Vertebrobasilar Flow Evaluation and Risk of Transient Ischaemic Attack and Stroke study (VERiTAS): rationale and design

Abstract

Background: Over one-third of ischaemic strokes occur in the posterior circulation, and a leading cause is atherosclerotic vertebrobasilar disease. Symptomatic vertebrobasilar disease carries a high annual recurrent stroke risk, averaging 10-15% per year. Endovascular angioplasty and stenting are increasingly used but carry risks, and the benefit remains unproven. Determining stroke predictors in this population is critical to identifying high-risk patients for future trials of intervention. Preliminary studies indicate that stroke risk in vertebrobasilar disease is strongly related to haemodynamic compromise, which can be measured noninvasively using quantitative magnetic resonance angiography.

Methods/study design: The Vertebrobasilar Flow Evaluation and Risk of Transient Ischaemic Attack and Stroke (VERiTAS) study, a prospective multicentre NIH-funded observational study of symptomatic vertebrobasilar stenosis (≥50%) or occlusion, is designed to test the hypothesis that patients demonstrating compromised blood flow as assessed by quantitative magnetic resonance angiography are at higher stroke risk. The study will recruit 80 patients at six sites in North America over 4-years. Upon enrollment, subjects will undergo haemodynamic assessment with blinded quantitative magnetic resonance angiography to assess large vessel flow in the vertebrobasilar territory, and be prospectively designated as compromised or normal flow. Patients will be re-imaged with quantitative magnetic resonance angiography at 6-, 12-, and 24-months, and followed for 12-24-months for the primary end-point of stroke in the vertebrobasilar territory.

Conclusion: The VERiTAS study is the first prospective study of haemodynamics and stroke risk in the posterior circulation. The results may impact the selection criteria for interventional candidates and also define a low-risk population in whom the risks of invasive interventions would be unnecessary.

Figure 1

QMRA 3- dimensional surface rendering of the cerebral vasculature based on time-of-flight MRA created by NOVA software. The standardized locations for placing the scan line (yellow square) for phase contrast imaging to obtain flow measurements are indicated. Arrow indicated direction of flow. A. Basilar artery – scan plane on straight segment proximal to SCA (distal to stenosis if present) B. Posterior cerebral arteries (left depicted) – scan plane on straight portion of the P2 segment, distal to the posterior communicating artery origin. C. Vertebral arteries (right depicted) – scan plane on straight segment of vertebral artery proximal to posterior inferior cerebellar artery. D. Posterior communicating artery (left depicted) – scan plane on straight mid segment E. Internal carotid artery (right depicted) – scan plane on straight portion below the petrous segment. F. Middle cerebral artery (right depicted) – scan plane on straight portion of M1 segment. G. Anterior cerebral artery, A1 segment (right depicted) – scan plane on straight mid segment of A1. H. Anterior cerebral artery, A2 segment (left depicted) – scan plane on straight proximal segment of A2 prior to branch points.