Metabolic syndrome (MetS) is associated with coronary microvascular dysfunction (CMD), both of which increase the risk of cardiovascular events after ST-segment elevation myocardial infarction (STEMI). However, the prognostic significance of CMD in STEMI patients with MetS remains unclear. This study aimed to evaluate the effects of CMD, assessed by the angiography-derived index of microcirculatory resistance, on cardiovascular outcomes in STEMI patients with and without MetS.

STEMI patients undergoing primary percutaneous coronary intervention were prospectively enrolled at 4 centers. MetS was defined as the presence of at least 3 out of 5 cardiometabolic abnormalities. CMD was defined as an angiography-derived index of microcirculatory resistance> 40 U.

Among 497 included patients, 316 (63.8%) patients had MetS. During 2.8 years follow-up, the cumulative incidence of adverse outcomes was significantly higher in the CMD group than in the non-CMD group among patients with MetS (30.3% vs 18.4%; P=.034), but not among those without MetS (12.6% vs 13.0%; P=.937). Both the presence of CMD and the angiography-derived index of microcirculatory resistance as a continuous variable predicted adverse outcomes in patients with MetS, but not in those without MetS. CMD was also significantly associated with left ventricular dysfunction (OR, 3.909; 95%CI, 1.330-11.489; P=.013) and lack of left ventricular ejection fraction recovery (OR, 3.367; 95%CI, 1.099-10.318; P=.034) at follow-up, independently of baseline function.

CMD assessed by the angiography-derived index of microcirculatory resistance independently predicts adverse outcomes and lack of left ventricular functional recovery in STEMI patients with MetS, but not in those without MetS.