Cardiovascular MR T2-STIR imaging does not discriminate between intramyocardial haemorrhage and microvascular obstruction during the subacute phase of a reperfused myocardial infarction

OBJECTIVE Microvascular obstruction (MVO) and intramyocardial haemorrhage (IMH) are known complications of myocardial ischaemia-reperfusion injury. Whereas MVO is an established marker for a poor clinical outcome, the clinical significance of IMH remains less well defined. Cardiovascular MR (CMR) and T2 weighted short tau inversion recovery (T2-STIR) imaging have been used to detect IMH and to explore its clinical importance. IMH is typically identified within the area-at-risk as a hypointense signal core on T2-STIR images. Because MVO will also appear as a hypointense signal core, T2-STIR imaging may not be an optimal method for assessing IMH. In this study, we sought to investigate the ability of T2-STIR to discriminate between MVO with IMH in a porcine myocardial ischaemia-reperfusion model that expressed MVO with and without IMH. METHOD MVO with and without IMH (defined from both macroscopic evaluation and T1 weighted CMR) was produced in 13 pigs by a 65-min balloon occlusion of the mid left anterior descending artery, followed by reperfusion. Eight days after injury, all pigs underwent CMR imaging and subsequently the hearts were assessed by gross pathology. RESULTS CMR identified MVO in all hearts. CMR and pathology showed that IMH was present in 6 of 13 (46%) infarcts. The sensitivity and specificity of T2-STIR hypointense signal core for identification of IMH was 100% and 29%, respectively. T2-values between hypointense signal core in the pigs with and without IMH were similar (60.4±3 ms vs 63.0±4 ms). CONCLUSIONS T2-STIR did not allow identification of IMH in areas with MVO in a porcine model of myocardial ischaemic/reperfusion injury in the subacute phase of a reperfused myocardial infarction.