Interstitial protein ‘wash‐down’, an early sign of cardiac failure?

Summary. An increase of interstitial fluid volume (IFV) with or without clinical oedema is an important sign of congestive heart failure. Without entering into a discussion of forward versus backward failure, we will briefly analyse this alteration of trans‐capillary fluid balance in peripheral tissues: the rise in IFV must result either from a rise in net capillary filtration, or from a decrease of lymph flow. Since lymph flow is increased rather than decreased in congestive heart failure (Langgård, 1963), we must conclude that a rise in IFV is caused by increased net capillary filtration. According to the Starling equilibrium, a rise in net filtration could result from (a) a rise in average capillary pressure (Pc), (b) a reduction of interstitial fluid hydrostatic pressure (Pi), (c) a fall in plasma colloid osmotic pressure (COPP), or from (d) an increase of interstitial fluid colloid osmotic pressure (COPi), Since COPp and Pi are normal in most cases of congestive heart failure, and since COP; and Pi tend to change opposite to the required direction (see below), it follows that the rise in IFV results mainly from a rise in mean capillary pressure.