Acute and Mid-Term Assessment of Microvascular Dysfunction with Index of Microcirculatory Resistance in ST-Segment Elevation Myocardial Infarction Patients.

In patients diagnosed with ST-segment elevation myocardial infarction (STEMI), despite exhibiting normal patency in the culprit arteries following percutaneous coronary intervention (PCI), coronary microvessels do not recover adequately, leading to microvascular dysfunction (MVD). Limited data are available regarding microcirculation assessed through invasive measures during the midterm period. This study aimed to investigate the assessment of MVD in STEMI patients using the index of microvascular resistance (IMR) during the midterm period.We prospectively evaluated 41 patients with STEMI who underwent PCI. IMR was measured by placing a coronary pressure wire with intravenous adenosine at 1 week as the acute phase and at 6 months after primary PCI as the midterm period. An improvement in IMR was observed from baseline to follow-up, with values changing from 30.00 (15.00-45.50) to 19.00 (10.50-30.50) (P = 0.020). The degree of MVD significantly decreased during follow-up (from 61.0% to 34.1%, McNemar's test: P = 0.016). Compared to patients with normal microcirculation, those with MVD (IMR > 25) at midterm follow-up exhibited significantly elevated levels of brain natriuretic peptide (180.25 [68.25-370.65] pg/mL versus 75.90 [18.70-169.70] pg/mL, P = 0.043) and prolonged symptom-onset-to-balloon time (727.00 [213.50-1170.00] minutes versus 186.00 [125.00-316.00] minutes, P = 0.002).These findings indicate that the extent of MVD 6 months post-PCI has significantly diminished compared to discharge levels and is associated with symptom-onset-to-balloon time. Therefore, MVD in patients with STEMI can potentially improve in the midterm under specific circumstances.