Impact of myocardial scarring on outcomes of cardiac resynchronization therapy: Extent or location?

Refining the criteria for patient selection for cardiac resynchronization therapy (CRT) may improve its outcomes. The study objective was to determine the effect of scar location, scar burden, and left ventricular (LV) lead position on CRT outcomes. Methods: The study included 213 consecutive CRT recipients with radionuclide myocardial perfusion imaging before CRT between January 2002 and December 2008. Scar localization and myocardial viability were analyzed using a 17-segment model and a 5-point semiquantitative scale. New York Heart Association (NYHA) class and echocardiography were assessed before and after CRT. The anatomic LV lead location in the 17-segment model was assessed by review of fluoroscopic cinegrams in right and left anterior oblique views. As in published studies, clinical response was defined as an absolute improvement in LV ejection fraction of $5 percentage points after CRT. Results: A total of 651 scar segments was identified in 213 patients. Eighty-three percent of scar segments were located in the LV anterior, posterior, septal, and apical regions, whereas 84% of LV leads were in the lateral wall. Only 11% of LV leads were positioned in scar segments. The extent of scarring was significantly higher in nonresponders than in responders (18.0% vs. 6%, P = 0.001). Compared with patients with scarring >22%, patients ≤70 y with scarring ≤22% of the left ventricle had a greater increase in LV ejection fraction (10.1% ± 10.5% vs. 0.8% ± 6.1%; P = 0.001) and improvement in NYHA class (-0.9 ± 0.7 vs. -0.5 ± 0.8; P = 0.02). Conclusion: LV leads were often located in viable myocardial regions. Less scar burden was associated with a greater improvement in heart failure but only in relatively younger CRT recipients.