Poor heart function. Stiffness of heart muscle from various causes most common being amyloidosis. This impairs filling of blood into the lower chamber of the heart. As a result the amount of blood leaving the heart is much lower causing fatigue and failure to thrive. Also there is build up of back pressure causing water logging of lungs, liver, abdomen and limbs causing shortness of breath, nausea, poor appetite.
Failure to fill. Restrictive cardiomyopathy is a disorder of cardiac muscle marked by impaired (diastolic) filling of the ventricle. Cardiac output (the amount of blood pumped) falls. The syndrome of congestive heart failure marked by shortness of breath and fluid retention can result. The national library of medicine has a nice summary at: http://www. Ncbi. Nlm. Nih. Gov/pubmedhealth/pmh0001241/.