Explanation of Postprocedural Fractional Flow Reserve Below 0.85

Background: Fractional flow reserve (FFR) after percutaneous coronary intervention is a predictor of adverse cardiovascular events during follow-up. However, the rationale for low post procedural FFR values remains often elusive based on angiographic findings alone. Methods and Results: FFR SEARCH (Stent Evaluated at Rotterdam Cardiology Hospital) is a prospective single-center registry in which post-percutaneous coronary intervention FFR was assessed in 1000 consecutive all-comer patients. FFR measurements were performed with a microcatheter ±20 mm distal to the most distal stent edge. In 100 vessels with a post procedural FFR ≤0.85, and 20 vessels >0.85 high definition intravascular ultrasound analysis was performed. In 100 vessels with a post-percutaneous coronary intervention FFR ≤0.85, mean post procedural FFR was 0.79±0.05. Minimal lumen area was 2.19 (1.81–3.19) mm2 , mean lumen area was 5.95 (5.01–7.03) mm2 , and minimal stent area was 4.01 (3.09–5.21) mm2 . Significant residual focal proximal lesions were found in 29% of the assessed vessels whereas, focal distal lesions were found in 30% of the vessels. Stent underexpansion and malapposition were found in 74% and 22% of vessels, respectively. Clear focal signs of luminal narrowing were found in 54% of the vessels analyzed. Although incidences of focal lesions, underexpansion, and malapposition were similar between both cohorts, minimal stent area was significantly smaller in vessels with a post-percutaneous coronary intervention FFR ≤0.85 as compared with those with an FFR >0.85.Conclusions: In patients with a post procedural FFR ≤0.85, intravascular ultrasound revealed focal signs of luminal narrowing in a significant number of cases.