Abstract des Autors

Rationale: A new diagnostic approach is reported, which combines Doppler echocardiography and a thermodilution technique for the calculation of mitral valve area at rest and during exercise. This method was applied to determine the magnitude of mitral valve reserve (= exercise-induced increase of mitral valve area) and to assess the hemodynamic relevance of mitral stenosis. Methods: 69 patients with mitral stenosis were included in this study. A Swan-Ganz catheter was used to measure exercise hemodynamics and transvalvular flow by a thermodilution technique. The mean transmitral flow velocity Vmean was determined by continuous wave Doppler. Measurements were performed simultaneously at rest and during stepwise bicycle ergometry. Effective mitral valve area was calculated according to the continuity equation method (MVACE=Flow/Vmean). Results: A significant exercise-induced increase of mitral valve area was found in the total group (rest to 25 W: 1.1+/-0.3 to 1.3+/-0.4 cm**2, p<0.001). Two subgroups were defined according to the presence or absence of mitral valve reserve: deltaMVA >/=20%: group A (n=30), deltaMVA <20%: group B (n=39). Both groups did not differ with regard to mitral valve area at rest. However, the increase of cardiac output and stroke volume was significantly higher in group A than in group B. An effective mitral valve area at 25 W of less than 1.2 cm**2 had an 80% sensitivity and an 83% specificity to detect a severe mitral stenosis. Conclusions: Because the presence and extent of mitral valve reserve cannot be predicted under resting conditions measurements under flow-increasing interventions are necessary. Our data demonstrate that exercise Doppler in conjunction with right-sided cardiac catheterization is most useful to determine mitral valve reserve and to assess the hemodynamic relevance of mitral stenosis. Verf.-Referat