An aortic rupture is a rare, but deadly, condition in the horse. It results from a spontaneous break in the wall of the aorta, the main artery that carries blood from the heart's left ventricle (the main pumping chamber) to all the other arteries except the pulmonary artery.While prosthetic aortas have been developed for humans, there are no medical or surgical cures for equine sufferers of aortic ruptures, writes Marcia King in the April edition of The Horse. Some collapse and die immediately. Others live for a while- their symptoms relieved by rest and medical therapy- before developing congestive heart failure. "Once a horse goes into heart failure, it's a very poor prognosis," said Janice Bright, a veterinarian who specializes in cardiology at Colorado State University. "Even with supportive treatment, these animals usually don't do well. Most horses with an aortic rupture that produces secondary heart failure have only a few weeks to maybe a month or two (to live)."Not much is known about why aortic ruptures occur. Congenital aneurysms, migrating parasites, and copper deficiencies are among the causes that have been suggested."Older horses are predisposed, especially older stallions," Bright said. "For reasons that aren't clear, it does tend to occur more commonly in the spring after the stallion services the mare. But while this is more common in older breeding stallions, this is a problem that can occur in younger horses, as well."Because the causes of aortic ruptures have not been pinned down, there is little anyone can do to stop them from occurring. "Good basic care of the horse- good deworming, good nutrition, and preventive medicine - will help, but they are not specific against preventing an aortic rupture," said Dr. Harold Schott II, an assistant professor of equine medicine at Michigan State University.As the horse matures, he added, an annual physical exam and "a good listen to the heart," might be helpful to screen for the development of heart murmurs. "A heart murmur might indicate an ultrasound should be performed," Schott explained. "If the ultrasound shows an aneurysm (although the aneurysm will not result in a murmur unless it ruptures), then we would make a recommendation that the horse should be retired to perhaps lessen the chance of a rupture occurring. Theoretically, it could reduce the risk a little, but probably not a whole lot."