Cardiac MRI of differing ischemia and reperfusion times in a myocardial infarction pig model

The closed-chest porcine model of myocardial ischemia is an essential tool for preclinical research in cardiology. Current literature reports heterogeneous results regarding myocardial ischemia and reperfusion injury (IRI). This retrospective analysis presents our experience and cardiac magnetic resonance (CMR) findings while establishing a porcine IRI model. 8 male and 12 female juvenile German Landrace pigs received general anesthesia and antiarrhythmic pre-treatment. Myocardial ischemia was induced using transfemoral catheterization and balloon-occlusion of the left anterior descending (LAD) or the left circumflex (LCX) coronary artery under X-ray fluoroscopy guidance. The duration of ischemia varied from 30 to 90 min. CMR was performed at a clinical 3 T system including functional imaging, T1 and T2 mapping and late gadolinium enhancement (LGE) 2-5 h or three days post-reperfusion. Ventricular fibrillation (VF) was a recurrent event, which was counteracted with amiodarone, high blood potassium levels and in one case with propranolol. Males were more likely to experience VF than females and 15 of 20 animals survived the experiment. Resuscitation was required in 47% of the further analyzed animals. CMR revealed IRI in 14 of 15 animals in cardiac segments analogous to those supplied by the respective artery in humans. The mean left ventricular ejection fraction was reduced to 52% and 47% of animals had an impaired wall motion. Ischemia durations of 30-45 min did not result in LGE and in no significant T2 increase, whereas T1 was significantly increased (p = 0.02). Occlusion durations of 60-90 min resulted in LGE and T1 and T2 values both increased compared to 30-45 min of ischemia (p < 0.001 for T1 and p = 0.021 for T2). CMR of porcine myocardial IRI showed varying T1 and T2 patterns for different ischemia and reperfusion durations. For IRI, T1 elevation was the most sensitive marker. Significant myocardial infarction indicated by LGE only occurred after ischemic durations ≥ 60 min; thus, an appropriate occlusion duration must be chosen in pigs to create myocardial IRI for scientific studies.