The lung water cascade in heart failure.

In heart failure patients, we hypothesize the occurrence of the "lung water cascade," with the various markers hierarchically ranked in a well-defined time sequence: (1) early, proximal hemodynamic event with increase in pulmonary capillary wedge pressure; (2) intermediate, direct imaging sign of pulmonary edema (easily detectable at bedside by lung ultrasound as B-lines); (3) late, distal clinical symptoms and signs such as dyspnea and pulmonary crackles. Completion of the cascade (from hemodynamic to pulmonary to clinical congestion) can require minutes (as with exercise), hours or even weeks (as with impending acute heart failure). Backward rewind of the downhill cascade can be achieved with timely pulmonary decongestion therapy, such as diuretics or dialysis, restoring a relatively dry lung. Any therapeutic intervention is more likely to succeed in the early steps of the cascade, at the imaging stage of asymptomatic pulmonary congestion, rather than downstream near to the end of the cascade, when clinical instability occurred.