Inappropriate Carotid Imaging Common in Asymptomatic Patients

April 21, 2016

Only 5% of carotid imaging in asymptomatic patients, those without a history of transient ischemic attack (TIA) or stroke, was performed for indications agreed to be appropriate, according to a new study in older individuals.

Researchers also found that 11.3% of the imaging was done for inappropriate reasons and the indication was "uncertain" in 83.4% of cases.

The study, published online in JAMA Internal Medicine on April 18, was conducted by a team led by Salomeh Keyhani, MD, University of California, San Francisco.

"We found that the vast majority of patients undergoing carotid screening had inappropriate or uncertain indications for such imaging," she told Medscape Medical News.

Dr Keyhani explained that physician groups participating in the Choosing Wisely campaign have identified carotid imaging in asymptomatic populations as being of low value, but the majority of patients who are evaluated for carotid stenosis and subsequently revascularized are asymptomatic.

"We wanted to look at why these individuals were being screened in the first place," she said.

For the study, Dr Keyhani and colleagues reviewed the reasons for carotid imaging in 4127 Veterans Administration (VA) patients 65 years and older undergoing carotid revascularization for asymptomatic carotid stenosis between 2005 and 2009.

Results showed the most common indications were carotid bruit (30%) and follow-up for carotid disease in patients who had previously documented carotid stenosis (20%). Multiple vascular risk factors were the next most common indication listed.

Among the most common inappropriate indications were dizziness/vertigo and syncope. Among the cohort, 83% received a carotid endarterectomy. Overall, 663 procedures were performed in patients 80 years and older.

"Mixed Messages"

"Our main message is that physicians are ordering carotid imaging for indications not supported by the guidelines. We are clearly ordering too many carotid imaging tests," Dr Keyhani said.

"The question is why. This was a VA study so there is no financial incentive for the physicians carrying out the procedures in this system, so I don't think it is financially driven in this case," she noted. "Rather, I think the main problem is the two main sets of guidelines on carotid screening do not agree with each other so clinicians are getting mixed messages."

She also believes culture plays a large role. "It is not just in this area where American doctors order too many tests. There is a culture of not leaving any stone unturned so we don't miss anything."

On the issue of the guidelines, Dr Keyhani explained that there are several different sets of recommendations on carotid screening in asymptomatic patents. "While the US Task Force says don't do it period, others, such as the AHA [American Heart Association] guidelines, suggest it may be appropriate if a patient has multiple risk factors, so there is no consensus."

She suggests this is due to a lack of hard evidence for either screening or not screening, "so the guidelines are based on expert opinion which of course can vary." She adds: "We need better guidelines — or at least they need to be consistent — especially around monitoring stenosis over long periods and evaluating carotid bruits. We also need to improve the evidence base so we have data on when screening is appropriate. At present there is so much uncertainty and patient selection is poor."

The authors also recommend use of decision support tools to help reduce use of low-value imaging.

Consider Risk/Benefit of Revascularization

Dr Keyhani further pointed out that according to revascularization guidelines, patients should be expected to live at least 5 years to be eligible for intervention. "This is because there is an upfront risk of stroke with the procedure and a life expectancy of at least 5 years is required for the benefit to outweigh the risk."

She says this should also apply to screening. "The main purpose of screening is to assess whether they need revascularization. If a patient is not expected to live 5 years and would therefore not be a candidate for revascularization, why would you screen them in the first place?"

"In our study we found that about a quarter of patents did not live 5 years after revascularization so obviously this is not being assessed correctly. Guidelines on screening should include consideration of whether a patient is suitable for revascularization or not."

In an accompanying editorial, Larry B. Goldstein, MD, University of Kentucky, Lexington, notes that the current study was performed in patients who ended up undergoing a revascularization procedure, and he suggests that the percentage of patients undergoing inappropriate screening might be even higher in those who did not undergo a revascularization intervention.

He agrees with Dr Keyhani that the guidelines are inconsistent, leading to the high level of "uncertain" indications.

Dr Goldstein also points out that there is uncertainty about whether asymptomatic patients with stenosis should receive revascularization or best medical therapy.

"In this situation, physicians face a dilemma when caring for individual patients," he writes. "Should a screening test be performed in the face of equivocal, limited, or conflicting data regarding the intervention that would be considered if the condition was detected? … How are these complicated issues best presented and discussed with patients who look to their clinician for guidance?"

He concludes that "despite the available evidence from randomized trials and practice guidelines, whether to proceed with testing can be a matter of informed opinion. In the setting of uncertainty, however, a conservative approach to screening and referral to a center participating in a relevant clinical trial seems the most appropriate strategy."

High Rate of Intervention "Worrisome"

Commenting on the study for Medscape Medical News, David Spence, MD, Stroke Prevention & Atherosclerosis Research Centre, Western University, London, Ontario, Canada, said it was "extremely worrisome" that 83% of the patients underwent endarterectomy.

"Ninety percent of patients with carotid stenosis would be better off with intensive medical therapy, and the few who could benefit from intervention can be identified by several methods, the best of which is transcranial Doppler embolus detection," he said. "Carotid imaging should be done for the purpose of enhancing medical management of atherosclerosis, not for the purpose of finding victims for inappropriate carotid endarterectomy or stenting."

Also commenting for Medscape Medical News, Alex Abou-Chebl, MD, associate professor of neurology, University of Louisville, Kentucky, said, "Given the uncertainty of benefit for revascularization compared to best modern medical therapy, clinicians should try to follow national recommendations for appropriate screening, which are limited to a few indications."

The study was supported by a National Institutes of Health/National Heart, Lung, and Blood Institute grant. The authors have disclosed no relevant financial relationships.

JAMA Intern Med. Published online April 18, 2016. Full text   Editorial

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