Vascular redistribution occurs when the upper-lobe pulmonary arteries and veins, which are usually smaller than those of the lower lobe because of less blood flow, actually become larger than the vessels in the lower lobes. This finding is detected by comparing the size of the vessels coming from the upper hilum on the chest x-ray to those coming from the lower hilum. If the upper ones do not look clearly larger and the lower ones look clearly too skinny, then there is probably not redistribution‚ present.
When does vascular redistribution‚ occur in congestive heart failure?
Many sources describe vascular redistribution‚ as a cardinal feature of congestive heart failure. However, this may be a particularly unhelpful sign. It is probably chronic pulmonary venous hypertension (e.g., mitral valve disease, chronic left ventricular failure) that causes vascular redistribution. The theory is that chronic venous hypertension may affect the lower-lobe arteries to a greater extent because of the greater blood flow to lower lungs and greater venous return pressure due to gravity. Thus, in the body’s attempt to maintain more normal blood flow and oxygenation, blood flow is diverted to the upper lungs.
Thus, redistribution is usually not helpful in the ICU patient with acute congestive failure. All of the pulmonary arteries probably look big, and upper-lobe vessels probably look about the same size as or a little smaller than the lower-lobe vessels. The upper-lobe vessels are larger than normal because of stasis of blood flow and because the patient is often supine, but there is not a true redistribution.‚