mechanical heart valve

Classification

• ball valve: Starr-Edwards
• tilting disc valve
  • Bjork-Shiley
  • St. Jude

Advantages

• good longevity of valve
• generally preferred for patients younger than 65 years of age

Disadvantages

• all mechanical valves have risk of thromboembolism
• hemolysis often occurs with mechanical valves, especially with perivalvular leakage (no thrombocytopenia)
• anticoagulation is required

Diagnostic procedures

• echocardiogram 2-3 months after surgery to establish baseline
• transesophageal echocardiogram (TEE)
  • if valve dysfunction is suspected
  • findings limited by acoustic shadowing & reverberations from prosthetic material
• routine monitoring with echocardiography not indicated

Complications

• mechanical valve thrombosis resulting in acute heart failure or embolism leading to embolic stroke or infarcts in other end-organs

Management

• anticoagulation (lifelong)
  • warfarin with target INR generally 2.5-3.5
    • except aortic valve replacement (AVR)
    • AVR: target INR=2.5-3.5 for 1st 3 months then, AVR: target INR=2-3; target INR=2.5
    • dabigatran associated with increased risk of thromboembolism & bleeding complications relative to warfarin
    • apixaban associated with more thromboembolic events than warfarin
  • aspirin 81 mg no longer routinely used with warfarin
    • decreases risk of stroke & may be indicated if indication for antiplatelet therapy
  • pregnancy
    • warfarin until week 6 if pre-conception daily dose is 5 mg or less, otherwise LMW heparin is preferred
    • week 6-12 increased fetal risk with warfarin
      • use LMW heparin or unfractionated heparin; LMW heparin must be adjusted to factor Xa activity
      • warfarin safest for mother; with lowest risk of thromboembolism for mother
      • ref suggests continuing warfarin until week 37
    • weeks 13-37
      • warfarin, LMW heparin or unfractionated heparin
      • warfarin safest for mother; with lowest risk of thromboembolism for mother
      • LMW heparin or unfractionated heparin safest for fetus
    • week 37 to delivery
      • stop warfarin, LMW heparin
      • start unfractionated heparin infusion
      • planned delivery
    • post-partum: restart warfarin when bleeding controlled
  • surgery
    • stop anticoagulation 5 days prior to surgery
    • allow INR to drop below 1.5
    • low-risk patients
      • aortic valve prosthesis*
      • no history of thromboembolism
      • sinus rhythm
      • ok to discontinue warfarin 3-5 days prior to surgery without heparin bridging
    • bridge with IV heparin for high risk patients;
      • start heparin when INR falls below 2.0
      • discontinue heparin 6 hours prior to surgery
      • restart heparin & warfarin 6-12 hours post-op
      • discontinue heparin when INR > 2
• antibiotic prophylaxis for bacterial endocarditis indicated
• surgery is indicated for mechanical valve thrombosis unless patient is hemodynamically stable & the clot burden is small

* includes 'contemporary' mechanical valves

Notes

• valve durability: tricuspid > aortic > mitral

More general terms

• prosthetic heart valve

More specific terms

• On-X aortic mechanical valve

Additional terms

• mechanical valve thrombosis; prosthetic valve thrombosis