Some Greyhounds are born with or develop a heart murmur (abnormal flow of blood through the heart). (neogreyhound.com)
In most animals, abnormal flow pressures within the thoracic duct are thought to lead to exudation of chyle from intact, but dilated, thoracic lymphatic vessels. (svsvet.com)
Diseases affecting the valves result in abnormal blood flow in the heart (valve disease is a common cause of murmurs), which places strain on the heart as it tries to compensate for abnormal flow through thickening of the muscles and dilation of the chambers. (morrisanimalfoundation.org)