Early Carotid Stenting Outcomes Linked to Operator, Hospital Volume

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Both site and operator volume are important determinants of perioperative outcomes after carotid artery stenting (CAS), according a study published in the February 2011 issue of JACC: Cardiovascular Interventions. Regardless, it appears the procedure can be safely performed in a variety of hospital settings by physicians who hail from different specialty backgrounds.

To assess physician- and site-related factors affecting CAS outcomes, William A. Gray, MD, of Columbia University Medical Center (New York, NY), and colleagues looked to the CAPTURE 2 study, an ongoing post-market clinical registry initiated in March 2006. The single-arm study was designed to measure the safety of the RX Acculink carotid stent and RX Accunet embolic protection device (Abbott Vascular, Santa Clara, CA). At 30-day follow-up, the combined death, stroke, and MI rate was 3.5%, and the death/stroke rate was 3.3%.

For the current analysis, the researchers focused on a subset of asymptomatic nonoctogenarians (n = 3,388) who were treated at 180 US hospitals by 459 operators between 2006 and 2009. All were high risk for endarterectomy and had at least 80% stenosis in the common or internal carotid artery. Compared with the larger CAPTURE 2 population, this group had slightly better safety outcomes; the 30-day rates of death/stroke/MI and death/stroke were 2.9% and 2.7%, respectively.

Patterns Consistent for Hospitals, Physicians

Most sites (66%) had no deaths or strokes within 30 days. Patient volumes ranged widely at these hospitals. Among the sites that did witness a death or stroke, there was an inverse association between volume and event rates. However, the study found no signs that hospital type, size, or geographic location influenced outcomes.

Individual operator characteristics also carried weight, showing a similar inverse relationship between volume and death/stroke rates. This correlation was consistent for physicians from all 5 specialties represented in the study: interventional cardiology, vascular surgery, neurosurgery, neuroradiology, and interventional radiology.

Using the 1998 American Heart Association carotid endarterectomy guidelines—which place the acceptable 30-day death/stroke rate in asymptomatic nonoctogenarians at 3%—as a comparison, the researchers calculated the minimum case number for physicians to reach this safety standard for CAS. The threshold, based on a regression model derived from the CAPTURE 2 study, was 72 procedures.

Patients treated by interventional cardiologists showed a trend toward lower death/stroke rates compared with the other specialties. Interestingly, the ratio of minor to major strokes was more favorable for interventional cardiology than for vascular surgery (the 2 specialties with sufficient patient volumes for comparison) at 2.5 vs. 1.25, “suggesting a potential difference in the mix of stroke severity between the 2 groups,” the paper notes, adding that no differences were observed for stroke location.

Although much research has been done since the advent of CAS to better understand patient-related factors such as age and symptom status, less is known about the influence of physician and hospital characteristics. “The current study illuminates the potential impact of these other factors,” the investigators conclude. “Interventionalists with different specialty-training backgrounds and experience levels are performing CAS. Training, competency, and credentialing standards will continue to be developed and defined for CAS operators—as was the case with [carotid endarterectomy]—and should be predicated on an understanding of the physician factors associated with successful CAS outcomes.”

Number a ‘Rough Ballpark’

In a telephone interview with TCTMD, Dr. Gray stressed that the threshold of 72 procedures, which “everyone is going to hang their hat on,” should be interpreted carefully.

While the analysis itself is solid, Dr. Gray noted, “remember that this is with one set of devices and it’s a certain era of carotid stenting, which is relatively late in the last decade.” Much of the learning curve for CAS in the broader community had been taken care of by the time this study was conducted, he explained. This analysis also included a mixed cohort of operators who may or may not have gained experience prior to CAPTURE 2.

“So there are a lot of caveats to that number. I don’t want people to get stuck on [72],” Dr. Gray stressed. “But I think it gives us a rough ballpark, [and questions the previously held assumption] that 12 or 13 solo procedures were going to be enough. Probably, it isn’t enough to get to the expert level we’re talking about.” He estimated that based on this analysis and data from Europe, the number appears to be in the range of 50 to 100 cases.

Asked about the feasibility of gaining such experience, he replied, “I would submit that there are already more than enough carotid stenters in the United States, probably over 1,000 people trained to do carotid stenting in this country, and that’s a lot.” That being said, Dr. Gray was unsure whether these operators came anywhere close to the 72-case threshold.

Bogged Down by the Process

Mark H. Wholey, MD, of the University of Pittsburgh Medical Center, Shadyside (Pittsburgh, PA), agreed that Dr. Gray and colleagues were on the right track with 72 cases but expressed frustration with the pace of the US Food and Drug Administration and Centers for Medicare and Medicaid Services (CMS) in reviewing CAS.

“The downside to all of this is we can do these analyses inside and out in these registries, but CMS couldn’t care less. . . . I’m not even sure they care about CREST,” Dr. Wholey said, referring to the 2,500-patient randomized trial that found stenting and surgery produced similar overall outcomes at 4 years. “There are pockets in the world where stenting is accepted, as it should be,” he added. “Only in this country, there’s a clique of neurologists and vascular surgeons who are destroying us. And I don’t have the answer to it.”

Because of restrictions on CAS, few operators are currently meeting the target of 72 cases, he said, noting, “We can’t do anyone except ultra high-risk patients with 80% stenosis or greater, so we’re still very limited. And there’s no reimbursement.”

The current situation is “just unexplainable. The difficulty is overwhelming. Some of these patients benefit so much from carotid stenting,” Dr. Wholey commented, reporting that CMS will meet with Abbott and others in approximately 1 month to discuss reimbursement. In January, an FDA advisory panel voted to extend the indication for CAS to patients even at standard surgical risk (see story).

Study Details

Patient medical histories were largely comparable between the hospitals that did or did not achieve death stroke/rates below 3%, although congestive heart failure was more prevalent among patients treated at the poorer performing sites. Vessel characteristics also tended to be similar, but hospitals with higher death/stroke rates treated patients with greater target lesion calcification, more complex aortic arch anatomy, and atherosclerotic arch involvement.

Although most baseline characteristics of patient populations treated by each physician subspecialty were similar among groups, there were a few differences. Vascular surgery patients were less likely to exhibit target lesion calcification and aortic valve disease, had fewer type III arches, were more apt to have previous endarterectomy, and showed more contralateral occlusion of the internal carotid artery. Interventional cardiology patients were more likely to have CAD, unstable angina, and PAD.

Note: Dr. Gray is a faculty member of the Cardiovascular Research Foundation, which owns and operates TCTMD.

Source:
Gray WA, Rosenfield KA, Jaff MR, et al. Influence of site and operator characteristics on carotid artery stent outcomes: Analysis of the CAPTURE 2 (Carotid Acculink/Accunet Post Approval Trial to Uncover Rare Events) clinical study. J Am Coll Cardiol Intv. 2011;4:235-246.

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