The evaluation of the uraemic heart using cardiovascular magnetic resonance imaging

Johnston, Nicola (2007) The evaluation of the uraemic heart using cardiovascular magnetic resonance imaging. MD thesis, University of Glasgow.

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Abstract

Cardiovascular disease (CVD) accounts for over 50% of morbidity and mortality in patients with end stage renal failure (ESRF), including those suitable for renal transplantation. Furthermore, CVD is the most common cause for loss of a functioning renal allograft. The strongest predictors of cardiovascular (CV) outcome in this population have been identified as left ventricular (LV) abnormalities, namely left ventricular hypertrophy (LVH), left ventricular dilation (LVDil) and left ventricular systolic dysfunction (LVSD). However, inaccuracies inherent to the measurement of LV mass and volumes using echocardiography have meant that, unlike other populations such as those with essential hypertension, there is no reliable, consistent evidence that regression of LV abnormalities is possible or whether regression of LV abnormalities improves long term outcome. Cardiovascular magnetic resonance (CMR) imaging is now established as the standard of reference for the measurement of LV mass, volumes and function, and unlike echocardiography is 'loading independent'. The aim of this thesis is to evaluate the uraemic heart using CMR, identify the determinants of LV abnormalities and define the relationship between coronary artery disease (CAD) and LV abnormalities in a population of patients with ESRF felt suitable for renal transplantation. Methods A total of 154 patients with ESRF who were either already awaiting renal transplantation or undergoing assessment for transplantation were recruited for the study. Patients underwent the standard CV risk assessment used by the West of Scotland transplant assessment clinic and in addition underwent CMR imaging and measurement of serum brain natriuretic peptide (BNP). A proportion of patients (60) also underwent an additional CMR protocol using a gadolinium based contrast agent and 84 patients returned after a mean period of 8 months for a follow-up CMR scan to study the natural history of LV abnormalities whilst patients await renal transplantation. Results In contrast to previous echocardiographic studies, rather than three types of uraemic cardiomyopathy, namely concentric LVH, eccentric LVH and LVSD, the results of this study suggest only two major types of uraemic cardiomyopathy exist; concentric LVH and ischaemic cardiomyopathy (ICM). The predominant type of cardiomyopathy was concentric LVH, which was associated with hypertension and diabetes and 50% of the total cohort were found to have this type of cardiomyopathy. Thereafter, LVDil was found to be associated with LVSD in the majority of cases and patients with LVDil and/or LVSD were much more likely to have associated CAD than patients with either normal ventricles or concentric LVH. Only a very small proportion of the total cohort was found to have eccentric LVH (6%) when a loading independent method of measurement was used for the assessment of LV abnormalities. With follow-up, 45% patients who were found to have an initially normal LV developed concentric LVH, whilst patients with an initially abnormal LV showed little further progression during the study period. Patients with LVSD or LVDil had a poorer outcome than those with concentric LVH or normal ventricles after 4 years of follow-up and patients who displayed contrast enhancement after administration of a gadolinium based contrast agent, indicative of myocardial necrosis/fibrosis also had a significantly poorer outcome compared to those with no evidence of contrast enhancement. Age, a prior history of ischaemic heart disease (IHD) or diabetes and an elevated BNP level were all found to be independent predictors of all cause mortality in this population after 4 years of follow-up. Conclusions LV abnormalities are common in patients with ESRF awaiting renal transplantation. The two major types of cardiomyopathy in this population, identified using CMR, are concentric hypertrophic cardiomyopathy and ICM. Concentric hypertrophic cardiomyopathy, which is the most prevalent type of cardiomyopathy, is determined by hypertension, diabetes and volume overload and future studies targeting regression of LVH in this population should concentrate on treatment in these areas. LVSD and LVDil are under recognised in this population and both abnormalities are closely associated with CAD. A finding of either LVSD or LVDil should precipitate careful investigation for underlying CAD and strategies for the early non-invasive detection of CAD, before the development of ICM, in this population are required. The mortality rate of patients awaiting renal transplantation remains high and is dependent on age, diabetes and IHD. In addition to established methods of CV risk stratification prior to renal transplantation, BNP level may prove to be a useful non- invasive marker of CV risk assessment in this population and further studies are warranted in parallel with those targeting LV abnormalities and CAD.

Item Type: Thesis (MD)
Qualification Level: Doctoral
Additional Information: Adviser: Alan Jardine
Keywords: Medicine, Medical imaging
Date of Award: 2007
Depositing User: Enlighten Team
Unique ID: glathesis:2007-74023
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 23 Sep 2019 15:33
Last Modified: 23 Sep 2019 15:33
URI: http://theses.gla.ac.uk/id/eprint/74023

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