Pædiatric Wolff-Parkinson-White Conduction

Report:

Sinus rhythm 190/min

Wolff-Parkinson-White conduction, type “A”

Comment:

At the age of one to two months, the rate below 191/min is not reported as tachycardia. Atrial activity is barely visible but, where seen, remains consistent with sinus rhythm. The PR interval is, approximately, 0.06” – short even for an infant.

The QRS complex is 0.10” long and has a monophasic R , or rR’ or Rs morphology in the precordial leads; the normal “septal” q waves are absent from the LV leads. The precordial sequence is essentially a positive concordant pattern seen in, e.g., masquerading BBB, VT or WPW type “A”. The first of those is not seen in infants, while VT is excluded by the presence of regularly associated P waves. Another differential diagnosis, RVH, is excluded by the absence of RAD and S waves in the LV leads, while a biventricular hypertrophy would be expected to show large equiphasic mid-precordial complexes (the Katz-Wachtel phenomenon). WPW conduction is the only reasonable diagnosis. In fact, in this case the diagnosis is WPW syndrome in view of the history of paroxysmal tachycardia.

Below (Fig 55a) is a trace taken a month later, with more distinct P and δ waves. There is now is greater AV nodal and lesser bundle of Kent contribution to the ventricular complex. That’s also why the axis has normalised.