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mechanical heart valve

Classification: 1) ball valve: Starr-Edwards 2) tilting disc valve a) Bjork-Shiley b) St. Jude Advantages: 1) good longevity of valve 2) generally preferred for patients younger than 65 years of age Disadvantages: 1) all mechanical valves have risk of thromboembolism 2) hemolysis often occurs with mechanical valves, especially with perivalvular leakage (no thrombocytopenia) 3) anticoagulation is required Special laboratory: - echocardiogram 2-3 months after surgery to establish baseline - transesophageal echocardiogram (TEE) a) if valve dysfunction is suspected b) findings limited by acoustic shadowing & reverberations from prosthetic material [2] - routine monitoring with echocardiography not indicated [2] Complications: - mechanical valve thrombosis resulting in acute heart failure or embolism leading to embolic stroke or infarcts in other end-organs Management: 1) anticoagulation (lifelong) a) warfarin with target INR generally 2.5-3.5 1] except aortic valve replacement (AVR) 2] AVR: target INR=2.5-3.5 for 1st 3 months then, AVR: target INR=2-3 [2]; target INR=2.5 [2] 3] dabigatran associated with increased risk of thromboembolism & bleeding complications relative to warfarin [6] 4] apixaban associated with more thromboembolic events than warfarin [8] b) aspirin 81 mg no longer routinely used with warfarin [2] - decreases risk of stroke & may be indicated if indication for antiplatelet therapy [2] c) pregnancy [2,5] 1] warfarin until week 6 if pre-conception daily dose is 5 mg or less, otherwise LMW heparin is preferred [2] 2] week 6-12 increased fetal risk with warfarin - use LMW heparin or unfractionated heparin; LMW heparin must be adjusted to factor Xa activity [2] - warfarin safest for mother [2]; with lowest risk of thromboembolism for mother [2] - ref [2] suggests continuing warfarin until week 37 3] weeks 13-37 a] warfarin, LMW heparin or unfractionated heparin b] warfarin safest for mother [2]; with lowest risk of thromboembolism for mother c] LMW heparin or unfractionated heparin safest for fetus 4] week 37 to delivery a] stop warfarin, LMW heparin b] start unfractionated heparin infusion c] planned delivery 5] post-partum: restart warfarin when bleeding controlled d) surgery 1] stop anticoagulation 5 days prior to surgery 2] allow INR to drop below 1.5 3] low-risk patients a] aortic valve prosthesis* b] no history of thromboembolism c] sinus rhythm [2] d] ok to discontinue warfarin 3-5 days prior to surgery without heparin bridging [2] 4] bridge with IV heparin for high risk patients; a] start heparin when INR falls below 2.0 [2] b] discontinue heparin 6 hours prior to surgery c] restart heparin & warfarin 6-12 hours post-op d] discontinue heparin when INR > 2 [2] 2) antibiotic prophylaxis for bacterial endocarditis indicated [2] 3) surgery is indicated for mechanical valve thrombosis unless patient is hemodynamically stable & the clot burden is small * includes 'contemporary' mechanical valves [2] Notes: - valve durability: tricuspid > aortic > mitral

Related

mechanical valve thrombosis; prosthetic valve thrombosis

Specific

On-X aortic mechanical valve

General

prosthetic heart valve

References

  1. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 56
  2. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 15, 16, 17, 18. American College of Physicians, Philadelphia 1998, 2006, 2009, 2012, 2015, 2018. - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  3. Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 668
  4. Shapira Y, Vaturi M, Sagie A. Hemolysis associated with prosthetic heart valves: a review. Cardiol Rev. 2009 May-Jun;17(3):121-4 PMID: 19384085
  5. Yinon Y, Siu SC, Warshafsky C et al Use of low molecular weight heparin in pregnant women with mechanical heart valves. Am J Cardiol. 2009 Nov 1;104(9):1259-63 PMID: 19840573
  6. Eikelboom JW et al. for the RE-ALIGN Investigators. Dabigatran versus warfarin in patients with mechanical heart valves. N Engl J Med. 2013 Sep 26;369(13):1206-14. PMID: 23991661 - Hylek EM. Dabigatran and mechanical heart valves - Not as easy as we hoped. N Engl J Med. 2013 Sep 26;369(13):1264-6. PMID: 23991659
  7. Turpie AG, Gent M, Laupacis A et al A comparison of aspirin with placebo in patients treated with warfarin after heart-valve replacement. N Engl J Med. 1993 Aug 19;329(8):524-9. PMID: 8336751 Free Article
  8. Wang TY et al. Apixaban or warfarin in patients with an On-X mechanical aortic valve. NEJM Evid 2023 May 6; [e-pub] PMID: 38320162 Clinical Trial. https://evidence.nejm.org/doi/10.1056/EVIDoa2300067