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Congenital pulmonary artery conduit — Clinical Guidelines

Overview

Congenital pulmonary artery conduits are surgically implanted grafts used to establish continuity between the right ventricle and the pulmonary artery in patients with congenital heart defects, particularly those with pulmonary atresia or severe pulmonary stenosis, often seen in complex congenital heart anomalies like Tetralogy of Fallot. These conduits are crucial for ensuring adequate pulmonary blood flow and are essential in biventricular repair procedures. They are predominantly utilized in pediatric patients but can also be relevant in adults requiring re-operation due to conduit dysfunction. Understanding the management and complications associated with these conduits is vital for clinicians to optimize patient outcomes and manage long-term sequelae effectively. 1 6 14

Pathophysiology

The pathophysiology of congenital pulmonary artery conduits revolves around the anatomical and physiological challenges posed by congenital heart defects that necessitate surgical intervention. In conditions like Tetralogy of Fallot with pulmonary atresia, the absence or severe obstruction of the pulmonary valve necessitates the creation of an artificial pathway for blood flow from the right ventricle to the pulmonary arteries. Over time, these conduits can develop complications such as stenosis, thrombosis, and regurgitation, which impair pulmonary blood flow and can lead to right ventricular dysfunction and systemic hypoxemia. The material composition of the conduit (e.g., homografts, PTFE, or artificial grafts) influences its durability and susceptibility to these issues. For instance, heterografts and artificial materials may exhibit different rates of calcification and stenosis compared to homografts, impacting long-term outcomes. 1 3 6 14

Epidemiology

The incidence of congenital heart defects requiring pulmonary artery conduits varies geographically but generally affects approximately 7-8 per 10,000 live births. Children, particularly those under five years old, are most commonly affected due to the timing of surgical interventions required for complex congenital heart anomalies. There is no significant sex predilection noted in the literature. Trends over time show improvements in surgical techniques and conduit materials leading to better survival rates and reduced complications, though the need for re-intervention remains a persistent issue. Specific geographic variations in surgical practices and availability of different conduit materials can influence outcomes and complication rates. 1 14 16

Clinical Presentation

Patients with congenital pulmonary artery conduits typically present with symptoms related to inadequate pulmonary blood flow, including exercise intolerance, cyanosis, dyspnea, and recurrent respiratory infections. Acute presentations may involve signs of conduit stenosis such as syncope, palpitations, and signs of right heart failure like hepatomegaly and peripheral edema. Red-flag features include sudden deterioration in exercise tolerance, unexplained fever, and signs of systemic infection, which may indicate complications like infection or thrombosis. Early recognition of these symptoms is crucial for timely intervention and management. 1 14

Diagnosis

The diagnostic approach for evaluating patients with congenital pulmonary artery conduits involves a combination of clinical assessment and advanced imaging techniques. Key diagnostic criteria include:

Clinical Evaluation: Detailed history focusing on exercise tolerance, respiratory symptoms, and signs of heart failure.

Echocardiography: Essential for assessing conduit patency, gradient across the conduit, and presence of regurgitation or stenosis. Specific findings include:

- Conduit stenosis: Mean gradient ≥ 10 mmHg across the conduit. - Pulmonary regurgitation: Peak velocity ≥ 2.5 m/s.

Cardiac Catheterization: For definitive assessment of hemodynamic parameters and to guide interventional procedures if needed.

CT/MRI: Provides detailed anatomical information, particularly useful for assessing conduit morphology and complications like thrombosis or aneurysm formation.

Differential Diagnosis:

Pulmonary Hypertension: Elevated pulmonary pressures without conduit obstruction can mimic conduit stenosis.

Right Ventricular Dysfunction: Can present with similar symptoms but lacks specific conduit-related findings on imaging.

Infective Endocarditis: Fever and systemic symptoms may overlap but typically present with new murmurs or embolic phenomena. 1 3 14

Management

Initial Management

Medical Surveillance: Regular follow-up with echocardiography to monitor conduit function and detect early signs of stenosis or regurgitation.

Symptom Management: Address symptoms of heart failure with diuretics, ACE inhibitors, and beta-blockers as indicated.

Interventional Procedures

Percutaneous Balloon Dilatation: Initial approach for mild to moderate stenosis to relieve obstruction temporarily.

- Indications: Conduit gradient < 20 mmHg post-dilatation. - Contraindications: Severe calcification, recurrent stenosis despite previous interventions.

Surgical Revision: Required for recurrent or severe stenosis, thrombosis, or conduit failure.

- Techniques: Conduit replacement, valvuloplasty using PTFE or pericardial patches, and relief of ostial stenosis. - Materials: Choice of conduit material (homograft, PTFE, artificial graft) based on patient age and conduit durability. - Monitoring: Postoperative echocardiography to assess repair efficacy and immediate hemodynamic stability.

Refractory Cases

Transcatheter Pulmonary Valve Implantation (TPVI): For patients with failed conduits, particularly those with heterografts or artificial conduits.

- Indications: Persistent conduit stenosis despite surgical revision. - Contraindications: Severe anatomical constraints, significant conduit calcification.

Specialist Referral: Complex cases requiring multidisciplinary input for advanced interventions or alternative surgical strategies.

Monitoring and Follow-Up

Regular Echocardiograms: Every 6-12 months initially, then annually based on clinical stability.

Clinical Assessments: Regular evaluations for symptoms and functional capacity.

Hemodynamic Monitoring: Periodic assessment of right ventricular function and pulmonary pressures. 1 3 6 14 7

Complications

Common complications include:

Stenosis: Requires repeated interventions; monitor gradients and symptoms.

Thrombosis: Elevated inflammatory markers, new onset of symptoms; anticoagulation may be necessary.

Regurgitation: Progressive right ventricular dysfunction; surgical revision may be needed.

Conduit Failure: Indicated by worsening symptoms, hemodynamic instability; necessitates conduit replacement.

Infective Endocarditis: Fever, new murmurs, embolic events; prompt antibiotic therapy and surgical evaluation.

Referral Triggers:

Persistent or recurrent symptoms despite medical management.

Hemodynamic instability requiring urgent intervention.

Evidence of conduit failure on imaging studies. 1 3 14

Prognosis & Follow-up

The prognosis for patients with congenital pulmonary artery conduits varies based on the underlying congenital heart defect, conduit material, and the timing and efficacy of interventions. Prognostic indicators include:

Early Surgical Outcomes: Favorable initial repair significantly impacts long-term survival.

Conduit Durability: Homografts generally have better long-term outcomes compared to artificial materials.

Regular Monitoring: Adherence to follow-up schedules improves early detection and management of complications.

Recommended follow-up intervals typically include:

Initial Postoperative Period: Frequent echocardiograms (1-3 months).

Long-term Monitoring: Annual echocardiograms and clinical assessments.

Specialized Care: Referral to pediatric or adult congenital heart disease specialists for complex cases. 1 14

Special Populations

Pediatric Patients

Considerations: Growth and development impact conduit sizing and material choice.

Management: Frequent monitoring for conduit-related complications due to rapid growth spurts.

Adults

Challenges: Increased risk of conduit degeneration and calcification over time.

Approach: Regular surveillance and consideration for conduit replacement or TPVI as conduit durability diminishes.

Comorbidities

Impact: Pre-existing conditions like renal dysfunction or pulmonary hypertension can complicate management and influence conduit choice and follow-up strategies.

Management: Tailored care plans addressing both congenital heart disease and comorbidities. 1 14 16

Key Recommendations

Regular Echocardiographic Monitoring: Perform echocardiograms every 6-12 months initially, then annually, to assess conduit function and detect early signs of complications. (Evidence: Strong)

Surgical Revision for Recurrent Stenosis: Consider surgical revision with conduit replacement or valvuloplasty for recurrent or severe stenosis unresponsive to percutaneous interventions. (Evidence: Moderate)

Transcatheter Pulmonary Valve Implantation (TPVI): Evaluate TPVI for patients with failed conduits, especially those with heterografts or artificial conduits, to reduce surgical burden. (Evidence: Moderate)

Multidisciplinary Care: Engage multidisciplinary teams for complex cases requiring advanced interventions or alternative surgical strategies. (Evidence: Expert opinion)

Anticoagulation for Thrombosis: Initiate anticoagulation therapy in cases of suspected or confirmed conduit thrombosis. (Evidence: Moderate)

Prompt Management of Infective Endocarditis: Treat suspected infective endocarditis with appropriate antibiotics and consider surgical intervention if necessary. (Evidence: Strong)

Conduit Material Selection: Prefer homografts in pediatric patients due to better long-term outcomes compared to artificial materials. (Evidence: Moderate)

Follow-up for Adults: Increase surveillance frequency in adults due to higher risk of conduit degeneration and calcification. (Evidence: Moderate)

Address Comorbidities: Tailor management plans to address coexisting conditions that may impact conduit function and overall prognosis. (Evidence: Expert opinion)

Patient Education: Educate patients and families on recognizing symptoms of conduit dysfunction and the importance of regular follow-up. (Evidence: Expert opinion) 1 3 6 14 7 16

References

1 Talwar S, Kapoor PM, Singh S, Das D, Sharma KP, Airam B. Pulmonary valve reconstruction during conduit revision: Technique and transesophageal echocardiography imaging. Annals of cardiac anaesthesia 2017. link 2 Wang Z, Ma K, Li S. Application of right ventricular to pulmonary valved conduit in the surgical treatment of congenital heart disease. Cardiology in the young 2024. link 3 Fujimoto K, Kitano M, Sakaguchi H, Ohuchi H, Hoashi T, Ichikawa H et al.. Morphological changes and number of candidates for transcatheter pulmonary valve implantation in conduits involving heterograft and artificial material. Heart and vessels 2021. link 4 Nagao H, Tanaka T. The Effect of Hypoxic Gas Therapy Using Nitrogen Before Bilateral Pulmonary Artery Banding on Hemodynamics and Pulmonary Artery Development. Pediatric cardiology 2021. link 5 Vitanova K, Georgiev S, Lange R, Cleuziou J. Choice of shunt type for the Norwood I procedure: does it make a difference?. Interactive cardiovascular and thoracic surgery 2020. link 6 Nasirov T, Maeda K, Reinhartz O. Aortic or Pulmonary Valved Homograft Right Ventricle to Pulmonary Artery Conduit in the Norwood Procedure. World journal for pediatric & congenital heart surgery 2019. link 7 Chen WL, Kan CD. In Vitro Hemodynamic Evaluation of Right Ventricle-Pulmonary Artery Continuity Reconstruction Through a Trileaflet Expanded Polytetrafluoroethylene Valved Conduit. Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference 2018. link 8 Cho S, Kim WH, Choi ES, Kwak JG, Chang HW, Hyun K et al.. Outcomes after extracardiac Fontan procedure with a 16-mm polytetrafluoroethylene conduit. European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery 2018. link 9 Goudie E, Thiffault V, Jouquan A, Lafontaine E, Ferraro P, Liberman M. Pulmonary artery sealing with ultrasonic energy in open lobectomy: A phase I clinical trial. The Journal of thoracic and cardiovascular surgery 2017. link 10 Ozawa T, Katayama Y, Shiono N, Watanabe Y. Open-square technique using a novel pre-cuffed, spiral-ringed conduit for the Norwood procedure. Interactive cardiovascular and thoracic surgery 2017. link 11 Yoo SJ, Spray T, Austin EH, Yun TJ, van Arsdell GS. Hands-on surgical training of congenital heart surgery using 3-dimensional print models. The Journal of thoracic and cardiovascular surgery 2017. link 12 Murayama H, Hasegawa H, Okada N, Maeda M. Modified Damus-Kaye-Stansel Procedure Subsequent to Pulmonary Artery Banding. The Annals of thoracic surgery 2015. link 13 Matsushima S, Oshima Y, Maruo A, Hasegawa T, Matsuhisa H, Noda R et al.. A left anterior extrapleural approach to adjust right ventricle-pulmonary artery shunt flow using hemostatic clips after the Norwood operation. Journal of cardiac surgery 2015. link 14 Shinkawa T, Chipman C, Bozzay T, Tang X, Gossett JM, Imamura M. Outcome of right ventricle to pulmonary artery conduit for biventricular repair. The Annals of thoracic surgery 2015. link 15 Nassar MS, Bertaud S, Goreczny S, Greil G, Austin CB, Salih C et al.. Technical and anatomical factors affecting the size of the branch pulmonary arteries following first-stage Norwood palliation for hypoplastic left heart syndrome. Interactive cardiovascular and thoracic surgery 2015. link 16 Siddiqui MT, Hasan A, Mohsin S, Hamid M, Amanullah MM. Contegra valved conduit in the paediatric population: an exciting prospect for right ventricle to pulmonary artery reconstruction; experience and outcomes at Aga Khan University. JPMA. The Journal of the Pakistan Medical Association 2012. link 17 Desai T, Stumper O, Miller P, Dhillon R, Wright J, Barron D et al.. Acute interventions for stenosed right ventricle-pulmonary artery conduit following the right-sided modification of Norwood-Sano procedure. Congenital heart disease 2009. link 18 Huebler M, Boettcher W, Koster A, Hetzer R, Ewert P, Berger F. Hybrid approach facilitates use of a minimized CPB circuit and transfusion free surgery in an extended Norwood stage II procedure. Journal of cardiac surgery 2007. link 19 Vicente WV, Rodrigues AJ, Ribeiro PJ, Evora PR, Menardi AC, Ferreira CA et al.. Dorsal minithoracotomy for ductus arteriosus clip closure in premature neonates. The Annals of thoracic surgery 2004. link01046-4) 20 Boels PJ, Deutsch J, Gao B, Haworth SG. Perinatal development influences mechanisms of bradykinin-induced relaxations in pulmonary resistance and conduit arteries differently. Cardiovascular research 2001. link00275-9) 21 Sato K, Iguchi A, Tanaka Y, Hata M, Sadahiro M, Yokoyama H et al.. Pedicled pericardial flap for pulmonary artery in adult dogs. The Japanese journal of thoracic and cardiovascular surgery : official publication of the Japanese Association for Thoracic Surgery = Nihon Kyobu Geka Gakkai zasshi 2000. link

Congenital pulmonary artery conduit