Basically, there are four types of valves in the heart of a human:  the pulmonary valves, the Mitral valves, the Tricuspid valves, and the Aortic valves. All these valves of the heart are fashioned in such a manner, that they can manage the path of blood flow through the heart.  The heartbeats are heard and measured by analyzing the closing and opening of these heart valves. The replacement of an Aortic valve is an open-heart surgical procedure that is conducted while the patient is under the influence of general anesthesia.  The sternum (breast bone) serves as the opening for the single valve surgery, as the primary incision is made on sternum only for initiating the surgery. Several medical tubes are utilized for re-routing the blood towards a heart-lung bypass machine that is away from the heart. This is done for preserving the blood in its oxygenated form and also, for the proper blood circulation throughout the body during the course of surgery.  Generally, the replacement of a heart valve is defined as a surgical treatment, in which the medical surgeons eradicate the injured valve from the heart and replace it with a vigorous and functional valve.

Reason and Safeguard:

All the above mentioned four essential valves of the heart escort the flow of blood from the entire body all the way through the heart. A single valve surgery is usually performed to repair any of these injured valves, which may breakdown due to a birth imperfection, illness, infection, or shock.  In case, if the stage of the malfunction reaches to a harsh situation, then it is likely to hamper the flow of blood, as a result of which an individual is likely to have heart tremors, respiring problems, and frequent fainting sessions. All these symptoms are highly possible of deteriorating with time and can even cause death in some extreme cases, if the injured valve is not substituted surgically as soon as possible. Generally, a single valve surgery is not conducted for certain ill-functional tricuspid valves, as they are not unable to root severe concerning symptoms. Gently or even fairly damaged mitral valves may also not require a single valve surgery, as the symptoms generated due to it are bearable and are also, curable with certain medications such as the calcium antagonists or the beta blockers, that somewhat relaxes the heart rate.  Although, a seriously damaged mitral valve needs to be restored or substituted, unless the patient is too sick for bearing the surgery due to certain other health problems or diseases. 

Reports:

The surgeons subsequent to incising the ribs and the breastbone, consigns the patient on a cardiopulmonary bypass machine that is bound to conduct the necessary tasks of the lungs and hearts during the surgery. The next step in the single valve surgery is to open up the heart for tracing the defective valves. After tracing it, the surgeons gently carves the boundaries of the valve by loosening it from the muscle cells that links it to the rest of the heart for inducing in the fresh valve and, finishes the surgery by sewing up the surgical opening.