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Pulmonary thromboendarterectomy

Murphy, Nancy PhD, RN, CNE

doi: 10.1097/01.CCN.0000553078.64152.9b
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Abstract: Pulmonary thromboendarterectomy is the preferred treatment option for patients with chronic thromboembolic pulmonary hypertension (CTEPH). This complicated surgical intervention offers patients a potential cure, although some patients with CTEPH are considered inoperable. This article reviews clinical manifestations, the procedure, potential complications, and nursing care including patient education.

Pulmonary thromboendarterectomy is a complicated surgical intervention and the preferred treatment option for patients with chronic thromboembolic pulmonary hypertension. This article covers the procedure, potential complications, nursing care, and patient education.

Nancy Murphy is an assistant clinical professor at Drexel University College of Nursing and Health Professions, Philadelphia, Pa.

The author has disclosed no financial relationships related to this article.

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Figure

Chronic thromboembolic pulmonary hypertension (CTEPH) is considered a rare disease; accurately calculating its incidence and prevalence is challenging, and it is likely that the number of patients diagnosed with CTEPH remains underestimated.1 However, it is one of the most common subtypes of precapillary pulmonary hypertension.1-8 CTEPH presents as a long-term complication in an estimated 4% to 9% of patients who have experienced an acute pulmonary embolic event.1,4,6,8-10 A notable number of CTEPH cases have occurred without a prior episode of pulmonary embolism or asymptomatic venous thromboembolic events.1,6,7 Although the exact incidence and prevalence of CTEPH is not clearly known, the estimated overall incidence ranges from 3 to 30 cases per million annually in the general population, according to the European CTEPH Registry.3,4,6,11

Patients who exclusively receive medical treatments for CTEPH experience higher mortality and decreased overall functional status compared with patients who receive surgical intervention.4 Identifying accurate CTEPH mortality statistics in the literature is equally as challenging as determining accurate incidence and prevalence of the disease. Pulmonary thromboendarterectomy (PTE) may be a curative treatment option for some patients and is the preferred treatment for patients with CTEPH.1,2,4,5,9,11,12 Positive patient outcomes are frequently long-lasting; recurrent CTEPH is extremely rare when patients have been properly treated.7 Interdisciplinary care management is critical in ensuring positive patient outcomes.13 In particular, nurses are essential in all phases of the patient's surgical journey, so they must possess knowledge and understanding of the PTE procedure, its potential complications, its care management, and patient and family education needs.14-16

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Clinical manifestations

CTEPH occurs as a result of a single or recurrent episode of thromboembolism in which the fibrotic changes of pulmonary arterial clots create a chronic obstruction, or stenosis, of the pulmonary arteries (main, lobar, segmental, and subsegmental) and remodeling in the microvasculature.3,4,6,8,9 (See Pulmonary circulation and Chronic pulmonary thromboembolism.)

Patients in the early phase of the disease typically complain of dyspnea and fatigue.9,16 The nonspecific signs and symptoms at this stage make diagnosing CTEPH difficult, which leads to underdiagnosis.9,17 As CTEPH progresses, the patient may develop right-sided heart failure.9,17 Right-sided heart failure varies in severity from mild to severe and includes lower extremity peripheral edema, ascites, jugular venous distension, hepatomegaly, and syncope.17 Patients may also report atypical chest pain, a cough, and palpitations.17

Auscultation of the heart reveals a loud, split second heart sound (S2) with an accentuated pulmonic component from increased pulmonary pressures, a palpable right ventricular heave may be noted, and a tricuspid regurgitation murmur auscultated at the left sternal border.17 As the disease progresses, a right-sided third heart sound (S3) may be noted, and in severe cases, an S4 may be heard.17

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Diagnostic studies

The diagnosis of CTEPH includes the presence of an occlusive thrombus or emboli following 3 to 6 months of effective anticoagulation treatment as well as a mean pulmonary artery pressure more than 25 mm Hg and a pulmonary capillary wedge pressure less than 15 mm Hg, as determined by right heart catheterization.2-8,17 A ventilation-perfusion scan (V/Q scan) and echocardiogram aid in establishing this diagnosis.7

The echocardiogram is used to evaluate for signs of pulmonary hypertension based on peak tricuspid regurgitation velocity (TRV) measurements and structural changes of the ventricles, pulmonary arteries, inferior vena cava, and right atrium, with the structural changes categorized as 1, 2, and 3, respectively.3 TRV measurements greater than 2.9 suggest an intermediate-to-high risk of pulmonary hypertension.3 Changes in the ventricles include a right/left ventricle basal diameter ratio greater than 1.0 and flattening of the interventricular septum.3 Measurements of the pulmonary artery reveal a diameter greater than 25 mm, right ventricular outflow Doppler acceleration time less than 105 m/s and/or midsystolic notching, and early diastolic pulmonary regurgitation velocity greater than 2.2 m/s.3 Last, in regard to the inferior vena cava and right atrium, echocardiography results demonstrate an increase of the diameter of the inferior vena cava to greater than 21 mm with a reduced inspiratory collapse, and right atrial area (end-systole) greater than 18 cm2.3 Not all of these findings are always present; however, at least two of these signs should be present to adjust the probability of pulmonary hypertension.3

The preferred initial diagnostic for CTEPH is combining ventilation/perfusion scan planar images on at least six views with single-photon emission CT.7 The diagnosis of CTEPH is ruled out if the results show a normal- or low-probability V/Q scan; at least 1 to 2 segmental larger-size defects, and mismatched perfusion defects indicating that CTEPH is probable.3,7 There is a sensitivity of 96% to 97% and a specificity of 90% to 95% related to these diagnostic findings.3

Finally, selective pulmonary angiography of the anterior-posterior and lateral projections is the last step in diagnostic evaluation and can reveal a complication such as pulmonary artery dilation, which leads to left main coronary artery compression and hypertrophied bronchial arterial collaterals, as well as other findings such as ring-like stenosis, webs (“slits”), pouches, wall irregularities, and complete vascular obstructions.3 It should be noted when determining patient operability, computed tomography pulmonary angiography is commonly and widely accepted in practice.12

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Operative considerations

A multidisciplinary medical team of CTEPH experts, composed of a pulmonologist whose specialty is pulmonary hypertension, cardiologist, radiologist, PEA surgeon, and balloon pulmonary angioplasty (BPA) interventionist, determine the appropriateness for surgical intervention.12 (See Factors that influence the surgical decision.)

Patients with significant distal (obstruction) disease, end-stage lung disease, or life-limiting malignancies are not suitable PTE candidates. Instead, options such as medical management for pulmonary hypertension or BPA are potential treatments for inoperable patients.9,17 The American College of Chest Physicians Guideline and Expert Panel Report on Pharmacotherapy for PAH have published updated guidelines on medication management, including combination therapies and palliative care.20 Another curative option is a lung transplant; however, decreased organ availability makes PTE more feasible.5,17

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Surgical intervention: PTE

PTE is a highly technical and challenging procedure; only a limited number of facilities around the globe can perform this surgery.9 The number of the procedures completed at the facility and surgical outcomes dictate the degree of competence of CTEPH team members.12 PTE requires the following:4,9,21

  • The surgical intervention is bilateral and done through a median sternotomy.4,9,21
  • Full visualization is obtained via cardiopulmonary bypass (CPB) with circulatory arrest intervals limited to 20 minutes, including hypothermia (cooling temperature of approximately 68° F [20° C]), to promote exposure and precision for the endarterectomies in a blood-free surgical field.4,5,9,11,21
  • The correct dissection plane—the media extending to distal vessels—is identified.

Preoperatively, the patient receives local anesthesia and mild I.V. sedation in the OR. A radial arterial line and introducer is inserted into the selected vein in preparation for the placement of pulmonary artery catheter in order to provide continuous monitoring of mixed venous oxygen saturation levels (SVO2) and cardiac output.11,21 Administration of anesthesia and intubation with a single-lumen endotracheal tube follows the placement of monitoring devices.11 Patients with severe pulmonary hypertension who cannot tolerate lying flat can have the monitoring devices placed after they receive anesthesia.21 Additional access includes the insertion of a subclavian triple lumen along with a femoral arterial line, as determined by the surgeon and the surgical team.11 The patient's core temperature is continuously monitored using temperature-monitoring devices.11,21,22 When the patient is prepped and draped, a transesophageal echocardiogram is completed.11

The surgery begins by exposing the heart through a median sternotomy.5,11 After heparinization, the aortic cannula is inserted into the ascending aorta and two caval cannulas are placed via the right atrium; all cannulas are secured with two purse-string sutures.5,11 The first cannula is placed in the superior vena cava to begin partial CPB along with decompression of the right atrium and ventricle.5,11 The initiation of partial CPB allows for adequate retraction of the right atrium before the second cannula is inserted into the inferior vena cava.11 The cooling process begins and during ventricular fibrillation, two vents are placed into the pulmonary vasculature; the first vent is put into the left ventricle by way of the right superior pulmonary vein, and the second vent goes into the proximal main pulmonary artery.5,11 The surgeon dissects the right and left main pulmonary arteries, and a cardioplegia cannula is positioned proximal to the aortic cannula in the ascending aorta.11 At core temperatures of 64.4° F to 68° F (18° C to 20° C), the surgeon is able to cross-clamp the aorta and provide myocardial protection through antegrade cardioplegia infusion.11 The right pulmonary artery is exposed, and an arteriotomy is then performed followed by the endarterectomy while the patient is under circulatory arrest.11 Cerebral oximetry permits monitoring of oxygenation to the brain.21 When completed, CPB resumes, the pulmonary artery is closed, and the patient is slowly warmed on CPB.4,5,21 If a left endarterectomy is indicated on the left pulmonary artery, the surgeon performs the procedure in a similar manner.5,11,21 Epicardial pacemaker wires and chest tube drains are inserted prior to closing the chest.11,21

Postoperatively, all patients remain intubated and are placed on a transport ventilator and moved to an intensive/critical care unit.21 If there are no complications, the patient may be extubated on postoperative day 1, and transferred from the ICU on postoperative day 2 or 3 with the expectation that discharge will occur 1 to 2 weeks after surgery.21

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Postoperative complications

PTE complications can include airway bleeding, reperfusion pulmonary edema (RPE), and residual/persistent pulmonary hypertension.21 If it is noted prior to complete separation from CPB, the surgical team can better identify the location by giving the heart time to eject while directly visualizing that area with fiber-optic bronchoscopy to isolate the affected segment using an endobronchial blocker to prevent blood from entering other segments.21 For example, a balloon-based endobronchial blocker can isolate the lungs for thoracic surgical procedures.23 Dark blood in the endotracheal tube immediately after separation from CBP suggests a blood-airway barrier disruption in one of the pulmonary artery branches.21 Management of the airway bleeding is based on the extent of the bleeding.21 Conservative management includes using positive end-expiratory pressure, lung isolation of the segment bleeding with bronchial blockade, reversal of heparin, a topical vasoconstrictor such as vasopressin or epinephrine, and coagulopathy corrections.21 Pink, frothy blood in the endotracheal tube indicates early and severe reperfusion injury from increased capillary permeability.21

RPE results from fluid collection in lung areas from which the thromboemboli were removed and can occur in the early postoperative period or up to 72 hours postsurgery with varying degrees of severity.17,21 Treatment of RPE remains mainly supportive and includes the use of diuretics, recruitment maneuvers and high positive end-expiratory pressure, inhaled nitric oxide (iNO), and extracorporeal membrane oxygenation in severe cases.17,19,21,24

Residual or persistent pulmonary hypertension develops if the PTE does not fully resolve distal chronic thromboembolic disease or distal small vessel vasculopathy.19,21 Treatment in severe cases requires pharmacologic management using inotropic support and the use of systemic vasodilators.21 Some patients benefit from using iNO.21

Like other patients who undergo other cardiothoracic surgical procedures, patients who have had PTE are at risk for such postoperative complications as delirium, atelectasis, pleural effusion, pericardial effusion, diaphragmatic dysfunction, and dysrhythmias.21 Hypoxemia, causing high oxygen demands, is also very common in this patient population.21 Management strategies are implemented to avoid these potential complications.

Postoperatively, all patients should remain mechanically ventilated for at least 1 night to monitor for RPE.21 Venous thromboembolism prophylaxis, including pneumatic compression devices and subcutaneous heparin, are used the evening of the surgical procedure.21 Anticoagulation therapy, typically warfarin, usually starts on postoperative day 1 when the pacing wires are removed.21 Lifelong anticoagulation therapy is recommended for all patients in order to prevent the reoccurrence of another thrombosis.2,5,21

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Postoperative nursing considerations

Nurses caring for the postoperative patient recognize the importance of ongoing assessment and monitoring in order to detect any physiologic, hemodynamic, or psychological changes in the patient's status.25 Postoperatively, all patients remain mechanically ventilated for at least 1 night in order to monitor for RPE.21 Assessment begins with the nurse evaluating the patency of the airway and correct placement of the endotracheal tube.25 Obtaining baseline vital signs (temperature, BP, pulse, respiratory rate, and oxygen saturation levels) follows.25 The nurse performs a systems assessment, implements appropriate nursing interventions in response to assessment findings, and reports any changes and/or variations from normal to the medical team.25 (See Systems assessment.)

Other considerations in caring for patients following PTE are assessment, monitoring, and evaluation as it relates to thermoregulation, fluid and electrolyte balance, and pain. Many factors impact the patient's body temperature and may include vasoconstriction or vasodilation of pharmacologic agents administered, such as anesthesia and/or preoperative medications, temperature of irrigation fluids, ambient air, and body surface exposure.25 Patients are at risk for electrolyte imbalances secondary to preoperative restriction of food and fluids, intraoperative blood and fluid loss, and the body's physiologic stress response to surgery.25 Nurses administer I.V. medications and replacement fluids as per prescriber orders.25 After extubation and assessment for the return of laryngeal and pharyngeal reflexes as well as gastrointestinal function, oral fluids and food are slowly reintroduced.25 Strict observance of input and output is necessary to accurately evaluate and adjust fluid management as well as to assess for signs or symptoms of kidney dysfunction.25 The nurse is responsible to document urinary output, surgical wound drainage, and drainage tube output, noting the amount, color, and any associated odors.25 Additionally, nurses examine and report abnormal results from ordered lab studies as part of fluid and electrolyte management.27,28 Equally important to a patient's recovery is adequate pain and anxiety management using pharmacologic and nonpharmacologic interventions as indicated, which requires the collaboration of the interdisciplinary team.25,29,30

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Patient education

Nursing assessment and education are essential components of transitions in care throughout the perioperative period.25 Preoperative patient education should include the details related to the preoperative preparation regimen, such as specific antibacterial agents used for showering prior to surgery and dietary restrictions related to fluid, food, and medications.31 The nurse should also incorporate information about the order and flow of events on the day of surgery, the perioperative environment, and the interdisciplinary team members involved in patient education plans.31 The anesthesia providers as well as the surgeon participate in patient education. They provide the patient with specific information about the type of anesthesia and include an overview of the procedure.31 Other important topics include the review of pain assessment and types of management strategies used to achieve adequate pain relief.31 The patient should understand the potential postoperative complications and interventions that are implemented in order to prevent them from occurring. The nurse should cover expectations related to ambulation, diet, and pulmonary hygiene activities.31

Preparing the patient for discharge is crucial to postsurgical recovery and enhances the patient's ability to participate fully in self-care activities.32 The nurse addresses postdischarge needs and addresses any resulting changes in the patient's medical regimen. For example, anticoagulation therapy involves a lifelong commitment to medication adherence and the necessary medical and diagnostic follow-up in order to prevent the development of a future thrombus.2,5,21 Supplemental materials, such as brochures or videos, are helpful tools that nurses can integrate into the patient education process.32

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Conclusion

A better understanding of CTEPH and its treatment options is needed. PTE is a highly involved surgical intervention that offers patients a potential curative option for CTEPH.1,2,4,5,9,11 Nurses are essential members of the interdisciplinary team in the execution of independent and collaborative interventions in the care and management of patients undergoing PTE. However, the literature is lacking in specific care recommendations for these patients in the postoperative period. Future research and publications to address these deficits is warranted. It is vital that nurses fully comprehend the complexity of this surgical intervention and related management strategies to reduce the risk of potential complications and contribute to patient recovery and discharge to home.

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Pulmonary circulation

The illustration below shows the pulmonary circulation. Although the intrapulmonary relationships are accurately demonstrated, the separation of the vessels of the root of the lung has been exaggerated in the hilar region to show them as they enter and leave the lung. Note that the right pulmonary artery passes under the arch of the aorta to reach the right lung and that the left pulmonary artery lies completely to the left of the arch.

Figure

Figure

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Chronic pulmonary thromboembolism

The image below is a frontal view of a right pulmonary angiogram in a 42-year-old female with an acute pulmonary embolus diagnosed and treated 6 months earlier. The proximal pulmonary arteries are dilated. The distal vessels taper rapidly and are irregular (arrows). Eccentric stenoses are present (arrowheads) as well as intraluminal webs (open arrow).

Figure

Figure

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Factors that influence the surgical decision5,9,11,17-19

This decision is based on a variety of factors, including:

  • symptom severity and disease state, such as pulmonary hypertension and right heart dysfunction
  • thrombus accessibility
  • obstruction extent
  • absence or presence of extensive distal disease, as demonstrated by pulmonary vascular resistance
  • other comorbidities that may create higher surgical risks, such as recurrent venous thromboembolism, antiphospholipid antibodies and lupus anticoagulant, inflammatory bowel disease, ventriculoatrial shunt, cardiac pacemaker, or a history of splenectomy or thyroid hormone replacement
  • procedural and technical difficulties
  • long-term patient benefits; surgery may be curative with resolution of right heart dysfunction and pulmonary hypertension
  • results of specialized testing; for example, right heart catheterization, pulmonary angiography, and computed tomography pulmonary angiogram.
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REFERENCES

1. Lang I. Chronic thromboembolic pulmonary hypertension: a distinct disease entity. Eur Respir Rev. 2015;24(136):246–252.
2. Galiè N, Hoeper MM, Humbert M, et al Guidelines for the diagnosis and treatment of pulmonary hypertension: The Task Force for the Diagnosis and Treatment of Pulmonary Hypertension of the European Society of Cardiology (ESC) and the European Respiratory Society (ERS), endorsed by the International Society of Heart and Lung Transplantation (ISHLT). Eur Heart J. 2009;30(20):2493–2537.
3. Galiè N, Humbert M, Vachiery JL, et al 2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension. The Joint Task Force for the Diagnosis and Treatment of Pulmonary Hypertension of the European Society of Cardiology (ESC) and the European Respiratory Society (ERS). Eur Respir J. 2015;46(4):903–975.
4. Jenkins D, Madani M, Fadel E, D'Armini AM, Mayer E. Pulmonary endarterectomy in the management of chronic thromboembolic pulmonary hypertension. Eur Respir Rev. 2017;26(143):160111.
5. Kooperkamp H, Mehta I, Fary D, Bates M. Pulmonary thromboendarterectomy for pulmonary hypertension before considering transplant. Ochsner J. 2017;17(1):66–70.
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Keywords:

cardiopulmonary bypass (CPB); chronic thromboembolic pulmonary hypertension (CTEPH); median sternotomy; pulmonary embolism; pulmonary thromboendarterectomy (PTE); right-sided heart failure; stenosis

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