Development of a Reproducible Swine Model of Chronic Ischemic Mitral Regurgitation: Lessons Learned

Abstract

Durability of mitral valve repair for ischemic mitral regurgitation (IMR) remains poor. We established a swine model of chronic IMR, and describe the methods and lessons learned from this model. Thirty-five swine underwent percutaneous myocardial infarction with ethanol ablation of the circumflex or obtuse marginal (OM) arteries. Swine were followed with routine echocardiography for the development of severe IMR. Once severe IMR was established, swine underwent mitral valve operations on cardiopulmonary bypass. After operation, swine were survived up to 7 weeks. Angiographic and echocardiographic features of swine who developed severe IMR (IMR swine) and those who did not (non-IMR swine) were compared. The median number of OM arteries was 3, with2 OM arteries infarcted. Acute survival after the myocardial infarction was 74% (26 of 35) with 3 (9%) early,postoperative deaths. Among the 23 swine with follow-up todetermine IMR status, 14 of 23 (61%) developed significant IMR. Among IMR pigs, left ventricular (LV) ejection fraction decreased from 65% pre-myocardial infarction to 45% pre-mitral valve intervention (P < .001). Among non-IMR swine, LV ejection fraction decreased nonsignificantly from baseline (60%) to latest follow-up (55%) (P= .443). LV end-diastolic dimension (P= .039), wall motion score (P= .027), global circumferential strain (P= .014), and global longitudinal strain (P= .023) were significantly worse in IMR compared with non-IMR swine. A reproducible percutaneous model ofsevere IMR in swine is feasible with a guided anesthetic and perioperative approach. This model canserve as a platform to better understand the mechanism of IMR and subsequently to test novel repair techniques.