Valve Repair and Replacement Procedures
The repair, rather than replacement, of a cardiac valve is referred to as valvuloplasty. The type of valvuloplasty depends on the cause and type of valve dysfunction. Repair may be made to the commissures between the leaflets in a procedure known as com-missurotomy, to the annulus of the valve by annuloplasty, to theleaflets, or to the chordae by chordoplasty.
Most valvuloplasty procedures require general anesthesia and often require cardiopulmonary bypass. Some procedures, how-ever, can be performed in the cardiac catheterization laboratory; these procedures do not always require general anesthesia or cardio-pulmonary bypass. Percutaneous partial cardiopulmonary bypass is used in some cardiac catheterization laboratories. The cardio-pulmonary bypass is achieved by inserting a large catheter (ie, cannula) into two peripheral blood vessels, usually a femoral vein and an artery. Blood is diverted from the body through the venous catheter to the cardiopulmonary bypass machine and returned to the patient through the arterial catheter.
The patient is usually managed in a critical care unit for the first 24 to 72 hours after surgery. Care focuses on hemodynamic stabilization and recovery from anesthesia. Vital signs are assessed every 5 to 15 minutes and as needed until the patient recovers from anesthesia or sedation and then every 2 to 4 hours and as needed. Intravenous medications to increase or decrease blood pressure and to treat dysrhythmias or altered heart rates are ad-ministered, and their effects are monitored. The intravenous medications are gradually decreased until they are no longer required or the patient takes needed medication by another route (eg, oral, topical). Patient assessments are conducted every 1 to 4 hours and as needed, with particular attention to neurologic, respiratory, and cardiovascular assessments.
After the patient has recovered from anesthesia and sedation, is hemodynamically stable without intravenous medications, and assessments are stable, the patient is usually transferred to a telemetry or surgical unit for continued postsurgical care and teaching. The nurse provides wound care and patient teaching regarding diet, activity, medications, and self-care. Patients are discharged from the hospital in 1 to 7 days. In general, valves that have undergone valvuloplasty function longer than replace-ment valves, and the patients do not require continuous anti-coagulation.
The most common valvuloplasty procedure is commissurotomy. Each valve has leaflets; the site where the leaflets meet is called the commissure. The leaflets may adhere to one another and close thecommissure (ie, stenosis). Less commonly, the leaflets fuse in such a way that, in addition to stenosis, the leaflets are also pre-vented from closing completely, resulting in a backward flow of blood (ie, regurgitation). A commissurotomy is the procedure performed to separate the fused leaflets.
Closed commissurotomies do not require cardiopulmonary by-pass. The valve is not directly visualized. The patient receives a general anesthetic, a midsternal incision is made, a small hole is cut into the heart, and the surgeon’s finger or a dilator is used to break open the commissure. This type of commissurotomy has been performed for mitral, aortic, tricuspid, and pulmonary valve disease.
Balloon valvuloplasty (Fig. 29-3) is anothertype of closed commissurotomy beneficial for mitral valve stenosis in younger patients, for aortic valve stenosis in elderly patients, and for patients with complex medical conditions that place them at high risk for the complications of more extensive surgical proce-dures. Most commonly used for mitral and aortic valve stenosis, balloon valvuloplasty also has been used for tricuspid and pulmonic valve stenosis. The procedure is performed in the cardiac catheter-ization laboratory, and the patient may receive a local anesthetic. Patients remain in the hospital 24 to 48 hours after the procedure.
Mitral valvuloplasty is contraindicated for patients with left atrial or ventricular thrombus, severe aortic root dilation, signif-icant mitral valve regurgitation, thoracolumbar scoliosis, rotation of the great vessels, and other cardiac conditions that require open heart surgery.
Mitral balloon valvuloplasty involves advancing one or two catheters into the right atrium, through the atrial septum into the left atrium, across the mitral valve into the left ventricle, and out into the aorta. A guide wire is placed through each catheter, and the original catheter is removed. A large balloon catheter is then placed over the guide wire and positioned with the balloon across the mitral valve. The balloon is then inflated with a dilute angio-graphic solution. When two balloons are used, they are inflated simultaneously. The advantage of two balloons is that they are each smaller than the one large balloon often used, making smaller atrial septal defects. As the balloons are inflated, they usually do not completely occlude the mitral valve, thereby permitting some forward flow of blood during the inflation period.
All patients have some degree of mitral regurgitation after the procedure. Other possible complications include bleeding from the catheter insertion sites, emboli resulting in complications such as strokes, and rarely, left-to-right atrial shunts through an atrial septal defect caused by the procedure.
Aortic balloon valvuloplasty also may be performed by passing the balloon or balloons through the atrial septum, but it is per-formed more commonly by introducing a catheter through the aorta, across the aortic valve, and into the left ventricle. The one-balloon or the two-balloon technique can be used for treating aortic stenosis. The aortic procedure is not as effective as the pro-cedure for the mitral valve, and the rate of restenosis is nearly 50% in the first 12 to 15 months after the procedure (Braunwald et al., 2001). Possible complications include aortic regurgitation, emboli, ventricular perforation, rupture of the aortic valve annulus, ven-tricular dysrhythmias, mitral valve damage, and bleeding from the catheter insertion sites.
Open commissurotomies are performed with direct visualization of the valve. The patient is under general anesthesia, and a me-dian sternotomy or left thoracic incision is made. Cardio-pulmonary bypass is initiated, and an incision is made into the heart. A finger, scalpel, balloon, or dilator may be used to open the commissures. An added advantage of direct visualization of the valve is that thrombus may be identified and removed, calci-fications can be seen, and if the valve has chordae or papillary muscles, they may be surgically repaired.
Annuloplasty is the repair of the valve annulus (ie, junction ofthe valve leaflets and the muscular heart wall). General anesthesia and cardiopulmonary bypass are required for all annuloplasties. The procedure narrows the diameter of the valve’s orifice and is useful for the treatment of valvular regurgitation.
There are two annuloplasty techniques. One technique uses an annuloplasty ring (Fig. 29-4). The leaflets of the valve are sutured to a ring, creating an annulus of the desired size. When the ring is in place, the tension created by the moving blood and contracting heart is borne by the ring rather than by the valve or a suture line, and progressive regurgitation is prevented by the repair. The other technique involves tacking the valve leaflets to the atrium with su-tures or taking tucks to tighten the annulus. Because the valve’s leaflets and the suture lines are subjected to the direct forces of the blood and heart muscle movement, the repair may degenerate more quickly than with the annuloplasty ring technique.
Damage to cardiac valve leaflets may result from stretching, short-ening, or tearing. Leaflet repair for elongated, ballooning, or other excess tissue leaflets is removal of the extra tissue. The elongated tissue may be folded over onto itself (ie, tucked) and sutured (ie, leaflet plication). A wedge of tissue may be cut from the middle of the leaflet and the gap sutured closed (ie., leaflet re-section) (Fig. 29-5). Short leaflets are most often repaired by chordoplasty. After the short chordae are released, the leaflets often unfurl and can resume their normal function of closing the valve during systole. A piece of pericardium may also be sutured to extend the leaflet. A pericardial patch may be used to repair holes in the leaflets.
Chordoplasty is the repair of the chordae tendineae. The mitralvalve is involved with chordoplasty (because it has the chordae tendineae); seldom is chordoplasty required for the tricuspid valve.
Regurgitation may be caused by stretched, torn, or shortened chordae tendineae. Stretched chordae tendineae can be shortened, torn ones can be reattached to the leaflet, and shortened ones can be elongated. Regurgitation may also be caused by stretched papillary muscles, which can be shortened.