RESUMO
OBJECTIVE: A significant proportion of patients with advanced heart failure present with dilated left ventricles and functional mitral regurgitation. These patients currently have limited treatment options. The MitraClip device (Abbott) has benefited only patients with smaller left ventricles (end-diastolic dimension <70 mm), whereas those with larger left ventricles did not benefit. A possible explanation is correcting functional mitral regurgitation alone may not adequately reduce the wall stresses of a dilated left ventricle. We have developed a beating-heart device that not only approximates the papillary muscles to reduce functional mitral regurgitation but also modifies the left ventricle size and shape to reduce wall stress. METHODS: Yorkshire swine (n = 16) had a myocardial infarction induced by permanent occlusion of the left circumflex with intracoronary ethanol. Three months later, the animals developed heart failure and moderate or greater functional mitral regurgitation. Through a transapical approach, the new device was implanted under echocardiography guidance to reshape the left ventricle and correct functional mitral regurgitation. The acute impact of this approach on the mitral valve and left ventricle was assessed with echocardiography and invasive hemodynamics. RESULTS: After reshaping, echocardiography showed a decrease in end-diastolic volume by 36.3 ± 30.5 mL (P < .001), a decrease in sphericity index by 0.143 ± 0.087 (P < .001), and an increase in ejection fraction of 5.90% ± 6.38% (P < .01). Mitral valve tenting area was reduced by 39.29 ± 33.66 mm2 (P < .001), coaptation length was increased by 2.12 ± 1.02 mm (P < .001), and posterior excursion angle was improved by 9.07° ± 9.14° (P < .01), resulting in functional mitral regurgitation reduction. CONCLUSIONS: Correction of functional mitral regurgitation with favorable changes in mitral valve geometry and reduction in left ventricle geometry is possible with the proposed device.
RESUMO
OBJECTIVE: Undersizing mitral annuloplasty (UMA) is a frequently used surgical repair technique to correct ischemic mitral regurgitation in patients with heart failure. In this study, we sought to test the hypothesis that downsizing the mitral annulus can adversely affect the shape and mechanics of the left ventricle inhibiting its functional recovery. METHODS: Eighteen farm swine that underwent an inferolateral myocardial infarction and developed ischemic mitral regurgitation of >2+ severity after 2 months were assigned as follows: 9 swine received an undersized mitral annuloplasty, 6 received papillary muscle approximation (PMA), and 3 animals did not receive any other intervention. Animals lived another 3 months and cardiac magnetic resonance imaging was performed before termination to assess ventricle mechanics and function. RESULTS: Ejection fraction was comparable between the 2 repair groups before surgery, but was significantly lower in UMA at 38.89% ± 7.91% versus 50.83% ± 9.04% in the PMA group (P = .0397). Animals receiving UMA had lower regional peak fractional shortening and reduced systolic and diastolic radial velocities compared with PMA and in some regions were lower than sham. Animals that underwent UMA had higher circumferential strain than sham, but lower than PMA. UMA animals have lower longitudinal strain compared to sham group and lower LV torsion than PMA. CONCLUSIONS: Undersizing the mitral annulus with an annuloplasty ring can restore valvular competence, but unphysiologically impair ventricle mechanics. Mitral valve repair strategies should focus not only on restoring valve competence, but preserving ventricle mechanics.
