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For patients with stenoses in small coronary arteries, choosing whether to implant a stent based on measuring fractional flow reserve (FFR) through the vessel appears to be safe, researchers found.

In fact, using FFR to guide the decision was associated with better clinical outcomes than using angiographic results to make the decision, according to Emanuele Barbato, MD, PhD, of the OLV Clinic in Aalst, Belgium, and colleagues.

The rate of death, myocardial infarction, or target vessel revascularization was significantly lower in patients who underwent FFR-guided percutaneous coronary intervention (PCI) than in those who underwent an angiography-guided procedure (14% versus 28%; HR 0.458), the researchers reported in the February issue of Circulation: Cardiovascular Interventions.

That clinical benefit was accompanied by a reduction in procedural costs ($4,264 versus $6,719, P<0.0001), mostly related to the use of fewer stents.

"Our results are particularly remarkable when one considers that the clinical benefit derived from revascularizing small vessels is uncertain," Barbato and colleagues wrote. "Optimal medical therapy, in fact, might be more effective than PCI for treating small areas of ischemic myocardium, which is usually the case in a small-vessel stenosis."

The decision to go ahead with PCI often depends on an angiographic evaluation of stenosis severity, although that does not always provide an accurate indication of whether the lesion is inducing a functionally relevant blockage of blood flow to the affected area of the heart.

In the PHANTOM trial, for example, only one-third of lesions identified in small vessels with angiography and intravascular ultrasound proved to be functionally significant as assessed by FFR (Am Heart J 2007; 153: 296 –297).

Because FFR, which gives a measure of the hemodynamic significance of a lesion, has been shown to be safe in large-vessel disease, Barbato and colleagues set out to assess the safety of such a strategy in small-vessel disease.

They performed a retrospective analysis of patients who underwent PCI at a single center for stable or unstable angina from 2004 through 2008. All had lesions in small native coronary vessels (both a vessel diameter and stent size less than 3 mm).

The study included 495 patients who underwent PCI after angiographic assessment and 222 in whom the PCI strategy was based on the FFR measurement. Of the latter group of patients, 35% had a positive FFR (<0.80) and received a stent, while the rest were deferred to optimal medical therapy alone.

Periprocedural MI occurred in 5% of the angiography-guided group and 0% of the FFR-guided group (P=0.0008). There were no major bleeds in either group.

Through a median follow-up of 3.3 years, clinical outcomes were better in the FFR-guided group.

After adjustment for differences between the angiography-guided and FFR-guided patients using propensity scoring, patients treated with FFR-guided PCI had improvements for the following endpoints (P≤0.007 for all):

• Death, MI, or target vessel revascularization (14% versus 28%, HR 0.458)
• Death or MI (6% versus 14%, HR 0.413)
• Nonfatal MI (1% versus 7%, HR 0.063)
• Target vessel revascularization (10% versus 18%, HR 0.517)

The mortality rate, however, was not significantly different between the two groups (5% with FFR guidance and 8% with angiographic guidance, P=0.255).

Stent thrombosis occurred in six patients in the angiography-guided group and zero in the FFR-guided group, which was not a significant difference.

Clinical outcomes tended to be best among the patients in the FFR-guided group who were deferred to optimal medical therapy, worst in those in the angiography-guided group, and intermediate in those who received a stent following FFR guidance.

But, the authors noted, "whether an FFR-guided PCI strategy plus optimal medical therapy of small-vessel disease is superior to a strategy of optimal medical therapy alone needs further investigation."

They acknowledged some limitations of the study, including the retrospective, nonrandomized design, the inability to account for factors that might have influenced an operator's decision to adopt one approach over the other, and the use of angiography rather than intravascular ultrasound to determine vessel size.

From the American Heart Association:

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