title: An echocardiographic survey of a random sample of the population of North Glasgow aged 55 to 74 years
Creators: name: Robb, Stephen D.
Publisher: name: University of Glasgow
Year: 2000
Subjects: subject: Echocardiography.

description: The syndrome of chronic heart failure resulting from left ventricular dysfunction, either systolic or diastolic, is a public health problem for the Western world. The study presented in this thesis looked at 1009 individuals aged between 55 and 74 years of age randomly selected from the population of north Glasgow - response rate 59.8%. Within the study cohort there was a significant prevalence of both hypertension (44.1%) and ischaemic heart disease (43.9%). Left ventricular (L.V.) systolic function was measured by calculating an echocardiographic left ventricular ejection fraction (L.V.E.F.) in 75% of participants. The median L.V.E.F. was 50.7% and significant left ventricular systolic dysftinction (L.V.D.) was shown to be represented by an L.V.E.F. of &lt; 35%; being present in 6.7% of the cohort with a measured L.V.E.F. The prevalence of L.V.D. rose with age and was higher in men than in women (9.4% v 4.0% P=0.004). The proportion which was considered symptomatic was 45.0% with no age or gender effect. The principle aetiological associate of L.V.D. was ischaemic heart disease with it accompanying 78% of all cases. Isolated hypertension was no more prevalent in individuals with L.V.D. than in the whole population. The L.V.D. was undertreated with only 16% of cases currently receiving treatment with an angiotensin converting enzyme inhibitor. The presence of L.V.D., even when apparently asymptomatic, was associated with a reduced effort capacity on treadmill testing. Similarly it was associated with impaired quality of life scores in affected individuals, being true for both symptomatic and for treated L.V.D. (using loop diuretics), and there was possibly a small effect seen in asymptomatic L.V.D. Transmitral Doppler indices were used to examine L.V. diastolic filling in participants and showed diastolic filling to be affected by several biological variables including gender, age, body mass index, blood pressure and relative L.V. wall thickness. Disease states such as hypertension, ischaemic heart disease and L.V.D. were all shown to be associated with abnormal L.V. diastolic filling. Looking at a group of individuals who reported breathlessness in the absence of either airways disease or L.V.D. showed that they had a higher prevalence of ischaemic heart disease but without any evidence of abnormal diastolic filling. Removing the individuals with ischaemic heart disease from this group revealed some abnormalities of diastolic filling but also removed any objective impairment of effort capacity. Circulating plasma concentrations of the natriuretic peptides N-terminal atrial natriuretic (N-ANP) and brain natriuretic (BNP) peptides were shown to be elevated in the presence of L.V.D.. Individuals with increased measurements of L.V. mass also had higher levels of both peptides; as did individuals with evidence, by transmitral Doppler indices, of elevated L.V. operating pressures. Examining their potential as screening blood tests for the presence of L.V.D. in the population showed that BNP fared better than N-ANP with a sensitivity of 82.0% and a specificity of 57.6% at a concentration of 15.20 pg./ml. BNP also performed better in a high risk group with ischaemic heart disease (sensitivity - 97.4%, specificity - 20.5%, concentration - 8.30 pg./ml) and had an excellent negative predictive value of 98.2% in this group. It also had a high negative predictive value in a group of breathless individuals for the presence of L.V. systolic dysfunction (97.1%). Natriuretic peptides were shown to lack some discriminatory power with reduced specificities and positive predictive values owing to the presence of confounding factors in the population. Their future role may therefore be to exclude the presence of L.V.D. in individuals. BNP concentrations measured in unextracted plasma using the relatively simpler, and recently commercially available, Shionoria immunoradiometric assay kit also performed well as screening blood tests but not as well those obtained using a standard radioimmunoassay from extracted plasma.