Heart failure (HF) is a clinical syndrome in which neurohormonal activation and cardiac remodelling occur in response to an index pathological event. Functional measures and biological markers of blood vessel function have been shown to be altered in HF, and abnormalities of microvascular function have been demonstrated in a variety of vascular beds. Treatment of HF involves medications which target abnormalities in the neurohormonal systems that regulate cardiovascular function, however the role of HMG Co-A reductase inhibitors (statins) in HF is unclear. Some observational and mechanistic studies have suggested benefit, however, results of prospective intervention trails have been disappointing. This thesis reports the vascular and biological abnormalities detectable in HF patients with systolic dysfunction compared to controls, and the vasular and biological effect of treatment with simvastatin in HF patients with systolic dysfunction. Treatment with simvastatin resulted in a significant reduction in Co Q IO levels in HF patients but not in coQ10ILDL ratio. There was a non-significant trend toward reduction in NT-proBNP levels. Other biomarkers studied were unchanged by treatment At baseline, differences between HF patients and controls were apparent in brachial artery flow mediated dilatation and doppler waveforms obtained from the retrobulbar circulation. No such differences were apparent in brachial artery waveforms. Treatment with simvastatin did not result in any change in doppler waveforms obtained from the retrobulbar circulation or brachial artery. Abnormalities in vascular function in HF are widespread and can be detected by novel wavelet analysis of doppler waveforms obtained from the retrobulbar circulation. 4 weeks of treatment with simvastatin did not produce improvements in measures of vascular function suggesting a lack of additional benefit over and above baseline treatment in this population at least over a short treatment period. Further research is required to see if longer periods of treatment may be effective .

Administration of bicalutamide to LNCaP tumours induces a rapid and sustained hypoxia in the prostate. This treatment-induced hypoxia (> 14 days) promotes an increased synthesis of the CXC-chemokine Interleukin-8(CXCL8) co-incident with increasing oxygen tension and the restoration of tumour vascularisation. Consequently, the hypothesis under investigation was that hypoxia-induced CXCL8 signalling underpins resistance to bicalutamide-treated tumours and facilitates the adoption of more aggressive cancer cells. Culturing of22Rvl and cells under hypoxic conditions (mimicking the microenvironment effects resulting from bicalutamide treatment) increased the transcriptional activity of the AR, HIF-Ia and NF-KB, inducing expression of downstream target genes, associated with survival, metabolic adaptation and angiogenesis. The magnitude and duration of these increases was greater in LNCaP cells. Administration of bicalutamide or siRNA-mediated down-regulation of the AR failed to reduce expression of pro-angiogenic, pro-survival and metabolism-associated genes. However, concurrent knockdown of both HIF-Ia and NF-KB activity using gene-targeted siRNAs resulted in an effective repression of these hypoxia-induced disease-progressing genes. Expression of CXCL8 and its receptors, CXCRl and CXCR2, was also up-regulated in particularly in hypoxic LNCaP cells. CXCL8 signalling was shown to underpin hypoxiainduced AR, HIF -1 and NF-KB transcription in hypoxic LNCaP cell s, up-regulating genes associated with survival and metabolic adaptation. We have previously shown that HIF-l and NF-KB activity underpin the transcription of the CXCRI and CXCR2 receptors, suggesting that either suppression of the TFs or targeting of the CXCR1I2 receptors may provide strategies to enhance anti-tumour responses in hypoxic prostate cancer cells. The proteasome inhibitor Bortezomib was shown to attenuate hypoxia-induced AR- and HIF-l- activation but failed to reduce NF -KB activity. Instead, a direct targeting of CXCL8 signalling increased the sensitivity of LNCaP cells to bilcalutamide, and repressed hypoxia-induced transcription and expression of disease-promoting genes. Targeting CXCL8 signalling may therefore be a relevant strategy to enhance tumour response to anti-androgen strategies .

Sustained injury of the myocardium can lead ultimately to heart failure. The restricted ability of the heart to repair after injury is due to inherent limited regenerative capacity of the bi-nucleated adult cardiomyocyte. A long sought goal has therefore been to identify approaches that facilitate cardiomyocyte proliferation and regeneration. CDKN1A interacting zinc finger protein 1 (CIZ1) is an alternatively spliced gene that has been shown to play a role in mammalian DNA replication in vitro. Full length CIZ1 protein localises to dynamic sub-nuclear foci, with co-localisation experiments suggesting significant association with DNA replication factories and active DNA synthesis. CIZ1 interacts directly with key regulators of the cell cycle, including Cdk2, cyclin E, cyclin A, and Cdk2 inhibitor p21. CIZ1 (and many of its splice variants) have been linked to a number of proliferative disorders, ranging from rheumatoid arthritis to cancer. In addition to actively proliferating cells, CIZ1 foci can be detected in terminally differentiated cells including adult cardiomyocytes. However, expression of new Ciz1 product at the mRNA level is very low in these cells, compared to non-myocyte cells of the heart. It is currently unclear whether the remaining protein retains function or is a remnant of the final round of cardiomyocyte DNA replication leading to the quiescent bi-nucleated state. This study aimed to investigate whether CIZ1 is a suitable candidate molecule for stimulating cardiomyocyte regeneration to aid restoration of normal heart function through re-establishment of cardiomyocyte self- renewal capacity. A conditional transgenic mouse model, in which CIZ1 is over- expressed specifically in cardiomyocytes has been generated. Transgenic hearts are enlarged due to cardiomyocyte hyperplasia, although Millar catheter assessment showed no evidence of cardiac dysfunction. Individual cardiomyocytes isolated from transgenic hearts exhibit altered nuclear dynamics, with a significant increase in the number of mono-nucleated cells relative to bi-nucleated. Furthermore, preliminary data using in vivo EdU DNA replication assays showed evidence of cell cycle reactivation in the transgenic hearts. Up-regulation of genes involved in G1 and G1/S phase transition has also been indicated. The results suggest that CIZ1 may be a suitable novel candidate for therapeutic application in cardiac regeneration following injury.

The role of the plasma membrane calcium ATPase (PMCA), a calcium extruding enzyme, in cardiac physiology is not yet entirely clear. Two isoforms of PMCA, PMCAl and 4, are expressed in the myocardium. In the heart PMCA had originally been thought to play a rather minor role in cardiac relaxation. However, our group has suggested a new function for PMCA4b as a modulator of signal transduction pathways through its interaction with neuronal nitric oxide synthase (nNOS) in a cellular model; however, the role of the PMCA4-nN0S complex in the heart is still unclear. In addition, the differential role of the isoforms 1 and 4 remained enigmatic. The aim of the current study was to investigate the molecular mechanisms by which PMCA isoforms (1 and 4) modulate cardiac contractility.

CHF is a complex disease that results in the remodelling of the heart at every level, from the gross anatomy down to the levels of the ion channel resulting in aberrant signalling and contractile dysfunction. The QT interval of the cardiac ECG is frequently increased in heart failure, suggesting ion channel remodelling which has proarrhythmic consequences. One of the aims of this study was to determine the changes that occur from the in vivo level, down to the level of the ion channel that may contribute to arrhythmogenesis.

This thesis studies techniques for maximising the effects of Cardiac Resynchronisation Therapy (CRT) which is a modern therapy for chronic heart failure. The ability of echocardiographic parameters of mechanical dyssynchrony to identify suitable candidate patients for CRT, and subsequently to optimise the interventricular delay, is disputed. In this study, I initially perform a systematic review to clarify the nature and extent of this problem. I then perform detailed mathematical simulations to understand what is feasible in an ideal setting. I then evaluate the realistic potential of several non-invasive approaches of optimising CRT devices by formal evaluation head-to-head. A fundamental requirement for any marker in optimisation of CRT devices, or in selection of patients for implantation, is that the marker must be reproducible and must change when the amount of dyssynchrony changes. I perform detailed experiments in patients where I interrogated a panel of echocardiographic parameters to answer the questions relating to the sensitivity of each parameter and looked at methods to improve this. I look at the effect of spontaneous variability, and the impact on each echocardiographic method including 3D echocardiography, tissue Doppler imaging and pulsed Doppler techniques including velocity time integrals and pre-ejection times. Finally, I perform an invasive study of the beat to beat physiological changes which occur after intra cardiac timings are altered, to evaluate alternative approaches to changes in cardiac performance that might be easier to automate.

Stress (Takotsubo) cardiomyopathy is a severe form of acute heart failure (HF) with rapid onset, characterized by hypocontraction of the heart from the mid-left ventricle to apex. It is precipitated by extreme stress and plasma levels of the catecholamines adrenaline and noradrenaline are significantly elevated. This thesis describes the development of a new model of Takotsubo cardiomyopathy through rapid intravenous injection of a supraphysiological dose of adrenaline into anaesthetised male Sprague- Dawley (SD) rats and real-time imaging of the heart using either 2D-echocardiography or cardiac magnetic resonance (CMR). This in vivo rat model was used, in conjunction with in vitro IonOptix video-edge detection of cardiomyocyte contractility, to firstly demonstrate that this syndrome results from an adrenaline-induced trafficking-switch of the coupling of the pleiotropic β2-adrenceptor (AR) from Gs-adenylyl cyclase (AC)-cyclic adenosine monophosphate (cAMP) cardiostimulant to Gi-activated cardiodepressant pathways. Cardiomyocyte β2AR:β1AR population ratios, determined by radioligand binding, suggested that an apical-basal gradient in β2AR expression accounted for the in vivo apical hypokinesis. Certain β-blockers can act as biased agonists of a Gi-coupled isoform of the β2AR in animal and human cardiomyocytes via a pathway that involves p38 MAPK. Administration of the clinical β-blockers propranolol and carvedilol 15 minutes after adrenaline either enhanced or failed to reverse apical hypocontractility. In vitro analysis demonstrated that β2AR-Gi signalling involves p38 MAPK activation. However, pre-treatment with either the p38 MAPK inhibitor SB203580 or the β2AR blocker ICI-118,551 prior to adrenaline resulted in significant mortality, which suggested that the β2AR-Gs/Gi coupling switch is a cardioprotective strategy. Gi-protein is upregulated in chronic HF, while β1ARs are down-regulated. In contractility studies of chronically failing human/rat cardiomyocytes, β2AR-Gs responses were present with minimal active Gi-protein component. This suggested that while in acute HF β2AR-Gs positively inotropic responses are impaired and β1ARs are preserved, the opposite may be true in chronic HF.

No description available.

Characterisation of ventricular activation through conventional mapping techniques has always been limited by the need for sequential mapping which is unsuitable for non-sustained or poorly tolerated rhythms. Non-contact mapping, with its ability to generate simultaneous, high resolution. isopotential maps from an entire cardiac chamber, enables characterisation of cardiac activation in the intact human heart to a detail not previously attainable. Characterisation of properties of the excitable gap of ventricular tachycardia (VT) circuits was performed by analysing the response to single programmed extrastimuli in an attempt to reset the circuit. The temporal and spatial properties of the EGap vary at different sites of entry to the circuit. The effects of single ventricular extrastimuli (SVE) preexciting such circuits are dependent on the degree of interval dependent conduction slowing (conduction in partially excitable myocardium) within the diastolic pathway or modification of functional block defining the circuit. All circuits could be preexcited over a range of SVE's, therefore failure to reset a tachycardia does not indicate the absence of an excitable gap and failure of entry to the circuit. Mapping and ablation of VT circuits was performed in 40 patients all with previous myocardial infarction. Non-contact mapping identified an exit site in 100% and diastolic pathway activity in 56% of VT and guided successful ablation in 88% of patients. VT recurrence necessitating ICD therapy was significantly reduced but new VT is seen probably reflecting the evolving underlying substrate. Using non-contact mapping, VT, exit site location was identified in 121 VT and compared with 12 lead ECG morphology during VT. A correlation, a positive predictive value of ~70%, was seen with 8 different ECG patterns, accounting for 57% of mapped VT. An algorithm was developed and tested prospectively which led to correct identification of 93% of VT exit sites. Non-contact mapping was used to characterise the timing and patterns of activation in 41 patients with remote myocardial infarction and impaired left ventricular function. Eighteen patients had normal QRS duration and 23 had left bundle branch block (LBBB). In patients with LBSB, the principal cause of QRS prolongation is not due to increased interventricular conduction but to increased intraventricular LV conduction time. Lack of benefit from cardiac resynchronization seen in a subset of patients may be due to this intraventricular conduction delay. Although ECG characteristics of LSBS do not correlate with sites of earliest or latest endocardial ventricular activation, they do identify a subset of patients with the longest intraventricular conduction delay.

Heart failure is a very common medical condition with significant mortality and morbidity. Patients hospitalised with heart failure are at high risk of death in the short term and patients with chronic heart failure in the community are also at a high risk of death in the medium to long term. It is difficult to accurately identify those at a higher risk of death as current methods of risk stratification lack both sensitivity and specificity. The available treatments for prevention of sudden death in patients with heart failure such as Implantable Cardioverter Defibrillators (ICD) are expensive and do not abolish the risk of sudden death completely. Hence it is necessary to improve risk stratification methods in patients with heart failure and identify factors predicting mortality in those patients with ICD protection. This thesis first describes a series of studies examining the clinical factors that predict increased risk of short-term mortality in patients with a recent hospitalisation for heart failure. These include examination of patient demographics, clinical history and examination, blood tests, electro-cardiographic and echo-cardiographic variables and medication. Based on these variables, I have formulated a simple scoring system to predict short term mortality in hospitalised patients with heart failure. This score was validated in a prospective study of contemporary heart failure population with a recent hospital admission. The relationship of cholesterol and risk of death in heart failure was examined in detail. Then, the utility of Holter monitoring and signal averaged electro cardiograms (SAECG) for risk stratification were examined based on the prognostic value of abnormalities found by these tests in patients with chronic heart failure. Finally patients with heart failure deemed at high risk of sudden death and had ICDs implanted were studied and factors predicting shocks and mortality were identified. Two separate studies were done, first in population who had ICDs mainly for secondary prevention and the second in patient population who had ICDs exclusively for primary prevention. From these studies, I have identified those clinical characteristics that are associated with high risk of death in patients with acute and chronic heart failure and those associated with death in patients with heart failure after ICD implantation.