Sequential assessment of mitral valve area during diastole using colour M-mode flow convergence analysis: New insights into mitral stenosis physiology

Aims: In mitral stenosis (MS) transvalvular flow and velocity continually change through-out diastole but for mitral valve area (MVA), flow-dependent variations (valve reserve) are unknown. These physiologic changes can be studied by the proximal isovelocity surface area (PISA) method, using the high temporal resolution of colour M-mode, essential for simultaneous measurements of flow and velocity. Hence, we aimed to validate the colour M-mode PISA method for measurement of MVA in MS and to define using this method the physiologic flow-dependent changes of MVA during diastole. Methods and results: In 50 patients with native MS, MVA was measured by planimetry (MVA-2D), Doppler pressure half-time (MVA-PHT), and two-dimensional PISA (2D-PISA). MVA measurement by colour M-mode PISA in early diastole (M-PISA) (1.27± 0.46 cm²) with rigorously timed flow and velocity measurements by continuous wave Doppler did not differ and correlated well with MVA-2D (1.29±0.44 cm², p=0.59; r=0.85, p<0.001) and MVA-PHT (1.30±0.41 cm², p=0.52; r=0.80, p<0.001). In contrast a trend towards underestimation of MVA by 2D-PISA was observed (1.23±0.42 cm²; p=0.10 and p=0.07). Timed analysis of transvalvular haemodynamics at early, mid, mid-late, and late diastole showed marked changes in flow and velocities (both p<0.0001) but not in MVA (respectively 1.27±0.46, 1.29±0.47, 1.28<0.51 and 1.27±0.49 cm²; ns). Conclusions: In MS, the high temporal resolution of colour M-mode PISA allows accurate MVA measurements. It also allows for the first time, sequential MVA assessment during diastole. Notwithstanding marked flow and velocities changes, MVA remained unchanged throughout diastole underscoring the lack of flow-related valvular reserve in MS.