Transition from congenital junctional ectopic tachycardia to complete AV bl
ock was observed in an 8 month old girl, over a 36 hour period, during init
ial hospital admission. Two years later she had evidence of a rapidly incre
asing left ventricular end diastolic diameter, associated with lowest heart
rates during sleep of < 30 beats/min. A transvenous permanent pacemaker wa
s therefore implanted. This finding supports the idea that a pathological p
rocess in the area of the AV junction, initially presenting as junctional e
ctopic tachycardia may later extend to sudden complete atrioventricular blo
ck.