Advances in the understanding of the pathophysiology and management of aortic stenosis: role of novel imaging techniques.

The management of asymptomatic patients with aortic stenosis (AS) is controversial and the mechanisms leading to symptom generation and adverse outcome are not fully understood. Novel imaging techniques offer a noninvasive tool for in vivo assessment of AS and its pathophysiological consequences on the myocardium. Exercise echocardiography provides insight into the mechanisms responsible for exercise limitation and symptom generation. Speckle tracking allows the detection of reduced myocardial strain, which is associated with adverse events in asymptomatic patients. Computed tomography scanning can accurately quantify valve calcification and is associated with disease severity. Positron emission tomography/computed tomography imaging has the potential to monitor disease activity (inflammation and microcalcification) for the first time. Cardiac magnetic resonance (CMR) imaging uniquely allows tissue characterization with identification of fibrosis, a key characteristic of failing myocardium. T1 mapping allows estimation of diffuse interstitial fibrosis and late gadolinium enhancement demonstrates focal fibrosis/scarring. Myocardial steatosis, assessed using CMR spectroscopy, is increased in severe AS and might contribute to myocardial dysfunction. Positron emission tomography and CMR imaging can quantify myocardial blood flow and assess microvascular dysfunction, which might contribute to symptom development and myocardial remodelling. These novel imaging techniques are now being assessed in prospective prognostic studies that will clarify their utility in risk stratification in AS, and lead to improved management and outcomes for these patients.