Echocardiography is useful in determining a definitive diagnosis of underlying structural disease as it provides a quantitative evaluation of heart chamber size, wall thickness, and the dynamic changes that occur during the cardiac cycle.1 (epictrial.com)
The clinical signs occur when the pressure in the enlarged heart chambers cause fluid to leak out of the blood vessels into the lungs (called pulmonary edema or «water on the lungs») and sometimes the belly (ascites). (tampabayvets.net)
Radiographs are also less sensitive than echocardiography in detecting subtle changes in heart chamber sizes. (themeowingvet.com)