Doppler US aids decisions in stroke prevention measures

Doppler ultrasonography (US) is an effective and relatively low-cost tool in identifying patients with asymptomatic carotid stenosis who would most benefit from more invasive treatment, according to a study published in the February edition of Radiology.

Carotid stenosis causes up to 20 percent of all ischemic strokes, according to the study authors, including Ankur Pandya, PhD, with Weill Cornell Medical College in New York. There are 400,000 patients over the age of 70 in the U.S. with asymptomatic carotid artery stenosis. However, aggressive methods of reducing stroke risk, like revascularization surgeries, are often controversial because of uncertain effectiveness and high cost compared to less aggressive approaches such as aggressive medical therapy.

In this study, the researchers attempted to project the healthcare benefits, costs and incremental cost-effectiveness of three different stroke prevention strategies in asymptomatic patients who have carotid artery stenosis. They include: immediate revascularization surgery followed by medical therapy; medical therapy for all patients with subsequent revascularization for those patients who progress; and the use of a decision-making rule for treatment—those with demonstrated cerebrovascular reserve (CVR), determined using Doppler US, would undergo immediate revascularization and all others would undergo medical therapy.

“The economic value of using transcranial Doppler US to assess CVR in asymptomatic patients with carotid artery stenosis is not only dependent on long-term health outcomes, but also on the costs associated with neuroimaging, revascularization and its associated risks, acute stroke events, and chronic care,” wrote Pandya and colleagues.

For the study, the researcher developed a decision analytic model that projected lifetime quality-adjusted life years (QALYs) and costs for asymptomatic patients with carotid stenosis with 70 to 89 percent carotid luminal narrowing at the time of the study. Risks of clinical events, costs, and quality-of-life values were estimated on the basis of published sources, the authors wrote.

The results showed that lifetime QALYs were lowest with the medical therapy strategy ($14,597 average cost and 9.8 QALYs). Doppler-based CVR testing resulted in an average cost of $16,583 and 9.934 QALYs followed by immediate revascularization ($20,950, 9.940 QALYs).

“The incremental cost-effectiveness ratio for the CVR-based strategy compared with the medical therapy–based strategy was $23,000 per QALY and for the immediate revascularization versus the CVR-based strategy was $760,000 per QALY,” the researchers wrote.

They also found that age/benefit relationships were intuitive. Younger patients with stenosis closer to occlusion would benefit most from successful revascularization. The lifetime benefits of revascularization are less pronounced in older patients with lower degrees of stenosis.

Pandya et al stressed the role of imaging as a tool in identifying carotid artery stenosis patients who would benefit from either revascularization procedures or from medical therapy. “Authors of future studies should seek greater accuracy in determining the cost of revascularization and develop methods that would allow more individualized decision making on the basis of patient stroke risk factors and predicted procedure complication risks.”