Ventricular systole. (Red arrow is path from left ventricle to aorta. Afterload is largely dependent upon aortic pressure.

In cardiac physiology, afterload is used to mean the tension produced by a chamber of the heart in order to contract. Cardiology (from Greek grc καρδίᾱ kardiā, "heart" and grc -λογία -logia) is the branch of Internal medicine Physiology (from Greek grc φύσις physis, "nature origin" and grc -λογία -logia) is the study of the mechanical physical The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic If the chamber is not mentioned, it is usually assumed to be the left ventricle. The left ventricle is one of four chambers (two atria and two ventricles in the Human Heart. However, the strict definition of the term relates to the properties of a single cardiac myocyte. It is therefore only of direct relevance in the laboratory; in the clinic, the term end-systolic pressure is usually more appropriate, although not equivalent.

Afterload can also be described as the pressure that the chamber of the heart has to generate in order to eject blood out of the chamber, and thus is a consequence of the arterial pressure, since the pressure in the ventricle must be greater than the systemic pressure in order to open the aortic valve. Blood pressure is also the title of a short story by Damon Runyan in Guys and Dolls and Other Stories Everything else held equal, as afterload increases, cardiac output decreases. Cardiac output (Q is the volume of blood being pumped by the Heart, in particular by a ventricle in a minute

Pathology

Disease processes that increase the left ventricular afterload include increased blood pressure and aortic valve disease. The left ventricle is one of four chambers (two atria and two ventricles in the Human Heart. Blood pressure is also the title of a short story by Damon Runyan in Guys and Dolls and Other Stories

Hypertension (Increased blood pressure) increases the left ventricular afterload because the left ventricle has to work harder to eject blood into the aorta. Hypertension, also referred to as high blood pressure, HTN or HPN, is a medical condition in which the Blood pressure is chronically elevated Blood pressure is also the title of a short story by Damon Runyan in Guys and Dolls and Other Stories The left ventricle is one of four chambers (two atria and two ventricles in the Human Heart. This is because the aortic valve won't open until the pressure generated in the left ventricle is higher than the elevated blood pressure.

Aortic stenosis increases the afterload because the left ventricle has to overcome the pressure gradient caused by the stenotic aortic valve in addition to the blood pressure in order to eject blood into the aorta. For instance, if the blood pressure is 120/80, and the aortic valve stenosis creates a trans-valvular gradient of 30 mmHg, the left ventricle has to generate a pressure of 110 mmHg in order to open the aortic valve and eject blood into the aorta. The torr (symbol Torr) is a non- SI unit of Pressure defined as 1/760 of an atmosphere.

Aortic insufficiency increases afterload because a percentage of the blood that is ejected forward regurgitates back through the diseased aortic valve. This leads to elevated systolic blood pressure. The diastolic blood pressure would fall, due to regurgitation. This would result in an increase pulse pressure.

Mitral regurgitation decreases the afterload. Mitral regurgitation ( MR) a Valvular heart disease also known as mitral insufficiency, is the abnormal leaking of blood through the Mitral valve During ventricular systole, the blood can regurgitate through the diseased mitral valve as well as be ejected through the aortic valve. The miter valve (also known as the bicuspid valve or left atrioventricular valve) is a dual flap (bi = 2 valve in the Heart that lies between This means that the left ventricle has to work less to eject blood, causing a decreased afterload. Afterload is largely dependent upon aortic pressure.

See also

• Preload
• Cardiac output

External links

• afterload at eMedicine Dictionary
• Overview at cvphysiology.com