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 Heart 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. "Cardiovascular 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 on the electrocardiogram.
Causes
Causes may be considered according to which chamber is affected.
Left ventricular volume overload
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Valvular heart disease
[ Left Ventricular Volume Overload , Discussion of echocardiography findings.]
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Aortic regurgitation
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Mitral regurgitation, also causing left atrium volume overload
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Congenital heart defects
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Patent ductus arteriosus
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Ventricular septal defect, also causing left atrial volume overload
[Gardiner M, Eisen S, Murphy C. Training in paediatrics: the essential curriculum. Oxford University Press, Oxford 2009.]
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Arteriovenous malformation and fistula
Right ventricular volume overload
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Valvular heart disease
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Tricuspid regurgitation
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Pulmonary regurgitation
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Congenital heart defects
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Atrial septal defect, also causing right atrial volume overload
See also
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Cardiac failure
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Frank–Starling law of the heart
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Preload (cardiology)
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Pressure overload
