Aortic valve replacement
Editor-In-Chief: C. Michael Gibson, M.S., M.D. 
Aortic valve replacement is a cardiac surgery procedure in which a patient's aortic valve is replaced by a different valve. The aortic valve can be affected by a range of diseases; the valve can either become leaky (aortic insufficiency / regurgitation) or partially blocked (aortic stenosis). Aortic valve replacement currently requires open heart surgery. percutaneous aortic valve replacement, which allows the implantation of valves using a catheter without open heart surgery is still being evaluated in clinical trials and is appearing to be promising in patients who are at high risk to undergo open heart surgery.
Types of Heart Valves
There are two basic types of artificial heart valve: mechanical valves and tissue valves.
Tissue heart valves are usually made from animal tissues, either animal heart valve tissue or animal pericardial tissue. The tissue is treated to prevent rejection and calcification.
There are alternatives to animal tissue valves. In some cases a homograft - a human aortic valve -- can be implanted. Homograft valves are donated by patients and harvested after the patient dies. The durability of homograft valves is probably the same for porcine tissue valves. Another procedure for aortic valve replacement is the Ross procedure (or pulmonary autograft). In a Ross procedure, the aortic valve is removed and replaced with the patient's own pulmonary valve. A pulmonary homograft (pulmonary valve taken from a cadaver) is then used to replace the patients own pulmonary valve. This procedure was first used in 1967 and is used primarily in children.
Mechanical valves are designed to outlast the patient, and have typically been stress-tested to last several hundred years. Although mechanical valves are long-lasting and generally only one surgery is needed, there is an increased risk of blood clots forming with mechanical valves. As a result, mechanical valve recipients must generally take anti-coagulant drugs such as warfarin for the rest of their lives, which effectively makes them borderline hemophiliacs.
Tissue valves tend to wear out faster with increased flow demands - such as with a more active (typically younger person). Tissue valves typically last 10-15 years in less active (typically elderly) patients, but wear out faster in younger patients. When a tissue valve wears out and needs replacement, the person must undergo another valve replacement surgery. For this reason, younger patients are often recommended mechanical valves to prevent the increased risk (and inconvenience) of another valve replacement.
Aortic valve replacement is most frequently done through a median sternotomy, meaning the chestbone is sawed in half. Once the pericardium has been opened, the patient is placed on cardiopulmonary bypass machine, also referred to as the heart-lung machine. This machine takes over the task of breathing for the patient and pumping his blood around while the surgeon replaces the heart valve.
Once the patient is on bypass, an incision is made in the aorta. The surgeon then removes the patient's diseased aortic valve and a mechanical or tissue valve is put in its place. Once the valve is in place and the aorta has been closed, the patient is taken off the heart-lung machine. Transesophageal echocardiogram (TEE, an ultra-sound of the heart done through the esophagus) can be used to verify that the new valve is functioning properly. Pacing wires are usually put in place, so that the heart can be manually paced should any complications arise after surgery. Drainage tubes are also inserted to drain fluids from the chest and pericardium following surgery. These are usually removed within 36 hours while the pacing wires are generally left in place until right before the patient is discharged from the hospital.
Hospital Stay and Recovery Time
Immediately after aortic valve replacement, the patient will frequently stay in a cardiac surgery intensive care unit for 12-36 hours. After this, the patient is often moved to a lower-dependency unit and then to a cardiac surgery ward. Total time spent in hospital following surgery is usually between 4 and 10 days, unless complications arise.
Recovery from aortic valve replacement will take 1-3 months if the patient is in good health. Patients are advised not to do any heavy lifting for 6-8 weeks following surgery to avoid damaging the sternum (breast bone) while it heals.
Surgical Outcome and Risk of Procedure
The risk of death or serious complications from aortic valve replacement is typically quoted as being between 1-5%, depending on the health and age of the patient, as well as the skill of the surgeon. Older patients, as well as more fragile ones, are sometimes inelegible for surgery because of elevated risks.
2008 and Incorporated 2006 ACC/AHA Guidelines for the Management of Patients with Valvular Heart Disease (DO NOT EDIT) 
Antithrombotic Therapy for Prosthetic Heart Valves (DO NOT EDIT) 
|"1. After AVR with bileaflet mechanical or Medtronic Hall prostheses, in patients with no risk factors,* warfarin is indicated to achieve an INR of 2.0 to 3.0. If the patient has risk factors, warfarin is indicated to achieve an INR of 2.5 to 3.5. (Level of Evidence B)"|
|"2. After AVR with Starr-Edwards valves or mechanical disc valves (other than Medtronic Hall prostheses), in patients with no risk factors,* warfarin is indicated to achieve an INR of 2.5 to 3.5. (Level of Evidence B)"|
|"3. After AVR or MV replacement with a bioprosthesis and no risk factors,* aspirin is indicated at 75 to 100 mg per day. (Level of Evidence C)"|
|"4. After AVR with a bioprosthesis and risk factors,* warfarin is indicated to achieve an INR of 2.0 to 3.0. (Level of Evidence C)"|
|"5. For those patients who are unable to take warfarin after MV replacement or AVR, aspirin is indicated in a dose of 75 to 325 mg per day. (Level of Evidence B)"|
|"1. During the first 3 months after AVR with a mechanical prosthesis, it is reasonable to give warfarin to achieve an INR of 2.5 to 3.5. (Level of Evidence C)"|
|"2. During the first 3 months after AVR or MV replacement with a bioprosthesis, in patients with no risk factors,* it is reasonable to give warfarin to achieve an INR of 2.0 to 3.0. (Level of Evidence C)"|
|“||* Risk factors include atrial fibrillation, previous thromboembolism, LV dysfunction, and hypercoagulable condition.||”|
Intraoperative Assessment (DO NOT EDIT) 
|"1. Intraoperative transesophageal echocardiography is recommended for valve replacement surgery with a stentless xenograft, homograft, or autograft valve. (Level of Evidence B)"|
|"1. Intraoperative transesophageal echocardiography is reasonable for all patients undergoing cardiac valve surgery. (Level of Evidence C)"|
Follow-Up Visits in Patients With Complications (DO NOT EDIT) 
|"1. Patients with LV systolic dysfunction after valve surgery should receive standard medical therapy for systolic heart failure. This therapy should be continued even if there is improvement of LV dysfunction. (Level of evidence B)"|
Treatment of Coronary Artery Disease (DO NOT EDIT) 
|"1. Patients undergoing AVR with significant stenoses (greater than or equal to 70% reduction in luminal diameter) in major coronary arteries should be treated with bypass grafting. (Level of evidence: C)"|
|"1. In patients undergoing AVR and coronary bypass grafting, use of the left internal thoracic artery is reasonable for bypass of stenoses of the left anterior descending coronary artery greater than or equal to 50% to 70%. (Level of evidence C)"|
|"2. For patients undergoing AVR with moderate stenosis (50% to 70% reduction in luminal diameter), it is reasonable to perform coronary bypass grafting in major coronary arteries. (Level of evidence C)"|
Patients Undergoing Coronary Artery Bypass Surgery (DO NOT EDIT) 
|"1. AVR is indicated in patients undergoing CABG who have severe AS who meet the criteria for valve replacement. (Level of evidence: C)"|
|"1. AVR is reasonable in patients undergoing CABG who have moderate AS (mean gradient 30 to 50 mm Hg or Doppler velocity 3 to 4 m per second). (Level of evidence B)"|
|"1. AVR may be considered in patients undergoing CABG who have mild AS (mean gradient less than 30 mm Hg or Doppler velocity less than 3 m per second) when there is evidence, such as moderate-severe valve calcification, that progression may be rapid. (Level of evidence C)"|
- 2008 Focused Update Incorporated Into the ACC/AHA 2006 Guidelines for the Management of Patients With Valvular Heart Disease 
- ↑ 1.0 1.1 1.2 1.3 Bonow RO, Carabello BA, Chatterjee K; et al. (2008). "2008 Focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 1998 Guidelines for the Management of Patients With Valvular Heart Disease): endorsed by the Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons". Circulation. 118 (15): e523–661. doi:10.1161/CIRCULATIONAHA.108.190748. PMID 18820172. Unknown parameter
- ↑ 2.0 2.1 2.2 Bonow RO, Carabello BA, Kanu C; et al. (2006). "ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (writing committee to revise the 1998 Guidelines for the Management of Patients With Valvular Heart Disease): developed in collaboration with the Society of Cardiovascular Anesthesiologists: endorsed by the Society for Cardiovascular Angiography and Interventions and the Society of Thoracic Surgeons". Circulation. 114 (5): e84–231. doi:10.1161/CIRCULATIONAHA.106.176857. PMID 16880336. Unknown parameter
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