The relationship between the volume within a chamber and the resulting pressure defines chamber compliance or distensibility. The top curve (red) is from a left atrium with low compliance; small changes in volume result in marked changes in pressure. In this situation large "v" waves due to mitral regurgitation will be seen. The lower curve (blue) is from a left atrium that is very compliant; changes in volume result in only small changes in pressure. In this situation, the same degree of mitral regurgitation will cause small "v" waves.
