The systemic inflammatory response in heart failure

The physiologic diagnosis of heart failure has changed very little over the past several decades: heart failure is the inability of the cardiac output to meet the metabolic demands of the organism. The clinical definition of heart failure (also relatively unchanged) describes it as ventricular dysfunction that is accompanied by reduced exercise tolerance. Our understanding of the true pathophysiologic processes involved in heart failure have, however, changed. We have moved from thinking of heart failure as primarily a circulatory phenomenon to seeing it as a pathophysiologic state under the control of multiple complex systems. Over the past several years the dramatic explosion of research in the fields of immunology and immunopathology have added an additional piece to the puzzle that defines heart failure and have lead to an understanding of heart failure, at least in some part, as an 'inflammatory disease'. In this review we will examine several of the key inflammatory mediators as they relate to heart failure while at the same time attempting to define the source(s) of these mediators. We will examine key elements of the inflammatory cascade as they relate to heart failure such as: cytokines, 'proximal mediators' (e.g. NF-kappaB), and distal mediators (e.g. nitric oxide). We will end with a discussion of the potential therapeutic role of anti-inflammatory strategies in the future treatment of heart failure. Also, throughout the review we will examine the potential pitfalls encountered in applying bench discoveries to the bedside as have been learned in the field of septic shock research.