Elsevier

Heart Rhythm

Volume 15, Issue 11, November 2018, Pages 1664-1672
Heart Rhythm

Clinical
Devices
Scar burden, not intraventricular conduction delay pattern, is associated with outcomes in ischemic cardiomyopathy patients receiving cardiac resynchronization therapy

https://doi.org/10.1016/j.hrthm.2018.05.027Get rights and content

Background

Patients with nonspecific intraventricular conduction delay (IVCD) benefit less from cardiac resynchronization therapy (CRT) than patients with left bundle branch block (LBBB).

Objective

The purpose of this study was to determine whether post-CRT outcome differences in patients with ischemic cardiomyopathy (ICM) relate to intrinsic QRS pattern and/or scar burden.

Methods

We analyzed 393 consecutive ICM patients with left ventricular ejection fraction (LVEF) ≤35%, QRS duration >120 ms, and LBBB or nonspecific IVCD who underwent single-photon emission computed tomography myocardial perfusion imaging and CRT-defibrillator implant. We compared scar burden; QRS duration; LVEF change; risk of death, transplant, or ventricular assist device; and risk of appropriate device shocks between LBBB and IVCD patients, using multivariable analyses to determine relative associations between QRS pattern vs scar burden and outcomes.

Results

Nonspecific IVCD is associated with greater scar burden and narrower baseline QRS duration than LBBB. IVCD patients demonstrated less QRS narrowing with CRT than LBBB patients, even when excluding IVCD patients with QRS duration <150 ms. LVEF improved less in patients with IVCD vs LBBB, but only scar burden not QRS morphology or duration was associated with LVEF increase ≥5%. During 39-month follow-up, IVCD was associated with shorter survival free from transplant/ventricular assist device and shorter time to first appropriate device shock. Scar burden but not QRS morphology was independently associated with these outcomes on multivariate analysis.

Conclusion

IVCD is associated with greater scar burden than LBBB in ICM CRT-defibrillator recipients. Scar burden, not QRS pattern, is independently associated with adverse clinical outcomes.

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.

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