Changes

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 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 definition of heart failure is: a complex syndrome initiated by an inability of the heart to maintain a normal cardiac output at a normal filling pressure.

The '''definition of heart failure''' is: a complex syndrome initiated by an inability of the heart to maintain a normal cardiac output at a normal filling pressure.

Heart failure can be further classified according to the cause, whether it leads predominantly to underperfusion or congestion (forward or backward failure) and whether the right or left side of the circulation is affected to a greater extent (right-sided failure or left-sided failure). In some cases, biventricular failure may occur.  

Heart failure can be further classified according to the cause, whether it leads predominantly to underperfusion or congestion (forward or backward failure) and whether the right or left side of the circulation is affected to a greater extent (right-sided failure or left-sided failure). In some cases, biventricular failure may occur.  

The most basic equations relating to regulation of circulation are:

The most basic equations relating to regulation of circulation are:

Cardiac Output (CO) = Heart Rate (HR) x Stroke Volume (SV)

* Cardiac Output (CO) = Heart Rate (HR) x Stroke Volume (SV)

Blood Pressure (BP) = Cardiac Output (CO) x Total Peripheral Resistance (TPR)

* Blood Pressure (BP) = Cardiac Output (CO) x Total Peripheral Resistance (TPR)

Cardiac Output (CO) = Venous Return (VR)

* Cardiac Output (CO) = Venous Return (VR)

== Mechanisms of failure  ==

== Mechanisms of failure  ==