Impact of microvascular resistance reserve on post-STEMI cardiac remodelling and diastolic function

Abstract Background Coronary microvascular dysfunction (CMD) is a common sequelae of ST-segment elevation myocardial infarction (STEMI), preventing adequate recovery of left ventricular (LV) perfusion. The interferences of con-commitment epicardial stenosis or hyperemic hemodynamic alterations limit traditional physiologic metrics. The microvascular resistance reserve (MRR) was developed to overcome these shortcomings. Purpose We aim to investigate the association between post-STEMI MRR, and the ensuing left ventricle (LV) diastolic dysfunction, and functional remodeling. Methods In this prospective, observational study, we enrolled STEMI patients with multivessel disease who successfully underwent primary percutaneous coronary intervention (PCI). At three months post-PCI, all patients received complete revascularization followed by coronary physiology assessment using the bolus thermodilution method to measure the fractional flow reserve (FFR), coronary flow reserve (CFR), and the index of microcirculatory resistance (IMR). MRR was calculated using the formula: MRR = (CFR/FFR) × (Pa rest/Pa hyper), where Pa rest and Pa hyper represent resting and hyperemic aortic pressure, respectively(1). CMD was defined as an MRR < 3.0 based on Boerhout et al(2). Diastolic dysfunction was defined according to the ASE 2016 guidelines. Functional LV remodelling (FLVR) was categorized according to Chimed et al(3). The relationship between CMD and the stages of FLVR and diastolic dysfunction was scrutinized over a 12-month follow-up period. Results We enrolled 210 patients, of whom 125 (59.5%) were men with a median age of 65 (IQR: 58–76). At the 3-month follow-up, the MRR was 3.46 (IQR 3.00, 3.92), with 56 (26.7%) patients having CMD (MRR<3.0). MRR is significantly correlated with the change of LVEF between primary PCI and 12 months (r=0.48, p<0.001, Fig1A). CMD patients have lower LVEF at 12 months (50.00% vs. 40.00%; p < 0.001) and demonstrated significantly less recovery in LV systolic function (-10.00% vs. 8.00%; p < 0.001, Fig 1B, 1C). CMD patients had a higher prevalence of grade 2 or 3 LV diastolic dysfunction (65.38% vs. 3.95%; p < 0.001, Fig 2A) and a higher incidence of advanced FLVR (Groups 3 and 4) compared to those without CMD (30.77% vs. vs. 10.53%; p < 0.001, Fig 2B). In multivariable logistic regression analysis, MRR was independently associated with LV diastolic dysfunction (0.17, 95%CI 0.08-0.33, p<0.001). Conclusions The novel parameter MRR is significantly related to LVEF recovery in STEMI patients and is an independent predictor for advanced LV diastolic dysfunction and FLVR. CMD patients, as diagnosed with MRR, showed a higher prevalence of advanced FLVR and diastolic dysfunction. These results suggest that MRR is a useful parameter for the identification and management of CMD in STEMI patients.