Relationship Between Microvascular Obstruction and Adverse Events

Study Questions:

What is the relationship between microvascular obstruction (MVO) assessed early after primary percutaneous coronary intervention (PCI) in ST-segment elevation myocardial infarction (STEMI) and all-cause mortality, hospitalization for heart failure (HF), and reinfarction?

Methods:

The investigators performed a pooled analysis using individual patient data from seven randomized primary PCI trials in which MVO was assessed within 7 days after reperfusion by cardiac magnetic resonance (CMR) using late gadolinium enhancement imaging (n = 1,688). Clinical follow-up was performed for at least 6 months after the index event. The impact of MVO on death, HF hospitalization, and reinfarction as well as the combination of death or HF hospitalization from the time of study entry to latest follow-up was assessed using Cox proportional hazards regression.

Results:

Median time to CMR after STEMI was 3 days (interquartile range [IQR], 2–4), and median duration of clinical follow-up was 365 days (IQR, 188–374). MVO was present in 960 (56.9%) patients, and median MVO (percent left ventricular myocardial mass) was 0.47% (IQR, 0.00–2.54). A graded response was present between the extent of MVO (per 1.0% absolute increase) and subsequent mortality (Cox adjusted hazard ratio [HR], 1.14; 95% confidence interval [CI], 1.09–1.19, P < 0.0001] and hospitalization for HF (Cox adjusted HR, 1.08; 95% CI, 1.05–1.12; p < 0.0001). MVO remained significantly associated with all-cause mortality even after further adjustment for infarct size (Cox adjusted HR, 1.09; 95% CI, 1.01–1.17; p = 0.03). MVO was not significantly related to subsequent reinfarction (p = 0.29).

Conclusions:

The authors concluded that the presence and extent of MVO measured by CMR after primary PCI in STEMI are strongly associated with mortality and hospitalization for HF within 1 year.

Perspective:

This pooled analysis from seven randomized trials of primary PCI in STEMI suggests a strong independent relationship between MVO measured within 7 days after reperfusion and the occurrence of all-cause death, hospitalization for HF, and the composite measure of all-cause death or HF hospitalization within 1 year. Furthermore, assessment of MVO contributed to the classification of patient risk and improved discrimination of the risk of death or HF hospitalization during 1-year follow-up. Prospective randomized trials are indicated to determine whether reducing MVO may improve survival or freedom from HF.


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