Intramyocardial haemorrhage (IMH) and microvascular obstruction (MVO) represent reperfusion injury after reperfused ST-elevation myocardial infarction (STEMI) with prognostic impact and “hypointense core” (HIC) appearance in T₂-weighted images. We aimed to distinguish between IMH and MVO by using T₂ ^*-weighted cardiovascular magnetic resonance imaging (CMR) and analysed influencing factors for IMH development.

A total of 151 patients with acute STEMI underwent CMR after primary angioplasty. T₂-STIR sequences were used to identify HIC, late gadolinium enhancement to visualise MVO and T₂ ^*-weighted sequences to detect IMH. IMH⁺/IMH⁻ patients were compared considering infarct size, myocardial salvage, thrombolysis in myocardial infarction (TIMI) flow, reperfusion time, ventricular volumes, function and pre-interventional medication. Seventy-six patients (50 %) were IMH⁺, 82 (54 %) demonstrated HIC and 100 (66 %) MVO. IMH was detectable without HIC in 16 %, without MVO in 5 % and HIC without MVO in 6 %. Multivariable analyses revealed that IMH was associated with significant lower left ventricular ejection fraction and myocardial salvage index, larger left ventricular volume and infarct size. Patients with TIMI flow grade ≤1 before angioplasty demonstrated IMH significantly more often.

IMH is associated with impaired left ventricular function and higher infarct size. T₂ and HIC imaging showed moderate agreement for IMH detection. T₂ ^* imaging might be the preferred CMR imaging method for comprehensive IMH assessment.

• Intramyocardial haemorrhage is a common finding in patients with acute reperfused myocardial-infarction.

• T ₂ ^* imaging should be the preferred CMR method for assessment of intramyocardial haemorrhage.

• Intramyocardial haemorrhage can be considered as an important influencing factor on patient’s outcome.