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 - Singh, A; Ford, I; Greenwood, J; Khan, J; Uddin, A; Berry, C; Neubauer, S; Prendergast, B; Jerosch-Herold, M; Williams, B; Samani, N; McCann, G (BMJ Open, 2013)