To evaluate the acute change in the mitral flow pattern, especially pressure half-time after percutaneous transvenous mitral commissurotomy (PTMC) and to investigate the factors influencing the mitral flow pattern, Doppler and two-dimensional echocardiographic studies were performed in 15 patients before and two, six, 10 and 24 hours and seven days after PTMC. Mitral valve area increased and the mean mitral pressure gradient decreased after PTMC (1.0 +/- 0.4 cm2 to 1.8 +/- 0.4 cm2; 11 +/- 6 mmHg, to 3 +/- 2 mmHg, p < 0.01). Pressure half-time also decreased two hours after surgery, from 292 +/- 70 msec to 176 +/- 48 msec (p < 0.01) and then gradually decreased to 140 +/- 47 msec within seven days of the procedure without remarkable changes in mitral valve area and the mean transmitral pressure gradient. Left atrial dimensions decreased and left ventricular end-diastolic dimensions gradually increased after PTMC (51 +/- 6 mm to 46 +/- 5 mm; 47 +/- 4 mm to 50 +/- 3 mm). The time course of this was similar to that of the pressure half-time. Further study, in which the changes in pressure half-time were evaluated within 30 minutes of PTMC in 17 patients, indicated that pressure half-time significantly decreased from 248 +/- 69 msec to 139 +/- 28 msec five minutes after balloon inflation, slightly increasing again after 30 minutes to 153 +/- 31 msec.(ABSTRACT TRUNCATED AT 250 WORDS)