Heart disease is a very common condition in dogs, occurring in up to 11% of the canine population . The most common cardiac disease in dogs is myxomatous atrioventricular valvular disease, while others include dilated cardiomyopathy, congenital defects, and tachycardiomyopathies [2,3]. Progression of cardiac disease may result in heart failure (HF) and the development of cardiogenic pulmonary oedema. A reduction in cardiac output secondary to heart disease activates neurohormonal mechanisms, including the sympathetic nervous system and renin–angiotensin–aldosterone system (RAAS). Activation of the sympathetic nervous system leads to tachycardia and vasoconstriction, which maintain blood pressure (BP) and tissue perfusion. Activation of the RAAS leads to retention of sodium and water and an increase in circulating volume . This in turn leads to an increase in cardiac preload and restoration of normal stroke volume.