Prosthetic heart valves

Choice of valve

• Depends on age, life expectancy, lifestyle, bleeding and thromboembolic risks, possibility of pregnancy, and patient preference
• Tissue valves
  • • Do not require life long anticoagulation
    • Anticoagulate for first 3 months (especially if MVR or TVR, less important for AVR)
    • Then long-term aspirin
• Tissue valve usually best for
  • • Older patients / short life expectancy
    • High risk of bleeding / anticoagulation contraindicated
    • Women contemplating pregnancy
    • If patient unlikely to have therapeutic INR
• Mechanical valves usually best for
  • • Younger patients (aged <60 in aortic, <65 in mitral valves)
    • Patients with another pre-existing indication for anticoagulation
• Usually do a coronary angiogram and cardiac MRI pre-op

---

Anticoagulation and metal valves

• For most modern mechanical valves target INR is 2-3
• For older valves, target is 2.5-3.5
• If additional pro-thrombotic risk factors (including EF <35%), add 0.5 to target INR
• Risk of cardioembolic or valve thrombosis without anticoagulation is around 12% per year (for the latest valves, higher for older ones)
• Education on anticoagulation is key – explain risks, monitoring, drug/food interactions, the modifiable and non-modifiable influences on INR
• Prescribe PPI with warfarin (reduces risk of bleeding by 40%)
• Aspirin can be used safely if needed with VKA if bleeding risk not high, but additional anti-platelets significantly increase risk, and use needs careful consideration if indicated
• Don’t usually hold warfarin for minor procedures on skin/eyes (including cataract surgery), dental extractions, PPM implantation, angiography or endoscopy
• For major surgery – usually hold warfarin at least 4 days prior, aim for INR <1.5 and resume 24 hours post-op. Often bridge with heparin as soon as INR subtherapeutic
• Might not need to bridge if patient has a new generation aortic valve replacement, and no other thromboembolic risk factors

---

Follow up

• Bridge with heparin post-op and start warfarin within 24 hours after metal heart valve implantation if safe
• Heparin can be stopped when the INR therapeutic for 2 consecutive days
• Serial echos – check transprosthetic gradients, effective valve area, leaflet motion and morphology (within 3 months after tissue valve implantation, again at 1 year, and annually thereafter, or sooner if new symptoms)
• Do a TOE for suspected prosthetic valve dysfunction or endocarditis

---

Complications

• Aortic tissue valve deterioration
  • • Suggested by increase in mean valvular gradient of >10mmHg and resulting in mean gradient >20mmHg (severe = increase of >20mmHg and mean of >30mmHg)
    • Or decrease in effective orifice area (>0.3cm2, or >25%) or decrease in DVI (>0.1)
    • Or moderate or severe AR
• Mitral valve deterioration
  • • Suggested by decrease in DVI >0.4 or 20% (resulting in DVI >2.2), or decrease in EOL >0.5cm2, or >25%, resulting in EOA <1.5cm2
    • Or moderate or severe MR
    • Valve in valve implantation is sometimes an option instead of redo open surgery. It comes with a risk of LVOT obstruction however
• Prosthetic valve thrombosis
  • • Mostly occurs in metal valves, but occasional tissue ones
    • Higher risk in MVRs (probably 5x risk in AVRs)
    • Higher risk in the old ball and cage valves
    • INR 3-4 is the spot in which there is a low rate of ischaemic and haemorrhagic strokes
    • A spectrum – important to differentiate:
      • • Can be non-obstructive and asymptomatic (incidental on echo), with hypo-attenuated leaflet thickening
        • Can be obstructive leading to heart failure, and/or thromboembolism. There will be elevated gradients
    • If echo uncertain – proceed to TOE and /or cardiac CT
    • Differential is pannus (scar-like tissue growing around the valve) and degeneration
    • Bioprosthetic valves have a risk of thrombosis in the first 180 days (usually we anticoagulant for just the first 3 months, unless another indication to do so like AF)
    • If no click with mechanical valve – think thrombus occlusion
    • Management of valve thrombosis
      • • If bioprosthetic or TAVI – start warfarin (usually long term), repeat echo in 3 months
        • If mechanical – give heparin if subtherapeutic INR, if not, increase target INR (and sometimes add aspirin)
        • If obstructive consider urgent thrombolysis or surgery
        • Surgery favoured if large thrombus >10mm, recurrent event, possible pannus, cardiogenic shock, thromboembolic event, contraindications to thrombolysis
• Paravalvular leak
  • • Diagnose by TOE
    • Can sometimes occur due to IE
    • Can cause haemolysis, with elevated LDH and low haptoglobin level, but rarely causes any symptoms (if it does, intervention required)
    • Treatment options are surgery, transcatheter PVL closure or medial therapy (iron, EPO, betablockers)
• Infective endocarditis
  • Antibiotic prophylaxis sometimes advised for patients with prosthetic valves undergoing surgery, including dental extractions and oral surgery