Cost-Effectiveness of Quantitative Magnetic Resonance Angiography Screening and Submaximal Angioplasty for Symptomatic Vertebrobasilar Disease

Abstract

Background and Purpose- The VERiTAS (Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke) study demonstrated posterior circulation distal flow status, determined by quantitative magnetic resonance angiography, is a robust predictor of vertebrobasilar stroke risk in patients with symptomatic atherosclerotic vertebrobasilar disease. Flow-compromised high-risk patients may benefit from flow-restoring endovascular procedures, such as submaximal angioplasty. In this study, we examine the cost-effectiveness of quantitative magnetic resonance angiography screening to identify patients who may benefit from submaximal angioplasty to restore vertebrobasilar flow. Methods- A Markov model was created comparing a no screening strategy with standard medical management alone and a screening strategy involving quantitative magnetic resonance angiography imaging and submaximal angioplasty for treatable patients with low vertebrobasilar flow for a 30-year time horizon. Outcomes included quality-adjusted life years (QALY) and lifetime costs. Rates of stroke and death were obtained from VERiTAS data, and disability rates and costs were derived from VERiTAS and the literature. A sensitivity analysis was performed with periprocedural stroke rate from angioplasty the primary variable of interest. Results- At a 6% periprocedural stroke risk, the screening strategy saved an average of 0.364 QALYs per patient and a lifetime cost savings of $7312 versus the no screening strategy. Among patients with low flow suitable for intervention, the benefit was substantially higher, averaging 1.485 QALYs saved and lifetime cost savings of $21 294. Across the entire cohort, QALY savings were observed at the end of the first year and economic savings at year 6. The benefit of screening declined at higher periprocedural risk. Conclusions- Quantitative magnetic resonance angiography screening and submaximal angioplasty with 6% periprocedural risk in suitable patients are cost effective both in terms of QALY and lifetime costs for patients with symptomatic vertebrobasilar occlusive disease. With potential health and economic savings, a clinical trial examining the periprocedural risk of submaximal angioplasty is warranted. Clinical Trial Registration- URL: http://www.clinicaltrials.gov . Unique identifier: NCT00590980.

Keywords: angioplasty; cost-benefit analysis; magnetic resonance angiography; quality-adjusted life years; stroke; vertebrobasilar insufficiency.

Figures

Figure 1:

Markov Model Decision Tree. For each patient, three states were possible: (1) alive, current health, (2) stroke survivor, and (3) dead. During each year cycle, patients had a certain probability of transitioning from alive to stroke or dead, or from stroke to dead based on yearly risks observed in VERiTAS for the first two years or extrapolated from VERiTAS thereafter. Screening and no screening strategies were compared. In the screening strategy, flow status was identified by qMRA, and intervenable low flow patients underwent submaximal angioplasty to restore stroke risk to the same as normal flow after an initial procedural event rate. In the no screening strategy, the flow status remained unknown and stroke risk remained stable to the baseline proportion of normal and low flow patients in the population. Transition probabilities were carried across 30 cycles for the 30y time horizon to identify QALY and cost totals for each strategy.

Figure 2:

Heath States over Time, Screening vs No Screening Strategies. The average number of healthy patients (white bars) decreased over time, with the greatest differential between the screening and no screening strategies observed at 10 years. This effect diminished by 20 years, however, when most patients had died of either stroke or other causes. Figure reflects all patients in study, at a 6% periprocedural stroke risk.

Figure 3:

QALY, Lifetime Costs, Screening vs No Screening Strategies. A QALY benefit was observed in the screening strategy (white circles) versus the no screening strategy (black circles) at the end of the first year, while an economic benefit was observed at the end of year six. The economic benefit at six years represents when the initial cost of qMRA and angioplasty is outweighed by the higher costs of stroke care in the no screening group.