Fractional flow reserve: can it predict adverse events accurately after coronary stenting?

BACKGROUND FRACTIONAL FLOW RESERVE (FFR) measurements have the ability to predict clinical events in patients after balloon angioplasty and coronary stent implantation. FFR assessment could help identify patients who have a good prognosis and would not benefit from further intervention. OBJECTIVE To determine whether FFR predicts the occurrence of clinical events accurately when adjusted for all available risk factors in patients with single-vessel stenosis treated by stent implantation. DESIGN In this retrospective analysis, men and women were studied who had ischernia when assessed by a stress test or symptoms of disrupted coronary blood flow. For inclusion, patients had to have undergone coronary stent implantation and successful FFR assessment after the procedure. If patients had chronic complete occlusion or acute coronary syndrome they were excluded. INTERVENTION All patients received 100 mg aspirin daily and a bolus dose of 7,000 IU heparin just before stent implantation. A 0.014 inch pressure guidewire and a size 6 or 8 French guiding catheter was used to measure FFR at maximum hyperemia, along with aortic and distal coronary pressure at rest, before stenting. Maximum hyperemia was achieved through intracoronary bolus injection of 30-150pg adenosine. Bare metal stents were used in all patients. For 4 weeks after implantation, patients were given 75mg clopidogrel daily. After the procedure, when hemodynamic conditions had stabilized after the final balloon angioplasty inflation, FFR was re-assessed. Patients' outcomes were recorded by hospital visits and telephone interviews. OUTCOME MEASURES This study measured the occurrence of major adverse cardiac events (MACE): revascularization of the target vessel within 6 months after implantation, myocardial infarction and death. RESULTS The 119 eligible patients (of whom 88 [75%] had been included in the earlier FFR registry) were followed up for 6 months. All patients underwent successful stent implantation and FFR measurements were recorded before and after the procedure for every patient. Average FFR improved significantly from 0.65 before, to 0.94 after stenting (P <0.0001). Of the 18 patients who had a MACE, average FFR after stent implantation was significantly lower than in the 101 patients who remained event-free (0.88 vs 0.95, P=0.001). Multivariate analysis showed that an FFR under 0.95 after stenting was an independent predictor of MACEs (odds ratio 6.22, 95% Cl 1.79-21.62, P = 0.004), along with left-ventricular function (odds ratio 0.95, 95% Cl 0.92-0.99, P=0.021). The risk of a MACE was increased 6 times in patients who had a post-stent FFR under 0.95, compared with patients with a FFR of at least 0.95. CONCLUSION When measured after coronary stenting, FFR can predict the occurrence of death, myocardial infarction and target vessel revascularization effectively. Whether patients with low post-procedural FFR would benefit from further intervention remains to be seen