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 (
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],
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.
David Carrick, Caroline Haig, Jaclyn Carberry, Vannesa Teng Yue May, Peter McCartney, Paul Welsh, Nadeem Ahmed, Margaret McEntegart, Mark C. Petrie, Hany Eteiba, Mitchell Lindsay, Stuart Hood, Stuart Watkins, Ahmed Mahrous, Samuli M.O. Rauhalammi, Ify Mordi, Ian Ford, Aleksandra Radjenovic, Naveed Sattar, Keith G. Oldroyd, Colin Berry
Three patients with acute ST-elevation myocardial infarction treated by primary percutaneous coronary intervention and with the same antithrombotic therapies, including aspirin, clopidogrel, heparin, and glycoprotein IIbIIIa inhibitor therapy with tirofiban.
Each patient had successful primary percutaneous coronary intervention (PCI), as evidenced by normal thrombolysis in myocardial infarction (TIMI) flow grade 3 the end of the procedure. Cardiac MRI was performed for each patient 2 days later. Coronary artery function was measured in 283 patients, of whom 281 (99%) had cardiac MRI and 213 (75%) had T2* MRI for assessment of myocardial hemorrhage. Top: A patient with normal index of microvascular resistance (IMR <25), normal coronary flow reserve (CFR >2.0), and no evidence of microvascular injury on MRI. A diagnostic guide wire study of microvascular function in the territory of the culprit coronary artery immediately after primary PCI. IMR and CFR measurements were derived from coronary thermodilution. Microvascular function was normal (IMR 12, CFR 2.6), indicating successful myocardial reperfusion. Two days later, MRI ruled out myocardial hemorrhage (middle right image) or microvascular obstruction (right). Middle: A patient with normal IMR, low CFR, and microvascular obstruction but no hemorrhage on MRI 2 days later. The diagnostic guide wire study of culprit artery microvascular function at the end of primary PCI indicated an abnormal CFR (0.9) but a preserved IMR (