Multiple reasons . The most common cause of heart disease resulting in cardiac surgery is either blocked coronary arteries or a problem with one of the heart valves.
Many reasons. Coronary artery dz in multiple vessels may need open heart. Valve problems may need replacement or repair by open heart. Congenital heart defects would be another reason for open heart.
It's complicated. That's a very open ended question. Heart surgery is typically indicated when the risks of surgery are outweighed by the benefits. Lots of studies have been done for various conditions to determine when it is a good idea. Considerations like symptoms (eg, chest discomfort, trouble breathing), or risk of dying (eg, large aortic aneurysms, type a dissection) are factored into the decision. Read more...