Contractile Reserve in Dyssynchrony: A Novel Principle to Identify Candidates for Cardiac Resynchronization Therapy

Cardiac resynchronisation therapy (CRT) has been documented to be a powerful treatment in patients with severe congestive heart failure. However, 30-40% of patients receiving a CRT are non-responders. In this study the investigators will use a previously validated method to estimate myocardial segment work non-invasively by speckle-tracking echocardiography and blood pressure. Furthermore, cardiac magnetic resonance imaging (CMR) with late gadolinium enhancement (LGE) will be performed in feasible subjects. The main purpose of the study is to determine if myocardial work by echocardiography in combination with viability assessment by LGE-CMR can predict response to CRT.