A perforation or tear in the heart or arteries is not a common occurrence with this procedure. However, if it does happen, it is usually related to the use of catheters or other devices that travel through your arteries and heart.
The bleeding that can result from this causes the thin layer of tissue around your heart to fill with fluid. This layer of tissue, or "heart sac" is a limited space and is not meant to hold a large quantity of fluid. Too much fluid causes the heart to stop pumping well. This may occur immediately or several weeks after your procedure. This situation requires surgery so the area can be drained.