Carotid Stenting Causes Early Drop in Blood Pressure Compared with Surgery

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Carotid artery stenting (CAS) leads to a greater decrease in blood pressure (BP) compared with carotid endarterectomy (CEA), although the effect is short-lived. What persists, though, according to results published online October 13, 2011, ahead of print in Stroke, is a decrease in antihypertensive medication use in CAS patients.

Researchers led by Aysun Altinbas, MD, of University Medical Center Utrecht (Utrecht, The Netherlands), looked at over 1,500 patients from the International Carotid Stenting Study (ICSS), which randomized subjects with a recently symptomatic carotid stenosis (> 50%) to CAS or CEA. In the new subanalysis, Dr. Altinbas and colleagues retrospectively compared the changes in BP following the 2 procedures over a period of up to 1 year after treatment.

While the long-term effects of CAS and CEA on BP are unclear, arterial hypotension has been frequently reported after CAS, attributed to manipulation of the carotid sinus and baroreceptor dysfunction. Meanwhile, both hypertension and hypotension have been noted after CEA.

Lower BP, Fewer Meds

In the study, baseline systolic BP and diastolic BP did not differ between the 2 groups (147/79 mm Hg for CAS, 146/78 mm Hg for CEA). Nor was there any difference in the percentage of patients with treated hypertension (69% with CAS, 70% with CEA).

In both groups, systolic and diastolic BP decreased significantly from baseline (P < 0.0001), but the decrease was larger in the CAS group at discharge (table 1).

Table 1. Change in BP from Baseline to Discharge

In a sensitivity analysis of just the patients with treated hypertension at baseline, mean differences between CAS and CEA stayed significant at discharge for the decreases in systolic (-9.2 mm Hg; P < 0.0001) and diastolic BP (-3.8 mm Hg; P = 0.0001).

However, the greater decrease in BP with CAS disappeared by 1 month (P = 0.370 for mean difference in systolic BP, P = 0.775 for mean difference in diastolic BP), and remained similar at 1 year (P = 0.147 for systolic BP, P = 0.793 for diastolic BP).

Meanwhile, the use of antihypertensive medications remained lower in the CAS arm throughout follow-up (table 2).

Table 2. Antihypertensive Medication Use During Follow-up

There were no major differences in use of antithrombotic medication or statins.

“The present study shows that both CAS and CEA are associated with a decrease in BP in the first days after treatment and that this decrease is larger after CAS than after CEA,” the researchers write.

They add that overall BP control in the ICSS trial was not satisfactory, with the majority of patients having systolic BP levels above guideline targets. They also note that in the current substudy, the lack of long-term difference in BP reduction despite lower use of antihypertensive agents in the CAS arm “suggests that CAS may have a long-term hypotensive effect compared with CEA. The analysis of data from further follow-up in ICSS beyond 1 year, which will be available after completion of the trial, may provide further insights into this effect.”

Homeostasis in a Month

In an e-mail communication with TCTMD, Dr. Altinbas explained that “blood pressure lowering early after CAS can be explained by stretching of the carotid baroreceptors, which inhibits sympathetic action and results in peripheral vasodilation and thereby in a reduction in blood pressure. Activation of the vagal nerves causes bradycardia, which in turn contributes to blood pressure lowering.” But, he added, “our study shows that apparently a new homeostasis is reached within one month after the intervention.”

According to Daniel J. McCormick, DO, of Drexel University College of Medicine (Philadelphia, PA), the study examines a phenomenon that clinicians have seen in clinical practice. “I’ve got patients who have had very brisk vasodepressor responses after the procedure, and they come back up, but not to the same level, and their hypertension is much more easily managed and controlled,” he told TCTMD in a telephone interview. “It definitely is part of the [CAS] procedure.”

Dr. McCormick added that the findings should definitely spur future research. “It’s certainly hypothesis generating,” he said. “It would be an additional boon or incentive for carotid stenting if it turned out that it did provide an enhanced effect for the reduction in blood pressure in patients with severe hypertension compared with endarterectomy.”

Not So Fast

However, according to Dr. Altinbas, any conclusions in this regard are premature. “Unfortunately, I do not think that we can make such a statement,” he said. “CEA has remained the gold standard for treating carotid artery stenosis, and CAS should only be considered in specific cases. The presence of hypertension has no role in this decision. It is important that in all patients, hypertension should be treated with antihypertensive medication according to guidelines for secondary prevention. This article does not justify less intensive antihypertensive treatment after carotid artery stenting, possibly except for the first few days or weeks.”

Instead, the real message from the study is that “the early reduction in blood pressure after both CAS and CEA has disappeared after one month, which means that physicians should consider reinitiating any antihypertensive medication that had been stopped in the early post-operative period,” Dr. Altinbas stressed.

Nevertheless, the study raises intriguing possibilities. “It might even be a stent effect,” Dr. McCormick theorized. “Some stents have more radial force than others. If that’s the case, that would be helpful to us because we would choose those stents to get more mechanoreceptor stimulation over time, and that might result in even better control of systolic and diastolic blood pressure in patients who come into the procedure with difficult-to-control hypertension.”

 

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Source:
Altinbas A, Algra A, Brown MM, et al. Effects of carotid endarterectomy or stenting on blood pressure in the International Carotid Stenting Study (ICSS). Stroke. 2011;Epub ahead of print.

 

 

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