Aortic valve replacement
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| Aortic valve replacement | |
|---|---|
| Intervention | |
| ICD-9-CM | 35.21-35.22 |
Aortic valve replacement is a cardiac surgery procedure in which a patient's failing aortic valve is replaced with an alternate healthy 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 is open heart surgery.
A catheter-based approach (percutaneous aortic valve replacement or PAVR), approved in Europe and in clinical trials in the United States, eliminates the need for open heart surgery, but is associated with a higher risk of stroke.
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[edit] Types of heart valves
There are two basic types of artificial heart valve: mechanical valves and tissue valves.
[edit] Tissue valves
Tissue heart valves are usually made from animal tissue, 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 comparable to porcine and bovine 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 patient's own pulmonary valve. This procedure was first used in 1967 and is used primarily in children, as the procedure allows the patient's own pulmonary valve (now in the aortic position) to grow with the child.
[edit] Mechanical valves
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 present a one-surgery solution, there is an increased risk of blood clots forming with mechanical valves. As a result, mechanical valve recipients must take anticoagulant (blood thinning) drugs such as warfarin for the rest of their lives, making the patient more prone to bleeding.
Warfarin is the traditional drug used as an anticoagulant. There is a study underway into the use of Plavix instead of Warfarin, which could significantly simplify blood clotting control. This study is estimated to be completed in March 2015.[1]
[edit] Valve selection
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.
There is a promising new valve replacement procedure called a Trans-catheter Aortic Valve (TCAV). It is currently only available for high risk patients and still in the research stage. In the future it may be possible for the recipient of a prosthetic tissue valve to have a much less invasive surgery performed to insert a new valve once the replacement valve wears out. A new valve is compressed and positioned orthoscopically and then it is expanded within the first replacement valve forcing it open and allowing the TCAV to operate. The current expected life span of the TCAV is approximately 10–15 years. It is also expected that yet another TCAV can be implanted within the first TCAV. As technology advances the lifespan of the TCAV may be extended.[2]
[edit] Surgical Procedure
Aortic valve replacement is most frequently done through a median sternotomy, meaning the incision is made by cutting through the sternum. Once the pericardium has been opened, the patient is put on a cardiopulmonary bypass machine, also known as the heart-lung machine. This machine takes over the task of breathing for the patient and pumping their blood around while the surgeon replaces the heart valve.
Once the patient is on bypass, a cut is made in the aorta and a crossclamp applied. 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.
[edit] Hospital stay and recovery time
After aortic valve replacement, the patient will frequently stay in an intensive care unit for 12–36 hours. The patient is often able to go home after this, in about four days, unless complications arise. Common complications include heart block, which typically requires the permanent insertion of a cardiac pacemaker.
Recovery from aortic valve replacement will take about three months, if the patient is in good health. Patients are advised not to do any heavy lifting for 4–6 months after surgery, to avoid damage to the sternum (the breast bone).
[edit] Surgical outcome and risk of procedure
The risk of death or serious complications from aortic valve replacement is typically quoted as being between 1-3%, 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 ineligible for surgery because of elevated risks.
[edit] Percutaneous aortic valve replacement
Percutaneous aortic valve replacement implants the valves using a catheter, without open heart surgery. It is used in Europe in patients who are at high risk to undergo open heart surgery, but is in clinical trials in North America, at Cedars-Sinai Medical Center and elsewhere. The SAPIEN valve is made by Edwards Lifesciences. The Medtronic Corevalve device is another device used for this procedure
In high-risk patients with severe aortic stenosis, transcatheter and surgical procedures for aortic-valve replacement had similar rates of survival at 1 year, although there were important differences in risks associated with the procedure.[3] The transcatheter procedure was associated with a higher risk of stroke than the surgical replacement (5.5% vs. 2.4% after 30 days; 8.3% vs. 4.3% after 1 year).[4]
[edit] See also
http://en.wikipedia.org/wiki/Pericardial_heart_valves
[edit] References
- ^ Randomized On-X Anticoagulation Trial
- ^ Transcatheter Aortic Valve Implantation for Stenosed and Regurgitant Aortic Valve Bioprostheses, see Patient #3; Whitley Valve Surgery in the Cath Lab only refers to first time valve replacement, not insertion of a TCAV into a prosthetic valve.
- ^ Smith, Craig R.; et al. (June 2, 2011). "Transcatheter versus Surgical Aortic-Valve Replacement in High-Risk Patients". N Engl J Med 364: 2187–2198. doi:10.1056/NEJMoa1103510. PMID 21639811. http://www.nejm.org/doi/full/10.1056/NEJMoa1103510.
- ^ Schaff, Hartzell V. (June 2, 2011). "Transcatheter Aortic-Valve Implantation — At What Price?". N Engl J Med 364: 2256–2258. doi:10.1056/NEJMe1103978. PMID 21639812. http://www.nejm.org/doi/full/10.1056/NEJMe1103978.
