Abstract 1745: Mitral Leaflet Adaptation to Ventricular Remodeling: Occurrence and Adequacy in 80 Patients With Functional Mitral Regurgitation
Functional mitral regurgitation (FMR) is caused by systolic traction on the mitral leaflets related to ventricular distortion. Little is known about how chronic tethering affects leaflet area, in part because of inability to reconstruct leaflet area in situ. Our aim was to do so in order to explore whether adaptive increases occur that meet the needs of tethered geometry in FMR, and to test the hypothesis that leaflet area influences MR.
Methods and Results. A new method for 3D echo measurement of mitral leaflet area was developed and validated in vivo against sheep valves, later excised. This method was used to study 80 consecutive patients in 3 groups: patients with normal hearts (n=20); with FMR (n=29) from inferior wall motion abnormality (IWMA) or dilated cardiomyopathy (DCM); and with IWMA or DCM but no MR (n=31). Patients with FMR had 23±5% increased leaflet area compared with normal subjects. The ratio of leaflet to annular area was 1.95±0.40, not different among groups (figure⇓), indicating a surplus leaflet area that adapts to left heart changes. In contrast, the ratio of total leaflet area to that required to close the orifice in mid-systole was decreased in patients with FMR versus normal (1.29±0.15 vs 1.78±0.39, p=0.001) and versus patients with IWMA or DCM but no MR (1.81±0.38, p=0.001). After adjusting for measures of LV remodeling and tethering, a leaflet-to-closure area ratio <1.7 was associated with significant MR (OR=23.2, p=0.02).
Conclusion. Mitral leaflet area increases in response to chronic tethering in patients with IWMA and DCM. However, the adequacy of leaflet adaptation to tethering geometry varies, and may partly explain the heterogeneity of FMR among patients.