Rationale and design of the PRognostic Importance of MIcrovascular Dysfunction in asymptomatic patients with Aortic Stenosis (PRIMID-AS): a multicentre observational study with blinded investigations.

INTRODUCTION: Aortic stenosis (AS) is the commonest valve disorder in the developed world requiring surgery. Surgery in patients with severe asymptomatic AS remains controversial. Exercise testing can identify asymptomatic patients at increased risk of death and symptom development, but with limited specificity, especially in older adults. Cardiac MRI (CMR), including myocardial perfusion reserve (MPR) may be a novel imaging biomarker in AS. AIMS: (1) To improve risk stratification in asymptomatic patients with AS and (2) to determine whether MPR is a better predictor of outcome than exercise testing and brain natriuretic peptide (BNP). METHOD/DESIGN: Multicentre, prospective observational study in the UK, comparing MPR with exercise testing and BNP (with blinded CMR analysis) for predicting outcome. POPULATION: 170 asymptomatic patients with moderate-to-severe AS, who would be considered for aortic valve replacement (AVR). PRIMARY OUTCOME: Composite of: typical symptoms necessitating referral for AVR and major adverse cardiovascular events. FOLLOW-UP: 12-30 months (minimum 12 months). PRIMARY HYPOTHESIS: MPR will be a better predictor of outcome than exercise testing and BNP. ETHICS/DISSEMINATION: The study has full ethical approval and is actively recruiting patients. Data collection will be completed in November 2014 and the study results will be submitted for publication within 6 months of completion. CLINICALTRIALSGOV IDENTIFIER: NCT01658345.