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Improving complex cardiac implantable electronic device therapy outcomes

Student thesis: Doctoral ThesisDoctor of Philosophy

Cardiac resynchronisation therapy (CRT) devices and implantable cardioverter defibrillators (ICDs) are frequently implanted in patients with heart failure and those at risk of ventricular arrhythmia (VA). Approximately 30-50% of patients undergoing CRT implantation fail to derive any improvement, depending on heart failure aetiology and the metric used to evaluate response. Furthermore, appropriate ICD therapy only occurs in one third of patients implanted with an ICD indicating better risk stratification of VA is needed. This thesis therefore aims to explore novel ways to improve complex cardiac implantable electronic device therapy outcomes.

Initially, this thesis explores the feasibility and potential benefit of using real-time cardiac CT image overlay guidance and multisite left ventricular (LV) pacing as two distinct approaches to improve CRT response rates through optimal LV lead delivery. Real-time CT image overlay appears safe and feasible with significant improvements in echocardiographic volumetric response outcomes at 6-months follow-up compared to baseline. However, whilst multisite LV pacing appears feasible and safe, no evidence was found to support its use in improving CRT response in patients with left bundle branch block and intermediate QRS prolongation of 120-150 ms.

Finally, this thesis investigates the role of scar heterogeneity, quantified by mean entropy using cardiac magnetic resonance texture analysis (CMR-TA), as a potential metric for ICD risk stratification. For the first time, mean entropy, calculated using CMRTA, was identified as an independent predictor of appropriate ICD therapy in patients with mixed cardiomyopathy and ischaemic cardiomyopathy-only, suggesting a potential role in predicting VAs and risk stratifying patients for ICD implantation. Furthermore, lower scar heterogeneity, quantified by mean entropy using cardiac MRI texture analysis, was found to be associated with successful ATP whereas higher scar heterogeneity was associated with more aggressive VAs unresponsive to ATP requiring shock therapy.
Original languageEnglish
Awarding Institution
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Award date1 Mar 2020

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