The Intersection of Venous Congestion and Arterial Underfilling in Cardiorenal Syndromes

The heart and kidneys are connected in both health and disease. Coordinated dysfunction of these organ systems is a result of complex interactions related to vascular and biochemical maladaptations. The historical perspective that kidney dysfunction in heart failure is overwhelmingly a product of reduced cardiac forward flow and arterial underfilling has been challenged by mounting evidence. Efforts in 2004 to introduce the term cardiorenal syndrome were based on observations that increased circulatory volume, specifically venous congestion, play a key role in kidney dysfunction. Contemporary studies done after 2004, as well as revisiting historical renal physiology experiments in a new light, have illuminated some of the pathophysiology of how venous congestion in decompensated heart failure causes the "congested kidney." Cardiorenal syndrome, specifically type 1 occurring in the setting of acute heart failure, in part is defined by the fact that renal venous hypertension drives kidney dysfunction. To illuminate this point further, we compare and contrast the importance of arterial underfilling in cardiogenic shock vs cardiorenal syndrome.