ClinicalDevicesScar burden, not intraventricular conduction delay pattern, is associated with outcomes in ischemic cardiomyopathy patients receiving cardiac resynchronization therapy
Introduction
Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in patients with systolic heart failure (HF) and prolonged QRS duration,1, 2 yet a substantial proportion of patients do not respond or they clinically deteriorate.3 Patients with ischemic cardiomyopathy (ICM) generally benefit less from CRT than patients without coronary artery disease,4, 5 and larger scar burden is associated with adverse outcomes in ICM patients.6, 7 Baseline nonspecific intraventricular conduction delay (IVCD) is also associated with worse clinical outcomes among CRT recipients compared to baseline left bundle branch block (LBBB).8, 9, 10
We examined a large CRT registry to examine the relationship between scar burden and QRS pattern in ICM patients. Specifically, we hypothesized that IVCD is associated with greater scar burden compared to LBBB, and that outcomes among CRT recipients with baseline IVCD would therefore be worse than in patients with baseline LBBB.
Section snippets
Patient selection
We screened a prospective CRT registry at the University of Pittsburgh Medical Center that includes all CRT implants since January 1998. In the present study, we included all patients with a cardiac resynchronization therapy–defibrillator (CRT-D) who met the following criteria: (1) left ventricular ejection fraction (LVEF) ≤35%; (2) native QRS duration >120 ms with baseline LBBB or nonspecific IVCD; (3) ICM; (4) New York Heart Association (NYHA) class II–IV HF; and (5) single-positron emission
Patient characteristics
Baseline demographic and clinical characteristics of the study population are listed in Table 1. Compared to patients with LBBB, IVCD patients were more frequently male, had shorter pre-CRT QRS duration and higher prevalence of atrial fibrillation, and more often required loop diuretics. As stated in the Methods, IVCD patients with QRS ≥150 ms and <150 ms were included together in the overall IVCD cohort because of relatively comparable clinical characteristics (Supplementary Table 1).
Myocardial perfusion imaging
MPI was
Discussion
We explored the relationship between QRS morphology and outcomes after CRT-D in ICM patients with nonspecific IVCD and LBBB who underwent SPECT MPI in a retrospective analysis of a prospective CRT-D registry. Patients with IVCD have greater scar burden compared to patients with LBBB, and scar burden but not QRS morphology is independently associated with clinical outcomes, including improvement in LV function; risk of death, transplant, or VAD; and risk of appropriate device shocks.
Patients
Conclusion
Among CRT-D recipients with ICM, patients with IVCD have greater scar burden compared to those with LBBB. Scar burden, not QRS morphology, is independently associated with adverse clinical outcomes after CRT-D implant, including less LVEF improvement; higher risk of death, transplant, or VAD; and greater risk of appropriate device shocks.
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Conflict of interest: None.