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Fractional Flow Reserve (FFR) is a standard method to evaluate the functional severity of coronary stenoses. Apart from epicardial involvement, the extent of microvascular disease is increasingly recognized as an essential component in the spectrum of ischemic heart disease. Coronary Flow Reserve (CFR) is an important marker of microvascular disease. There are however few studies that evaluate both values together and how it affects patient outcomes. We hypothesize that a consideration of both FFR and CFR values are important factors influencing long-term patient outcomes.
Patients with intermediate coronary stenoses and functional evaluation of FFR and invasive CFR values were followed up prospectively. Where the patient had a percutaneous coronary intervention, the post-procedure measurements were used if available. They were stratified into 4 groups using FFR>0.80 and CFR>2.0 as cut-offs for normality. Major adverse cardiac events (MACE), defined as hospitalizations for angina, non-ST elevation myocardial infarction, ST elevation myocardial infarction, and heart failure were assessed. The mean follow-up duration was 6.5 years (SD 1.5 years).
A total of 104 (81.7% males) patients from a single tertiary center were recruited and assessed. The mean age was 58.5 years (SD 10.1) and the left anterior descending artery formed the largest proportion (75/104) that was evaluated. 33.7% of the patients had diabetes and 87.5% and 89.4% of the patients had hypertension and hyperlipidemia respectively. There was discordance between FFR and CFR in 29/104 patients (27.9%). There were 63 patients who had FFR>0.8 CFR >2.0 and 24 (38.1%) patients had MACE, p=0.281. In the group with FFR>0.8 CFR<2.0, there were 17 patients, of which 6 (35.3%) had MACE, p=0.522. There were 12 patients in the FFR<0.8 and CFR<2.0 group and 5 (41.7%) patients had MACE, p=0.962. The FFR<0.8 CFR>2.0 group had 12 patients and 9 (75%) had MACE, p=0.015.
A significant proportion of patients have discordant FFR and CFR values and a consideration of both values together during evaluation of coronary artery disease may be helpful. Discordant values of FFR<0.80 and CFR>2.0 predict increased hospitalization rates for cardiac MACE.