『Prosthetic Heart Valve Selection and Clinical Management Guide for the Hospitalist』のカバーアート

Prosthetic Heart Valve Selection and Clinical Management Guide for the Hospitalist

Prosthetic Heart Valve Selection and Clinical Management Guide for the Hospitalist

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概要

 In this episode of Hospital Medicine Unplugged, we sprint through prosthetic heart valves—how to choose between mechanical and bioprosthetic valves, manage anticoagulation safely, recognize complications, and navigate the expanding role of transcatheter valve replacement. We begin with the two major categories of prosthetic valves: mechanical valves and bioprosthetic (tissue) valves. Mechanical valves are constructed from durable materials such as pyrolytic carbon and are designed to last decades, but their thrombogenic surface requires lifelong anticoagulation with a vitamin K antagonist. Anticoagulation targets depend on valve position and risk factors. • Mechanical aortic valve: target INR 2.5 • Mechanical mitral valve or high-risk aortic valve: target INR 3.0 In most patients, low-dose aspirin (75–100 mg daily) is added to vitamin K antagonist therapy to further reduce thromboembolic risk. Bioprosthetic valves, in contrast, are made from porcine valves or bovine pericardium. These valves are less thrombogenic, which allows for short-term anticoagulation (typically 3–6 months) after implantation followed by lifelong antiplatelet therapy with aspirin. The trade-off is durability—structural valve degeneration (SVD) eventually occurs due to calcification, fibrosis, or leaflet tearing. Choosing between valve types requires balancing durability versus anticoagulation risk. Mechanical valves generally offer better long-term durability, while bioprosthetic valves avoid lifelong anticoagulation but may require future reoperation. Age is one of the most important factors in valve selection. Evidence from large observational studies demonstrates that mechanical valves provide survival advantages in younger patients, particularly: • Aortic valve replacement: survival benefit up to about age 55 • Mitral valve replacement: survival benefit up to about age 70 Current ACC/AHA guidelines generally recommend: • Mechanical valves: younger patients (<50 years for aortic position, <65 years for mitral) • Bioprosthetic valves: older patients or those with contraindications to long-term anticoagulation The treatment landscape has changed dramatically with the development of transcatheter aortic valve replacement (TAVR). Initially reserved for patients with prohibitive surgical risk, TAVR is now widely used across risk groups. Landmark trials such as PARTNER 3 demonstrated that in low-risk patients with severe aortic stenosis, TAVR produced outcomes comparable to surgical valve replacement at five years. TAVR offers advantages including lower rates of atrial fibrillation and bleeding, though it carries higher risks of paravalvular regurgitation and pacemaker implantation. Guidelines now recommend: • TAVR as a Class I option for patients who are inoperable or high surgical risk • Either TAVR or surgical replacement for patients aged 65–80 years, depending on anatomy and patient factors Anticoagulation management remains one of the most critical aspects of prosthetic valve care. Direct oral anticoagulants (DOACs are contraindicated in mechanical valves). The RE-ALIGN trial showed increased thromboembolic and bleeding complications with dabigatran compared with warfarin, leading to early termination of the study. More recently, the PROACT Xa trial evaluating apixaban in patients with On-X mechanical valves also demonstrated excess thromboembolic events. For bioprosthetic valves, however, DOACs may be used in patients who develop atrial fibrillation, although long-term data remain limited. Despite technological advances, prosthetic valves carry important complications. One of the most serious is prosthetic valve endocarditis (PVE), which is associated with high mortality. Management requires prolonged intravenous antibiotics, typically for at least six weeks, and surgery may be required for heart failure, uncontrolled infection, or large vegetations. Another major complication is prosthetic valve thrombosis, particularly with mechanical valves. Management depends on clinical severity and thrombus size. Options include urgent surgery or low-dose, slow-infusion fibrinolysis, with modern thrombolytic protocols achieving over 90% success rates and low complication rates. A subtler but clinically important issue is prosthesis–patient mismatch (PPM). This occurs when the effective orifice area of the prosthetic valve is too small relative to the patient’s body surface area, creating persistent obstruction despite valve replacement. Severe PPM is defined as indexed effective orifice area <0.65 cm²/m² and is associated with higher mortality, reduced left ventricular mass regression, and worse heart failure outcomes. Certain populations require special consideration. Pregnancy with mechanical valves carries substantial maternal and fetal risk due to the competing challenges of anticoagulation and thrombosis prevention. Warfarin provides the most reliable valve protection but carries risk of embryopathy ...
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