Response of the right ventricle to exercise in isolated mitral stenosis

Eight patients in sinus rhythm, with varying degrees of isolated mitral stenosis (mitral valve area 0.6 to 1.3 cm2 and total pulmonary vascular resistance 5.0 to 17.5 U-m2), underwent supine rest and symptom-limited exercise radionuclide ventriculography to determine right ventricular (RV) and left ventricular ejection fraction (EF). Cardiac catheterization with hemodynamic measurements at rest and at peak exercise was performed within 24 hours of radionuclide ventriculography. Four of the 8 patients underwent corrective mitral surgery resulting in normal mean pulmonary artery pressures and total pulmonary vascular resistance at rest. These 4 patients had repeat radionuclide ventriculography at rest and during exercise 1 to 2 months after surgery. Preoperatively, all 8 patients had an abnormal exercise RVEF response (mean change +/- standard deviation [SD], -5.0 +/- 4.5%), coincident with an increase in mean pulmonary artery pressure during exercise (mean change, 15 +/- 5.0 mm Hg). The change in RVEF from rest to exercise, corrected for duration of exercise, correlated with peak exercise mean pulmonary artery pressure (r = -0.71, p = 0.05), as well as total pulmonary vascular resistance at rest (r = -0.82, p = 0.02). Postoperatively, all 4 patients who underwent surgical correction showed a normal RVEF response during exercise (mean change +/- SD, +6.8 +/- 4.0%). Thus, in patients with acquired mitral stenosis and no coronary artery disease (1) loading conditions and not contractility are prime determinants of RV exercise response, and (2) an exercise-induced decrease in RVEF may be a sensitive marker for increased total pulmonary vascular resistance and pulmonary hypertension.