In order to understand your pets’ heart disease, it is important to first understand normal circulation in the heart. Blood drains from the body into the right collecting chamber (the right atrium). It then passes through the tricuspid valve into the right pumping chamber (the right ventricle).  From here, blood is pumped via the pulmonary artery to the lungs to receive oxygen. Oxygenated blood then drains into the left atrium, through the mitral valve and into the left ventricle. From here, it is pumped via the aorta to deliver oxygenated blood to all tissues of the body.