Preload (cardiology)

Preload (cardiology)

In cardiac physiology, preload is the pressure stretching the ventricle of the heart, [eMedicineDictionary|ventricular+preload] after atrial contraction and subsequent passive filling of the ventricle. If the chamber is not mentioned, it is usually assumed to be the left ventricle.

Preload is theoretically most accurately described as the initial stretching of a single cardiac myocyte prior to contraction. This cannot be measured "in vivo" and therefore other measurements are used as estimates. Estimation is inaccurate, for example in a chronically dilated ventricle new sarcomeres may have formed in the heart muscle allowing the relaxed ventricle to appear enlarged. The term end-diastolic volume is better suited to the clinic, although not exactly equivalent to the laboratory term preload.


Quantitatively, preload can be calculated as

:frac{LVEDP cdot LVEDR}{2h}

where LVEDP=Left Ventricular end diastolic pressure, LVEDR= Left ventricular end diastolic radius (at the ventricle's midpoint), and h=thickness of the ventricle. This calculation is based on the Law of Laplace.

Factors affecting preload

Preload is affected by venous blood pressure and the rate of venous return. These are affected by venous tone and volume of circulating blood.

Preload relates to the ventricular end-diastolic volume: a higher end-diastolic volume implies a higher preload, but the relationship is not simple, because of the restriction of the term preload to single myocytes. Single myocytes are not connected simply, but in an interdigitated manner.

Preload increases with exercise (slightly), increasing blood volume (overtransfusion) and excitement (sympathetics).

See also

* Afterload
* Cardiac output
* Frank-Starling law of the heart


External links

* [ Overview at]

Wikimedia Foundation. 2010.

Игры ⚽ Нужно сделать НИР?

Look at other dictionaries:

  • Preload — may mean:* Preload (cardiology), a term used in cardiology (the study of the heart) * preload (software), a free Linux program * Preload (engineering), a term used in mechanical engineering to describe the load applied to a fastener merely as a… …   Wikipedia

  • Cardiology — [ ECG indicator; diagrams like this are used in Cardiology.] Cardiology (from Greek gr. καρδίᾱ, kardiā , heart ; and gr. λογία, logia ) is the branch of internal medicine dealing with disorders of the heart and blood vessels. The field is… …   Wikipedia

  • Aortic insufficiency — See also: mitral regurgitation and tricuspid insufficiency Aortic insufficiency Classification and external resources Micrograph of myxomatous degeneration – a cause of aortic insufficiency …   Wikipedia

  • Heart failure — Classification and external resources The major signs and symptoms of heart failure. ICD 10 I5 …   Wikipedia

  • Hypertrophic cardiomyopathy — Classification and external resources ICD 10 I42.1–I42.2 ICD 9 …   Wikipedia

  • Enhanced external counterpulsation — External counterpulsation (ECP) is a procedure performed on individuals with ischemic cardiomyopathy in order to diminish the symptoms of their ischemia. In various studies, ECP has been shown to relieve angina1,2, improve exercise tolerance³,… …   Wikipedia

  • Electrocardiography — ECG redirects here. For other uses, see ECG (disambiguation). Not to be confused with echocardiogram, electromyogram, electroencephalogram, or EEG. Electrocardiography Intervention Image showing a patient connected to the 10 electrodes necessary …   Wikipedia

  • Blood pressure — For information about high blood pressure, see Hypertension. Blood pressure Diagnostics A sphygmomanometer, a device used for measuring arterial pressure. MeSH …   Wikipedia

  • Circulatory system — This article is about the organ system. For the band, see Circulatory System. For transport in plants, see Vascular tissue. Circulatory system …   Wikipedia

  • Nitric oxide — Not to be confused with nitrous oxide or nitrogen oxides. For other uses, see NO (disambiguation). Nitric oxide …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”