Congenital Complete Heart Block

Report:

Sinus rhythm 100 – 108/min

Third degree AV block

Junctional escape rhythm 54/min

Nonspecific T wave changes

Comment:

The criteria for AV block as the cause of AV dissociation are fulfilled in that the atrial rate is almost twice faster than the ventricular. It is most unlikely that a slower junctional escape rate or a faster sinus discharge would have resulted in any captures.

There are features in this tracing indicative of heart disease beyond the block. The T waves’ inversion in leads 1 and aVL is definitely abnormal; even in the precordial leads the inversion is rather deep and pointed for a mere “juvenile pattern”.

The P waves, too, have a P congenitale pattern, perhaps reflecting atrial hypertrophy from contracting against often closed AV valves. The right axis, approximately +120o, is normal for a child of two. On the other hand, it hadn’t been always thus: at four months (Fig 58a below) it was less to the right and the P and T waves were less abnormal. The RS in V1 has become qRsr’; this could be at least in part positional.

A good quality echocardiogram would be of value. A good phrase in this context is that ‘something else may be going on’. There were no clinical data on her ECG forms.

The rhythm strip shows P waves apparently at the same rate as the QRS complexes; the former are positioned half-way between the latter. This illustrates, superficially, the Bix rule, even though careful mapping reveals the atrial activity is completely dissociated. For more on Bix rule, see Case 70.