Delayed Improvement in Skeletal Muscle Metabolism and Exercise Capacity in Patients With Mitral Stenosis Following Immediate Hemodynamic Amelioration by Percutaneous Transvenous Mitral Commissurotomy
摘要
The abrupt improvement in hemodynamics after successful percutaneous transvenous mitral commissurotomy (PTMC) does not immediately enhance exercise capacity. Improved exercise capacity several months after PTMC has been reported. We hypothesized that the delayed improvement in exercise capacity is due partly to the slow improvement in the metabolism of skeletal muscle. This study examined the short- and long-term effects of PTMC on exercise capacity and skeletal muscle metabolism in patients with mitral stenosis. Treadmill exercise testing with respiratory gas analysis was performed in 11 patients with symptomatic mitral stenosis before and 3, 30, and 90 days after successful PTMC. On the same schedule, forearm metabolism of high-energy phosphates was measured by magnetic resonance spectroscopy during and after handgrip exercise. Ten healthy volunteers were also examined. PTMC resulted in an immediate symptomatic improvement. However, exercise capacity and skeletal muscle metabolism remained unchanged 3 days after PTMC. AT 30 days after PTMC, there were significant improvements in peak oxygen consumption (p <0.05), intracellular pH at end-exercise (p <0.05), and time constant for phosphocreatine recovery (mean ± SD 88.9 ± 11.3 vs 106.3 ± 11.7 seconds, p <0.01) compared with these baseline values. These improvements remained even at 90 days after PTMC. Exercise capacity improved with some time delay after immediate hemodynamic amelioration by PTMC. Long-term improvement in exercise capacity depends partly on the slowly progressing improvement in skeletal muscle metabolism after long-standing mitral stenosis.