QRS axis in isolated perimembranous ventricular septal defect and influences of morphological factors on QRS axis.

To detect the frequency of left axis deviation (LAD) in isolated perimembranous ventricular septal defects (VSD) we retrospectively analyzed electrocardiograms of 59 patients, aged 8 months to 15 years. Patients were grouped into those having ventricular septal aneurysm (VSA) formation (n:20) and those who did not have VSA (n:39). Patients with VSA were then stratified into 2 groups according to the presence of left ventricular-to-right atrial (LV-RA) shunt. Four hundred healthy children served as the control group. We found that 12 (20.3%) of 59 patients with isolated perimembranous VSD had a LAD. Five of 6 patients with perimembranous outlet VSD and 6 with perimembranous inlet VSD had abnormal LAD with a qR pattern in I and aVL and rS in aVF. Abnormal LAD was more prevalent in patients with VSA (40%) than without VSA (7.7%) (P <.01). We also found that mild right ventricular hypertrophy (RVH) with the rsR' or rSR' pattern in V1 was more frequent in patients with VSA, especially those who had LV-RA shunt. However, we could not find significant difference between patients with or without LV-RA shunt for the incidence of abnormal LAD and mild RVH. Localization of perimembranous VSD was not found to have an effect on frequency of abnormal LAD and mild RVH in this patient group. In patients with clinical findings of VSD, the existence of abnormal LAD especially if it is associated with mild RVH, should raise the possibility of perimembranous VSD with VSA formation.