Fluid Volume Homeostasis in Heart Failure: A Tale of 2 Circulations

Abstract

Fluid volume homeostasis in health and heart failure (HF) requires a complex interaction of 2 systems, the intravascular and interstitial-lymphatic circulations. With the development of HF both the intravascular and interstitial compartments undergo variable degrees of volume remodeling which can include significant expansion. This reflects the impact of multiple pathophysiologic mechanisms on both fluid compartments which initially play a compensatory role to stabilize intravascular circulatory integrity but with progression in HF can evolve to produce the various manifestations of volume overload and clinical HF congestion. The intent of this review is to help enhance recognition of the pathophysiologic and clinical importance of the interlinked roles of these 2 circulatory systems in volume regulation and chronic HF. It would also be hoped that a better understanding of the interacting functions of the intravascular and interstitial-lymphatic fluid compartments can potentially aid development of novel management strategies particularly addressing the generally undertargeted interstitial-lymphatic system and help bring such approaches forward through a more integrated view of these 2 circulatory systems.

Keywords: fluid; interstitial‐lymphatic; intravascular; review.

Figure 1. Conceptual framework for change in interstitial and intravascular compartment volume profiles, normal to heart failure.

Figure 2. Pathways of fluid volume homeostasis and congestion in heart failure.

BV indicates blood volume; CVP, central venous pressure; GFR, glomerular filtration rate; Na+, plasma sodium; and UNa+, urinary sodium excretion.

Figure 3. Absolute changes (mL) in intravascular and interstitial fluid compartment volumes by tertiles of diuresis‐related body weight loss–large volume decreases in interstitial volume, but small decreases in intravascular volumes even with large plasma volume expansion at hospital admission.