FIRST: Fractional Flow Reserve and Intravascular Ultrasound Relationship Study

Objectives FIRST (Fractional Flow Reserve and Intravascular Ultrasound Relationship Study) aimed to determine the optimal minimum lumen area (MLA) by intravascular ultrasound (IVUS) that correlates with fractional flow reserve (FFR) and to assess the correlation between virtual histology IVUS and FFR for intermediate coronary lesions. Background FFR is considered the gold standard for assessing intermediate coronary lesions. Measurements of ≤0.8 are considered clinically significant and indicative of physiological ischemia. Methods FIRST is a multicenter, prospective, international registry of patients with intermediate coronary lesions, defined as 40% to 80% stenosis by angiography. In total, 350 patients (367 lesions) were enrolled at 10 U.S. and European sites. Patients were followed through hospital discharge. Results Overall, an MLA