[Exercise tolerance in mitral stenosis and chronic obstructive pulmonary disease: evaluation by anaerobic threshold...

Serial radionuclide ventriculography was performed using a newly developed "real-time" system, and left ventricular ejection fraction (LVEF), right ventricular ejection fraction (RVEF), stroke volume (SV), and cardiac output (CO) were measured during graded supine exercise in five patients with mitral stenosis (MS), in five patients with chronic obstructive pulmonary disease (COPD) and in five healthy subjects. Simultaneous pulmonary gas exchange analysis permitted determining the anaerobic threshold, which is the point during incremental exercise when lactate begins to accumulate in the blood. LVEF at the anaerobic threshold was not significantly changed in any patient groups and in healthy subjects, but RVEF at the anaerobic threshold was lower in COPD and MS patients as compared with healthy subjects. In MS, SV during exercise was reduced at the anaerobic threshold, but not in COPD or in healthy subjects. In conclusion, reduced working capacity is related to decreased RVEF in both COPD and MS, but the inhibited increase in CO during exercise is also important for the working capacity in MS.