BACKGROUND:
Chronic congestive heart failure (CHF), caused by left ventricular dysfunction (LVD), is a major cause of morbidity and mortality. CHF is the major form of cardiovascular disease that is increasing in prevalence, LVD progresses from an asymptomatic phase to a severe symptomatic phase. Recent clinical trials have proven that angiotensin converting enzyme inhibitor reduced mortality, morbidity, and disease progression in asymptomatic patients with objectively measured LVD. However, available estimates of LVD prevalence are based on symptomatic patients, not on objectively measured ventricular function parameters. The distributions of ventricular function parameters in the United States population are unknown. Since the prevalence of objectively measured asymptomatic LVD is unknown, the total number of patients with LVD who could benefit from medical therapy is also not known. Furthermore, screening techniques to identify persons with treatable asymptomatic LVD have not been evaluated in a population-based setting. The plasma concentration of n-atrial natriuretic peptide (n-ANP) is a marker for the presence of asymptomatic LVD that may be a valuable screening tool for asymptomatic LVD.
DESIGN NARRATIVE:
This is a population-based study of the distribution of ventricular function parameters in 2,050 adult residents of Olmsted County, MN and, in collaboration with the Strong Heart study, in 1,522 adult Northern Plains American Indians. This group of Northern Plains Indians is at increased risk for LVD, having a higher prevalence of cardiovascular disease than the general United States population. Subjects undergo echocardiography to measure ventricular function parameters, as well as a clinical assessment of symptoms, signs and risk factors for LVD. Plasma concentration of n-ANP are measured in these populations to determine the accuracy of n-ANP as a noninvasive marker for asymptomatic LVD. These studies provide: comparative population-based estimates of ventricular function parameters and LVD in Olmsted County and Northern Plains Indians; estimates of the magnitude of the population of patients that could benefit from current therapy; current data on risk factors for prevalent CAD in these populations; a foundation upon which future studies of incidence and clinical course of asymptomatic LVD could be based. They also assess the accuracy of plasma n-ANP in identification of asymptomatic LVD.
The study was renewed in May 2001 and will end in March 2005. Studies continue on testing the hypotheses: that abnormalities of left ventricular systolic/diastolic function and left ventricular structure worsen over time; that increasing plasma brain natriuretic peptide is associated with progressive change of left ventricular structure and function; and that abnormal left ventricular structure/function and brain natriuretic peptide are associated with incident clinical events.
