Right ventricular ejection fraction during exercise in patients with recent myocardial infarction: Effect of the interventricular septum

Abstract

To investigate the effect of interventricular septum (IVS) on right ventricular function during exercise, radionuclide angiocardiography was performed in 50 patients with recent myocardial infarction. Twenty-five patients had involvement of IVS according to thallium uptake in IVS (group I), and 25 patients were free of IVS involvement (group II). Although there was no statistical difference between the two groups in right ventricular ejection fraction (EF) at rest (45% +- 10% vs 48% ± 8%), patients in group I had significantly lower left ventricular (LV) EF (40% ± 11% vs 53% ± 11%, p < 0.01) and larger LV end-diastolic volume (129 ± 46 vs 106 ± 31 ml, p < 0.05) than those in group II. All parameters increased significantly during exercise in both groups, but patients in group I had significantly lower exercise right ventricular EF (50% ± 10 vs 56% ± 9%, p < 0.05), LVEF (44% ± 11% vs 56% ± 13%, p < 0.01), and larger LV end-diastolic volume (155 ± 44 vs 129 ± 37 ml, p < 0.05) than those of group II. Significant correlations were observed between right ventricular EF and LV end-diastolic volume at rest and during exercise ( r = −0.48, p < 0.05, and r = −0.68, p < 0.01, respectively) in group I, but right ventricular EF correlated with LVEF only at peak exercise ( r = 0.65, p < 0.01). In contrast, right ventricular EF did not correlate with any variables at rest or during exercise in group II. Eight of 25 patients in group I had normal right ventricular reserve during exercise (exercise-resting right ventricular EF > 5%), whereas 16 of 25 patients had normal right ventricular reserve in group II. The presence or absence of IVS involvement is a significant determinant of right ventricular response to exercise ( p < 0.05), but IVS function was not associated with LV reserve. Thus IVS contraction may be important for the maintenance of right ventricular function in patients with impaired LV function.