Purpose: There are an estimated 400,000 patients over the age of 65 years in the United States with extracranial internal carotid artery stenosis, which accounts for 15-20% of ischemic strokes. Revascularization has been shown to decrease stroke risk by 45%, but this procedure carries substantial costs and risks. Carotid stenosis patients with image-determined cerebrovascular reserve (CVR) impairments have been shown to be at a four-fold increased risk of stroke. We projected health benefits, risks, and costs of three competing strategies (treat, test, or neither) for carotid stenosis patients.
Methods: We developed a decision analytic model to compare the following interventions for asymptomatic carotid stenosis patients (50-99% extracranial internal carotid artery blockage): 1) treat all with revascularization (carotid endarterectomy); 2) only perform revascularizations for those with image-determined (transcranial Doppler ultrasound [TCD]) CVR impairments, and use medical therapy alone for all others; and 3) medical therapy alone for all patients. Model input parameters were estimated from published sources. Healthcare costs for revascularization, TCD, acute stroke, and annual long-term stroke care were $14,130, $265, $65,800, and $31,000, respectively. Estimates for baseline annual risk of stroke and probability of revascularization complications (death, stroke, or myocardial infarction) were 1.5% and 2%, respectively. Discounted lifetime costs and health benefits (quality-adjusted life years [QALYs]) were projected for each strategy.
Results: The medical therapy alone strategy resulted in higher total costs ($47,000 per person, driven by stroke-related costs) and lower lifetime QALYs (11.379) compared to image-based CVR testing ($40,800, 11.535 QALYs) or revascularization for all ($44,800, 11.555 QALYs). The incremental cost-effectiveness ratio for the revascularization for all versus CVR testing strategy was $210,000/QALY. Cost-effectiveness results were most sensitive to plausible variations in revascularization risks, costs and benefits; strength of association between CVR impairment and future stroke; and baseline stroke risk. Figure 1 shows the two-way sensitivity analysis results for revascularization complication rates and baseline stroke risk. Model results were robust to variations in TCD costs; acute and long-term stroke costs; and stroke utility values.
Conclusions: CVR testing can be a cost-effective tool to identify asymptomatic carotid stenosis patients most likely to benefit from revascularization. The economic value of this tool depends on accurate assessments of baseline stroke risk and the likelihood of procedure complications, factors that vary by patient and provider.
