Step-by-Step Pulmonary Thromboendarterectomy for Chronic Thromboembolic Disease

Introduction 

Pulmonary thromboendarterectomy (PTE) is an effective but complex procedure for treating chronic thromboembolic pulmonary disease. Learning to perform PTE is crucial for cardiothoracic surgeons in training; however, the exposure and depth of the dissection plane can make this arduous. Technical descriptions of PTE often rely on text or poor-quality media that were not intended for teaching. When capturing the videos included here, the surgeons used a 10 mm 30-degree rigid endoscope instead of a head-mounted camera, which allowed good visualization of every step of the surgery. The scope provides better visualization for the staff participating in the procedure, especially the first assistant, and may also be used to check the patency of the distal segmental branches after the endarterectomy. 
 
Patient Selection 

Detailed patient selection criteria for PTE are beyond the scope of this report. Objective criteria remain a topic of ongoing debate among surgical experts, making it difficult to establish formal, universally applicable guidelines. Ultimately, the decision to perform surgery in patients with chronic thromboembolic disease (CTED) or chronic thromboembolic pulmonary hypertension (CTEPH) is based on several factors, including the severity of symptoms, pulmonary hypertension, and right ventricular dysfunction. Additionally, the extent of obstruction and its correlation with symptoms and pulmonary hypertension must be considered, along with the presence of comorbidities and the technical challenges associated with surgery (1, 2).  

The typical candidate for PTE is a patient with World Health Organization (WHO) Class III or IV symptoms, along with main pulmonary artery to segmental obstruction (UCSD Level I-III) and pulmonary hypertension due to thromboembolic disease. However, these criteria can vary, and an increasing number of patients with milder symptoms and no evident pulmonary hypertension at rest are being referred for surgery. It is critical to thoroughly discuss the risks and benefits of the procedure with the patient and set realistic expectations regarding the surgical outcomes. Some selection criteria, such as the operability in patients with distal disease (UCSD Level IV) or those with prior chest surgeries, are also influenced by the surgeon's expertise. 

An important contraindication for surgery is the presence of severe emphysema or interstitial lung disease, as these patients are less likely to benefit from PTE. In such cases, the procedure often does not lead to significant improvement in perfusion, and there is an increased risk of respiratory failure postoperatively. 
 
Preoperative Evaluation and Preparation 

The surgeon should always review relevant tests, including echocardiogram, computed tomography (CT), and pulmonary artery (PA) angiography, because optimal planning for the procedure relies on knowledge of the disease anatomy. Additionally, the risk of hemodynamic deterioration is significant, especially when right ventricular dysfunction coexists. Therefore, the whole team should be prepared to initiate mechanical circulatory support if necessary. 

For the procedure, several preparations are required, including the placement of  
right upper extremity and left femoral arterial lines, a PA catheter via the right internal jugular vein, and a Foley catheter with a temperature probe. A nasal temperature probe may also be utilized, along with an optional electroencephalogram. Transesophageal echocardiography (TEE) should be performed, and cranial near-infrared spectroscopy is recommended during the procedure.  
 
Sternotomy and Cannulation 

After performing the median sternotomy, the pericardium should be opened longitudinally, and pericardial sutures should be placed to expose the heart. The  
cannulas must be placed sequentially, starting with an 18-22Fr cannula in the aorta, followed by a 22-24Fr right-angle venous cannula in the superior vena cava (SVC). Next, a 28-34Fr straight plastic-tip cannula should be positioned in the inferior vena cava. Additionally, a flexible vent cannula is required for left ventricle decompression during cardiopulmonary bypass (CPB), and the correct positioning of the vent may be assessed by palpating the posterior atrial wall or using TEE. Using flexible cannulas facilitates retraction and optimizes exposure, precluding the need for more distal or higher cannulations. 

To facilitate exposure, loops of umbilical tape should be placed around the aorta and SVC. Once all cannulations are complete, initiate CPB and patient cooling. Achieving a core temperature of 20 degrees Celsius usually takes approximatelyl 60 minutes. Once the target temperature is reached, the deep hypothermic circulatory arrest (DHCA) can be initiated. If an electroencephalogram (EEG) is used, it is essential to ensure that the isoeletric status is achieved before initiating DHCA. 

During cooling, the right pulmonary artery (RPA) and left pulmonary artery (LPA) should be dissected. The authors typically start the endarterectomy on the right side, but this decision is based on the surgeon’s discretion. Retract the SVC and aorta laterally using a cerebellar retractor to fully dissect the RPA, while also identifying the first bifurcation point, which will be used as a reference for the arteriotomy extent. During LPA dissection, take caution to avoid the left phrenic nerve, which is situated slightly above the LPA. 

Before initiating circulatory arrest, it is advisable to review the endarterectomy steps with everyone in the room to optimize efficiency and decrease the time spent in DHCA. Also, place the Scoville nerve retractor, a long Beaver blade, Madani forceps, a Jamieson dissection aspirator, long DeBakey forceps, vessel sutures, and sealants on a separate Mayo table for easy access during the procedure.  

Thromboendarterectomy, Rewarming, and Immediate Postoperative Care 

The authors typically start PTE with the RPA. The aorta and SVC should be retracted laterally. Create the arteriotomy with a scalpel while the artery is still congested to minimize the risk of misaligned entry. After making the incision, place the pump-sucker inside the vessel for effective drainage. Then, place a pledgeted 4-0 polypropylene suture on each side of the arteriotomy and apply gentle traction to open it.  

The first assistant should use a Scoville retractor at the distal corner of the arteriotomy to enhance the exposure of the dissection area. Then, inspect the RPA and initiate DHCA to decrease the blood in the surgical field, allowing for proper endarterectomy down to the subsegmental branches. Typically, one interval of DHCA, lasting a maximum of 20 minutes, is sufficient to remove all disease from one side; however, additional intervals can be added if necessary (3).  

The thromboendarterectomy should be conducted efficiently, avoiding unnecessary movements. Use a Beaver blade to create the initial dissection plane until the intra-medial plane is reached. In some patients, dissection may need to be initiated at the origin of the involved branches or at a segmental level. Extend the initial plane in a circumferential manner and then raise and hold the plane with a combination of DeBakey and Madani forceps while using the Jamieson aspirator to extend the plane distally. Dissection should first be performed on the upper branches. This facilitates better traction during the subsequential removal of disease from the lower branches. Take special caution to avoid complete rupture of the vessel. En bloc removal of the thrombus is preferred to ease traction. 

After ensuring the complete removal of disease, wash the interior of the RPA with heparinized saline. Finally, place a double-layer suture with a 5-0 polypropylene starting from the distal corner of the arteriotomy, and a sealing agent over the suture and resume circulatory perfusion. 

Before performing the arteriotomy on the LPA, allow at least 10 to 20 minutes of reperfusion between each DHCA. During this time, blood cardioplegia can be administered, and an additional retraction suture should be placed in the proximal portion of the LPA for caudal traction. The same steps used for the RPA should be followed for the LPA thromboendarterectomy. 

Rewarming typically takes 60 to 75 minutes. During rewarming, additional procedures, such as patent foramen ovale closure or valve repair, can be performed. These procedures can also be performed during the cooling period, depending on the surgeon’s preference. Pacing wires and chest tubes should also be placed with a typically hard tube positioned posteriorly and two Blake drains placed anteriorly.  

Once the core temperature is above 35 degrees Celsius, CPB can be weaned, and the cannulas should be removed. Before closing the sternum, meticulous hemostasis must be achieved. 

In the postoperative period, consider the following measures to prevent reperfusion injury and new thrombus formation. It is advisable to avoid using inotropes, such as epinephrine. Norepinephrine and vasopressin are preferred alternatives. Additionally, refrain from using inhaled nitric oxide or other pulmonary vasodilators unless absolutely necessary, such as in patients with profound postoperative hypoxemia, to prevent injury to the reperfused territories. Finally, initiate heparin as soon as possible, typically approximately eight hours postoperatively. 

At the authors’ institution, before patient discharge, a SPECT-CT to assess improvement in perfusion is performed.

References

1. Madani M, Mayer E, Fadel E, Jenkins DP. Pulmonary Endarterectomy. Patient Selection, Technical Challenges, and Outcomes. Annals ATS. 2016;13(Supplement_3):S240-S247. doi:10.1513/AnnalsATS.201601-014AS
2. Verbelen T, Godinas L, Maleux G, et al. Chronic thromboembolic pulmonary hypertension: diagnosis, operability assessment and patient selection for pulmonary endarterectomy. Annals of cardiothoracic surgery. 2022;11(2):82.
3. Stein E, Ramakrishna H, Augoustides JGT. Recent Advances in Chronic Thromboembolic Pulmonary Hypertension. Journal of Cardiothoracic and Vascular Anesthesia. 2011;25(4):744-748. doi:10.1053/j.jvca.2011.03.182
4. Kratzert WB, Boyd EK, Saggar R, Channick R. Critical Care of Patients After Pulmonary Thromboendarterectomy. Journal of Cardiothoracic and Vascular Anesthesia. 2019;33(11):3110-3126. doi:10.1053/j.jvca.2019.03.005

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