Pulmonary Thromboendarterectomy: Indications, Techniques, and Outcomes

Pulmonary thromboendarterectomy (PTE), also known as pulmonary endarterectomy (PEA), is a complex and life-saving surgical procedure performed to remove organized clots from the pulmonary arteries. These clots cause chronic thromboembolic pulmonary hypertension (CTEPH), a condition that leads to progressive right heart failure and is potentially fatal if left untreated. The procedure, though intricate, offers the potential for a complete cure in patients suffering from CTEPH, making it a cornerstone of surgical treatment for this condition.

This article will provide an in-depth exploration of PTE, including its indications, preoperative evaluation, contraindications, surgical techniques, postoperative care, possible complications, alternative treatment options, prognosis, and recent advances in the field.

Indications for Pulmonary Thromboendarterectomy

PTE is primarily indicated for patients diagnosed with CTEPH, a form of pulmonary hypertension caused by chronic obstruction of the pulmonary arteries due to unresolved blood clots. The following are specific indications for PTE:

1. Diagnosis of CTEPH: Confirmed through right heart catheterization and imaging studies like pulmonary angiography, CT pulmonary angiography, or ventilation-perfusion (V/Q) scans.
2. Symptomatic Disease: Patients with symptoms such as dyspnea, fatigue, and decreased exercise tolerance, despite anticoagulation therapy.
3. Significant Pulmonary Hypertension: Mean pulmonary artery pressure (mPAP) greater than 25 mmHg at rest, with evidence of right heart strain.
4. Operable Disease: Disease location within the pulmonary arteries must be accessible surgically. Proximal and certain distal clot formations are amenable to PTE.

Preoperative Evaluation

The success of PTE relies heavily on meticulous preoperative evaluation, which includes:

1. Comprehensive Hemodynamic Assessment: Right heart catheterization is essential to measure pulmonary artery pressures, cardiac output, and pulmonary vascular resistance (PVR). High PVR (>300 dynes·sec/cm^5) often correlates with a higher surgical risk but also the potential for significant hemodynamic improvement post-surgery.
2. Imaging Studies:
   • Pulmonary Angiography: Gold standard for identifying the location and extent of thromboembolic disease.
   • CT Pulmonary Angiography (CTPA): Provides detailed anatomical information about the pulmonary arteries and can identify the central and segmental distribution of clots.
   • Ventilation-Perfusion (V/Q) Scan: Helpful in detecting mismatches between ventilation and perfusion, which are characteristic of CTEPH.
3. Cardiopulmonary Exercise Testing: Assesses the functional capacity of the patient and helps in risk stratification.
4. Lung Function Tests: To evaluate the underlying lung disease that might affect surgical outcomes.
5. Assessment of Comorbidities: Conditions such as coronary artery disease, chronic obstructive pulmonary disease (COPD), and renal insufficiency must be evaluated and optimized before surgery.
6. Multidisciplinary Team Evaluation: A team comprising surgeons, pulmonologists, cardiologists, anesthesiologists, and radiologists should be involved in the decision-making process.

Contraindications

While PTE offers a potentially curative approach for CTEPH, certain contraindications must be considered:

1. Inoperable Disease: Distal clots that are not accessible surgically, often located in small peripheral pulmonary arteries, make PTE unfeasible.
2. Severe Comorbidities: Patients with significant heart, lung, or kidney disease may not tolerate the procedure.
3. Severe Left Heart Dysfunction: As PTE is primarily focused on right heart dysfunction due to pulmonary hypertension, significant left heart disease can complicate outcomes.
4. Pulmonary Veno-Occlusive Disease (PVOD): Often presents similarly to CTEPH but involves small veins and venules, which PTE cannot address.
5. Patient’s Refusal: Despite thorough counseling, some patients may decline surgery due to perceived risks or personal reasons.

Surgical Techniques and Steps

PTE is one of the most challenging cardiothoracic surgeries, requiring a specialized surgical team and facilities. The procedure typically involves the following steps:

1. Preoperative Preparation: Patients are placed under general anesthesia, and cardiopulmonary bypass (CPB) is initiated. Hypothermia (18°C) is induced to protect the brain and other vital organs during the periods of circulatory arrest.
2. Median Sternotomy: The surgical approach is usually through a median sternotomy, providing access to the heart and pulmonary arteries.
3. Cardiopulmonary Bypass and Deep Hypothermic Circulatory Arrest (DHCA): CPB is established, and DHCA is initiated. Circulatory arrest allows for a bloodless field, which is crucial for precise dissection within the pulmonary arteries.
4. Pulmonary Artery Exploration: The pulmonary arteries are incised longitudinally. The surgeon meticulously dissects the intima of the pulmonary arteries to remove organized thromboembolic material.
5. Endarterectomy: The organized thrombus and fibrotic material are carefully removed from both the right and left pulmonary arteries, extending into segmental and subsegmental branches if necessary. This requires exceptional skill to avoid perforation and to ensure complete removal of obstructive material.
6. Rewarming and Weaning from CPB: After the endarterectomy is completed, the patient is gradually rewarmed, and CPB is weaned off. Intraoperative transesophageal echocardiography (TEE) is used to assess the heart function and confirm the removal of the thromboembolic material.
7. Closure: The pulmonary artery incisions are sutured, and the sternum is closed in the usual fashion.

Postoperative Care

Postoperative management is crucial for a successful outcome and includes:

1. Intensive Care Monitoring: Patients are transferred to the ICU for close monitoring of hemodynamics, oxygenation, and ventilation.
2. Ventilation Support: Mechanical ventilation is typically required postoperatively, with a gradual weaning process based on the patient’s respiratory status.
3. Hemodynamic Support: Inotropes may be necessary to support right heart function immediately after surgery.
4. Management of Reperfusion Injury: A common complication post-PTE, characterized by pulmonary edema due to reperfusion of the previously obstructed pulmonary arteries. This condition requires careful fluid management, diuretics, and sometimes inhaled nitric oxide or prostacyclin to reduce pulmonary pressures.
5. Anticoagulation Therapy: Lifelong anticoagulation with warfarin or direct oral anticoagulants (DOACs) is recommended to prevent recurrent thromboembolic events.
6. Pulmonary Rehabilitation: Encouraged postoperatively to improve functional capacity and quality of life.

Possible Complications

Despite the potential for excellent outcomes, PTE is associated with several complications:

1. Reperfusion Injury: Pulmonary edema due to reperfusion can cause significant respiratory distress and is a leading cause of postoperative morbidity.
2. Residual Pulmonary Hypertension: Persistent pulmonary hypertension may occur if there is incomplete removal of thromboembolic material or due to small vessel disease not addressed by surgery.
3. Right Heart Failure: Can occur postoperatively due to the sudden reduction in pulmonary vascular resistance, leading to an acute increase in right ventricular afterload.
4. Bleeding: Due to the extensive dissection required during the procedure, there is a risk of significant intraoperative and postoperative bleeding.
5. Infection: As with any major surgery, there is a risk of wound infection, pneumonia, or sepsis.
6. Neurological Complications: Despite the use of DHCA, there is a risk of stroke or other neurological deficits.

Different Techniques and Advances

Over the years, advancements in surgical techniques and perioperative care have significantly improved the outcomes of PTE:

1. Selective Cerebral Perfusion: Used during DHCA to provide targeted protection to the brain, reducing the risk of neurological complications.
2. Hybrid Approaches: Combining PTE with balloon pulmonary angioplasty (BPA) or riociguat therapy in patients with residual pulmonary hypertension.
3. Intraoperative Imaging: Advanced imaging techniques, such as intraoperative pulmonary angiography and TEE, allow for real-time assessment of the completeness of thromboendarterectomy.
4. ECMO Support: Extracorporeal membrane oxygenation (ECMO) is used in severe cases of reperfusion injury or right heart failure postoperatively.

Prognosis and Outcome

The prognosis following PTE is generally excellent, with significant improvements in hemodynamics and quality of life. The following factors influence the outcome:

1. Preoperative PVR: Higher preoperative PVR is associated with greater postoperative improvement, although it also correlates with a higher risk of complications.
2. Completeness of Thromboendarterectomy: Complete removal of the thromboembolic material is crucial for optimal hemodynamic recovery.
3. Presence of Small Vessel Disease: Patients with small vessel disease may have persistent pulmonary hypertension postoperatively.
4. Experienced Surgical Center: Outcomes are better in high-volume centers with experienced surgical teams.

Alternative Options

For patients who are not candidates for PTE, alternative treatment options include:

1. Balloon Pulmonary Angioplasty (BPA): A catheter-based procedure that dilates the narrowed pulmonary arteries, used primarily in patients with inoperable CTEPH.
2. Medical Therapy: Riociguat, a soluble guanylate cyclase stimulator, is approved for the treatment of inoperable CTEPH or persistent/recurrent CTEPH after PTE.
3. Lung Transplantation: Considered for patients with end-stage disease and no other treatment options.

Average Cost

The cost of PTE varies widely depending on the country and healthcare system. In the United States, the procedure can cost between $100,000 to $200,000, including preoperative evaluation, surgery, and postoperative care. Insurance coverage and hospital billing practices significantly influence the final cost to the patient.

Recent Advances

Recent advances in PTE include:

1. Improved Imaging Techniques: Enhanced CT and MRI technologies allow for better preoperative planning and postoperative assessment.
2. Hybrid Procedures: Combining PTE with BPA or medical therapies to improve outcomes in complex cases.
3. ECMO Integration: Use of ECMO as a bridge to recovery in patients with severe postoperative complications.
4. Personalized Medicine: Tailoring anticoagulation and postoperative care based on individual patient risk factors.