do they? not usually...can they? yes it's called Cardiomyopathy
http://www.medhelp.org/medical-information/show/1579/Cardiomyopathy which is a weakening of the heart muscle or a change in heart muscle structure and is often associated with inadequate heart pumping or other heart function problems.
You would need to have very frequent pvc's which CAN but doesnt always lead to pvc induced cardiomyopathy and normally reverses when they are treated. For this to happen dr's say it's around 15% or more of your normal 24 hour HB's constantly for "awhile" is what I was quoted...what that awhile means I think can vary between dr's.
If you have a normal heart that beats 100,000 times in a 24 hour period, then that would be roughly 15,000+ day pvc's in day and Cardiomyopathy may develop.
Pac's I don't know much about sorry.