CONTRIBUTION OF MITRAL-VALVE RESERVE CAPACITY TO SUSTAINED SYMPTOMATIC IMPROVEMENT AFTER BALLOON VALVULOTOMY IN MITRAL-STENOSIS - IMPLICATIONS FOR RESTENOSIS

Objectives. To explain the discrepancy between the symptomatic status of patients and the hemodynamically calculated mitral valve area during long term follow up after mitral balloon valvulotomy, mitral valve orifice variability after dobutamine infusion was investigated in two groups of patients. Background. A significant increase in aortic valve area with increased aortic transvalvular flow has been reported in patients with calcific aortic stenosis after aortic balloon valvulotomy. A similar phenomenon with regard to the mitral valve has not been studied in detail. Methods. Group 1 comprised 10 patients (mean age 33 +/- 9 years) with untreated mitral stenosis. Group 2 comprised 29 consecutive patients (mean age 32 +/- 7 years) who underwent successful percutaneous mitral balloon valvulotomy 13 +/- 2 months before the study. Results. After dobutamine infusion, heart rate and cardiac index increased significantly in both groups. The mean pulmonary artery pressure, mitral valve gradient and pulmonary capillary pressure remained unchanged in Group 2 but increased significantly in Group 1. The mean mitral valve area was significantly larger in Group 2 after dobutamine infusion than at baseline (1.9 +/- 0.5 vs. 2.4 +/- 0.6 cm(2), p < 0.0001) but was unchanged in Group 1 (1.2 +/- 0.2 vs. 1.3 +/- 0.3 cm(2), p = NS). The mean mitral valve area in seven patients in Group 2 (24%) was less than or equal to 1.5 cm(2) before dobutamine infusion (1.3 +/- 0.4 cm(2)), which was defined as restenosis. In five of these seven patients who had minimal or no symptoms, the mitral valve area increased significantly after dobutamine infusion (1.3 +/- 0.1 vs. 1.9 +/- 0.1 cm(2)). In the other two patients who were symptomatic, the mitral valve area did not change after dobutamine infusion. These two patients were identified as having ''true'' restenosis, and redilation of the mitral valve was performed in both. Conclusions. In patients who underwent mitral balloon valvulotomy, increased mitral valve reserve capacity contributed to symptomatic improvement on long-term follow-up. Dobutamine infusion may be helpful in detecting clinically significant restenosis.