Background: To evaluate outcomes after carotid artery stenting in larger real-world populations, the Food and Drug Administration mandated that companies conduct postmarketing surveillance (PMS) studies of approved stent systems. Whether PMS studies are representative of carotid artery stenting in routine clinical practice has not been established.
Methods and results: Within the National Cardiovascular Database Registry-Carotid Artery Revascularization and Endarterectomy (NCDR CARE) Registry, we compared patient and procedural characteristics, in-hospital outcomes, and subsequent all-cause mortality after carotid artery stenting in PMS study participants and nonparticipants. We conducted both crude and propensity score-adjusted comparisons for all outcomes between groups. Compared with nonparticipants, participants in PMS studies had lower rates of symptomatic carotid artery disease within the preceding 6 months, prior stroke, and acute evolving stroke at baseline. The PMS study participants had lower unadjusted rates of combined in-hospital death, stroke, or myocardial infarction (2.3% versus 4.1%; P<0.001), driven by lower rates of stroke (1.7% versus 2.7%; P=0.005) and death (0.3% versus 1.4%; P<0.001). Differences in survival persisted after propensity score adjustment (odds ratio, 0.44; 95% confidence interval, 0.21 to 0.95; P=0.04 for in-hospital mortality; and hazard ratio, 0.80; 95% confidence interval, 0.66 to 0.97; P=0.02 for 2-year mortality). Baseline differences in neurological history explained the largest proportion of the difference in outcomes between groups.
Conclusions: Participants in PMS studies for carotid artery stenting have different clinical and procedural characteristics and lower mortality compared with nonparticipants. Extrapolating results from PMS studies of carotid artery stenting to larger real-world settings should be done only with great caution.