Among patients who underwent fractional flow reserve and in whom revascularization was deferred, patients with low coronary flow reserve were more likely to experience adverse events during 5-year follow-up than those with preserved coronary flow, according to new data.
The study included consecutive patients who underwent clinically indicated coronary angiography and FFR and coronary flow reserve measurements for at least one coronary artery at five university hospitals in the Republic of Korea.
Differences in outcomes
Of the 519 patients (737 vessels) who did not undergo revascularization, 83.4% of patients presented with stable angina and had a mean percent diameter stenosis of 38.9%, a mean FFR of 0.89 and a mean coronary flow reserve of 3.1. Less than 20% of patients (18.9%) had an FFR of 0.8 or lower and 21.6% had a coronary flow reserve of 2 or lower. There was modest agreement between FFR and coronary flow reserve (kappa = 0.08; P = .024), with 30.6% of the study population having discordant results between the two measurements.
During 5-year follow-up, patients with low FFR had increased risk for the vessel-oriented composite outcome — vessel-related cardiac death, vessel-specific MI and vessel-specific revascularization — compared with those with high FFR (12.2% vs. 4.5%; HR = 2.774; 95% CI, 1.37-5.616). Patients with low coronary flow reserve vs. high coronary flow reserve also had a threefold higher risk for the vessel-oriented composite outcome (11.2% vs. 3.7%; HR = 3.171; 95% CI, 1.664-6.042).
In a subgroup of patients with high FFR, low coronary flow reserve was identified as an independent predictor for the vessel-oriented composite outcome (HR = 4.999; 95% CI, 2.104-11.879), according to the data.
Furthermore, in a four-group classification according to both FFR and coronary flow reserve, patients with low FFR and low coronary flow reserve had the highest risk for the vessel-oriented composite outcome (17.9%; overall P < .001) compared with the other groups.
The researchers noted that the per-patient analysis for the patient-oriented composite outcome — all-cause mortality, any MI and any revascularization — showed similar results.
“Integration of CFR into a prediction model with FFR improved the discrimination ability for the occurrence of clinical events,” the researchers wrote. “These results support the value of CFR in patients who undergo FFR measurement.”
In an accompanying editorial, Javier Escaned, MD, PhD, and Hernán Mejía-Rentería, MD, from the Hospital Clinico San Carlos IDISSC and Universidad Complutense in Madrid, wrote that the combined analysis of FFR and coronary flow reserve proved interesting, as it shed light on both patients with concordance and discordance in FFR and coronary flow reserve.
However, Escaned and Mejía-Rentería also pointed out that use of additional methodological approaches, such as calculating coronary flow capacity and microcirculatory resistance, could have strengthened the results.
“Yet, the evidence gathered in this study supports the value of CFR in obtaining a more comprehensive assessment of patients with ischemic heart disease and the need for simpler and more accurate tools to measure intracoronary flow,” they wrote. “For the time being, what we have learned from our Korean colleagues is that in the iFR/FFR era, CFR is too valuable an index to be neglected in the catheterization laboratory.” – by Melissa Foster
Disclosure: Please see the study for a full list of the authors’ relevant financial disclosures. Escaned and Mejía-Rentería report no relevant financial disclosures.