BACKGROUND: Alterations in ventricular loading conditions lead to changes in action potential duration via mechanoelectrical feedback. A decrease in load immediately leads to prolongation of repolarization. QT interval and QT dispersion were measured to determine the long-term effect of changes in ventricular systolic load on the ventricular repolarization. METHOD: Corrected QT interval and QT dispersion were measured in 26 patients before and 3-6 months after valvuloplasty for pulmonary stenosis. To determine the effect of ventricular load on ventricular repolarization, patients were divided in 2 groups; Group 1 was those patients with a greater than 30 mmHg and Group 2 was those patients with a less than 30 mmHg decrease in right ventricular systolic pressure. RESULTS: Corrected QT interval (412.6+/-14.5 msec vs 426.4+/-16.8 msec, p < 0.05) and QT dispersion (35.0+/-7.3 msec vs 45.7+/-14..1 msec, p < 0.05)were increased significantly only in Group 1 after vlavuloplasty. CONCLUSION: It suggested that mechanoelectrical interactions are operative for long duration in humans that changes in ventricular load after successful pulmonary valvuloplasty showed long-term effect on the ventricular repolarization.