volume overload
{{Distinguish|Hypervolemia}}
File:Response of cardiac stroke volume to ventricular filling under normal conditions.jpg to left ventricular filling under normal conditions. There is an optimum end-diastolic volume at which maximum stroke volume and cardiac output is achieved. Beyond this, there is volume overload, and stroke volume is diminished.]]
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.{{cite book |author=Costanzo, Linda S. |title=Physiology |publisher=Lippincott Williams & Wilkins |location=Hagerstwon, MD |year=2007 |pages=[https://archive.org/details/physiology00cost_0/page/81 81] |isbn=978-0-7817-7311-9 |oclc= |doi= |url-access=registration |url=https://archive.org/details/physiology00cost_0/page/81 }}
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.{{cn|date=March 2021}}
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.{{cn|date=March 2021}}
Left ventricular volume overload may produce inverted u waves on the electrocardiogram.{{cite journal |vauthors=Conrath C, Opthof T |title=The patient U wave |journal=Cardiovasc Res |volume=67 |issue=2 |pages=184–6 |year=2005 |pmid=15979057 | doi = 10.1016/j.cardiores.2005.05.027|doi-access=free }}
Causes
Causes may be considered according to which chamber is affected.{{cn|date=March 2021}}
Left ventricular volume overload
- Valvular heart disease[http://www.echoincontext.com/int2/skillI2_04.asp Left Ventricular Volume Overload], Discussion of echocardiography findings.
- Aortic regurgitation
- Mitral regurgitation, also causing left atrial volume overload{{cite journal |vauthors=Gehl LG, Mintz GS, Kotler MN, Segal BL |title=Left atrial volume overload in mitral regurgitation: a two dimensional echocardiographic study |journal=Am J Cardiol |volume=49 |issue=1 |pages=33–8 |year=1982 |pmid=7053608 |doi=10.1016/0002-9149(82)90274-0}}
- Congenital heart defects
- Patent ductus arteriosus
- Ventricular septal defect, also causing left atrial volume overloadGardiner M, Eisen S, Murphy C. Training in paediatrics: the essential curriculum. Oxford University Press, Oxford 2009.
- Arteriovenous malformation and fistula
- Giant hepatic haemangioma
- High-output haemodialysis fistula
Right ventricular volume overload
- Valvular heart disease
- Tricuspid regurgitation
- Pulmonary regurgitation
- Congenital heart defects
- Atrial septal defect, also causing right atrial volume overload