Post-mortem CMR in a model of sudden death due to myocardial ischemia: validation with connexin-43

Objectives: We sought to evaluate the effectiveness of post-mortem cardiac magnetic resonance (PM-CMR) for the identification of myocardial ischemia as cause of sudden cardiac death (SCD) when the time interval between the onset of ischemia and SCD is ≤ 90 min. Methods: PM-CMR was performed in 8 hearts explanted from pigs with spontaneous death caused by occlusion of the left anterior descending coronary artery: 4 with SCD after ≤ 40 min of coronary occlusion and 4 between 40 and 90 min. PM-CMR included conventional T1 and T2-weighted image and T1, T2, and T2* mapping techniques. Imaging data were compared and validated with immunohistochemical evaluation of the altered proportion and redistribution of phosphorylated versus non-phosphorylated connexin 43 (CX43 and npCX43, respectively), an established molecular marker of myocardial ischemia. Results: At T2-weighted images, the ischemic core was hypointense (core/remote ratio 0.67 ± 0.11) and surrounded by and hyperintense border zone. Compared to remote myocardium, the ischemic core had higher T1 (p = 0.0008), and lower T2 (p = 0.007) and T2* (p = 0.002). Cytoplasmatic npX43 and the npCX43/CX43 ratio were significantly higher in animals deceased > 40 min than in others. Conclusion: PM-CMR can reliably detect early signs of myocardial damage induced by ischemia, based on conventional pulse sequences complemented by a novel ad hoc application of quantitative mapping techniques. Key points: • Post-mortem MRI may help to understand cause of sudden cardiac death. • Post-mortem MRI allows detection of signs of myocardial ischemia as cause of sudden cardiac death within 90 and 40 min following coronary occlusion as demonstrated in a pig model of myocardial ischemia. • Signs of myocardial ischemia using conventional and mapping MRI technique are associated with the immunohistochemical changes of phosphorylated and dephosphorylated connexin-43 which is an established molecular marker of myocardial ischemia.