congestion

Congestion is what happens behind a backed-up chamber — like water rising upstream of a partly blocked river. When a heart chamber cannot empty its incoming blood fast enough, pressure climbs in the vessels feeding it, and fluid and blood pile up in the organs that drain into that chamber.

The pattern depends on which side is affected. Left-sided congestion raises pressure in the pulmonary veins, flooding the lungs and causing breathlessness; right-sided congestion raises pressure in the systemic veins, swelling the legs, distending the neck veins, and engorging the liver. Congestion is the ‘backward’ face of heart failure, in contrast to ‘forward’ failure, where too little blood reaches the organs that need it.

Crucially, congestion is mostly about pressure, not just total fluid. A patient can be congested even without dramatic weight gain if pressures are high, and relieving congestion — lowering those filling pressures — is one of the chief goals of treatment because high venous pressures themselves damage the kidneys, liver, and gut over time.