INVITED COMMENTARY

Abstract

The search for the ideal pulmonary valve substitute continues to challenge surgeons, and the choice of prosthesis remains an important decision in clinical practice. Although bioprostheses and homografts are most commonly used for pulmonary valve replacement (PVR), limited durability necessitates reoperation for most patients. Late results of mechanical valves in the pulmonary position are conflicting. Indeed, in the few available reports, mechanical valve thrombosis occurred in 25% to 56% of patients [1Ilbawi M.N. Lockhart C.G. Idriss F.S. et al.Experience with St. Jude Medical valve prosthesis in children: a word of caution regarding right-sided placement.J Thorac Cardiovasc Surg. 1987; 93: 73-79PubMed Google Scholar, 2Ilbawi M.N. Lockhart C.G. Idriss F.S. et al.Valve replacement in children: guidelines for selection of prosthesis and timing of surgical intervention.Ann Thorac Surg. 1987; 44: 398-403Abstract Full Text PDF PubMed Scopus (45) Google Scholar, 3Miyamura H. Kanazawa H. Hayashi J. et al.Thrombosed St. Jude valve prosthesis on the right side of the heart in patients with Tetralogy of Fallot.J Thorac Cardiovasc Surg. 1987; 94: 148-150PubMed Google Scholar]. However, it is important to note that inadequate anticoagulation or no anticoagulation was documented in many patients who had thrombotic complications develop in many of these retrospective reviews. Haas and colleagues report their results of 14 patients (average age 24.8 yr) who after several prior operations underwent PVR with a mechanical valved conduit. There were no valve-related complications during short-term follow-up (mean age, 2.9 yr), and all patients were anticoagulated with warfarin with a target international normalized ratio of 3.0 to 4.5. The important point of this report in contrast to prior studies is the absence of valve thrombosis. Their technique of valve implantation employs a Dacron conduit, and a limitation of this report is the lack of truly late results with the use of a conduit as a part of their reconstruction. In most older patients, an adequate sized pulmonary prosthesis can be inserted with no prosthetic material or by using only an anterior patch of pericardium to augment the valve annulus. The potential disadvantage of preferential use of valved conduits is late development of obstructive intimal fibrocalcific peels within the right-sided Dacron conduits [4Agarwal K.C. Edwards W.D. Feldt R.H. et al.Clinicopathological correlates of obstructed right-sided porcine-valved extracardiac conduits.J Thorac Cardiovasc Surg. 1981; 81: 591-601PubMed Google Scholar]. We have utilized a mechanical prosthesis in 17 adult patients who required PVR (0.7% of all PVR performed at our clinic), and in late follow-up of the first 10 patients (mean follow-up, 8.3 yr; maximum follow-up, 25 yr) there was no instance of valve thrombosis. Our implantation technique differs in that we prefer to perform an isolated PVR with patch reconstruction of the previous conduit bed or native pulmonary artery using autologous or bovine pericardium. Currently we consider mechanical PVR for patients who have had multiple prior operations, or who are on warfarin for another reason. In general, we have not advised mechanical PVR in children, but would give consideration to mechanical PVR if anticoagulation is required for a mechanical prosthesis on the left side of the heart. In addition to adequate anticoagulation with warfarin (target international normalized ratio, 3.0 to 4.0), antiplatelet therapy should be considered [5Salem D.N. Stein P.D. Al-Ahmad A. et al.Antithrombotic therapy in valvular heart disease – native and prosthetic: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy.Chest. 2004; 126 (457S–82S)PubMed Google Scholar]. These measures will not prevent valve thrombosis in all patients, and regular surveillance with Doppler echocardiography is necessary. If valve thrombosis is detected, initial treatment by optimizing anticoagulation with or without thrombolysis may be sufficient to restore valve function and avoid reoperation. Thrombolytic therapy of tricuspid and pulmonary mechanical valves would be expected to have fewer serious complications compared with prostheses in the aortic and mitral positions [6Lengyel M. Fuster V. Keltai M. et al.Guidelines for management of left-sided prosthetic valve thrombosis: a role for thrombolytic therapy Consensus Conference on Prosthetic Valve Thrombosis.J Am Coll Cardiol. 1998; 32: 550-551PubMed Google Scholar, 7Bolz D. Kuhne T. Jivraj R. et al.Thrombolysis of prosthetic tricuspid valve thrombosis with human recombinant tissue plasminogen activator in an adolescent.Pediatr Cardiol. 2000; 21: 397-400Crossref PubMed Scopus (11) Google Scholar].