Author Identifier

Zhisheng Chen

http://orcid.org/0000-0002-8418-7962

Date of Award

2025

Document Type

Thesis - ECU Access Only

Publisher

Edith Cowan University

Degree Name

Doctor of Philosophy

School

School of Medical and Health Sciences

First Supervisor

Lois Balmer

Second Supervisor

Manshu Song

Third Supervisor

Wei Wang

Fourth Supervisor

Xuerui Tan

Abstract

Heart failure (HF) is the advanced stage of heart disease, posing a significant global health burden, with high mortality and poor prognosis, particularly in patients with prolonged QRS duration. Cardiac resynchronization therapy (CRT) is recommended to improve cardiac function and prognosis in these patients. However, approximately 30% of patients fail to respond to CRT, highlighting the need for more precise criteria to select appropriate candidates for the therapy.

This thesis aims to: 1) summarize the critical information of CRT through a comprehensive literature review; 2) investigate the horizontal QRS axis as a predictor of CRT response in HF patients with left bundle branch block (LBBB); and 3) identify additional factors associated with CRT response in HF patients with prolonged QRS duration, developing and validating a prediction model that incorporates the horizontal QRS axis.

The thesis commences with a comprehensive literature review that evaluates the evidence, clinical practice guidelines, and predictors of CRT response, providing an overview of strategies for optimizing CRT candidate selection in HF patients with prolonged QRS duration. It then examines the horizontal QRS axis as a novel predictor of CRT response in HF patients with LBBB. The findings reveal that CRT responders exhibit a distinct horizontal QRS axis, characterized by greater backward deviation and larger magnitude. Both the direction and magnitude of the horizontal QRS axis, whether considered separately or in combination, reliably predict CRT response and long-term prognosis.

To extend its applicability to the broader population with prolonged QRS duration, this thesis further develops and validates a prediction model that integrates the horizontal QRS axis with established clinical predictors, including left ventricular end-diastolic dimension (LVEDD), LBBB, New York Heart Association (NYHA) functional class, hypertension, the direction and magnitude of horizontal QRS axis. The internally validated model demonstrates robust predictive performance and significant clinical utility, providing an effective tool for optimizing CRT candidate selection.

In conclusion, this thesis establishes the horizontal QRS axis as a promising predictor for refining CRT candidate selection. Integrating the horizontal QRS axis into clinical CRT practice could improve decision-making and potentially enhance the prognosis of HF patients with prolonged QRS duration.

DOI

10.25958/xcp6-ng51

Access Note

Access to this thesis is embargoed until 14th May 2028

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