the block in each of the three fascicles. This paper, we believe, describes the first documented case of con¬ genital intraventricular trifascicular block. The electrocardiographic ex¬ pressions were intriguingly complex and unstable. The rapid progression of the clinical course necessitated an urgent and decisive approach in its management.Report of a Case A 3,600 gm (8 lb) girl was born to a 20-year-old mother, para 1-0-1-1, by cesarean section on Aug 19, 1971. The pregnancy was unremarkable except that, one month before term, the mother was admitted to another hospital for four days' observation because of a transient period of fetal bradycardia of about 40 beats per minute. When the mother was hospitalized at term, in active labor, at the Brooklyn-Cumber¬ land Medical Center, a fetal heart rate of approximately 50 beats per minute was again noted. At birth, the baby's heart rate was 68 beats per minute. The Apgar score was nine at one minute. On arrival at the nur¬ sery, she was in no distress. The heart tones were good. A grade 2/6 low-pitched systolic murmur was heard along the left sternal border. The liver was not palpable.Chest roentgenograms revealed moder¬ ate cardiomegaly and normal pulmonary vascularity. The first electrocardiogram, obtained
