Hughes, Rebecca Kathryn; (2023) The Deep Phenotype of Apical Hypertrophic Cardiomyopathy. Doctoral thesis (Ph.D), UCL (University College London).

Text Rebecca Hughes PhD thesis_final.pdf - Accepted Version Access restricted to UCL open access staff until 1 January 2025. Download (5MB)

Abstract

Apical hypertrophic cardiomyopathy (ApHCM) accounts for 10-25% of HCM cases and displays clear imaging and clinical differences, yet the diagnosis and management are undifferentiated. Furthermore, typical imaging and electrocardiographic features of the disease are often appreciated in those with less than the 15mm apical hypertrophy required for diagnosis. Cardiac magnetic resonance imaging (CMR) using quantitative perfusion mapping enables visual assessment of perfusion defects and quantification of myocardial blood flow (MBF) at stress and rest. This technique is useful in exploring both epicardial as well as microvascular blood flow, which has been shown to be reduced in other forms of HCM, both in areas of hypertrophy and remote to this. Advanced echocardiography enables the assessment of circumferential and longitudinal strain, which can be altered in HCM despite preserved ejection fraction. This can also be assessed during exercise, which, coupled with cardiopulmonary exercise testing (CPEX), enables a thorough assessment of exercise capacity/limitation and myocardial response to exercise. Lastly, typical electrocardiogram (ECG) features of ApHCM (precordial tall R waves and deep T-wave inversion) are well known, but the ECG cannot be relied upon alone for diagnosis, and often acts as a gatekeeper for cardiac imaging. Advanced-ECG (A-ECG) enables the assessment of conventional ECG parameters, derived vectorcardiographic and polarcardiographic measures, and of waveform complexity. The aim of this work is to explore ApHCM across the phenotypic spectrum, including those with less than 15mm apical hypertrophy (relative ApHCM), using advanced imaging and electrocardiographic analysis, to seek new imaging biomarkers and better improve the diagnostic accuracy. This thesis includes chapters exploring perfusion mapping CMR in ApHCM, and additionally in pre-clinical genotype positive HCM; using CMR-derived assessment of wall thickness to improve the diagnostic accuracy of ApHCM; combining exercise echocardiography and CMR to explore exercise limitation (CPEX) in ApHCM; and using A-ECG analysis to accurately diagnose ApHCM.

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