The aortic valve functions as a one-way valve between the heart and the rest of the body. Blood is pumped from the left ventricle of the heart, through the valve, and down the aorta, which in turn supplies blood to all of the organs in the body (see Figure 1). Between heart contractions, the valve closes, preventing blood from flowing backwards into the heart. The function of the aortic valve is then twofold: (1) It provides a route for which blood can leave the heart, and (2) It prevents blood that has already left the heart from leaking backwards into the heart.
Damage to the aortic valve can occur from a congenital defect, the natural aging process, and from infection or scarring. This damage will cause the valve to either “leak”, resulting in “aortic insufficiency” or to become “restricted” and not open fully, resulting in “aortic stenosis”. Both aortic insufficiency and aortic stenosis create an extra workload for the heart … ultimately resulting in weakening of the heart muscle and eventual heart failure. Once a valve becomes sufficiently damaged, it may need to be replaced, in order to prevent heart failure and premature death.
The operation to replace an aortic valve takes 2-3 hours to perform. The damaged valve is removed and replaced with either a “tissue” valve or a “mechanical” valve. Although tissue and mechanical valves function similarly, there are distinct advantages and disadvantages of each. The advantage of mechanical valves, which are made from ceramic, is that they last forever. The disadvantage of mechanical valves is that they require anticoagulation with blood thinners for the remainder of a patient’s life. The advantage of tissue valves, which are made from cow or pig hearts, is that they do not require formal anticoagulation. The disadvantage of tissue valves, however, is that they generally wear out after 12-15 years, at which time another operation would be required to replace the worn out valve.
The operation itself requires general anesthesia … the patient is asleep for the entire course of the operation. The surgeon opens the chest by dividing the breast bone or sternum. Tubes and cannulae are inserted into the heart and major blood vessels surrounding the heart in preparation for cardiopulmonary bypass with the heart-lung machine. At this point, blood is redirected from the heart into the heart-lung machine, the heart is stopped, and the aorta is clamped. This permits the surgeon to safely open and operate on the heart without blood pumping thorough it. The heart-lung machine continues to pump freshly oxygenated blood to the rest of the body, in effect, taking over the roles of the heart and lungs.
The surgeon then opens the aorta and exposes the damaged aortic valve. The valve is then removed and non-absorbable sutures with bolsters or “pledgets” are placed through the rim or “annulus” of the valve. These sutures are then brought through the sewing ring of the valve, the valve is lowered into position (see Figure 2), and all the sutures are tied. The aorta is then sutured closed, the clamp on the aorta is removed, and all remaining air is evacuated from the heart. As the heart regains its strength, the patient is weaned from the heart-lung machine and the heart and lungs resume their normal functions.
Drainage catheters are placed around the heart … these are usually removed after 24 hours. Temporary pacing wires to regulate the patient’s heart rate, are sewn to the surface of the heart … these are removed before the patient goes home. The cannulae are removed from in and around the heart, and the sternum and skin are closed.
Following the operation, patients are transported to the Cardiac Post-Anesthesia Care Unit, a specialized unit caring exclusively for open-heart surgery patients. Patients generally awaken from anesthesia 4-6hr after the operation. The following morning all drainage catheters and monitoring lines are usually removed, and patients are transferred to a standard hospital room in the cardiac recovery wing of the hospital. Patients undergoing an AVR operation are usually hospitalized for 4-5 days following the surgery. To see what to expect during the recovery of this operation, please refer to our education section.
Minimally Invasive Aortic Valve Replacement
Replacement or repair of the aortic valve can be performed through a small incision in the upper portion of the patient’s chest and the groin, avoiding the traditional sternal split incision. This may result in less trauma to the patient, decrease sternal wound complication and rapid recovery. Not all patient are appropriate candidates for this minimally invasive procedure. MASA surgeons are quite experienced with this advanced technique that is not offered at many cardiac centers.