Relation of the ischaemic substrate to left ventricular remodelling by cardiac magnetic resonance at 1.5 T in rabbits

Objectives Contrast-enhanced cardiac magnetic resonance (CMR) for infarct sizing has been validated in large animals, but studies and follow-up are restricted. We sought to (1) validate CMR for assessment of myocardial area at risk (MAR) and infarct size (IS) in a rabbit model of reperfused myocardial infarction (MI); (2) analyse the relation between ischaemic substrates and subsequent left ventricular (LV) remodelling. Methods Experimental reperfused acute MI was induced in 16 rabbits. Ten animals underwent cross-registered cine and contrast-enhanced CMR and histopathology at day 3 for assessment of MAR and IS (group 1). The remaining six rabbits underwent serial CMR for the study of LV remodelling (group 2). Results In group 1, mean IS was 12.7 ± 6.4% and 12.7 ± 6.9% of total LV myocardial mass on CMR (late-enhancement technique) and histopathology ( P = 0.52; r = 0.93). No significant difference occurred between CMR and histopathology for the calculation of MAR and IS/MAR ratio ( P = 0.18 and P = 0.17), whereas correlations were strong ( r = 0.92 and r = 0.95). In group 2, mean LV end-diastolic, end-systolic volumes and LV mass were significantly increased at 3 weeks compared with measurements at day 3 ( P < 0.01). Significant correlations between initial IS and the increase in LV end-diastolic volume ( r = 0.66) and the increase in LV mass ( r = 0.48) were observed, as well as correlations between initial MAR and the increase in LV end-diastolic volume ( r = 0.70) and the increase in LV mass ( r = 0.37). Conclusions Comprehensive CMR provides accurate assessment of IS and MAR in reperfused rabbit MI. Infarct size is closely related to LV remodelling. Through the infarct size/MAR ratio, this approach has great potential for assessing interventions aimed at cardioprotection.