Learning Curve Demonstrated in Complications From Carotid Stenting

By Mitchell L. Zoler

PHILADELPHIA -- Minimizing the complications from carotid artery stenting may require accumulating experience with up to 200 patients, according to the records at a single medical center in Italy.

An analysis of the correlates of death or major stroke in a series of more 600 patients treated with carotid artery stenting at the University of Perugia during 2001-2006 showed that the only strongly significant link was with the time when the stenting was done, Dr. Piergiorgio Cao said at the Vascular Annual Meeting.

Patients who were among the first 195 treated with carotid stenting in Perugia, during 2001-2003, had an average incidence of perioperative death or major stroke of about 3%, compared with a 1% rate among the next 432 patients who were treated in 2004-2006, said Dr. Cao, a vascular surgeon at the University of Perugia.

The difference seen in the rate of major events between the two time periods was found to be statistically significant, he said.

"It's striking to see how the first interval [of cases] carries a higher risk. In our experience, the learning curve was a crucial aspect of our results," Dr. Cao added.

In some of the major trials of carotid artery stenting, the committees that were running the trials required the operators to have performed at least 30 stenting procedures as a criterion for participating, noted Dr. Robert Hobson, who is the chief of vascular surgery at the University of Medicine and Dentistry of New Jersey in Newark.

But despite this, Dr. Cao hesitated to recommend an alternative, minimum number based on the findings of his study.

"The prior suggested number [of 30 cases] seems too low to ensure the safety of carotid artery stenting," Dr. Cao said. But "our results do not equal guidelines." He did recommend, however, that operators start by performing carotid stenting in "low-risk patients with easy-access vessels."

Another facet of the analysis looked at the time during carotid stenting when complications occurred.

To run this analysis, the Perugia researchers divided the carotid stenting procedure into a total of five phases: Phase 1 involved the initial catheterization of the carotid artery, phase 2 was crossing the stenosis, phase 3 was the deployment of the protective device and the stent, phase 4 was the first 24 hours following the procedure, and phase 5 was the period beyond the first 24 hours through 30 days of follow-up.

When all 10 patients who had major strokes in the full series were analyzed by phase, 4 had strokes during phase 1 and 6 had strokes during phase 3.

But there were no strokes during phase 1 among patients treated during 2004-2006. "That can be strictly related to the learning curve effect," Dr. Cao said.