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. 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.

Causes

Causes may be considered according to which chamber is affected.

Left ventricular volume overload

Valvular heart disease

• Aortic regurgitation

• Mitral regurgitation, also causing left atrial volume overload

Congenital heart defects

• Patent ductus arteriosus

• Ventricular septal defect, also causing left atrial volume overload

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

See also

• Cardiac failure

• Frank–Starling law of the heart

• Preload (cardiology)

• Pressure overload

References