Circulatory system

Abstract: Knowledge about the role of the right ventricle in health and disease historically has lagged behind that of the left ventricle. Less muscular, restricted in its role to pumping blood through a single organ, and less frequently or obviously involved than the left ventricle in diseases of epidemic proportions such as myocardial ischemia, cardiomyopathy, or valvulopathy, the right ventricle has generally been considered a mere bystander, a victim of pathological processes affecting the cardiovascular system. Consequently, comparatively little attention has been devoted to how right ventricular dysfunction may be best detected and measured, what specific molecular and cellular mechanisms contribute to maintenance or failure of normal right ventricular function, how right ventricular dysfunction evolves structurally and functionally, or what interventions might best preserve right ventricular function. Nevertheless, even the proportionately limited information related to right ventricular function, its impairment in various disease states, and its impact on the outcome of those diseases suggests that the right ventricle is an important contributor and that further understanding of these issues is of pivotal importance. For this reason, the National Heart, Lung, and Blood Institute convened a working group charged with delineating in broad terms the current base of scientific and medical understanding about the right ventricle and identifying avenues of investigation likely to meaningfully advance knowledge in a clinically useful direction. The following summary represents the presentations and discussions of this working group. The right ventricle is affected by and contributes to a number of disease processes, including perhaps most notably pulmonary hypertension caused by a variety of lung or pulmonary vascular diseases (cor pulmonale). Other diseases affect the right ventricle in different ways, including global, left ventricular–, or right ventricular–specific cardiomyopathy; right ventricular ischemia or infarction; pulmonary or tricuspid valvular heart disease; and left-to-right shunts. The right ventricle pumps the same …

Abstract: A 70 percent reduction in the rate of blood flow through the common carotid artery in rabbits caused a 21 percent decrease in the diameter of this artery within 2 weeks. The smooth muscle relaxant papaverine did not attenuate the response; therefore, such reductions in diameter probably reflect a structural modification of the arterial wall rather than sustained contraction of smooth muscle. This arterial response to reduced blood flow was abolished when the endothelium was removed from the vessels. It appears that the endothelium is essential for the compensatory arterial response to long-term changes in luminal blood flow rates.