Abstract 4343: Mechanisms of Reduction of Mitral Regurgitation by Cardiac Resynchronization Therapy: By Analysis of Left Ventricular Morphology
In patients with heart failure, functional mitral regurgitation(MR) is a main problem. It’s well known the mechanism of functional MR is geometric distortion of the mitral apparatus by LV dilatation, which increases leaflet tethering and restricts closure. We assessed the hypothesis that LV morphologic change contributes to the reduction of MR after cardiac resynchronization therapy(CRT). We studied 50 non-ischemic cardiomyopathy patients who met the criteria for CRT, and 50 normal controls. Echocardiography was used to assess the severity of MR, LV shape, mitral valve morphology, and displacement of papillary muscles(PM). In patients, LV shape was more spherical (sphericity index Fig 1⇓: 1.55±0.25 vs. 1.93±0.25 p<0.001), anterior PM shifted posteriorly (angle B Fig 3⇓: 151.6±19.4 vs. 176.7±15.1° p<0.001), and mitral leaflets were more tethered (tethering area Fig 2⇓: 1.66±0.56 vs. 0.43±0.06cm2 p<0.001) than that of normal controls. However at 6 months after CRT, sphericity index (1.51±0.20 to 1.89±0.40 p<0.001) and angle B (146.6±16.5 to 167.7±17.7°p<0.001) increased significantly. Moreover tethering area (1.63±0.72 to 1.03±0.77cm2 p<0.001), and MR jet area (28.7±16.1 to 16.1±19.3% of LA area p<0.01) were reduced in responder (n=34 73.9%), but did not change in non-responder. Indeed, tethering area correlated with sphericity index (r=−0.39 p<0.001), and angle B (r=−0.29 p<0.01). CRT reduced the subvalvar traction by changing the shape of LV and restored displaced anterior PM toward original position. These morphological change contributes to the reduction of functional MR in patients treated with CRT.