Choice and Managment of Prosthetic Valves
Valve repair may be useful for tricuspid, mitral, and occasionally aortic regurgitation. Likewise, percutaneous or open valvulotomy may be indicated in mitral, pulmonary, and tricuspid stenosis. Nonetheless, the number of valve replacement procedures continues to increase as a result of the aging of the population. The choice of a mechanical device versus a bioprosthesis is often a difficult one, balancing the risk of chronic anticoagulation and thromboembolism (mechanical) versus the need for eventual reoperation (bioprosthesis).
In general, otherwise healthy patients below age 65 should receive mechanical valves unless anticoagulation is contraindicated, because their life expectancy is greater than the durability of tissue prostheses. Furthermore, deterioration of bioprostheses is accelerated in younger patients. In patients with a small left ventricular cavity or aortic annulus, mechanical disk valves have significant hemodynamic advantages. Finally, patients who will require anticoagulation in any case, such as those in atrial fibrillation, should receive mechanical valves. Bioprostheses are preferable in older patients with life expectancies less than 10 years and when anticoagulation is contraindicated.
However, hemodialysis patients should not receive tissue valves because they have a high failure rate. As noted previously, the Ross procedure offers another option in younger patients with aortic stenosis.
The identification of valve dysfunction may be difficult, but Doppler echocardiography, especially via the transesophageal approach, can identify regurgitation and stenosis in most cases. In patients with mechanical valves, careful anticoagulation is required with a target INR of 3.0-4.0. Anticoagulation should rarely be discontinued. For elective surgery, oral warfarin can be stopped 2-3 days preoperatively with heparin coverage until effective anticoagulation is resumed. Management of anticoagulation during pregnancy is difficult, since warfarin may be teratogenic in the first trimester and should be discontinued in advance of delivery. Some experts recommend substitution with low-molecular-weight heparin in the first trimester. In one controlled study, aspirin, 100 mg daily, in addition to warfarin, reduced emboli and the mortality rate.
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Revision date: June 11, 2011
Last revised: by Andrew G. Epstein, M.D.