Learning curve of transfemoral carotid artery stenting in the Vascular Quality Initiative registry

Objective: With the recent expansion of the Centers for Medicare and Medicaid Services coverage, transfemoral carotid artery stenting (tfCAS) is expected to play a larger role in the management of carotid disease. Existing research on the tfCAS learning curve, primarily conducted over a decade ago, may not adequately describe the current effect of physician experience on outcomes. Because approximately 30% of perioperative strokes/deaths post-CAS occur after discharge, appropriate thresholds for in-hospital event rates have been suggested to be <4% for symptomatic and <2% for asymptomatic patients. This study evaluates the tfCAS learning curve using Vascular Quality Initiative (VQI) data. Methods: We identified VQI patients who underwent tfCAS between 2005 and 2023. Each physician's procedures were chronologically grouped into 12 categories, from procedure counts 1-25 to 351+. The primary outcome was in-hospital stroke/death rate; secondary outcomes were in-hospital stroke/death/myocardial infarction (MI), 30-day mortality, in-hospital stroke/transient ischemic attack (stroke/TIA), and access site complications. The relationship between outcomes and procedure counts was analyzed using the Cochran-Armitage test and a generalized linear model with restricted cubic splines. Our results were then validated using a generalized estimating equations model to account for the variability between physicians. Results: We analyzed 43,147 procedures by 2476 physicians. In symptomatic patients, there was a decrease in rates of in-hospital stroke/death (procedure counts 1-25 to 351+: 5.2%-1.7%), in-hospital stroke/death/MI (5.8%-1.7%), 30-day mortality (4.6%-2.8%), in-hospital stroke/TIA (5.0%-1.1%), and access site complications (4.1%-1.1%) as physician experience increased (all P values < .05). The in-hospital stroke/death rate remained above 4% until 235 procedures. Similarly, in asymptomatic patients, there was a decrease in rates of in-hospital stroke/death (2.1%-1.6%), in-hospital stroke/death/MI (2.6%-1.6%), 30-day mortality (1.7%-0.4%), and in-hospital stroke/TIA (2.8%-1.6%) with increasing physician experience (all P values <.05). The in-hospital stroke/death rate remained above 2% until 13 procedures. Conclusions: In-hospital stroke/death and 30-day mortality rates after tfCAS decreased with increasing physician experience, showing a lengthy learning curve consistent with previous reports. Given that physicians' early cases may not be included in the VQI, the learning curve was likely underestimated. Nevertheless, a substantially high rate of in-hospital stroke/death was found in physicians' first 25 procedures. With the recent Centers for Medicare and Medicaid Services coverage expansion for tfCAS, a significant number of physicians would enter the early stage of the learning curve, potentially leading to increased postoperative complications.