Paediatrics (RCH) - Theses
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ItemAtrioventricular valve function during single ventricle palliation( 2021)Single ventricle anomalies encompass a spectrum of the most severe congenital heart disease. Staged surgical palliation culminates in the Fontan circulation, wherein the functional single ventricle pumps blood to the systemic circulation and returning blood flows passively through the pulmonary circulation, without the support of a subpulmonic ventricle. Surgical modifications and advancements in non-operative management have led to a significant decline in early mortality following the Fontan operation. As such, the population of patients living with a Fontan circulation is expected to double over the next 20 years, including a growing proportion of patients surviving well into adulthood. Due to inherent anatomical and physiological limitations, the Fontan circulation is characterised by elevated systemic venous pressure and reduced cardiac output. Atrioventricular valve (AVV) regurgitation impairs pulmonary venous return leading to increased post-capillary venous pressures and further increasing systemic venous pressure. Furthermore, AVV regurgitation increases the volume load on the single ventricle which can lead to ventricular dilatation and impaired function. Studies have demonstrated that AVV regurgitation and AVV surgery are associated with worse clinical outcomes during the initial stages of single ventricle palliation, but little is known about the cumulative impact of AVV regurgitation and AVV surgery over the lifetime of patients undergoing single ventricle palliation. The aim of this thesis was to (i) determine the cumulative incidence of, and risk factors for, moderate or greater AVV regurgitation during the lifetime of patients undergoing Fontan palliation, (ii) determine the impact of moderate or greater AVV regurgitation on clinical outcomes in patients with a Fontan circulation, and (iii) determine the impact of AVV surgery on long-term AVV competency and clinical outcomes in patients undergoing single ventricle palliation. The studies contained within this thesis were conducted with data primarily from the Australia and New Zealand Fontan Registry, which is the largest database of Fontan survivors in the world. In this thesis I have demonstrated that: (i) there is a high rate of moderate or greater AVV regurgitation during the lifetime of patients with a Fontan circulation, (ii) risk factors for moderate or greater AVV regurgitation and AVV surgery include right ventricular (RV) dominance, atrioventricular septal defect (AVSD), mitral atresia, right atrial isomerism, aortic atresia, and prior AVV repair, (iii) moderate or greater AVV regurgitation in patients with a Fontan circulation is associated with an over two-fold increased risk of death or transplantation, but only in patients with RV dominance, (iv) in patients with AVSD and a Fontan circulation, the high rate of moderate or greater AVV regurgitation is primarily due to the anatomy of the common AVV, and is not impacted by ventricular dominance, (v) AVV surgery itself is not a risk factor for death or transplantation in patients with a Fontan circulation, but rather it is the patient’s characteristics necessitating AVV surgery that are associated with an increased risk of death or transplantation, (vi) patients with tricuspid valve repair failure are at high risk of death or transplantation, but successful tricuspid valve repair improves transplantation-free survival rates in patients with moderate or greater AVV regurgitation, (vii) patients with functional AVV regurgitation and impaired ventricular systolic function are at increased risk of death or transplantation after AVV repair, (viii) AVV closure is a safe and effective surgical technique for management of AVV regurgitation in patients with a Fontan circulation and two AVVs, where the diminutive valve is regurgitant. This thesis has revealed the enormous burden of AVV regurgitation and AVV surgery in patients with a Fontan circulation. In doing so, it has drawn attention to AVV regurgitation as one of the most important issues in the management of patients undergoing single ventricle palliation. Ultimately, by improving our understanding of the incidence and natural history of AVV regurgitation, this thesis will improve the long-term outcomes of many patients living with a single ventricle circulation.
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ItemCardiovascular associations of HIV infection in children( 2015)Vertically-acquired HIV infection is a devastating disease in childhood that may affect any organ, including the cardiovascular system. With increased survival of HIV infected children due to antiretroviral (ART) treatment availability, chronic cardiovascular problems become a confronting challenge, not only because HIV infection may cause cardiac problems readily manifesting in childhood but also because it potentially increases future cardiovascular disease risk in adulthood. This thesis explores various possible cardiovascular effects of HIV infection in children, particularly the differential effects of ART-naïve compared to ART-exposed HIV infection on left ventricular (LV) remodelling, pulmonary hypertension, and arterial elasticity. We conducted a cross-sectional study enrolling 56 ART-naïve, 59 ART-exposed HIV infected, and 51 healthy children in Jakarta, Indonesia and performed cardiac/vascular ultrasound, and blood tests for biomarkers. There were marked differences in the cardiovascular parameters between the two groups. We found that ART-naïve HIV infection was associated with LV dilation while the ART-exposed seemed to cause concentric hypertrophic remodelling. ART-exposed HIV infected children who showed evidence of higher pulmonary artery pressure than healthy children, whereas the ART-naïve children had reduced right ventricular function. For arterial elasticity, the ART-naïve had higher strain and lower elastic modulus, but thicker intima-media thickness, whereas the ART-exposed had similar vascular properties as healthy children. In conclusion, HIV infection in children have significant impacts on childhood cardiovascular system with particular differential effects between ART-naïve and ART exposed HIV infection. Routine cardiovascular surveillance is needed for children with HIV infection.