Ann Thorac Surg 1997;64:257-258
© 1997 The Society of Thoracic Surgeons
Invited Commentary
Invited Commentary
Scott M. Bradley, MD
Division of Cardiothoracic Surgery, Medical University of South Carolina, 171 Ashley Avenue, Charleston, SC 29425-1095
See also page 255.
This case report by Burger and associates raises two interesting and related questions. The first is whether there is an adequate anticlotting regimen for mechanical valves in the pulmonary position. Burger and associates switched their patient from aspirin to warfarin and suggest that warfarin will provide more effective anticlotting prophylaxis. Extrapolation of the data available in adults with left-sided mechanical valves, where warfarin is more effective than antiplatelet agents, makes it tempting to conclude Burger and associates are correct. However, because the total number of patients with mechanical pulmonary valves is small, there is too little information available to make any meaningful comparison of warfarin and antiplatelet agents in this setting. The sum of the information available in case reports and small case series does indicate that the rate of mechanical valve thrombosis is far higher in the pulmonary (and probably tricuspid) position than in the aortic or mitral position. As discussed by Burger and associates, thrombosis has occurred in spite of treatment with antiplatelet agents, warfarin, or both. It therefore appears that there may be no anticlotting regimen that can reduce mechanical pulmonary valve thrombosis to the levels achieved on the left side of the circulation. High thrombosis rates, along with the availability of other options (homografts, bioprosthetic valves, valve excision without replacement), have led most to abandon the use of mechanical valves in the pulmonary position.
The second question is whether mechanical valve thrombosis, in general and specifically in the pulmonary position, should be treated by thrombolysis or operation. Traditional treatment for valve thrombosis has been valve replacement. However, the risk of reoperation can be high, particularly in patients with congestive heart failure preoperatively. Thrombolysis has proved to be an effective alternative in many cases of thrombosis, but has its own risks and limitations. These include bleeding, embolization, and rethrombosis. Moreover, thrombolysis fails in 15% to 30% of cases, usually due to obstruction of the valve from pannus, rather than thrombus. Thrombolysis also requires time to work, making it unsuitable for use in hemodynamically unstable patients and risking deterioration in marginally stable patients. The mortality of thrombolysis and operation may not differ significantly: patients in class III or IV heart failure are at high risk with either approach. The choice between thrombolysis and operation thus needs to be made by weighing the risks and benefits of the two approaches in each particular patient.
In this case of mechanical pulmonary valve thrombosis, an argument can be made for proceeding directly with operation. Although thrombolysis was successful, it is a short-term solution. The patient is subsequently subjected to the risks and lifestyle limitations of anticoagulation with warfarin, as well as to an ongoing risk of rethrombosis despite adequate anticoagulation. On the other hand, surgical risk in this setting is relatively low. Repeat sternotomy for revision or replacement of a right ventricle-to-pulmonary artery connection is now commonly performed with operative mortalities less than 5%. Femoral cannulation to decrease the risk of sternal reentry, although not always feasible in children, would have been an option in this patient. In the absence of intracardiac shunts, pulmonary valve operations can be carried out without aortic cross-clamping, avoiding cardiac ischemia and reperfusion injury. One surgical option is replacement of the mechanical valve with either a homograft or bioprosthesis. Another option, given large central and branch pulmonary arteries and low pulmonary vascular resistance, is removal of the mechanical valve without replacement. Any of these choices would make anticoagulation unnecessary, and would be expected to give a good long-term outcome. Although thrombolysis has the apparent appeal of avoiding reoperation and had good short-term success in this case, the best long-term solution for mechanical pulmonary valve thrombosis may be valve replacement with a homograft or bioprosthesis, or valve removal without replacement.
Related Article
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Successful Thrombolysis After Prosthetic Pulmonary Valve Obstruction Under Aspirin Monotherapy
- Wolfram Burger, Georg-Dieter Kneissl, Andreas Hartmann, Rupert Bauersachs, Volker Döring, Ulrike Spengler, Guntram Neumann, and Karl Wolfgang Rothe
Ann. Thorac. Surg. 1997 64: 255-257.
[Abstract]
[Full Text]
