Poststent Dilation in Carotid Stenting Linked to Hemodynamic Depression
During carotid artery stenting (CAS), post-deployment dilation increases the incidence of hemodynamic instability almost fourfold and may raise the risk of periprocedural major adverse events, according to an observational study published online December 16, 2013, ahead of print in the Journal of Vascular Surgery.
Mahmoud B. Malas, MD, MHS, and colleagues at the Johns Hopkins University (Baltimore, MD), looked at 103 patients who underwent CAS at their institution between September 2005 and June 2012. All patients underwent dilation before stent implantation. In addition, 70% (n = 72) received poststent dilation if completion angiography showed greater than 40% residual stenosis that was visually deemed significant by the operator.
More Hemodynamic Depression with Poststent Dilation
Overall, 72 patients (70%) experienced hemodynamic depression (6 cases of hypotension alone, 32 of bradycardia alone, and 32 of both), but the condition was more common among those who underwent poststent dilation than those who did not (78% vs. 52%; P < 0.01).
MACE (death, stroke, MI) occurred in 6.8% of the overall cohort. Two strokes (1 major, 1 minor) and 1 death were seen in the poststent dilation group (none in the no-poststent dilation group), for an overall combined stroke/death rate of 2.9%. Among the 84% of patients with Doppler ultrasound follow-up, there was no difference in restenosis rates between those who did and did not undergo poststent dilation (P = 1.0).
After adjustment, the only predictor of intra- or postoperative hemodynamic instability was poststent dilation (OR 3.8; 95% CI 1.3-11; P < 0.01).
In a separate analysis, also after adjustment, independent predictors of postoperative hospital stay exceeding 1 day included:
- Symptomatic status (OR 6.6; 95% CI 1.7-5.8; P < 0.01)
- Recent MI (OR 6.1; 95% CI 1.3-32; P < 0.01)
- Hyperlipidemia (OR 5.4; 95% CI 1.1-27; P = 0.04)
- CAD (OR 9.3; 95% CI 2.1-41; P < 0.01)
The authors observe that in the randomized CREST trial “only 6.3% of [CAS] patients did not receive [poststent dilation] compared with 30% in our study. We believe that withholding [poststent dilation] from a greater number of patients is one of the factors that contributed to our lower periprocedural MACE rate.” However, they admit, other factors may have played a role, including:
- Careful prestent dilation
- Meticulous patient selection
- Conservative dilation technique
- Use of a transcervical approach in difficult aortic arches
- Use of reverse flow protection for critically stenotic lesions
Dr. Malas and colleagues acknowledge several study limitations, including small sample size, lack of randomization, and a disproportional event rate. In addition, the fact that there were no events in the group without poststent dilation did not permit enough power to show if there is a relation between the manoeuver and MACE, or between hemodynamic depression and MACE.
Nonetheless, Dr. Malas said in a press statement, “Our work suggests that doctors should never balloon a stent after placing it. There is no upside.”
Conclusion Assumed, Not Proven
But in a telephone interview with TCTMD, Christopher J. White, MD, of the Ochsner Heart and Vascular Institute (New Orleans, LA), said the study is fatally flawed in that it failed to control for the reason for poststent dilation. The investigators chose to perform dilation in certain patients, presumably to improve flow and reduce the chance of restenosis, he noted. The dilation and associated hemodynamic disturbance “may have been a good or a bad thing, but they simply assume that it’s a bad thing and ignore the fact that the restenosis rates between the groups were the same, which may have been because they [performed poststent dilation],” he explained. “They never correlated the hemodynamic disturbance with events.”
In effect, the authors “preconceived an outcome and then collected data to support it,” Dr. White asserted.
Another study weakness is the failure to provide information on the size of the balloon used for dilation, Dr. White observed. “The bigger the balloon, the more hemodynamic embarrassment,” he said. “If you use tiny balloons, you don’t get into much trouble.” Moreover, there is no reason to think that the hemodynamic risk is different for poststent and prestent dilation, he commented.
Dr. White pointed to another potential confounder: More patients in the non-postdilation group had undergone prior endarterectomy, which removes the carotid nerves. Thus, this group was inherently less sensitive to hemodynamic depression.
In addition, Dr. White observed, a variety of embolic protection devices were used, including proximal protection. If the latter is not done quickly, the interruption of blood flow can itself cause hemodynamic disturbance, he said.
While the study fails to make the case against poststent dilation, Dr. White said, its overall point is valid: ‘Less is more’ in any carotid procedure. “Unless there is a significant narrowing, poststent inflation is not necessary,” he said, noting that he uses a threshold of 50% residual stenosis to trigger the technique. Moreover, he added, there is no good evidence that restenosis rates are impacted by poststent dilation.
Currently, the technique is performed in only about one-third of cases, Dr. White estimated. That is a major change from a decade ago, when dilation was routine, he noted, but the decline is due not to concern over hemodynamics but to the increased risk of embolization.
The authors conclude, “[W]e believe that the use of [poststent dilation] in CAS should be further examined via a large randomized controlled trial that allows for sufficient power to control for potential confounders, determine causality, and minimize bias.”
With that, Dr. White emphatically agreed.
Hemodynamic instability was defined as bradycardia (heart rate of < 60 beats/min) or hypotension (systolic BP of < 90 mm Hg) during the procedure and postoperative period.
Patients’ mean age was about 68 years; those who underwent poststent dilation were more likely to have diabetes than those who did not.
Qazi U, Obeid TE, Enwerem N, et al. The effect of ballooning following carotid stent deployment on hemodynamic stability. J Vasc Surg. 2013;Epub ahead of print.
- Dr. Malas reports no relevant conflicts of interest.
- Dr. White reports serving as the steering committee chair for the NCDR CARE Registry.