BACKGROUND Atrial septal defect (ASD) closure is one of the most representative cardiac operations, but there have been few assessments of right ventricular (RV) performance during the perioperative period. RESULTS Using transesophageal echocardiography with automated border detection system, the RV pressure - area (P-A) loops were measured in 6 patients immediately before and after an ASD closure. Multiple RV P-A loops obtained by the inferior vena cava occlusion technique were used to evaluate end-systolic maximal elastance (Ees), preload recruitable stroke work (MEW), external work (EW) and the systolic P-A area (PAA). Ees and MEW are indices of contractility, and PAA represents the total mechanical energy. RV Ees and MEW did not change after the operation (from 3.36 +/- 2.20 to 3.70 +/- 2.04 mmHg/cm2, p = 0.4; and from 10.3 +/- 5.0 to 10.5 +/- 4.5 mmHg, p = 0.8, respectively), whereas EW and PAA were significantly reduced (from 121.4 +/- 77.4 to 48.7 +/- 26.6 mmHg/cm2, p < 0.05; and from 274.8 +/- 212.8 to 92.7 +/- 52.8 mmHg/cm2, p < 0.05, respectively). ASD closure reduced the EW and total mechanical energy of the right ventricle without influencing contractility. CONCLUSIONS These results indicate that ASD closure preserved RV function and reduced RV myocardial oxygen consumption. Assessment of the RV P-A relationship in the operating room demonstrates the beneficial effects of ASD closure on RV performance.