Is the aortic valve operation dangerous?

It depends: A heart valve operation, like any procedure has risks and benefits. The task is to determine the risk vs. Benefit of the said procedure and proceed with the proper action. So, while a heart valve operation may have some risk associated with it, leaving a patient in need of the said operation maybe the less safe thing to do. Your cardiologist and ct surgeon would be the best judges of this.

Major surgery: It's a major operation. Survival is >98% in most series. Other premorbid medical conditions like previous stroke, COPD or kidney disease increases the risk. General good health and younger age lower the risk.