Knight, DS; (2016) Novel imaging techniques for assessing disease affecting the right heart. Doctoral thesis , UCL (University College London).

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Abstract

Right ventricular (RV) size and function are prognostic in congenital and acquired heart disease. Two-dimensional echocardiography (2DE) is the most readily available modality for RV assessment, but is limited by its complex shape. Furthermore, biventricular function is intimately related through a shared septum and pericardium. The simplest metric of left ventricular (LV) function is ejection fraction (LVEF). However, LVEF is often maintained in pulmonary hypertension (PH), for example. Therefore better indicators of LV function are required to identify patients at risk of deterioration. In this thesis, novel imaging techniques for assessing cardiac function in right heart disease are investigated. The first experiment tested the hypothesis that single-beat threedimensional echocardiography (3DE) accurately and reproducibly quantifies RV volumes. 3DE traditionally acquires sub-volumes over consecutive heartbeats, whereas novel 3DE transducers can acquire datasets in a single cardiac cycle. Single-beat 3DE was compared against CMRI in 100 subjects including patients with PH and carcinoid heart disease. Single-beat 3DE was feasible and accurate for RV volumetric quantification, but with limitations of test-retest reproducibility. The second experiment tested the hypothesis that 2D knowledge-based reconstruction (2DKBR) accurately and reproducibly quantifies RV volumes. 2DKBR involves 2DE-acquired RV coordinates localized in 3D space and connected by reference to a disease-specific RV catalogue. This was validated against CMRI in 28 PH patients, and test-retest reproducibility was assessed. 2DKBR was feasible and accurate for RV volumetric quantification in PH, and more reproducible than conventional 2DE. The final experiment tested the hypothesis that multi-directional myocardial velocities could be assessed in PH by CMRI. A tissue phase mapping sequence was utilized in 40 PH patients and 20 healthy volunteers. Over a median follow-up period of 20 months, LV early diastolic wave velocities were the only independent predictors of functional capacity and clinical worsening in a model that includes conventional metrics of biventricular function.

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