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volume overload
Volume overload refers to the state of one of the chambers of the heart in which too large a volume of blood exists within it for it to function efficiently. Ventricular volume overload is approximately equivalent to an excessively high preload. It is a cause of cardiac failure.
==Pathophysiology==
In accordance with the Frank–Starling law of the heart, the myocardium contracts more powerfully as the end-diastolic volume increases. Stretching of the myofibrils in cardiac muscle causes them to contract more powerfully due to a greater number of cross-bridges being formed between the myofibrils within cardiac myocytes.〔Klabunde, Richard E. "Cardiovacular Physiology Concepts". Lippincott Williams & Wilkins, 2011, p. 74.〕 This is true up to a point, however beyond this there is a loss of contractile ability due to loss of connection between myofibrils; see figure.
Various pathologies, listed below, can lead to volume overload. Different mechanisms are involved depending on the cause, however the common theme is that of a high cardiac output with a low or normal afterload. The output may be high due to the inefficiency in valve disease, or it may be high due to shunting of blood in left-to-right shunts and arteriovenous malformations.
Left ventricular volume overload may produce inverted u waves on the electrocardiogram.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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