Prosthetic Valves

Introduction

  • Types:
    • Mechanical Valves
        • Ball-in-cage
        • Single tilting Disc
        • Bi-leaflet
      • Advantages:
        • Very durable (ideal for young patients)
      • Disadvantages:
        • Higher thrombotic risk
        • No transcatheter options (all surgical)
    • Bioprosthetic Valves
      • Made of pericardial/bovine/cadaver tissue
      • Advantages:
        • Low risk of thrombosis, many not require anticoagulation
        • Some can be inserted minimally invasive (i.e. Transcatheter – TAVR)
      • Disadvantages:
        • Earlier wear/degeneration (generally ~ 10y longevity)
    • Internists MUST appreciate types of mechanical valves to understand anticoagulation targets
    • Internists may not need to know difference in types of bioprosthetic valves.  

Mechanical Valve Types

Ball-in-CageSingle Tilting DiskBi-leaflet Tilting Disk New Generation Bi-leaflet  Tilting Disk
Starr-Edwards

Bjork-Shiley
Medtronic Hall
Lillehei-Kaster Valve

Medtronic bileaflet
St. Jude

On-X Valve
  • Largely obsolete
  • Very high thrombotic risk
  • Lower thrombotic risk due to fewer leaflets
  • Prone to early wear due to sliding components
  • Low risk of thrombosis (regurgitant washing jets)
  • OnX Valve
  • Very low risk of thrombosis
    (INR Target 1.5 in low risk patients)

Bioprosthetic Valves

Surgical ValvesTranscatheter Self-Expanding (TAVR)Transcatheter Balloon Expandable (TAVR)
  • Surgically implanted
  • Can be retrieved and repositioned
  • High risk of AV block
  • Single deployment (cannot retrieve)
  • lower risk of AV block

Complications of prosthetic valves

  • Paravalvular leak (regurgitation around the valve)
  • Valve stenosis (i.e. pannus ingrowth)
  • Patient prosthesis mismatch (i.e. valve is too small for patient’s size, leading to functional stenosis)
  • Valve thrombosis (can present with stroke)
  • Valve endocarditis

Anticoagulation / Thrombotic Risk

  • All prosthetic valves have a risk of thrombosis.

Mechanical Valves

  • Risk of thrombosis:
    • Mechanical
    • Mitral position (Tricuspid position – VERY high risk)
    • Other thrombotic risk factors (AF, low LVEF, prior embolism)
  • ALL patients with mechanical valves require LIFELONG anticoagulation with a vitamin K antagonist (Warfarin) (DOACs are contraindicated)
  • ASA 81mg daily for MOST patients with mechanical or bioprosthetic valves (unless contraindications exist)
INR TargetCases

3.0
+ ASA

Most cases
(esp mitral/tricuspid positions)
2.5

Need ALL Of:
– Bileaflet or Medtronic Hall single leaflet
– Aortic Position
– No other risk factors of thrombosis (see below)

1.5-2.0

+ ASA

(≥ 3mo
post-op)

Need ALL Of:
– OnX Valve
– Aortic Position
– No other risk factors of thrombosis (see below)

** INR target is 0.5 above and below single digit above

Risk Factors for Thrombosis
AHA/ACC Valve Guidelines 2020
  1. Atrial Fibrillation
  2. Reduced LVEF (< 30%)
  3. Prior thromboembolism
  4. Hypercoagulable state
  5. Multiple mechanical valves

Bioprosthetic Valves

  • Surgical Bioprosthetic AVR
    • Post-Op 3-6mo: VKA (warfarin) with INR target 2.5 for 3-6mo
    • Lifelong: ASA 81mg daily
  • Transcatheter (TAVR)
    • Post-Op 3-6mo: ASA + clopidogrel OR VKA (warfarin with INR target 2.5)
    • Lifelong: ASA 81mg daily

Trips for managing INR

  • (See Thrombosis Canada for a detailed guide)
  • Do not reverse supratherapeutic INR with vitamin K without clinically significant bleeding.  (INR < 10)
    • INR > 10 consider reversal in some clinical situations
  •  INR takes 3-7 days to respond to a dosing change, which is the time taken to metabolize clotting factors.
  • Common drugs that increase INR:
    • Antibiotics/antifungals (esp. quinolones)
    • Amiodarone
    • Statins (except atorvastatin/pravastatin)
    • Acetaminophen > 1g/day
    • Levothyroxine dose changes
  • ASA and NSAID drugs combined with warfarin increase risk of bleeding, but generally do not affect INR

Bridging for surgery

  • Bridging is not required for minor dental procedures (dental extractions, cataract procedures)
  • Patients with bileaflet valves in an aortic position with no risk factors for thrombosis generally do not require bridging.  Their anticoagulation can be interrupted for procedures, and re-intiated.
    • NOTE: These are generally patients who have an INR target of 2.5 or 1.5-2.0.
    • Patients with an INR target of 3.0 generally need bridging due to high risk of thrombosis.  However, decisions must be individualized. 

Further Reading

Authors

  • Primary Author: Dr. Pavel Antiperovitch (MD, FRCPC Cardiologist)