How to assess and manage prosthetic mismatch in patients after surgery?

Assessment and Management of Prosthetic Mismatch After Valve Surgery

Prosthesis-patient mismatch (PPM) should be systematically assessed in all patients after valve surgery using echocardiography, with severe PPM requiring intervention when symptomatic or associated with poor left ventricular function.

Definition and Diagnosis of Prosthetic Mismatch

Prosthesis-patient mismatch occurs when the effective orifice area (EOA) of an implanted prosthetic valve is too small in relation to the patient's body size, resulting in abnormally high postoperative gradients despite normal valve function 1, 2.

Diagnostic Criteria:

• Aortic position:
  • Moderate PPM: indexed EOA ≤0.85 cm²/m²
  • Severe PPM: indexed EOA <0.65 cm²/m² 1, 3
• Mitral position:
  • Severe PPM: indexed EOA ≤1.2 cm²/m² 3

Diagnostic Approach:

1. Transthoracic echocardiography (TTE) is the first-line imaging modality 1:

   • Measure transprosthetic gradients
   • Calculate effective orifice area using continuity equation
   • Assess Doppler velocity index (DVI)
   • Evaluate ventricular size and function

2. Transesophageal echocardiography (TOE) when TTE is inconclusive 1:

   • Better visualization of prosthetic valve structure
   • Assessment of leaflet motion and thickening
   • Evaluation of paravalvular leaks

3. Advanced imaging when needed:

   • CT imaging to assess leaflet motion and exclude thrombosis 1
   • Fluoroscopy for mechanical valve leaflet mobility 1

Clinical Impact of Prosthetic Mismatch

PPM has significant clinical consequences:

• Increased mortality (1.5-2.0 fold) with severe PPM 4
• Higher rates of heart failure rehospitalization 4
• Persistent left ventricular hypertrophy 2
• Higher rates of perioperative stroke and renal failure 2
• Decreased exercise capacity and quality of life 5

PPM is particularly detrimental in patients with:

• Pre-existing LV dysfunction 1, 3
• Young patients with active lifestyles 5
• Small aortic annulus 3

Management Algorithm

1. Initial Post-Operative Assessment (First 30 days):

• Establish baseline echocardiographic parameters 1:
  • Transprosthetic gradients
  • Effective orifice area
  • Indexed effective orifice area
  • Ventricular function

2. Follow-up Assessment:

• First post-operative visit within 6 weeks (without rehabilitation) or 12 weeks (with rehabilitation) 1
• Assess:
  • Symptomatic status and physical signs
  • Heart rhythm and ECG
  • Chest X-ray
  • Echocardiography to evaluate prosthetic function
  • Laboratory tests including hemolysis markers 1

3. Management Based on Severity:

For Moderate PPM (Aortic: iEOA 0.65-0.85 cm²/m²):

• Regular clinical and echocardiographic follow-up
• Medical therapy for heart failure symptoms if present 1
• Outcomes generally similar to patients without PPM 2

For Severe PPM (Aortic: iEOA <0.65 cm²/m²; Mitral: iEOA ≤1.2 cm²/m²):

• If asymptomatic:

  • Close monitoring with echocardiography every 6-12 months
  • Assess for LV dysfunction and pulmonary hypertension

• If symptomatic:

  1. First exclude other causes of increased gradients:

     • Prosthetic valve thrombosis
     • Structural valve deterioration
     • Pannus formation 1

  2. If confirmed PPM with persistent symptoms:

     • Consider reoperation in suitable candidates 1
     • For bioprosthetic valves, consider valve-in-valve transcatheter procedure 1, 4

4. Special Considerations for Bioprosthetic Valve Thrombosis:

• If suspected (increased gradients, reduced leaflet motion on imaging):
  • In hemodynamically stable patients without contraindications to anticoagulation, initial treatment with vitamin K antagonist is reasonable 1
  • Surgery or thrombolysis for hemodynamically unstable patients 1

Prevention of Prosthetic Mismatch

Prevention is critical as PPM is largely avoidable 5:

1. Preoperative planning:

   • Calculate predicted indexed EOA based on patient's BSA and reference EOA values for available prostheses 4
   • Identify patients at high risk (small annulus, large BSA)

2. Surgical strategies:

   • Implant newer generation prosthetic valves with better hemodynamics 4, 3
   • Consider aortic root enlargement procedures for small aortic annulus 4, 3
   • Consider stentless bioprostheses which have less PPM than stented valves 3
   • Consider transcatheter valve implantation in appropriate candidates 4

Pitfalls in Assessment

• High velocity across bileaflet mechanical valves may be due to normal flow patterns and pressure recovery, not PPM 1
• Increased gradients during high cardiac output states (sepsis, anemia) may not indicate PPM 1
• PPM must be differentiated from prosthetic valve stenosis or thrombosis 1
• Measurement of EOA by continuity equation may be challenging and requires expertise 1, 3

By systematically assessing for PPM after valve surgery and implementing appropriate management strategies, clinicians can improve outcomes for patients with this common complication.