ACC.17: Revascularization strategies guided by FFR, iFR have similar adverse cardiac event rates

At 12 months, patients with stable angina or acute coronary syndrome had similar rates of major adverse cardiac events whether they underwent revascularization guided by instantaneous wave-free ratio (iFR) or fractional flow reserve (FFR), according to a randomized, registry-based trial.

After a year, 6.7 percent of patients in the iFR group and 6.1 percent of patients in the FFR group had a primary endpoint event, which the researchers defined as a composite of death from any cause, nonfatal MI or unplanned revascularization.

Lead researcher Matthias Götberg, MD, PhD, of the Skane University Hospital in Lund, Sweden, presented results of the IFR-SWEDEHEART study in a late-breaking clinical trial session at the ACC scientific session on March 18 in Washington, D.C.

The findings were simultaneously published online in the New England Journal of Medicine.

“In FFR we have a good diagnostic method, but people are not using it enough because of the side effects,” Götberg said in a news release. “Our study shows that for cardiologists who currently use FFR, iFR provides a similar clinical benefit but without patient discomfort. For cardiologists who are hesitant to use FFR, iFR might provide an opportunity to increase adoption rates of coronary physiology and benefit more patients.”

Previous randomized trials found that FFR was better than angiographic assessment at detecting hemodynamically important coronary artery stenosis, according to the researchers. They added that using FFR to guide coronary revascularization has been shown to improve outcomes. Meanwhile, they noted that iFR is a new physiological index used to assess the severity of stenosis.

For this study, the researchers assessed 2,019 patients, all of whom were enrolled in the Swedish Coronary Angiography and Angioplasty Registry that contains data on patients from all 30 coronary intervention centers in Sweden and one center in Iceland. The study also included one center in Denmark.

From May 2014 to October 2015, the researchers randomized patients in a 1:1 ratio to iFR or FFR. The patients had stable angina pectoris, unstable angina or non-ST-segment MI, and an indication for physiologically guided assessment of a coronary lesion with 40 percent to 80 percent stenosis on visual examination.

At baseline, the mean age was 68 years old, and approximately 75 percent of patients were males. In addition, 21.8 percent of patients had diabetes, 62 percent had stable angina and 33 percent had a previous MI.

The researchers assessed 1,568 lesions in the iFR group (1.55 lesions per patient) and 1,436 lesions in the FFR group (1.43 lesions per person). The mean iFR was 0.91, and the mean FFR was 0.82. Further, 29.1 percent of lesions in the iFR group and 36.8 percent of lesions in the FFR group were hemodynamically important.

Physicians performed revascularization in 53.2 percent of patients in the iFR group and 56.2 percent of patients in the FFR group. The researchers mentioned that 81.4 percent of patients who underwent revascularization had PCI as their primary procedure.

At 12 months, there were 15 deaths in the iFR group (8 from cardiovascular causes) and 12 deaths in the FFR group (6 from cardiovascular causes), which did not represent a statistically significant difference. The rates of nonfatal MI, unplanned revascularization and target lesion revascularization were similar between the groups, as well.

The researchers mentioned that one patient in the iFR group and two patients in the FFR group had stent thrombosis, while restenosis occurred in 1.9 percent and 1.8 percent of patients, respectively. In addition, 3 percent of patients in the iFR group and 68.3 percent of patients in the FFR group had chest discomfort, which was a statistically significant difference.

“If patients could choose between the two methods, given that there is no difference in outcomes, patients would probably appreciate not having to experience the side effects of the vasodilator,” Götberg said in a news release.

The overall event rates in the trial were lower than the researchers expected and allowed for a more generous confidence interval for the hazard ratio, which they noted was a limitation of the study. They cited other limitations, including that they enrolled patients treated with CABG and reported a continuous biologic variable in a dichotomous manner. They also mentioned that the treating physicians and patients were aware of the group assignments.