Microvascular Resistant Reserve: Impact on STEMI Patients

Coronary Microvascular Dysfunction (CMD) is being increasingly considered a common consequence of STEMI. Its presence partly explains the persistence of angina symptoms in over 50% of patients after PCI, despite successful epicardial artery reperfusion. Also, CMD has been independently associated with worse left ventricular ejection fraction recovery, which leads to worse prognosis, including recurrent events, cardiac failure and hospitalizations. 

El TAVI presenta menos IAM post procedimiento que la cirugía de reemplazo valvular aórtico

However, diagnosing CMD continues to be difficult. Even though there are several techniques to assess microvascular circulation, many are impractical outside a clinical research environment because of their complexity. There is a way to measure microvascular resistance through microvascular resistance reserve (MRR). In order to identify the presence of CMD, < 3.0 MMR is considered significant. This tool has been validated in chronic coronary syndromes, but not in patients with acute coronary syndromes. 

The aim of this prospective, observational cohort study was to look into CMD prevalence in STEMI patients after primary PCI, and to assess the prognosis performance of several parameters, especially MRR. 

The primary outcome was 12-month incidence of major adverse cerebrovascular and cardiovascular events (MACCE), defined as all cause death, AMI, revascularization, stroke (hemorrhagic and ischemic) and hospitalization for cardiac failure. Secondary end points included the individual components of primary end point and ventricular function deterioration at 12 months. 

Read also: TAVR vs SAVR in Los Risk Patients: 10-Year Outcomes of the NOTION Trial.

210 STEMI patients were included, mean age 65, mostly men. The prevalence of female sex and diabetes was higher in CMD patients. MACCE at 12 months resulted higher in patients with CMD vs those without CMD (48,2% vs 11,0%; P < 0,001). MRR was independently associated to 12-month MACCE (HR: 0,45; CI 95%: 0,31-0,67; P < 0,001) and also stroke, cardiac failure and worse recovery of left ventricular systolic function. As regards prognosis, coronary flow reserve (CFR), microvascular resistance index (MRI) and MRR resulted similar.


In conclusion, this study has shown that MRR is a prognostic marker of MACCE in STEMI patients with similar prognostic performance to CFR and IMR’s. More long term multicenter randomized studies are required to consolidate these findings. 

Dr. Andrés Rodríguez.
Member of the Editorial Board of SOLACI.org.

Original Title: The Impact of Microvascular Resistance Reserve on the Outcome of Patients With STEMI.

Reference: Tsung-Ying Tsai, MD et al J Am Coll Cardiol Intv 2024.

Subscribe to our weekly newsletter

Get the latest scientific articles on interventional cardiology