The mitral valve orifice area (MVOA) is difficult to assess accurately by 2D echocardiography because of geometric assumptions; therefore, 3D planimetry may offer advantages. We studied the differences in MVOA measurements between the most frequently used methods, to determine if 3D planimetry would result in the re-grading of severity in any cases, and whether it was a more accurate predictor of clinical outcomes.
This was a head-to-head comparison of the three most commonly used techniques to grade mitral stenosis (MS) by orifice area and to assess their impact on clinical outcomes. 2D measurements (pressure half-time (PHT), planimetry) and 3D planimetry were performed retrospectively on patients with at least mild MS. The clinical primary endpoint was defined as a composite of MV balloon valvotomy, mitral valve repair or replacement (MVR) and/or acute heart failure (HF) admissions.
Forty-one consecutive patients were included; the majority were female (35; 85.4%), average age 55 (17) years. Mean and peak MV gradients were 9.4 (4) mmHg and 19 (6) mmHg, respectively. 2D and 3D measures of MVOA differed significantly; mean 2D planimetry MVOA was 1.28 (0.40) cm2, mean 3D planimetry MVOA 1.15 (0.29) cm2 (P = 0.003). Mean PHT MVOA was 1.43 (0.44) cm2 (P = 0.046 and P < 0.001 in comparison to 2D and 3D planimetry methods, respectively). 3D planimetry reclassified 7 (17%) patients from mild-to-moderate MS, and 1 (2.4%) from moderate to severe. Overall, differences between the two methods were significant (X2, P < 0.001). Only cases graded as severe by 3D predicted the primary outcome measure compared with mild or moderate cases (odds ratio 5.7).
3D planimetry in MS returns significantly smaller measurements, which in some cases results in the reclassification of severity. Routine use of 3D may significantly influence the management of MS, with a degree of prediction of clinical outcomes.