Nonechocardiographic imaging in evaluation for cardiac resynchronization therapy

In patients with heart failure and prolonged QRS duration, randomized clinical trials have shown that cardiac resynchronization therapy (CRT) is associated with improvement in quality of life, left ventricular (LV) remodeling, and survival.^1–3 The improvements are believed to be mediated by more effective synchronized contraction in the presence of a wide QRS, but mechanical and electrical dyssynchrony are not equivalent.^4,5 Although the concept of CRT response remains problematic,⁶ 20% to 40% of patients who receive CRT based on electrical dyssynchrony criteria (ie, QRS duration) do not derive symptom improvement or demonstrate reverse remodeling.^7–10 Scar burden^11–13 and failure to place the LV pacing lead at the site of latest onset of contraction^14–17 have been linked to a poor response. Thus, optimal clinical decision-making for CRT must include a comprehensive evaluation of all these factors to identify patients with heart failure who will benefit.