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== Introduction  ==

== Introduction  ==

The heart pumps unoxygenated blood from the venous circulation into the lungs where it is oxygenated. Newly oxygenated blood then travels to the left atrium and ventricle where it is pumped into the arterial circulation to meet the oxygen demands of the body. Heart failure is a condition that begins when the heart is unable to pump enough blood (cardiac output) at normal filling pressures to meet the body’s requirements. Heart failure is the end result of heart disease (heart abnormality). Under normal circumstances the heart can adapt to moderate increases of pressure or volume using its functional reserve capacity.  

The heart pumps deoxygenated blood from the venous circulation into the lungs, where it is oxygenated. Newly oxygenated blood travels via the pulmonary veins to the left atrium and left ventricle, where it is ejected via the aorta into the arterial circulation to supply oxygenated blood to peripheral tissue. Heart failure arises when structural or functional abnormalities prevent the heart adequately filling with or ejecting blood, resulting in the inability to meet metabolic needs of peripheral tissue. The cardiovascular system has a large reserve capacity, so overt clinical signs are only seen with severe disease when the heart cannot compensate for the decreased function.  

 

The cardiovascular system has a large reserve capacity so overt clinical signs are only seen with severe disease when the heart cannot compensate for the decreased function.  

Factors affecting cardiac output include:  

Factors affecting cardiac output include: