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.

Methods and 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.

Keywords: microcirculation; myocardial infarction; physiology.

Conflict of interest statement

Conflict of Interest Disclosures: Dr. Fearon receives institutional research support from St. Jude Medical. The other authors have no conflicts of interest related to this manuscript.

Figures

Figure 1

A. The percentage of patients suffering death or rehospitalization for heart failure based on presence or absence of an IMR > 40, FFR < 0.80, and an IMR > 40 or FFR < 0.80. B. The percentage of patients suffering death based on presence or absence of an IMR > 40, FFR < 0.80, and an IMR > 40 or FFR < 0.80.

Figure 1

A. The percentage of patients suffering death or rehospitalization for heart failure based on presence or absence of an IMR > 40, FFR < 0.80, and an IMR > 40 or FFR < 0.80. B. The percentage of patients suffering death based on presence or absence of an IMR > 40, FFR < 0.80, and an IMR > 40 or FFR < 0.80.

Figure 2

A. The Kaplan-Meier curves displaying the relationship between IMR > 40 and survival free of death or rehospitalization for heart failure. B. The Kaplan-Meier curves displaying the relationship between IMR > 40 and survival free of death.

Figure 2

A. The Kaplan-Meier curves displaying the relationship between IMR > 40 and survival free of death or rehospitalization for heart failure. B. The Kaplan-Meier curves displaying the relationship between IMR > 40 and survival free of death.