Chronic ischemic mitral regurgitation induced in pigs by catheter-based coronary artery occlusion.

ABSTRACT

BACKGROUND AND AIM OF THE STUDY Ischemic mitral regurgitation (IMR) appears in 20-50% of patients after acute myocardial infarction, and entails an increased long-term mortality. In order to compensate for the diversified pathology in humans, this disease entity has been developed in pigs in order to allow investigations of therapeutic options against IMR. METHODS: The left circumflex coronary artery was occluded using catheter-based intracoronary coil deployment in 24 female pigs (body weight 50 kg). This was followed by a rapid pacing protocol. The left ventricular (LV) volumes at end-diastole and end-systole were assessed with multi-slice, short-axis cardiovascular magnetic resonance imaging. From these image sequences the mitral regurgitant volume (MRV) was quantified by subtracting the aortic flow volume from the LV stroke volume. The extension of myocardial infarction was quantified using a delayed contrast (gadolinium) enhancement technique. Five pigs served as controls. RESULTS: During the procedure, seven animals died due to intractable ventricular fibrillation and technical problems. Eleven of the remaining 17 pigs fitted with coils survived the six-week follow up period. Of these animals, nine had a transmural inferior-lateral LV wall infarction and significant IMR (MRV = 10.5 +/- 6.3 ml). None of the control pigs had IMR. There was a positive correlation between the size of the myocardial infarction and the mitral regurgitant volume. CONCLUSION: A catheter-based porcine model has been established for chronic IMR which balances between an adequate infarct size and acceptable mortality. The model provides a platform for further investigations of the geometric and hemodynamic features of chronic IMR in order to identify potential geometric targets of the disease. The model also allows the evaluation of innovative surgical approaches to reverse LV remodeling.