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Evaluation of Coronary Flow Reserve After Myocardial Ischemia Reperfusion in Rats
Published on: June 28, 2019
Microvascular resistance of the culprit coronary artery in acute ST-elevation myocardial infarction
David Carrick1,2, Caroline Haig3, Jaclyn Carberry1,2
1BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom.
Insights
The index of microvascular resistance (IMR) better predicts outcomes after ST-elevation myocardial infarction (STEMI) than coronary flow reserve (CFR). IMR is closely linked to microvascular damage and left ventricular remodeling, impacting patient prognosis.
Area of Science:
- Cardiology
- Interventional Cardiology
- Cardiovascular Imaging
Background:
- Failed myocardial reperfusion is a significant concern post-acute ST-elevation myocardial infarction (STEMI).
- Assessing microvascular function is crucial for understanding STEMI outcomes.
Purpose of the Study:
- To investigate the prognostic value of coronary flow reserve (CFR) and index of microvascular resistance (IMR) in STEMI survivors.
- To correlate these microvascular parameters with cardiac MRI findings and clinical outcomes.
Main Methods:
- IMR and CFR were measured acutely in the culprit artery of STEMI patients using guide wire-based thermodilution.
- Cardiac MRI assessed left ventricular pathology and function at 2 days and 6 months post-STEMI.
- Clinical outcomes, including all-cause death and heart failure hospitalization, were adjudicated during long-term follow-up.
Main Results:
- IMR and CFR were associated with the presence and severity of myocardial hemorrhage and microvascular obstruction.
- IMR, but not CFR, was independently associated with changes in left ventricular end-diastolic volume.
- IMR demonstrated significant prognostic value for predicting all-cause death or heart failure hospitalization, comparable to ST-segment resolution on ECG.
Conclusions:
- The index of microvascular resistance (IMR) is more closely associated with microvascular pathology, left ventricular remodeling, and adverse health outcomes than traditional angiographic measures or CFR.
- IMR provides valuable prognostic information in STEMI survivors.
Background:
Failed myocardial reperfusion is common and prognostically important after acute ST-elevation myocardial infarction (STEMI). The purpose of this study was to investigate coronary flow reserve (CFR), a measure of vasodilator capacity, and the index of microvascular resistance (IMR; mmHg × s) in the culprit artery of STEMI survivors.
Methods:
IMR (n = 288) and CFR (n = 283; mean age [SD], 60 [12] years) were measured acutely using guide wire-based thermodilution. Cardiac MRI disclosed left ventricular pathology, function, and volumes at 2 days (n = 281) and 6 months after STEMI (n = 264). All-cause death or first heart failure hospitalization was independently adjudicated (median follow-up 845 days).
Results:
Myocardial hemorrhage and microvascular obstruction occurred in 89 (42%) and 114 (54%) patients with evaluable T2*-MRI maps. IMR and CFR were associated with microvascular pathology (none vs. microvascular obstruction only vs. microvascular obstruction and myocardial hemorrhage) (median [interquartile range], IMR: 17 [12.0-33.0] vs. 17 [13.0-39.0] vs. 37 [21.0-63.0], P < 0.001; CFR: 1.7 [1.4-2.5] vs. 1.5 [1.1-1.8] vs. 1.4 [1.0-1.8], P < 0.001), whereas thrombolysis in myocardial infarction blush grade was not. IMR was a multivariable associate of changes in left ventricular end-diastolic volume (regression coefficient [95% CI] 0.13 [0.01, 0.24]; P = 0.036), whereas CFR was not (P = 0.160). IMR (5 units) was a multivariable associate of all-cause death or heart failure hospitalization (n = 30 events; hazard ratio [95% CI], 1.09 [1.04, 1.14]; P < 0.001), whereas CFR (P = 0.124) and thrombolysis in myocardial infarction blush grade (P = 0.613) were not. IMR had similar prognostic value for these outcomes as <50% ST-segment resolution on the ECG.
Conclusions:
IMR is more closely associated with microvascular pathology, left ventricular remodeling, and health outcomes than the angiogram or CFR.
Trial Registration:
NCT02072850.
Funding:
A British Heart Foundation Project Grant (PG/11/2/28474), the National Health Service, the Chief Scientist Office, a Scottish Funding Council Senior Fellowship, a British Heart Foundation Intermediate Fellowship (FS/12/62/29889), and a nonfinancial research agreement with Siemens Healthcare.
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