EXERCISE TOLERANCE IN PATIENTS WITH MITRAL-STENOSIS BEFORE AND AFTER ACUTE PERCUTANEOUS MITRAL VALVULOPLASTY - ROLE OF LUNG DIFFUSING-CAPACITY LIMITATION

The aim of this study was to specify in patients with tight mitral ste nosis whether lung diffusing capacity could play a role in their exerc ise intolerance. A similar study was recently carried out in patients with moderate chronic heart failure. Ten patients with tight mitral st enosis were studied before and 6 months after successful percutaneous transvenous balloon valvuloplasty and compared to six control subjects . Measurements of diffusing capacity, evaluated by the lung transfer f actor (TLCO) and by the transfer coefficient (TLCO/VA), obtained at re st and during early recovery after cardiopulmonary exercise testing we re performed. Cardiac output was determined non-invasively, both at re st and during exercise, using the carbon dioxide exponential rebreathi ng technique. Prior to valvuloplasty, TLCO and TLCO/VA were not differ ent at rest between the two groups. During exercise, patients differed from control subjects, with lower oxygen uptake (P<0.001) and lower c ardiac output at peak exercise (P<0.001). These values at peak exercis e were significantly correlated (P=0.02; r=0.75). Moreover, patients d iffered from control subjects at early recovery after peak exercise wi th an absence of increase in TLCO (P<0.05). Six months after valvulopl asty, a decrease of both TLCO (P<0.01) and TLCO/VA (P<0.05) was observ ed at rest. During exercise, comparison of patients demonstrated a sig nificant increase of both peak exercise oxygen uptake (SLVO(2), P<0.01 ) and cardiac output (P<0.001). At early recovery after peak exercise there was a significant increase in TLCO (P<0.05) and TLCO/VA (P<0.01) , such that a Delta TLCO and a Delta TLCO/VA appeared (P<0.05) identic al to that observed in control subjects. Moreover, Delta SLVO(2), was significantly correlated in patients with Delta Q+Delta TLCO/VA (P=0.0 2; r=0.72). In conclusion, this study suggests a role, at least partia l, of lung diffusing capacity in exercise intolerance in patients with tight mitral stenosis and in the improvement of their aerobic exercis e capacity demonstrated after successful percutaneous balloon valvulop lasty.