The learning curve of transcarotid artery revascularization

In the pivotal U.S. Food and Drug Administration approval trial, ROADSTER, transcarotid artery revascularization (TCAR) using the ENROUTE Transcarotid Neuroprotection System (Silk Road Medical Inc, Sunnyvale, Calif) was shown to have one of the lowest reported complication rates, not only for carotid artery stent placement, but also for any carotid intervention, including endarterectomy. The number of cases required for a surgeon to gain the proficiency to realize these outcomes has not been studied. Our objective was to determine the learning curve for vascular surgeons performing the TCAR procedure. We examined the effect of surgeon procedural experience on intraoperative data and postoperative outcome.

This retrospective review analyzed data from a prospectively maintained database of 188 consecutive patients from three large academic centers who underwent TCAR. Procedures were ordered chronologically for each surgeon and grouped into bins of five. Operative times and flow reversal times were analyzed by analysis of variance. Results led to comparison of surgeons' early experience (cases 1-15) with their later experience (cases 16-50). The primary outcome was postoperative stroke and death.

The mean procedural time for all cases was 75.0 ± 23.8 minutes. When the procedural time of cases 1 through 15 (mean, 79.0 ± 28.3 minutes) were compared with cases 16 through 50 (mean, 71.8 ± 19.0 minutes), a significant difference was noted (P = .02). The mean flow reversal time was 10.6 ± 6.8 minutes. When flow reversal times were compared using analysis of variance testing, cases 1 through 15 were statistically similar and cases 11 through 50 were also similar, but the two groups differed from each other (P < .001). For flow reversal, cases 1 through 15 had mean reversal times of 13.3 ± 8.8 minutes compared with 8.5 ± 3.5 minutes for cases 16 through 50 (P < .001). Postoperative stroke rates were similar in the 1 through 15 and 16 through 50 case groups (2.4% vs 1.0%; P = .59), as were death rates (0.0% vs 1.0%; P > .99). The combined stroke/death rates were also comparable at 2.4% in the early cohort vs 1.9% in the late cohort (P > .99).

There seems to be a relatively short learning curve for the TCAR procedure. After 15 cases, surgeons are able to reduce procedural decrease by 10% (from 79.0 to 71.8 minutes), and flow reversal times by an average of 40% (from 13.3 to 8.5 minutes). More important, the rates of stroke and death do not differ between early and late experience with TCAR. The TCAR procedure may be quickly and safely adopted by vascular surgeons for carotid intervention.