The risk of death after high-risk surgeries is dropping among Medicare patients, a new study found.

Eight different cancer and cardiovascular surgeries were studied over 10 years: abdominal aortic aneurysms, coronary artery bypass grafting, aortic valve replacement, carotid endarterectomy and operations to treat cancers of the esophagus, pancreas, lung and bladder. The procedure with the steepest decline of death rates was surgery to repair abdominal aortic aneurysms (AAA), which occurs when the large blood vessel that supplies blood to the abdomen, pelvis, and legs becomes abnormally large. The death rate from AAA repair dropped 36% between 2000 and 2008, largely due to improved imaging technology, according to the study.

The researchers noted that while fewer hospitals are doing these types of procedures, those that do perform them do so much more frequently and therefore gain more experience in treating high-risk patients. They also concluded that improved patient safety measures, such as operating-room checklists, outcomes-measurement and feedback programs, have also contributed to success. This analysis was published in the current issue of the New England Journal of Medicine.