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Improved CAS Protocol Reduced Embolic Events


 

SAN DIEGO — Significant reductions in peri-procedural embolic events were achieved after implementation of quality improvement measures for carotid angioplasty and stenting, results from a single-center study showed.

In a previous report, Dr. Maureen M. Tedesco and her associates in the division of vascular and endovascular surgery at Stanford (Calif.) University found a 70% incidence of microemboli in patients who underwent carotid angioplasty and stenting (CAS) as detected by diffusion weighted MRI, compared with no microemboli in those who received carotid endarterectomy for carotid disease (J. Vasc. Surg. 2007;46:244–50).

“Although there was a much higher incidence of microemboli after CAS, most of the emboli were asymptomatic; only two of the CAS patients who had microemboli demonstrated temporary neurologic symptoms that resolved within 24 hours,” Dr. Tedesco said at the Vascular Annual Meeting. “Of all patient demographic, anatomic, and procedure-related factors that were analyzed, only the performance of arch angiography and history of significant coronary artery disease were associated with an increased risk of microemboli formation.”

Before publication of that report, the vascular group at Stanford demonstrated that a multidisciplinary peer review process for carotid procedures at Stanford University Medical Center reduced the risk and cost of surgical endarterectomy (Arch. Surg. 2000; 135; 939–42). In an effort to study the impact of this peer review process since the advent of the CAS program at Stanford, two time periods were compared before and after quality-improvement measures were implemented, under the direction of the project's principal investigator, Dr. Jason T. Lee, director of endovascular surgery at Stanford University Medical Center.

Period 1 (November 2004 through April 2006) included a review of 27 patients undergoing CAS with pre- and postprocedure diffusion-weighted MRI. “During period 1, our standard protocol for CAS included performance under local anesthesia, routine arch angiography, use of a distal protection device, pre- and poststent deployment balloon dilatation, and completion intracranial cerebral angiograms,” Dr. Tedesco said.

Period 2 (May 2006 through February 2008) was a prospective analysis of 20 patients undergoing CAS who underwent pre- and postprocedure MRI. The quality improvement measures implemented during period 2 included early heparinization “as soon as groin access was obtained as opposed to period 1 when heparinization was instituted after sheath placement into the target common carotid artery; the preferential change to a closed cell carotid stent system [Abbott Xact stent], and elimination of routine arch angiography.”

The researchers then reviewed the hospital records of all patients and collected symptoms, comorbidities, lesion characteristics, preprocedural information, and postoperative outcomes. They used diffusion-weighted MRI to determine the incidence and location of acute, postprocedural microemboli.

The mean age of patients was 70 years and most (90%) were male. There were no differences between period 1 and period 2 patients with respect to gender, the presence of diabetes, hypertension, or hyperlipidemia. However, there was a higher percentage of smokers in period 1 and a higher incidence of obesity in period 2 patients. In addition, analysis of comorbidities revealed that there were no differences between period 1 and period 2 in terms of history of coronary artery disease, chronic obstructive pulmonary disease, peripheral vascular disease, atrial fibrillation, redo CAS procedures, or symptomatic patients.

Compared with period 1 patients, period 2 patients had significantly more calcified lesions (68% vs. 27%, respectively), longer lesions (15.9 mm vs. 8.2 mm), and ulceration of their lesions (55% vs. 27%), but there were no differences between the two groups in the type of arch. “[These data suggest] that the period 2 lesions were perhaps technically more challenging than the period 1 lesions,” Dr. Tedesco commented.

Further analysis showed no differences between the two groups in fluoroscopy time or in the number of stents used. However, period 2 patients received significantly less contrast volume than did period 1 patients (58 mL vs. 77 mL, respectively). This difference “is likely due to the elimination of the routine arch angiography,” she said.

Dr. Tedesco reported the main findings of the study, that 20 patients from period 1 (74%) and 7 patients from period 2 (35%) demonstrated acute microemboli on postprocedural MRI, a difference that was statistically significant. The mean number of microemboli was 4.1 in period 1 patients, and 1.5 in period 2 patients, a difference that was also statistically significant.

Even with these microemboli, however, only two patients in period 1 and one of the patients in period 2 experienced temporary neurologic symptoms that resolved within 24 hours. The 30-day stroke rate in both groups was 0%.

“The long-term neurologic benefits associated with reduced subclinical neurologic events remains to be determined, but there remains a significant risk of microemboli as identified by diffusion- weighed magnetic resonance imaging following carotid angioplasty and stenting,” Dr. Tedesco concluded. “Efforts to reduce these subclinical radiographic findings may have a positive impact on long-term outcomes after CAS with respect to device improvement, procedural modifications, and patient selection.”

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