Is the magnet a better crystal ball for predicting response to cardiac resynchronization therapy?

Cardiac resynchronization therapy (CRT) is undoubtedly of great benefit to many heart failure patients with widened QRS and depressed ejection fraction (1–3). The pathological feature that appears to be a large reason for response to CRT is correction of abnormalities of timing in regional left ventricular (LV) mechanical activation, known as dyssynchrony (4). Improvements in synchrony of regional LV contraction results in hemodynamic improvements, decreases in mitral regurgitation, and LV reverse remodeling (4–6). However, a consistent proportion of patients who undergo CRT do not seem to respond favorably, either with an improvement in clinical symptoms or LV function. The prevailing hypothesis has been that patients who are nonresponders to CRT are in large part those curious individuals who have QRS widening, but no significant dyssynchrony (7). The