Often cardiomyopathy is due ischemia (occluded vessels), hypertension, congenital, and control of the underlying cause can stop progression, but idiopathic indicates the cause is unknown and whether or not there is progression or possibly reversal would also be unknown.
For some insight of diastolic dysfunction, the heart muscle (myocardium) behaves like a ballon made of unusually thick rubber. Pressure may be normal but there is a problem with the filling phase as the heart walls do not expand normally limiting the amount of blood pumped into circulation with each heartbeat....also there is abnormality of intra-chamber pressures As a result, pressure rises in the atrium and is transmitted back to the pulmonary venous system thereby increasing its hydrostatic pressure and thus promoting pulmonary edema...worst case scenario.