Left ventricular dyssynchrony in patients with left bundle branch block and patients after myocardial infarction: integration of mechanics and viability by cardiac magnetic resonance.

AIMS To quantify left ventricular (LV) dyssynchrony in patients with left bundle branch block (LBBB) and in patients after myocardial infarction (MI) applying an accelerated three-dimensional (3D) tagging cardiac magnetic resonance (CMR) technique, and to combine dyssynchrony information with viability data obtained by late gadolinium enhancement (LGE) CMR. METHODS AND RESULTS Thirty-two patients (59 +/- 11 years) after first MI (Pats(MI)), 10 patients (63 +/- 10 years) with LBBB (ejection fraction < 40%; Pats(LBBB<40)), 13 patients (63 +/- 11) with LBBB (ejection fraction >or= 40%; Pats(LBBB >or=40 )), and 15 healthy controls (53 +/- 10 years) underwent 3D tagging CMR and LGE imaging at 1.5 T. As a measure of mechanical LV dyssynchrony, the standard deviation of T(max) over the LV, the circumferential uniformity ratio estimate (CURE) index, and a segmental-based circumferential systolic dyssynchrony index (SDI) were calculated. All three parameters detected significantly increased circumferential dyssynchrony in patients compared with controls. The CURE and SDI showed a good correlation (r = 0.93, P < 0.0001) and detected most severe dyssynchrony in Pats(LBBB<40) (P < 0.001 vs. controls, P < 0.005 vs. Pats(MI)). Systolic dyssynchrony index additionally allowed integration of localized viability information to yield SDI(viable) which was highest in Pats(LBBB<40). CONCLUSION Dyssynchrony patterns in the LV can be quantified globally and regionally by 3D tagging CMR. Combination of viability and dyssynchrony information allows for a comprehensive dyssynchrony quantification in patients with LBBB or post-MI. Future studies are required to test the value of the method to predict responsiveness to resynchronization.