The oxygen shortage at high elevations causes increased resistance to blood flow in small arteries in the lungs. The heart compensates for higher resistance by stretching and building up a higher pressure. The pressure can continue to build up until fluids leak out of the blood stream and collect in the chest cavity, the brisket, and other places. Eventually, the heart wears out and stops beating. The losses from the disease can vary depending on the origin of the cattle.
Cattle differ in how they respond to oxygen shortage.
Some cattle are able to tolerate high pressures for a longer period of time, while others die quickly. Brisket disease is not limited to one sex or breed. It affects both sexes and has been found across all breeds including crossbreds. This indicates that cattlemen can successfully select against the disease by curing cattle with high pulmonary arterial pressures. Pressure waves are observed on a heart monitor and the monitor gives a direct readout of the true average pressure.