Abstract 3380: Predicting Response to Cardiac Resynchronization Therapy in Ischemic Cardiomyopathy: The Effect of Global and Regional Scar Burden by Myocardial Perfusion Imaging
Background: Although cardiac resynchronization therapy (CRT) has rapidly become an integral component of advanced heart failure (HF) treatment, 30% of patients meeting clinical criteria do not respond to this therapy. We hypothesized that global scar burden and scar density at the LV pacing site predict poor response to CRT in patients with ischemic cardiomyopathy (ICM).
Methods: Forty-nine patients (age 68.2 ± 9.0; 83.7% male; mean LVEF 19.9 ± 5.3%) with ICM who underwent CRT-D implantation and Tl201 SPECT myocardial perfusion imaging (MPI) were included. MPI studies were read quantitatively, assigning each of 17 myocardial segments a perfusion score (0 – 4), and cumulatively generating a summed perfusion score (SPS). LV lead position was determined by chest radiography in two projections. Echocardiograms were performed before and after (12.8 ± 11.4 months) CRT.
Results: Echocardiographic response to CRT, defined as ≥15% relative increase in LVEF from baseline, was achieved in 27 (55.1%) patients. The mean SPS was 18.9 ± 11.5 in responders vs. 33.7 ± 11.1 in nonresponders (p=0.00004), and average scar density in the segments immediately adjacent to the LV lead was lower in responders (0.72 ± 0.92 vs. 1.64 ± 0.82; p=0.001). Both global scar burden (r=-0.51; p<0.0002) and scar burden near the LV lead (r=-0.48; p=0.0005) inversely correlated with LVEF change. The number of segments with a score of 4, representing transmural infarct, also correlated negatively with LVEF change (r=-0.51; p<0.001).
Conclusions: Higher overall scar burden, greater scar density near the LV lead tip, and number of severely scarred segments portend an unfavorable response to CRT in ICM patients. CRT may not produce reverse echocardiographic remodeling once certain global and local scar thresholds are crossed. Prospective confirmation of these findings is warranted.