Junctional ectopic tachycardia evolving into complete heart block

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.