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Objectives: This study used optical coherence tomography to investigate the mechanism of false lumen (FL) formation in spontaneous coronary artery dissection (SCAD) by studying: 1) differences between fenestrated and nonfenestrated SCAD; 2) vasa vasorum density; and 3) light attenuation characteristics of the FL. Background: SCAD is an increasingly recognized cause of acute coronary syndromes, characterized by FL formation and compression of the true lumen (TL). The mechanisms underlying FL formation remain poorly understood. Methods: A total of 65 SCAD patients (68 vessels) who underwent acute OCT imaging as part of routine clinical care were included. Images were classified by the absence or presence of a connection (fenestration) between the TL and FL. Indexed measurements of TL stenosis, external elastic lamina (EEL) area, FL area, and light attenuation of the FL were assessed. Vasa vasorum densities of SCAD cases were compared with those in control non-SCAD myocardial infarction cases. Results: In nonfenestrated cases, there was significantly larger expansion of the EEL area (9.1% vs. −1.9%; p

The noninferiority design is used extensively in current clinical research, but its complex features may hamper the appropriate interpretation of such trials. Thus, understanding the pillars of noninferiority design is indispensable. The authors discuss fundamental concepts regarding the design and interpretation of noninferiority trials and then explore some common methodological criticism by analyzing a sample of contemporary coronary stent trials. Finally, the authors give an overall perspective to enhance the design and conduct of future trials.