Cardiorenal syndrome - a new classification and current evidence on its management

Patients with chronic kidney disease (CKD) are at high risk for major cardiovascular (CV) morbidity and mortality, especially when they range among the elderly. The co-existence of renal dysfunction is common in patients with chronic heart failure (CHF), and renal failure is among the strongest predictors of mortality in patients with heart failure. Approximately one-third of dialysis patients also suffer from heart failure. The term "cardiorenal syndrome" has been increasingly described in recent literature, as there is growing recognition of the frequent association of combined renal and cardiac dysfunction. The pathophysiology of the cardiorenal syndrome involves interrelated hemodynamic and neurohormonal mechanisms, including the sympathetic nervous system, the renin-angiotensin-aldosterone system, and endothelin and arginine vasopressin system activation. Recently, a new classification of cardiorenal syndrome has been proposed with five subtypes that reflect the pathophysiology, the bidirectional nature of heart and kidney interaction and the time-frame. The management of the cardiorenal syndrome remains a challenge in spite of the advances in medical therapy and novel agents. Novel agents such as B-type natriuretic peptide (BNP) derivative, endothelin antagonist, adenosine antagonist or vasopressin antagonist have been evaluated in randomized controlled trials, and their results are discussed in this review. Mechanical support like hemodialysis and ultrafiltration are found to be useful in acute cardiorenal syndrome. There has been renewed interest in b-blockers in chronic cardiorenal syndrome patients to prevent sudden cardiac death from arrhythmia. In this review, we discuss the evidence behind the definition, pathophysiology, new proposed classification and the various therapeutic measures available for acute cardiorenal syndrome as well as chronic cardiorenal syndrome.