Twenty-one patients with moderate to severe mitral stenosis were treated with percutaneous balloon mitral valvuloplasty (PBMV) using Inoue mitral double-lumen balloon catheters. Creatinine phosphokinase MB isoenzyme (CPK-MB) levels were measured at baseline, 5 min, 6 h, and 18 h post dilatation. Haemodynamic indexes, 12-lead ECGs, and 2-dimensional echocardiograms were performed to evaluate systolic function postprocedure. CPK-MB levels were modestly increased at 5 min and at 6 h postprocedure compared with the baseline level (p < 0.001) but were still within the normal reference range, except for one patient who had a level at 5 min minimally above the upper limit of normal. CPK-MB levels were not significantly increased at 18 h after the procedure. No significant changes in ejection fractions, 12-lead ECGs, and regional wall motion occurred in any of the patients studied. In conclusion, PBMV causes modest early elevation of CPK-MB. This elevation is not associated with changes in LV systolic function and does not interfere with the diagnosis of acute myocardial infarction using the enzyme elevation criteria.