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Case 020: Bioprosthetic Valve Dysfunction in Adolescent

Clinical Presentation

Setting: Pediatric cardiology clinic

Patient: 17-year-old female with history of congenital aortic stenosis, presenting for routine follow-up

Surgical History: - Age 2: Surgical aortic valvotomy for critical AS - Age 8: Ross procedure (pulmonary autograft) for progressive AS with significant AR - Age 14: RV-PA conduit replacement (23mm Contegra bovine jugular vein conduit) for severe RVOT obstruction

Current Visit: 3 years post-conduit replacement, routine surveillance

Symptoms: Patient reports decreased exercise tolerance over past 6 months. Previously ran track, now gets winded walking up stairs at school. No chest pain, syncope, or palpitations.

Initial Assessment

Vital Signs: - HR 88 - BP 118/72 - SpO2 98% on RA

Physical Exam: - General: Well-appearing adolescent - Cardiac: RV lift, loud P2, 4/6 systolic ejection murmur at LUSB with thrill, soft diastolic murmur - JVP: Mildly elevated - Lungs: Clear - Extremities: Trace peripheral edema - Hepatomegaly: 2cm below costal margin

Diagnostic Workup

ECG: - Sinus rhythm - Right axis deviation - RVH with strain pattern (new from baseline)

Echocardiogram:

Parameter Current Prior (1 year ago)
RV-PA conduit gradient Peak 75mmHg, mean 45mmHg Peak 35mmHg, mean 18mmHg
Pulmonary regurgitation Moderate Mild
RV size Severely dilated Mildly dilated
RV function Moderately reduced Normal
Tricuspid regurgitation Moderate Trace
TR velocity 4.2 m/s 3.0 m/s
Neo-aortic valve (autograft) Mild AR, no stenosis Mild AR

Assessment: Severe conduit dysfunction with stenosis and regurgitation, RV failure

Clinical Reasoning Questions

Question 1

What is happening to this patient's RV-PA conduit and why?

Answer **Bioprosthetic Conduit Degeneration:** **This Patient Has:** 1. **Progressive conduit stenosis** (gradient increased from 35→75 mmHg peak) 2. **Worsening pulmonary regurgitation** (mild→moderate) 3. **Combined lesion** = both stenosis AND regurgitation **Why Conduits Fail:** | Mechanism | Description | |-----------|-------------| | **Calcification** | Glutaraldehyde-fixed tissue calcifies over time | | **Fibrosis** | Intimal proliferation causes narrowing | | **Leaflet degeneration** | Cusps stiffen, fail to coapt | | **Somatic outgrowth** | Patient grows, conduit doesn't | | **Immune response** | Inflammatory reaction to xenograft | **Contegra Conduit Specifically:** - Bovine jugular vein with natural valve - Known for higher stenosis rates than homografts - Median freedom from reintervention ~7-10 years - Smaller sizes fail faster **This Patient's Timeline:** - Placed at age 14 (23mm conduit) - Now age 17 (3 years post) - Earlier than expected failure, but not unusual for growing adolescent **Risk Factors for Early Failure:** - Younger age at implantation - Smaller conduit size - Conduit type (Contegra > homograft in some studies) - Multiple previous surgeries - Calcium/phosphate abnormalities

Question 2

What are the indications for reintervention in RV-PA conduit dysfunction?

Answer **Indications for Intervention (2020 ACC/AHA Guidelines):** **Class I (Should Intervene):** - Symptomatic severe PR or RVOT obstruction - RV dysfunction regardless of symptoms - RV dilation regardless of symptoms (if severe) - Peak gradient >50mmHg with symptoms or RV dysfunction **Class IIa (Reasonable to Intervene):** - Asymptomatic severe PR with: - Progressive RV dilation - Progressive RV dysfunction - Progressive TR - Peak gradient >50mmHg even if asymptomatic **This Patient Meets Multiple Indications:** - ✓ Symptoms (decreased exercise tolerance) - ✓ Severe stenosis (peak 75mmHg) - ✓ Moderate PR - ✓ RV dysfunction - ✓ RV dilation - ✓ TR from RV failure **Why Not Wait?** - Progressive RV failure - Irreversible RV damage if too delayed - Quality of life impaired - Risk of arrhythmias **Key Point:** Earlier intervention preserves RV function better than waiting for severe symptoms.

Question 3

What are the intervention options for this patient?

Answer **Options for RV-PA Conduit Dysfunction:** **1. Transcatheter Pulmonary Valve Replacement (TPVR)** | Pros | Cons | |------|------| | Avoids surgery | Needs adequate conduit size | | Shorter recovery | Limited durability data | | Can be repeated | Not all anatomies suitable | | Lower acute morbidity | Risk of conduit rupture (stenting) | **Available Devices:** - Melody valve (Medtronic) - up to ~22mm conduits - Sapien (Edwards) - larger conduits - Harmony (Medtronic) - native RVOT (limited data) **2. Surgical Conduit Replacement** | Pros | Cons | |------|------| | Can upsize | Redo sternotomy risks | | Addresses all anatomy | Longer recovery | | Known durability | Adhesions from prior surgeries | | Can address other lesions | Bleeding, mortality risk | **Conduit Options:** - Homograft (human cadaveric) - Contegra (bovine jugular vein) - Hancock (porcine) - Pulmonic valve in conduit **For This Patient:** - 23mm conduit may be suitable for Melody or Sapien - However, combined stenosis + regurgitation - RV significantly dilated - may benefit from surgery to fully address - This is her 4th cardiac surgery - adhesions are a concern **Decision:** - Likely TPVR attempt if anatomy suitable (CT angiography to assess) - Surgical backup if TPVR not feasible

Question 4

What preprocedural imaging is needed before TPVR?

Answer **Preprocedural Assessment for TPVR:** **1. CT Angiography (Essential):** | Assessment | Why | |------------|-----| | **Conduit size** | Must fit device | | **Conduit calcification** | Risk of rupture with stenting | | **Coronary proximity** | Risk of compression | | **PA anatomy** | Branch stenosis | | **Relationship to sternum** | Rupture risk if adherent | **Coronary Compression Risk:** - Critical assessment - Balloon interrogation during cath - If coronary compromised during test occlusion → contraindication to TPVR **2. Cardiac MRI:** - Accurate RV volumes and function - PR quantification - Myocardial fibrosis (gadolinium enhancement) **3. Diagnostic Catheterization:** - Confirm gradients - Test balloon occlusion of conduit - Coronary angiography during balloon inflation - Assess for conduit fracture risk **This Patient's CT Shows:** - 23mm conduit (suitable for Melody or Sapien 29) - Moderate calcification - Coronary arteries well away from conduit - Small area of conduit-sternum contact **Risk Assessment:** - Conduit rupture risk: Low-moderate - Coronary compression risk: Low - **Likely candidate for TPVR**

Question 5

The patient undergoes Melody valve placement. What is the expected durability and follow-up?

Answer **Melody Valve Outcomes:** **Durability Data:** | Timepoint | Freedom from Reintervention | |-----------|---------------------------| | 5 years | 75-85% | | 10 years | 55-65% | **Modes of Failure:** - Stent fracture (reduced with prestenting) - Endocarditis (requires lifelong SBE prophylaxis) - Neo-intimal ingrowth - Valve degeneration **Endocarditis Risk:** - Higher than native valves - **Lifelong antibiotic prophylaxis required** - Dental hygiene critical - 3-4% cumulative risk at 5 years **Post-TPVR Follow-Up:** | Timing | Evaluation | |--------|------------| | 1 month | Echo, clinical exam | | 6 months | Echo | | Annual | Echo, possibly MRI | | As needed | CXR for stent fracture surveillance | **What to Monitor:** - Valve function (gradient, regurgitation) - RV size and function (should improve!) - Stent fracture (CXR, fluoroscopy) - Signs of endocarditis - Clinical symptoms **Expected Improvement:** - Symptoms should resolve/improve - RV size should decrease - RV function should improve - TR should improve **This Patient Post-Procedure:** - Melody valve placed successfully - Post-procedure gradient 15mmHg - Trivial PR - Discharged day 1 post-procedure - Prescribed lifelong SBE prophylaxis

Question 6

During long-term follow-up, what other issues need monitoring given her surgical history?

Answer **Comprehensive Long-Term Surveillance:** **1. Ross Procedure Autograft (Neo-Aortic Root):** | Concern | Monitoring | |---------|------------| | Autograft dilation | Annual echo, may need CT/MRI | | Neo-aortic regurgitation | Echo (currently mild) | | Neo-aortic stenosis | Rare | **Ross Autograft Issues:** - Progressive dilation occurs in 10-30% over 10-20 years - AR may progress requiring reoperation - Autograft replacement (valve-sparing vs. composite) may be needed - Her current mild AR needs surveillance **2. Melody Valve:** - Gradient surveillance - Endocarditis risk - Stent fracture - Will need future reintervention **3. Right Ventricle:** - Even after valve replacement, RV may not fully normalize - Monitor for arrhythmias - Exercise capacity **4. Arrhythmia Risk:** - Multiple RV surgeries - RV incisions - Risk of VT/sudden death - May need Holter monitoring - Consider electrophysiology evaluation **5. Psychosocial:** - Multiple surgeries in childhood - Body image (scars) - Transition to adult congenital care - Reproductive counseling - Career/insurance planning **6. Exercise/Activity:** - Generally can exercise - Avoid isometric/burst activity if dilated autograft - Follow exercise test to guide restrictions **7. Pregnancy Counseling:** - Will need pre-conception counseling - Ross patients generally tolerate pregnancy well - Conduit may need intervention before pregnancy - High-risk OB needed **Follow-Up Schedule:** - Every 6-12 months in pediatric cardiology - Transition to ACHD (adult congenital) at 18-21 - Lifelong follow-up required

Outcome

The patient underwent successful Melody valve implantation. At 6-month follow-up: - Symptoms resolved, back to running track - Peak gradient 18mmHg, trace PR - RV size improved (still mildly dilated) - RV function normalized - No stent fracture

She was counseled about lifelong SBE prophylaxis, the likelihood of future reinterventions, and transition planning to adult congenital heart disease care.

Key Teaching Points

  1. Bioprosthetic conduits have limited lifespan - expect reintervention in growing children
  2. Contegra conduits may have higher stenosis rates than homografts
  3. Intervene before RV function deteriorates - waiting too long causes irreversible damage
  4. TPVR (Melody, Sapien) is first-line for suitable anatomy
  5. CT angiography is essential before TPVR - assess coronary proximity, conduit size, rupture risk
  6. Melody valve requires lifelong SBE prophylaxis - endocarditis risk is significant
  7. Ross patients need dual surveillance - autograft AND pulmonary conduit
  8. Multiple surgeries = arrhythmia risk - monitor long-term
  9. Transition planning to adult congenital care is essential

References

  • McElhinney DB, et al. Melody Valve Outcomes. Circulation. 2020
  • 2020 ACC/AHA Guidelines for ACHD Management