2.2.13 Volume overload
Volume overload is a term which is frequently used in the context of valvular heart disease. In fact, volume overload can occur in other situations, but valvular incompetence is by far the most common cause in horses.
Increased chamber volume results from compensatory mechanisms which increase blood volume so that blood pressure can be maintained (see above), and as a direct consequence of regurgitation. Eccentric hypertrophy results in the ability to pump a greater stroke volume (within limits). In addition, the regurgitant fraction must be accommodated in the receiving chamber (e.g. the LA in the case of MR, the LV in the case of aortic incompetence). The degree of volume overload is a helpful indicator of the severity of valvular regurgitation (see section 4.2.6 and section 6.2.6). Volume overload is also seen in severe myocardial disease.