[AQRS left axial deviation of more than -30 degrees and incomplete right branch block in isolated ventricular septal defects]

Electrocardiographic findings in five out of forty-three cases of isolated Ventricular Septal Defects (VSD) demonstrated incomplete Right Bundle Branch Block (RBBB) with left AQRS deviation of more than -30 degrees. These features are said to be characteristic of VSD of the Persistent Common Atrioventricular Canal type. However, in two of our five cases a defect of the Inlet Septum was documented angiographically; in the remaining three cases a defect of the peri-Membranous septum was clearly demonstrated. Moreover hemodynamic data in our patients indicate that right ventricular diastolic overload could not account for RBBB in all of the cases. The clinical importance derived from this experience is that ECG findings of RBBB and left AQRS deviation of more than -30 degrees are not necessarily associated with, and therefore do not represent certain proof of the presence of VSD of the A-V Canal type. The association of this ECG pattern with VSD's other than the A-V Canal type, as previously observed, appears to have an anatomic explanation, which however needs further substantiation through electrophysiologic studies.