Ventricular septal flattening at end systole falsely predicts right ventricular hypertension in patients with ostium primum atrial septal defects

Purpose: To assess the reliability of ventricular septal position in predicting elevated right ventricular pressure (RVP) in patients with ostium primum atrial septal defects (ASD 1). Methods: Echocardiograms of 4 groups were retrospectively analyzed: Patients with ASD 1 and low RVP, patients with ASD 1 and high RVP, and 2 age-matched control groups: one with isolated ostium secundum atrial septal defects (ASD 2), and 1 with normal cardiac findings. End-systolic left ventricular sectional diameters along the midmitral diameter (D1) and a diameter orthogonal to it (D2) were measured off-line by a blinded observer. The ratio D2/D1, the eccentricity index (EI), was calculated; a higher index represents greater septal flattening. Results: The mean EI in the ASD 1 with low RVP group was significantly higher than both the group with ASD 2 and the healthy control group. The mean EI of the ASD 1 group with high RVP was significantly higher than the mean El of the ASD 1 group with low RVP, although there was a poor correlation between EI and RVP in this group, r = 0.54. Conclusion: The ventricular septum is flatter in the ASD 1 patients with low RVP than in an age-matched control group with ASD 2 and compared with an age-matched control group of healthy subjects, giving a false impression of elevated RVP in the ASD 1 group. Although the mean EI is significantly higher in the ASD 1 group with high RVP than in the group with low RVP, there is a poor correlation between EI and RVP, which limits the reliability of this index.