Objective: To investigate the impact of microvascular obstruction (MVO) on the global and regional myocardial function by cardiac magnetic resonance feature-tracking (CMR-FT) in ST-segment-elevation myocardial infarction (STEMI) patients after percutaneous coronary intervention.

Methods: Acute STEMI patients who underwent cardiac magnetic resonance at 1-7 days after successfully reperfusion were included in this retrospective study. Based on the presence or absence of MVO on late gadolinium enhancement images, the STEMI patients were divided into the group with MVO and without MVO. The infarct zone, adjacent zone and remote zone were determined based on a myocardial 16-segment model on late gadolinium enhancement images. The radial strain (RS), circumferential strain (CS) and longitudinal strain (LS) of the global left ventricle and infarct, adjacent and remote zone strains were measured by CMR-FT from cine images. The global and regional strains in patients with and without MVO were compared using independent-samples t-test. Logistic regression analysis was used to assay the association of MVO with the reduced left ventricular function.

Results: A total of 157 STEMI patients (mean age 56.66 ± 11.38 years) were enrolled in the study. The MVO was detected in 59 of 157 (37.58%) STEMI patients and MVO mean size was 3.00 ± 3.76 ml. STEMI patients with MVO had reduced global RS (20.25% ± 4.75% vs. 24.14% ± 5.96%, t = -4.30, P < 0.001), global CS (-12.85% ± 2.52% vs. -14.99% ± 2.66%, t = 4.99, P < 0.001) and global LS (-10.80% ± 3.39% vs. -12.64% ± 3.03%, t = 3.51, P = 0.001) than those without MVO. In addition, RS (12.05% ± 5.83% vs. 15.92% ± 8.42%, t = -3.38, P = 0.001) and CS (-8.53% ± 4.83 % vs. -10.87% ± 5.70%, t = 2.64, P = 0.01) in infarct zone were significantly diminished and the infarct size (36.55 ± 16.55 ml vs. 17.97 ± 11.23 ml, t = 8.37, P < 0.001) was larger in patients with MVO, compared with patients without MVO. In univariable logistic regression analysis, the presence of left ventricular MVO [OR 4.10 (95%CI 2.05-8.19)] and left ventricular MVO size [OR 1.38 (95%CI 1.10-1.72)] were significantly associated with reduced left ventricular global CS.

Conclusion: The infarct size was larger in STEMI patients with MVO and MVO deteriorates the global and regional myocardial function of left ventricle.

Key words: cardiac magnetic resonance feature-tracking, ST-segment-elevation myocardial infarction; microvascular obstruction, myocardial strain