Microvascular Injury Patterns After STEMI

May 23, 2024
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Authors:
Lechner I, Reindl M, Stiermaier T, et al.
Citation:
Clinical Outcomes Associated With Various Microvascular Injury Patterns Identified by CMR After STEMI. J Am Coll Cardiol 2024;83:2052-2062.
Summary By:
Debabrata Mukherjee, MD, FACC

Quick Takes

  • Intramyocardial hemorrhage is the determining factor for the prognosis of patients with microvascular injury after reperfusion for STEMI.
  • In fact, patients with microvascular obstruction only have a prognosis similar to those without microvascular injury.
  • These findings are pertinent not only for optimizing risk stratification of post-STEMI patients using CMR, but also for the developing future therapies targeting microvascular injury in this setting.

Study Questions:

What is the prognostic significance of various microvascular injury (MVI) patterns after ST-segment elevation myocardial infarction (STEMI)?

Methods:

The investigators analyzed 1,109 STEMI patients included in three prospective studies. Cardiac magnetic resonance (CMR) was performed 3 days (interquartile range [IQR] 2-5) after percutaneous coronary intervention and included late gadolinium enhancement imaging of microvascular obstruction (MVO) and T2* mapping of intramyocardial hemorrhage (IMH). Patients were categorized into those without MVI (MVO-/IMH-), those with MVO but no IMH (MVO+/IMH-), and those with IMH (IMH+). Cox proportional hazards regressions were performed to determine the prognostic significance of IMH+ and MVO+ (comprising patients with MVO with or without additional IMH) on major adverse cardiovascular events (MACE) from the time of study entry to latest follow-up.

Results:

MVI occurred in 633 (57%) patients, of whom 274 (25%) had an MVO+/IMH- pattern and 359 (32%) had an IMH+ pattern. Infarct size was larger and ejection fraction lower in IMH+ than in MVO+/IMH- and MVO-/IMH- (infarct size: 27% vs. 19% vs. 18%, p < 0.001; ejection fraction: 45% vs. 50% vs. 54%, p < 0.001). During a median follow-up of 12 (IQR 12-35) months, a clinical outcome event occurred more frequently in IMH+ than in MVO+/IMH- and MVO-/IMH- subgroups (19.5% vs. 3.6% vs. 4.4%, p < 0.001). IMH+ was the sole independent microvascular injury parameter predicting MACE (hazard ratio, 3.88; 95% confidence interval, 1.93-7.80; p < 0.001).

Conclusions:

The authors report that MVI is associated with future adverse outcomes only in patients with a hemorrhagic phenotype (IMH+).

Perspective:

This multicenter study reports that IMH is the determining factor for the prognosis of patients with MVI after reperfusion for STEMI. In fact, patients with MVO only (MVO+/IMH-) have a prognosis similar to those without MVI (MVO-/IMH-). Taken together, these results highlight the critical importance of IMH, but not MVO only, in assessing risk after STEMI. This is pertinent not only for optimizing risk stratification of post-STEMI patients using CMR, but also for the developing future therapies targeting MVI in this setting. Additional studies are indicated to assess whether specific treatment strategies may improve outcomes for patients with IMH after mechanical reperfusion for STEMI.

Clinical Topics: Noninvasive Imaging, Stable Ischemic Heart Disease, Vascular Medicine, Magnetic Resonance Imaging, Chronic Angina

Keywords: Magnetic Resonance Imaging, ST Elevation Myocardial Infarction


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