Early and late microvascular obstruction (MO) assessed by magnetic resonance imaging (MRI) are prognostic markers for combined clinical endpoints after ST-elevation myocardial infarction (STEMI). However, there are only limited data for hard endpoints and no consensus exists which of the two best predicts clinical outcome. Furthermore, it is unclear whether the assessment of MO by MRI adds incremental prognostic information independent of traditional outcome markers.

STEMI patients reperfused by primary angioplasty (n = 438) <12 h after symptom onset underwent MRI at a median of 3 days after the index event. Microvascular obstruction was measured 1 and 15 min after gadolinium injection (early and late MO). Clinical follow-up was conducted after a median of 19 months. The primary endpoint was defined as a composite of death, non-fatal myocardial re-infarction, and congestive heart failure. In contrast to the presence and extent of early MO, the presence and extent of late MO were independently associated with the composite primary endpoint in the multivariable Cox regression analysis adjusting for post-percutaneous coronary intervention TIMI-flow, ST-resolution, TIMI-risk score, ejection fraction, and infarct size. The presence of late MO was identified as the strongest independent predictor for the occurrence of the composite endpoint (hazard ratio 4.23, 95%CI 1.73–10.34, P = 0.002). Furthermore, the presence and extent of late MO provided an incremental prognostic value above the traditional prognostic markers.

In contrast to early MO, the presence and extent of late MO are strong independent prognosticators after STEMI.

www.ClinicalTrials.gov: NCT00299377.