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 durin g long term follow up after mitral balloon valvulotomy, mitral valve o rifice variability after dobutamine infusion was investigated in two g roups of patients. Background. A significant increase in aortic valve area with increased aortic transvalvular flow has been reported in pat ients with calcific aortic stenosis after aortic balloon valvulotomy. A similar phenomenon with regard to the mitral valve has not been stud ied in detail. Methods. Group 1 comprised 10 patients (mean age 33 +/- 9 years) with untreated mitral stenosis. Group 2 comprised 29 consecu tive patients (mean age 32 +/- 7 years) who underwent successful percu taneous mitral balloon valvulotomy 13 +/- 2 months before the study. R esults. After dobutamine infusion, heart rate and cardiac index increa sed significantly in both groups. The mean pulmonary artery pressure, mitral valve gradient and pulmonary capillary pressure remained unchan ged in Group 2 but increased significantly in Group 1. The mean mitral valve area was significantly larger in Group 2 after dobutamine infus ion than at baseline (1.9 +/- 0.5 vs. 2.4 +/- 0.6 cm(2), p < 0.0001) b ut 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 l ess 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 patie nts who had minimal or no symptoms, the mitral valve area increased si gnificantly 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 mitra l valve was performed in both. Conclusions. In patients who underwent mitral balloon valvulotomy, increased mitral valve reserve capacity co ntributed to symptomatic improvement on long-term follow-up. Dobutamin e infusion may be helpful in detecting clinically significant restenos is.