Epidemiology of ventricular dysfunction and heart failure in high risk populations

ABSTRACT Heart failure and ventricular dysfunction are common with high morbidity and mortality and significant health care costs. Our understanding of these conditions has increased in the last decade enormously, and we now have the ability to retard or prevent heart failure in some individuals, and those with heart failure are surviving longer. Despite these major gains in understanding, we nonetheless remain unable to effectively and cost-effectively identify individuals with asymptomatic cardiac changes prior to the development of symptoms when prognosis and survival is already adversely affected and treatment gains likely greatest. Over recent years there has been an epidemiological transition of underlying risk factors, with declines in coronary artery disease, but exponential rises in diabetes and obesity. How these changes will impact on future heart failure burden and whether they underlie the lack of decline in heart failure incidence, despite improvements in treatment and prevention, is unclear. Moreover, data are lacking for populations at highest risk of heart failure, in particular Indigenous Peoples and the elderly with risk factors, but they suggest poorer outcomes. This thesis focuses on two populations at high risk for heart failure, one an elderly population and the other a relatively young Indigenous population. The Heart of the Heart study is an Indigenous cohort (mean age 44 years; n=436) recruited across remote Central Australia. Participants underwent comprehensive cardiovascular assessment for heart failure, asymptomatic ventricular dysfunction and heart failure risk factors, including cardiac ultrasound and B-type natriuretic peptide estimation. This cohort had a very high risk factor burden: 5% were adjudicated to have heart failure, 60% of which was not previously diagnosed. Heart failure and ventricular dysfunction were associated with “traditional” risk factors, such as diabetes, hypertension and obesity. Although rheumatic heart disease was present and associated with heart failure, the numbers of individuals affected were small. SCREEN HF is a cohort of community participants over 60 years with at least one heart failure risk factor but without pre-existing left ventricular dysfunction or heart failure diagnosis. We enrolled 3550 participants and after baseline assessment stratified them into those at highest risk for heart failure by NT-proB natriuretic peptide (NT-proBNP) level. Those in the highest risk group (top quintile of NT-proBNP) underwent further assessment including cardiac ultrasound. In this highest risk group we found a large burden of systolic and diastolic dysfunction. Systolic dysfunction was associated with male gender, coronary artery disease and NT-proBNP level. In this cohort, where everyone had at least one risk factor, age, diabetes and NT-proBNP were associated with poorer diastolic function, but there was no significant relationship between other heart failure risk factors and diastolic function. A high burden of ventricular dysfunction was observed in these high risk populations, reaffirming the need to focus efforts on developing screening strategies for the prevention and early detection of heart failure. This challenge will be the next major frontier in heart failure management.