Repolarization changes in patients with heart failure receiving cardiac resynchronization therapy-signs of cardiac memory

Background and Purpose: Cardiac memory is known as T-wave inversions and other repolarization changes after a period of altered ventricular activation, previously mainly studied in structurally normal hearts. We investigated repolarization changes in failing hearts undergoing cardiac resynchronization therapy (CRT). Methods: Electrocardiogram and vectorcardiogram were recorded before and 1 day and 2 weeks after initiation of CRT in 23 patients with heart failure and left bundle-branch block. Results: After 1 day of CRT, the T vector during intrinsic conduction (left bundle-branch block) had rotated toward the direction of the paced QRS vector; T-vector size had increased with further increase after 2 weeks (T-vector amplitude, 889 +/- 277 vs 651 +/- 225 mu V; T area, 169 +/- 70 vs 102 +/- 39 mu Vs; P <.01) accompanied by prolonged repolarization (T peak-to-end, 174 +/- 34 vs 127 +/- 16; QT interval corrected for heart rate, 541 +/- 59 vs 493 +/- 33 milliseconds; P <.01). Conclusions: Repolarization changes are present in patients with heart failure, although less pronounced compared with after right ventricular pacing in structurally normal hearts.