Don't forget about mechanical valves!!!

Current evidence for prosthesis selection: What can we really say?

Mechanical heart valves require anticoagulation to prevent valve-associated thrombosis and thromboembolic stroke. Oral vitamin K antagonists such as warfarin are prescribed universally; however, oral agents do not act immediately and usually require at least 5 days to achieve a therapeutic effect. Article p 564 Measurement of the prothrombin time, which is standardized by reporting the result as the international normalized ratio (INR), assesses the anticoagulant effect of warfarin. For most mechanical heart valves, the target INR ranges between 2.0 and 3.5. In the postoperative cardiac surgical setting, patients are usually started on low doses of warfarin because they tend to have impaired hepatic metabolism and suboptimal nutritional status. Even with low initial doses of warfarin, mechanical heart valve replacement patients are susceptible to excessively high INRs.1 This known exaggerated initial response to warfarin after heart valve replacement can lead to the habitual prescription of such low warfarin doses that warfarin as monotherapy may not achieve a stable and therapeutic INR for weeks after its initiation. To minimize the delay in achieving therapeutic anticoagulation, a “bridging” anticoagulant is prescribed. The “bridge” is administered parenterally, thereby providing an immediate anticoagulant effect. Traditionally, the “bridging” agent has been unfractionated heparin (UFH). More recently, physicians tend to select low-molecular-weight heparin (LMWH), even though few studies exist to validate the efficacy and safety of either LMWH or UFH in this setting. The rationale for shunning UFH has been to avoid the known perils and inconveniences of its use as a continuous peripheral intravenous infusion. UFH is rarely administered in an immediately therapeutic dose because of fear of precipitating bleeding complications. Especially in postoperative mechanical valve replacement patients, there is reluctance to follow the high dosing requirements for initial bolus and infusion regimens published in standardized nomograms. Instead, UFH is usually started in cautious small …

Invited Commentary

Commentary: Tissue is the issue—Bioprosthetic versus mechanical valves in dialysis-dependent patients

The following are highlights from the new series, Circulation: Cardiovascular Quality and Outcomes Topic Reviews. This series will summarize the most important manuscripts, as selected by the Editor, which have been published in the Circulation portfolio. The objective of this new series is to provide our readership with a timely, comprehensive selection of important papers that are relevant to the quality and outcomes as well as general cardiology audience. The studies included in this article represent the most significant research in the area of valvular heart disease. ( Circ Cardiovasc Quality and Outcomes . 2012;5:-e103.) In recent years, no field of clinical cardiology has experienced a great influx of transformational therapeutic options as has the area of valvular heart disease. Treatment of severe aortic stenosis (AS) has been revolutionized by transcatheter aortic valve replacement (TAVR), which has been shown to improve life expectancy and functional outcomes in patients with inoperable AS1,2 and to have short-term outcomes comparable to surgical aortic valve replacement (AVR) in patients at high perioperative risk.3,4 Analogously, mitral valve disease has been amenable to percutaneous valve replacement,5,6 as well as clipping procedures7 that can substantively reduce severe mitral regurgitation (MR) and improve functional outcomes. Even right-sided heart disease involving valves in pulmonary8,9 and tricuspid10 positions has been treated successfully with endovascular techniques. Yet, even with this growing focus on percutaneous valvular interventions, open surgical techniques remain the dominant treatment strategies and standard of care for most advanced lesions. Surgical valve repair and replacement account for 10% to 20% of all cardiac surgical procedures,11–13 approximately two thirds of which are for AS.11–13 For patients undergoing surgery, there remains considerable debate about risk stratification,14 intraoperative technique,15 and postoperative …

Thromboembolism and bleeding during therapeutic anticoagulation are the major chronic risks for patients after mechanical prosthetic heart valve replacement. Prophylaxis for thromboembolism based on pathogenesis and risk and the involvement of both fibrin and platelets has led to permanent long-term oral anticoagulant therapy for consistent protection.1 2 3 The incidence of thromboembolic events is related to the type of valve and its location; the incidence after aortic valve replacement is lower than after mitral valve replacement.2 3 The peak incidence of thromboembolism is during the first 3 months after surgery, probably reflecting the lack of endothelialization of the newly implanted prosthetic materials and delay in achieving therapeutic anticoagulation in the early days after operation.4 5 The Dacron sewing ring is common to all prosthetic heart valves and forms a substrate for platelet deposition as soon as blood flows across the valve.2 Current recommendations are levels of oral anticoagulation that prolong the prothrombin time ratio to an international normalized ratio (INR) of 2.5 to 3.5 for tilting-disk and bileaflet valves and probably for caged-ball valves.3 The study reported in this issue of Circulation by Acar et al and the AREVA Group6 is well designed, well conducted, and focused on lower-risk patients. It addresses the optimal target level for anticoagulation. They compared a target INR of 2.0 to 3.0 with 3.0 to 4.5 in a randomized trial after a single mechanical prosthetic valve replacement with either of two bileaflet mechanical prostheses (St Jude valve in 81% and Omnicarbon valve in 19% of the 433 patients) placed in …

Prosthesis-Patient Mismatch After Aortic Valve Replacement: Impact of Age and Body Size on Late Survival

Aortic homografts: Unrealized expectations and hard reoperations at the end

Commentary: Greater risk of infective endocarditis after biologic valve replacement: A word of caution before expanding the indications to younger patients

Bioprosthetic Valve Thrombosis while on a Novel Oral Anticoagulant for Atrial Fibrillation

Mechanical valves and bioprosthetic heart valves are widely used for aortic valve replacement (AVR). Mechanical valves are associated with risk of bleeding because of oral anticoagulation, while the durability and structural valve deterioration (SVD) represent the main limitation of the bioprosthetic heart valves. The implantation of bioprosthetic heart valves is increasing precipitously due aging population, and the widespread use of transcatheter aortic valve replacement (TAVR). TAVR has become the standard treatment for intermediate or high surgical risk patients and a reasonable alternative to surgery for low risk patients with symptomatic severe aortic stenosis. Moreover, TAVR is increasingly being used for younger and lower-risk patients with longer life expectancy; therefore it is important to ensure the valve durability for long-term transcatheter aortic valves. Although the results of mid-term durability of the transcatheter heart valves are encouraging, their long-term durability remains largely unknown. This review summarises the definitions, mechanisms, risk factors and assessment of SVD; overviews available data on surgical bioprosthetic and transcatheter heart valves durability.

Self-Expanding Versus Balloon-Expandable Valve: Are We at the Cusp of Delivering a Perfect Transcatheter Aortic Valve?

Failed bioprosthetic valve approaches: Transcatheter aortic valve replacement approach

Choice of prosthetic heart valve for adult patients

Antithrombotic Therapy in Patients With Mechanical and Biological Prosthetic Heart Valves