Electrocardiographic changes following surgical repair of ostium primum defect.

A four-year-old boy had an OPD with an ECG showing a LAH pattern. After surgical repair the ECG changed to a pattern of LBBB with right axis deviation. This case suggests that early activation of the posterior left ventricular wall associated with partial impairment in the anterior portion of the left bundle, and abnormal hemodynamics, accounts for the superiorly oriented frontal plane QRS axis in patients with OPD.