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Fractional flow reserve (FFR)-guided percutaneous coronary intervention (PCI) was as effective in patients with unstable angina and non-ST-segment elevation myocardial infarction as in those with stable angina, researchers found.

In an analysis of a subgroup of patients from the Fractional Flow Reserve versus Angiography for Guiding PCI in Patients with Multivessel Coronary Artery Disease (FAME) study, the absolute reduction in major adverse cardiovascular events (MACE) at two years in those with unstable angina or non-ST-segment elevation myocardial infarction (NSTEMI) was 5.1%, compared with 3.7% in patients with stable angina, reported Nico H.J. Pijls, MD, from Catharina Hospital in Eindhoven, the Netherlands, and colleagues.

In the analysis, researchers found that FFR guidance was associated with similar relative risk reductions of the composite of MACE, death, MI, and death or MI in the higher-risk patients compared with those with stable angina, according to the study, which was published in the Nov. 29 issue of the Journal of the American College of Cardiology: Cardiovascular Interventions.

Pijls and colleagues said that the reduction of events in the higher-risk patients is obtained by using fewer stents than in those with stable angina -- an average of one stent less per patient.

"This observation can be explained because, also in unstable angina or NSTEMI in patients with multivessel coronary disease, unnecessary stenting of nonischemic lesions increases the chance of stent thrombosis, in-stent restenosis, and periprocedural complications, which -- in contrast to ischemic lesions -- is not outweighed by the benefit of relieving myocardial ischemia," the investigators wrote.

They noted a common practice is to stent all lesions based on characteristics consistent with vulnerable plaque in patients with unstable angina or NSTEMI. However, this subgroup analysis did not support such stenting.

In fact, none of the follow-up MIs in these higher-risk patients "occurred on previously deferred lesions, underlining the safety of deferring nonsignificant lesions even in unstable coronary disease," investigators wrote.

The original FAME study had shown that FFR-guided PCI compared with angiography-guided PCI in patients with multivessel disease resulted in a significant reduction of MI and mortality at two years.

For the current study, Pijls and colleagues analyzed data from 328 patients (out of 1,005 enrolled in the FAME study) who had unstable angina or NSTEMI. Of them, 178 were randomized to angiography-guided PCI and 150 to FFR-guided PCI.

Compared with those with stable angina, the higher-risk group had more women, more often had a previous MI, more often used beta-blockers and clopidogrel, but less often used statins. They had a higher Euro-score, but the Syntax score and FFR measurements were not different.

Stable and unstable patients had a similar number of indicated lesions per patient and a similar percentage of successfully treated lesions. One of the significant differences between the two groups was a longer hospital stay for unstable patients (4.5 days versus 3.1 days, P<0.01).

In the group of stable patients, MACE occurred in about 20% and 16% of those in the angiography and FFR arms, respectively, compared with about 26% and 21% in the unstable group. The relative risk reduction of using FFR was 18% and 19%, respectively.

Separately, the relative risk reduction of using FFR for death between the stable and unstable groups was 29% and 40%; for MI 33% and 41%; for death or MI 27% and 41%; and for CABG or repeat PCI 20% and 5%.

Investigators said that the higher event rate for patients who present with unstable angina or NSTEMI (24.1% versus 18.2%) is indicative of the "negative impact of unstable coronary disease on prognosis and at the same time show[s] that these patients in the FAME population are in fact at increased risk of MACE, compared with stable patients."

A limitation of this study is that the FAME study itself was not powered to show superiority of one treatment over another in smaller subgroups. Therefore, "the statistically nonsignificant heterogeneity test must be interpreted as absence of evidence for different effects but is not a proof for the equality of effects across subgroups," they noted.

Also, the usefulness of FFR in acute coronary syndromes is still debated because it can be limited by microvascular obstruction, the authors said. But in FAME, the definition of unstable angina and NSTEMI of <1,000 U/I should have limited the degree of microvascular obstruction, they said.

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