Korean Circ J.  2020 Oct;50(10):890-903. 10.4070/kcj.2020.0083.

Long-term Patient Prognostication by Coronary Flow Reserve and Index of Microcirculatory Resistance: International Registry of Comprehensive Physiologic Assessment

  • 1Division of Cardiology, Department of Internal Medicine, Heart Vascular Stroke Institute, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
  • 2Department of Medicine, Inje University Ilsan Paik Hospital, Goyang, Korea
  • 3Department of Medicine, Keimyung University Dongsan Medical Center, Daegu, Korea
  • 4Division of Cardiology, Ulsan Hospital, Ulsan, Korea and Department of Cardiology, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea
  • 5Division of Cardiovascular Medicine, Tsuchiura Kyodo General Hospital, Ibaraki, Japan
  • 6Department of Cardiovascular Medicine, Tokyo Medical and Dental University, Tokyo, Japan
  • 7Cardiovascular Institute, Hospital Clinico San Carlos, Madrid, Spain
  • 8Centro Nacional de Investigaciónes Cardiovasculares Carlos III (CNIC), Madrid, Spain
  • 9Department of Internal Medicine and Cardiovascular Center, Seoul National University Hospital, Seoul, Korea
  • 10Institute on Aging, Seoul National University, Seoul, Korea


Background and Objectives
Recent guideline recommends evaluation using of coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) in patients with functionally insignificant stenosis. We evaluated clinical implications of CFR and IMR in patients with high fractional flow reserve (FFR) and deferred revascularization.
A total of 867 patients (1,152 vessels) consigned to deferred revascularization who underwent comprehensive physiologic assessments were enrolled. Patients with high FFR (>0.80) were categorized by CFR (≤2) and IMR (≥23 U). Clinical outcome was assessed by patient-oriented composite outcome (POCO), a composite of any death, myocardial infarction (MI), and revascularization at 5 years.
Patients with low CFR (≤2) showed significantly greater risk of POCO than those with high CFR (>2) in both high-FFR (p=0.024) and low-FFR (p=0.034) groups. In patients with high FFR, those with low CFR and high IMR (overt microvascular disease) displayed the greatest risk of POCO overall (p=0.015), surpassing those with high CFR and low IMR (HR, 2.873; 95% CI, 1.476–5.594; p=0.002) and showing significantly greater risk of cardiac death or MI (HR, 5.662; 95% CI, 1.984–16.154; p=0.001). Overt microvascular disease was independently associated with POCO in the high-FFR population (HR, 2.282; 95% CI, 1.176–4.429; p=0.015).
Among patients with deferred revascularization, those with low CFR showed significantly greater risk of POCO than those with high CFR, regardless of FFR. In patients with high FFR, those with overt microvascular disease showed significantly greater risk of POCO and cardiac death or MI at 5-year, compared with the others.


Myocardial ischemia; Coronary artery disease; Fractional flow reserve; Coronary flow reserve; Index of microcirculatory resistance; Percutaneous coronary intervention
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