title: Prognostic value of the Index of Microcirculatory Resistance measured after primary percutaneous coronary intervention.
abstract: BACKGROUND
  Most methods for assessing microvascular function are not readily available in the cardiac catheterization laboratory. The aim of this study is to determine whether the Index of Microcirculatory Resistance (IMR), measured at the time of primary percutaneous coronary intervention, is predictive of death and rehospitalization for heart failure.
  
  
  RESULTS
  IMR was measured immediately after primary percutaneous coronary intervention in 253 patients from 3 institutions with the use of a pressure-temperature sensor wire. The primary end point was the rate of death or rehospitalization for heart failure. The prognostic value of IMR was compared with coronary flow reserve, TIMI myocardial perfusion grade, and clinical variables. The mean IMR was 40.3±32.5. Patients with an IMR >40 had a higher rate of the primary end point at 1 year than patients with an IMR ≤40 (17.1% versus 6.6%; P=0.027). During a median follow-up period of 2.8 years, 13.8% experienced the primary end point and 4.3% died. An IMR >40 was associated with an increased risk of death or rehospitalization for heart failure (hazard ratio [HR], 2.1; P=0.034) and of death alone (HR, 3.95; P=0.028). On multivariable analysis, independent predictors of death or rehospitalization for heart failure included IMR >40 (HR, 2.2; P=0.026), fractional flow reserve ≤0.8 (HR, 3.24; P=0.008), and diabetes mellitus (HR, 4.4; P<0.001). An IMR >40 was the only independent predictor of death alone (HR, 4.3; P=0.02).
  
  
  CONCLUSIONS
  An elevated IMR at the time of primary percutaneous coronary intervention predicts poor long-term outcomes.
authors.affiliation: Stanford University Medical Center, Stanford, CA 94305, USA. wfearon@stanford.edu
authors.forename: William F
authors.initials: WF
authors.lastname: Fearon
authors.forename: Adrian F
authors.initials: AF
authors.lastname: Low
authors.forename: Andy S
authors.initials: AS
authors.lastname: Yong
authors.forename: Ross
authors.initials: R
authors.lastname: McGeoch
authors.forename: Colin
authors.initials: C
authors.lastname: Berry
authors.forename: Maulik G
authors.initials: MG
authors.lastname: Shah
authors.forename: Michael Y
authors.initials: MY
authors.lastname: Ho
authors.forename: Hyun-Sook
authors.initials: HS
authors.lastname: Kim
authors.forename: Joshua P
authors.initials: JP
authors.lastname: Loh
authors.forename: Keith G
authors.initials: KG
authors.lastname: Oldroyd
mesh_terms: D015906:Angioplasty, Balloon, Coronary; D003326:Coronary Circulation; D003331:Coronary Vessels / Q000503:physiopathology; D006801:Humans; D008297:Male; D008833:Microcirculation; D009203:Myocardial Infarction / Q000503:physiopathology; D062645:Percutaneous Coronary Intervention; D011379:Prognosis; D014655:Vascular Resistance
keywords: microcirculation; myocardial infarction; physiology