Chronic thromboembolic pulmonary hypertension: Pulmonary thromboendarterectomy

INTRODUCTION — Pulmonary thromboendarterectomy (PTE; also known as pulmonary endarterectomy) is the only definitive therapy for patients with chronic thromboembolic pulmonary hypertension (CTEPH) [1-3].

Preparation for PTE, postoperative management, and outcomes following PTE are reviewed here. Initial management of CTEPH, patient selection for PTE, and treatment of CTEPH with pulmonary hypertension-specific therapy are described separately. (See "Chronic thromboembolic pulmonary hypertension: Initial management and evaluation for pulmonary artery thromboendarterectomy" and "Chronic thromboembolic pulmonary hypertension: Pulmonary hypertension-specific therapy".)

The approach outlined in this topic is, for the most part, consistent with guidelines set out by several international societies [4-7].

PATIENT SELECTION — For patients with chronic thromboembolic pulmonary hypertension (CTEPH), the decision to proceed with pulmonary thromboendarterectomy (PTE) is complex and best undertaken at a center experienced in the care of these patients. The decision is based upon the location and extent of chronic thromboembolic obstruction, the associated hemodynamic impairment, and comorbidities that might contribute to the risk of surgery (algorithm 1). Details of this evaluation are provided separately. (See "Chronic thromboembolic pulmonary hypertension: Initial management and evaluation for pulmonary artery thromboendarterectomy", section on 'Evaluation for pulmonary thromboendarterectomy'.)

SPECIFIC PREOPERATIVE ASSESSMENT — For patients with chronic thromboembolic pulmonary hypertension (CTEPH), we evaluate for general, cardiac, pulmonary, and other factors that may contribute to the risk of pulmonary thromboendarterectomy (PTE). Evaluation for PTE-specific factors, including the need for coronary angiography and an inferior vena cava (IVC) filter, is discussed in this section, while general preoperative assessment is discussed separately. (See "Overview of the principles of medical consultation and perioperative medicine" and "Evaluation of perioperative pulmonary risk" and "Surgical risk and the preoperative evaluation and management of adults with obstructive sleep apnea" and "Preoperative evaluation and perioperative management of patients with rheumatic diseases" and "Preoperative assessment of bleeding risk" and "Evaluation of cardiac risk prior to noncardiac surgery" and "Management of cardiac risk for noncardiac surgery".)

Coronary angiography — For patients who are at risk for coronary artery disease (CAD) in whom PTE is planned, we perform coronary angiography prior to surgery. This is often done at the same time as right heart catheterization and pulmonary angiography when assessing a patient’s suitability for PTE. CAD is treated prior to PTE but if indicated, coronary artery bypass grafting can be performed during the same operation as PTE [8]. (See "Evaluation of cardiac risk prior to noncardiac surgery" and "Management of cardiac risk for noncardiac surgery".)

Data to support this practice are limited. In one review that evaluated routine coronary angiography in 462 patients prior to PTE, significant CAD was detected in 16 percent of patients who were ≥50 years of age. CAD was found in only 5 percent of patients <50 years of age; furthermore, significant CAD was only found in those with three or more coronary risk factors present (diabetes, hypertension, hyperlipidemia, body mass index [BMI] >25 kg/m², tobacco use, or a family history of CAD) [9].

Inferior vena cava filter placement — While in the past it was routine, we now no longer routinely place IVC filters prior to PTE since our clinical experience suggests they are not necessary and patients are typically anticoagulated indefinitely.

However, in patients with an unusually high risk of thromboembolic recurrence, we sometimes place a temporary IVC filter prior to surgery (eg, those with a recent episode of acute, proximal lower extremity venous thrombosis) [10]. Under this unusual circumstance, a retrievable IVC filter can be placed several days prior to surgery in order to avoid bleeding complications at the insertion-site during the perioperative period [1]. A percutaneous transjugular approach is preferred in order to avoid lower extremity insertion site thrombosis.

Details regarding placement of IVC filters and their complications are discussed separately. (See "Placement of vena cava filters and their complications".)

SURGICAL TECHNIQUE

Pre-operative management of anticoagulation — We discontinue anticoagulant therapy (eg, warfarin or direct oral anticoagulation [DOAC]) at least three days prior to pulmonary thromboendarterectomy (PTE) and use bridging therapy with subcutaneous low molecular weight heparin (LMWH) until the day prior to surgery. (See "Perioperative management of patients receiving anticoagulants".)

Standardized approach — Although subject to minor variation, the surgical approach pioneered at the University of California, San Diego has been standardized over the past decade and involves the following elements [1,4,11-16]:

●Median sternotomy – A median sternotomy allows access to both pulmonary arteries intrapericardially without having to breach the pleural space. It also assures more complete removal of the chronically obstructing material and decreases the likelihood that bronchial artery collateral flow will be disrupted.

●Double lung ventilation – Most patients undergo double lung ventilation for PTE.

●Cardiopulmonary bypass with periods of deep hypothermic circulatory arrest - Cardiopulmonary bypass with periodic hypothermic circulatory arrest provides the bloodless operative field essential for meticulous lobar and segmental dissections of the chronic thromboembolic material.

Periods of circulatory arrest are limited to 20-minute intervals. After each period of circulatory arrest, reperfusion is carried out until either the pulmonary venous saturations reach 90 percent or at least 10 minutes have passed. At the completion of the unilateral or bilateral PTE, circulation is re-established and the patient is rewarmed.

●Dissection of the pulmonary artery and removal of chronic thrombus – The main, lobar, and segmental branches of typically both pulmonary arteries are targeted for endarterectomy. An entire unilateral endarterectomy can usually be accomplished by an experienced surgeon within a single 20-minute period of hypothermic circulatory arrest.

Endarterectomy is started by separating the adventitia from the media circumferentially at the most proximal aspect of the surgically visualized chronic thrombus. This requires careful dissection of chronic endothelialized material from the native intima. There are several levels within the vessel where an endarterectomy plane can be established, but only one will strip easily away from the underlying media. Establishing the correct plane is essential. A plane that is too deep results in perforation of the vessel, while a plane that is too superficial will not result in an adequate endarterectomy. Once this plane is identified proximally, dissection is continued distally into the segmental and subsegmental branches (picture 1).

●Atrial septum inspection – Following dissection, the atrial septum is routinely inspected, since a previously unidentified atrial septal defect (ASD) or patent foramen ovale is uncovered during surgery in approximately 25 percent of cases and can often be repaired during the same operative setting.

●Additional procedures – Additional procedures that are indicated, such as ASD repair, coronary bypass grafting, or valve replacement, are performed after dissection and rewarming.

Alternative techniques — Several alternative techniques have been explored in an effort to reduce the neurologic complications of hypothermia and circulatory arrest, but none have proven superior to the traditional technique [1]. These include the use of moderate rather than deep hypothermia, aortic bronchial artery occlusion with a balloon catheter, antegrade cerebral artery perfusion with and without total circulatory arrest, and the application of negative pressure in the left ventricle [17-19]. The theoretical advantage of these alternatives is that surgery can be prolonged to achieve a more precise and complete removal of thrombotic material including the removal of more distal thrombus [20], and that cerebral perfusion may be better preserved.

POSTOPERATIVE MANAGEMENT — For patients with chronic thromboembolic pulmonary hypertension (CTEPH) who have undergone pulmonary thromboendarterectomy (PTE), vigilant postoperative monitoring is necessary because the postoperative course can be complex and it is the period of greatest mortality [21]. Early management should focus on providing adequate oxygenation, optimizing right ventricular preload, and providing inotropic support. Management of an acute pulmonary hypertensive crisis is discussed separately. (See "Treatment and prognosis of pulmonary arterial hypertension in adults (group 1)" and "Treatment and prognosis of pulmonary arterial hypertension in adults (group 1)", section on 'Management of acute pulmonary hypertensive crisis'.)

Intensive care unit postoperative care — All patients require intensive care unit (ICU) admission following surgery and are typically intubated and mechanically ventilated. Veno-veno-extracorporeal membrane oxygenation (V-V ECMO) is rarely needed, although veno-arterial ECMO (V-A ECMO) is more commonly required perioperatively [22].

In the immediate postoperative period, patients typically have the following in place:

●A pulmonary artery catheter to monitor cardiac output and pulmonary artery pressure

●A Foley catheter to monitor urine output

●Temporary transcutaneous pacing wires

●An arterial catheter to monitor systemic blood pressure and provide access for arterial blood gas measurements

●One or more mediastinal tubes to aid with mediastinal drainage

A daily assessment is performed that includes a physical examination, routine laboratories, coagulation studies, and, if indicated, an electrocardiogram or chest radiograph. Echocardiography is not routinely performed unless a cardiac complication was suspected (eg, acute myocardial infarction). Careful ICU monitoring during the early postoperative period is critical since two phenomena, pulmonary artery steal and reperfusion pulmonary edema (RPE), can occur during this early period. Both conditions can occur in isolation or together and can result in profound hypoxemia. These conditions are described below. (See 'Monitoring for pulmonary endarterectomy-specific complications' below.)

Balloon inflation of the Swan Ganz catheter is not performed due to the risk of disruption of the pulmonary artery suture lines. The Swan Ganz catheter is typically removed when vasoactive medication support is able to be discontinued. (See "Pulmonary artery catheterization: Indications, contraindications, and complications in adults" and "Pulmonary artery catheters: Insertion technique in adults" and "Pulmonary artery catheterization: Interpretation of hemodynamic values and waveforms in adults".)

Pacer wires are removed when a stable sinus rhythm has been achieved. (See "Temporary cardiac pacing".)

Extubation is undertaken, usually on the first or second postoperative day in the majority of patients, when the patient is awake and alert and gas exchange is adequate such that mechanical ventilatory support is no longer required. (See "Extubation management in the adult intensive care unit" and "Initial weaning strategy in mechanically ventilated adults".)

Once patients are extubated, they can be transferred to the floor for further monitoring including telemetry given the risk of postoperative atrial arrhythmias. The median ICU length of stay is approximately three to four days, with a total postoperative hospital length of stay of 10 to14 days.

Venous thromboembolism prophylaxis and resumption of therapeutic anticoagulation — Patients with CTEPH are at high postoperative risk of recurrent thromboembolism. For the majority of patients, we initiate pharmacologic thromboprophylaxis 8 to 12 hours after the surgical procedure provided there are no contraindications and the mediastinal output has decreased to approximately 30 mL/hour.

Prophylactic anticoagulation can be provided in a variety of ways, but our method of choice is intravenous unfractionated heparin targeting an anti-Xa level in the low therapeutic range (0.3 to 0.5 international units/mL). This preference is based upon the potential need to discontinue anticoagulation should the need arise (eg, procedures, bleeding). Once the patient is no longer critically ill and the pacing wires are removed, therapeutic anticoagulation is initiated. (See "Prevention of venous thromboembolic disease in acutely ill hospitalized medical adults".)

Once therapeutically anticoagulated with unfractionated heparin, we transition to oral warfarin. We prefer to use warfarin for the first several months after surgery given its ability to be monitored and its ease of reversal should bleeding complications occur. Thereafter, anticoagulation with warfarin or a direct oral anticoagulation (DOAC) is maintained indefinitely. (See "Warfarin and other VKAs: Dosing and adverse effects", section on 'Warfarin administration' and "Chronic thromboembolic pulmonary hypertension: Initial management and evaluation for pulmonary artery thromboendarterectomy", section on 'Anticoagulant therapy (indefinite)'.)

Monitoring for pulmonary endarterectomy-specific complications — Patients with CTEPH who undergo PTE may experience complications that are common to other types of cardiothoracic surgery (eg, arrhythmias, atelectasis, wound infection, pericardial effusions, and delirium) (see "Overview of the management of postoperative pulmonary complications" and "Postoperative mediastinitis after cardiac surgery" and "Postoperative complications among patients undergoing cardiac surgery"). They may also experience two unique complications that can significantly impair gas exchange: pulmonary artery steal and RPE, which are discussed in the sections below. These complications can occur in isolation or together.

Pulmonary artery steal — Pulmonary artery steal occurs in approximately 70 percent of patients following PTE. Pulmonary artery steal refers to the postoperative redistribution of pulmonary arterial blood flow from originally well-perfused segments into the newly endarterectomized segments, with subsequent ventilation-perfusion mismatching and hypoxemia [23].

Pulmonary artery steal presents with nonspecific features of hypoxemic respiratory failure immediately after surgery, typically in the absence of infiltrates on imaging. Treatment is supportive (ie, low-flow or high-flow supplemental oxygen, mechanical ventilation). Pulmonary vascular steal resolves in most patients within a few days. Supplemental oxygen needs resolve within two weeks of hospital discharge [24].

Reperfusion pulmonary edema — RPE occurs in approximately 30 percent of patients following PTE. RPE is a type of high-permeability (ie, non-cardiogenic) pulmonary edema that typically occurs in areas of the lung from which proximal thromboemboli were removed [25,26]. (See "Noncardiogenic pulmonary edema".)

RPE typically appears up to 72 hours after surgery. Presentation features include hypoxemic respiratory failure and bilateral infiltrates, ranging from mild postoperative hypoxemia to severe hemorrhagic pulmonary edema that results in profound hypoxemia and, rarely, death.

We manage patients with RPE in a similar fashion to patients with acute respiratory distress syndrome (ARDS; eg, diuresis, lung protective ventilator strategy). Although not routine, small case series suggest that inhaled nitric oxide may improve oxygenation in this population [26-29]. Veno-venous extracorporeal membrane oxygenation may be required in patients who fail this approach. We do not perform prone ventilation due to the fresh sternotomy. (See "Acute respiratory distress syndrome: Clinical features, diagnosis, and complications in adults" and "Acute respiratory distress syndrome: Ventilator management strategies for adults" and "Acute respiratory distress syndrome: Fluid management, pharmacotherapy, and supportive care in adults".)

Predicting which patients will develop RPE is difficult. In one study, the Pulmonary Edema Predictive Scoring Index (PEPSI) was reported in patients undergoing percutaneous transluminal balloon pulmonary angioplasty (BPA) as therapy for CTEPH. PEPSI is a measure of the change in pulmonary arterial blood flow before and after angioplasty [30]. A higher PEPSI score (cut-off value of 35.4) was associated with a higher risk of RPE. PEPSI requires greater validation before it can be routinely used to predict the risk of RPE following BPA or PTE. (See "Chronic thromboembolic pulmonary hypertension: Initial management and evaluation for pulmonary artery thromboendarterectomy", section on 'Percutaneous balloon pulmonary angioplasty'.)

Low tidal volume ventilation or nitric oxide administration does not appear to prevent RPE [31].

Pulmonary hemodynamics — Following PTE, hemodynamic improvement in pulmonary artery pressures and pulmonary vascular resistance (PVR) is typically dramatic and immediate (table 1) [1,32-34]. Most of the hemodynamic improvement occurs during the first few hours to days, with small improvements in the weeks to months thereafter. In most patients, the assessment for the degree of improvement takes place six weeks to three months after PTE, and it is rare that repeat PTE or medical therapy is considered in the early postoperative setting. (See 'Expected course for pulmonary hemodynamics and symptoms' below and 'Residual pulmonary hypertension' below.)

In one study, the mean reduction in PVR in the immediate postoperative period was nearly 70 percent, and a PVR in the range of 200 to 350 dyne seconds/cm⁵ (2.5 to 4.4 Wood units) was frequently achieved; although the higher end of this range is still in keeping with mild pulmonary hypertension (PH; eg, ≥240 dynes per second per cm-⁵ [≥3 Wood units]) [35]. Normalization of PVR can occur but typically only in those with lower pulmonary pressures prior to PTE.

The hemodynamic improvement is associated with improvement of symptoms, physical signs, exercise capacity, functional capacity, and oxygen requirement. Symptoms, exercise, and function may continue to improve slightly over the ensuing three months. (See 'Expected course for pulmonary hemodynamics and symptoms' below.)

Echocardiography demonstrates a decrease in right atrial and right ventricular chamber size, normalization of the interventricular septum, and decrease or resolution of tricuspid regurgitation [36-39]. (See "Clinical features and diagnosis of pulmonary hypertension of unclear etiology in adults", section on 'Echocardiography'.)

Some patients have residual pulmonary hypertension, the details of which are discussed below. (See 'Residual pulmonary hypertension' below.)

While occasionally needed, V-A ECMO may be required in patients who have acute decompensated right ventricular function after surgery [22,40].

Perioperative mortality — Perioperative mortality among patients undergoing PTE for CTEPH has decreased over the last few decades and in our experience is typically 2 to 4 percent [13,41-44].

●In one study of 500 patients who had undergone PTE, perioperative mortality fell from 16 percent before 1990 to 7 percent between 1990 and 1999, and 4 percent between 1998 and 2002 [42].

●Data analysis from an international registry reported an in-hospital postoperative mortality rate of 4.7 percent between 2007 and 2009 [43].

●Another study reported in-hospital mortality rates as low as 2.5 percent between 2011 and 2016 [44].

●Among low-risk patients, a perioperative mortality rate of only 1.3 percent has been reported [13].

RPE and right ventricular failure due to residual PH are the most common causes of death [1]. Other causes of perioperative mortality include cardiac arrest, multiorgan failure, uncontrollable mediastinal bleeding, sepsis, and massive pulmonary hemorrhage. (See 'Reperfusion pulmonary edema' above.)

Predictors of mortality have been reported. Important predictors of perioperative mortality include [44-49]:

●Elevated PVR - Patients with preoperative PVR <1,000 dynes per second per cm^-5 (<12.5 Wood units) have an estimated mortality <1.6 percent while those with a preoperative PVR ≥1,000 dynes per second per cm^-5 (≥12.5 Wood units) have a mortality of 4 percent

●Age – Patients older than 70 years have an estimated mortality of 8 percent.

●Distal (ie, microvascular) disease – Patients with distal embolic disease have an estimated mortality of 8 percent.

Other factors include intraoperative complications, additional cardiac procedures (eg, coronary artery bypass grafting), and co-morbidities.

FOLLOW-UP — After pulmonary thromboendarterectomy (PTE), patients are followed long term.

●We routinely see patients within one to two weeks after discharge and every six weeks to six months thereafter, where we inquire about symptoms and ensure therapeutic anticoagulation.

●We repeat a ventilation perfusion scan and echocardiogram approximately six weeks to three months after PTE in order to establish new baseline studies.

●In patients with features suggestive of residual PH and patients with a postoperative mean pulmonary artery pressure ≥30 mmHg, we additionally perform right heart catheterization to determine if further interventions are indicated (eg, PH-specific therapy and/or balloon pulmonary angioplasty). (See "Chronic thromboembolic pulmonary hypertension: Initial management and evaluation for pulmonary artery thromboendarterectomy", section on 'Inoperable candidates' and 'Residual pulmonary hypertension' below.)

LONG TERM OUTCOMES

Survival — Following discharge, additional deaths may be expected, approximately one-half from conditions other than progressive right ventricular failure and the remainder due to pulmonary hypertension (PH)-related issues (ie, failed PTE). The overall three-year survival is approximately 85 percent at one year but declines over time [44,46,49]:

●In one study of 880 patients who underwent PTE, the overall survival was 86 percent at one year, 84 percent at three years, 79 percent at five years, and 72 percent at 10 years [46]. Few deaths were due to right heart failure.

●Similarly, another study of 239 patients reported the three-, five-, and ten-year survival as 84, 77, and 62 percent, respectively [44].

Among patients with CTEPH who survive three months post-PTE, mortality is low:

●In an observational study that followed 137 patients with CTEPH who survived three months following PTE, 4 percent died from CTEPH-related causes during the four-year follow-up period [50].

●A similar study demonstrated one- and three-year mortality rates of 1 and 6 percent, respectively [41].

Predictors for reduced long-term survival are poorly studied [44,46,49]. However, one study reported that an elevated mean pulmonary artery pressure (mPAP) ≥38 mmHg and a pulmonary vascular resistance (PVR) ≥425 dynes per second per-cm^-5 identified patients at a higher risk of death from CTEPH [46].

Expected course for pulmonary hemodynamics and symptoms — Hemodynamic and symptomatic improvement occur in the vast majority of patients following PTE. Long-term improvement is likely due to reduced right ventricular afterload (due to a reduction in PH), resolution of postoperative anemia and deconditioning, and improved ventilation-perfusion matching as postoperative pulmonary artery steal resolves. Improvement generally persists following surgery according to studies that have followed patients for up to 24 months (table 1) [32,33,51,52]. Most patients are New York Heart Association (NYHA) functional Class III or IV preoperatively and improve to NYHA Class I or II postoperatively (table 2 and table 3). Many patients resume normal activity, including employment [51]. A small proportion develop slowly progressive PH over several years that may warrant medical therapy. (See "Chronic thromboembolic pulmonary hypertension: Pulmonary hypertension-specific therapy" and 'Residual pulmonary hypertension' below.)

PTE also appears to have a lasting impact on peripheral oxygen extraction and cardiac performance [53]. One study of 20 patients who underwent serial cardiopulmonary exercise testing (CPET) reported ongoing improvement of peak oxygen uptake, ventilatory efficiency, and exercise capacity, reaching a plateau one to six months after surgery. Improved exercise capacity may be due to decreased PVR, or improved ventilation or stroke volume index [54]. General principles of CPET are discussed elsewhere. (See "Exercise physiology" and "Cardiopulmonary exercise testing in cardiovascular disease".)

Recurrent thromboembolism — Recurrent acute thromboembolism is rare since these patients are indefinitely anticoagulated and if thromboembolism does occur, it is typically due to sub-therapeutic anticoagulation. Less than 0.5 percent of all patients who have undergone PTE develop recurrent thromboembolic disease, and it is equally rare that repeat PTE is required [55].

For patients who do develop recurrent embolism, we suggest a three-month period of anticoagulation to allow thrombus resolution before evaluating whether a repeat endarterectomy procedure might be indicated. Management of recurrent thromboembolism while on anticoagulant therapy is discussed separately. (See "Treatment, prognosis, and follow-up of acute pulmonary embolism in adults", section on 'Management of recurrence on therapy'.)

Residual pulmonary hypertension — Although PH normalizes in many patients following PTE, some have residual PH. Rates range from 15 to 51 percent (on average 30 percent) [41,46,56-58]. The variation of the estimates likely reflects whether a threshold of 20 mmHg, 25 mmHg, or 30 mmHg is used to define postoperative residual PH.

We use a postoperative mPAP≥30 mmHg as a plausible threshold to define which patients require consideration of additional therapies for residual PH, such as PH-specific medication and/or balloon pulmonary angioplasty (BPA) [46]. Our practice is to perform a repeat right heart catheterization 6 to 12 weeks after the thromboendarterectomy procedure in patients with a postoperative mPAP ≥30 mmHg or those with symptoms suggestive of PH to determine if these additional interventions are indicated.

Management of residual PH varies and is dependent upon the severity of the underlying PH as well as functional capacity and etiology of the PH (eg, residual distal disease or residual thromboembolism, recurrent CTEPH). In this population we consider the following principles:

●For patients with residual PH who have Class I NYHA symptoms (table 3), we typically observe them clinically for symptoms of progressive disease, which, if present, should prompt further investigation for recurrent CTEPH. (See "Epidemiology, pathogenesis, clinical manifestations and diagnosis of chronic thromboembolic pulmonary hypertension".)

●For patients with residual PH who have NYHA functional Class II to IV symptoms (table 3) who are not suitable for additional surgery, we typically initiate PH-specific therapy. The initiation of PH-specific therapy requires a detailed assessment by a specialist in PH in a PH center. (See "Chronic thromboembolic pulmonary hypertension: Pulmonary hypertension-specific therapy".)

Alternatively, preliminary data suggest that BPA with or without PH-specific therapy may be an option in this population if accessible target lesions are identified on pulmonary angiography, the details of which are also discussed separately. (See "Chronic thromboembolic pulmonary hypertension: Initial management and evaluation for pulmonary artery thromboendarterectomy", section on 'Percutaneous balloon pulmonary angioplasty' and "Chronic thromboembolic pulmonary hypertension: Initial management and evaluation for pulmonary artery thromboendarterectomy", section on 'Combined therapy'.)

●For patients with refractory PH following PTE, transplantation may be the only option. PH-specific therapy may be needed as a bridge to transplantation. (See "Chronic thromboembolic pulmonary hypertension: Initial management and evaluation for pulmonary artery thromboendarterectomy", section on 'Double lung transplantation'.)

●For patients who experience recurrent thromboembolism associated with PH, we re-evaluate patients for repeat PTE. (See "Chronic thromboembolic pulmonary hypertension: Initial management and evaluation for pulmonary artery thromboendarterectomy", section on 'Evaluation for pulmonary thromboendarterectomy'.)

Repeat PTE has been performed successfully. The morbidity and mortality of the second surgery is comparable to the primary procedure, but the improvement in hemodynamics is typically less impressive [55].

It is possible for patients with residual PH to achieve functional improvement and a survival equivalent to those who do not have persistent PH following surgery [58]. However, the outcomes vary depending on the therapy chosen, their response to medications, and degree of residual PH.

Residual PH is unclear but likely due to distal (ie, surgically inaccessible) thromboemboli or irreversible vasculopathy. One imaging study reported residual disease in 45 percent of patients, but subsegmental pulmonary vasculature was only abnormal in 20 percent; this suggested that residual undetectable microvascular lesions may contribute to PH in this population [59]. Alternatively, irreversible vasculopathy may have contributed to PH, more than what was originally suspected at the time of the PTE evaluation.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Pulmonary hypertension in adults".)

SUMMARY AND RECOMMENDATIONS

●Pulmonary thromboendarterectomy (PTE) is the only definitive therapy for patients with chronic thromboembolic pulmonary hypertension (CTEPH). Selecting ideal candidates for PTE should occur at a center experienced in the care of these patients. The decision to proceed with PTE is based upon the location and extent of chronic thromboembolic obstruction, the associated hemodynamic impairment, and comorbidities that might contribute to the risk of surgery. (See 'Patient selection' above and "Chronic thromboembolic pulmonary hypertension: Initial management and evaluation for pulmonary artery thromboendarterectomy".)

●We evaluate patients with CTEPH in whom PTE is planned for general, cardiac, pulmonary, and other factors that may contribute to the risk of PTE. Specific to PTE are the following (see 'Specific preoperative assessment' above):

•For patients who are at risk for coronary artery disease in whom PTE is planned, we perform coronary angiography prior to surgery. (See 'Coronary angiography' above.)

•We suggest not routinely placing an inferior vena caval (IVC) filter (Grade 2C). We sometimes place an IVC filter in patients with a higher than usual risk of thromboembolic recurrence in the perioperative period; in such patients, we place a retrievable filter several days prior to surgery and use the transjugular approach. (See 'Inferior vena cava filter placement' above.)

●PTE typically involves a median sternotomy and cardiopulmonary bypass with periods of hypothermic circulatory arrest. The main, lobar, and segmental branches of typically both pulmonary arteries are targeted for removal of chronic thrombus. An entire unilateral endarterectomy can usually be accomplished by an experienced surgeon within 20 minutes of hypothermic circulatory arrest. Additional surgeries that are indicated, such as atrial septal defect repair, coronary bypass grafting, or valve replacement, are performed after dissection and rewarming. Alternative techniques have been explored, but none have proven superior to the traditional technique. (See 'Surgical technique' above.)

●Patients with CTEPH who undergo PTE should undergo vigilant postoperative monitoring because the postoperative course can be complex, and it is the period of greatest mortality. We monitor for the typical postoperative complications that are common to other types of cardiothoracic surgery (eg, arrhythmias, atelectasis, wound infection, pericardial effusions, and delirium). (See "Overview of the management of postoperative pulmonary complications" and "Postoperative mediastinitis after cardiac surgery" and "Postoperative complications among patients undergoing cardiac surgery".)

Monitoring for issues specific to PTE include the following:

•All patients require intensive care unit (ICU) admission and are typically intubated and mechanically ventilated. Most patients have a pulmonary artery catheter in place (no balloon inflation) as well as a Foley catheter, temporary transcutaneous pacing wires, an arterial catheter, and one or more mediastinal tubes. We perform daily assessment with physical examination, routine laboratories, coagulation studies, and, if indicated, an electrocardiogram or chest radiograph. (See 'Intensive care unit postoperative care' above.)

•For the majority of patients, we suggest initiating pharmacologic thromboprophylaxis postoperatively, provided there are no contraindications (Grade 2C). We typically start thromboprophylaxis 8 to 12 hours after PTE, provided the mediastinal output has decreased to approximately 30 mL/hour. Agent choice is center-specific. We suggest intravenous unfractionated heparin targeting an anti-Xa level in the low therapeutic range (0.3 to 0.5 international units/mL) as our preferred method (Grade 2C). This preference is based upon the potential need to discontinue anticoagulation should the need arise (eg, procedures, bleeding). Once the patient is no longer critically ill and the pacing wires removed, we initiate therapeutic anticoagulation. Choice of agent for long-term anticoagulation is discussed separately. (See 'Venous thromboembolism prophylaxis and resumption of therapeutic anticoagulation' above and "Chronic thromboembolic pulmonary hypertension: Initial management and evaluation for pulmonary artery thromboendarterectomy", section on 'Anticoagulant therapy (indefinite)'.)

•Two complications that are unique to PTE can occur in isolation or together. These are pulmonary artery steal and reperfusion pulmonary edema. Both conditions are typically self-limiting and treated supportively but occasionally can result in profound hypoxemia, pulmonary hemorrhage, and rarely death. We use strategies that are similar to those used in patients with acute respiratory distress syndrome, the details of which are discussed separately. (See 'Monitoring for pulmonary endarterectomy-specific complications' above and "Acute respiratory distress syndrome: Ventilator management strategies for adults" and "Acute respiratory distress syndrome: Fluid management, pharmacotherapy, and supportive care in adults".)

•Improvement in pulmonary hemodynamics is typically dramatic and immediate following PTE, with marked reductions in pulmonary artery pressures and pulmonary vascular resistance (PVR) (table 1). (See 'Pulmonary hemodynamics' above.)

●The perioperative mortality among patients undergoing PTE for CTEPH is typically 2 to 4 percent, with lower rates in low-risk patients (eg, those with PVR <1000 dynes per second per cm^-5 [<12.5 Wood units], no comorbidities) and higher rates in others (eg, those with a PVR ≥1000 dynes per second per cm^-5 [≥12.5 Wood units], older age >70 years, distal disease), and those who undergo additional cardiac procedures or develop complications of thoracic surgery. (See 'Perioperative mortality' above.)

●The long-term beneficial effects of PTE include continued hemodynamic and symptomatic improvement, improved functional class (table 3), and probably, decreased mortality. The overall three-year survival is approximately 85 percent at one year but declines over time. Recurrent thromboembolism is rare and often relates to subtherapeutic anticoagulation. (See 'Long term outcomes' above and 'Expected course for pulmonary hemodynamics and symptoms' above and 'Survival' above and 'Recurrent thromboembolism' above.)

●Somewhere between 15 to 51 percent of patients have residual PH (on average 30 percent). Management of residual PH varies and is dependent upon the severity of the underlying PH as well as functional capacity and etiology of the PH. Further details regarding PH-specific therapy are provided separately. (See 'Residual pulmonary hypertension' above and "Chronic thromboembolic pulmonary hypertension: Pulmonary hypertension-specific therapy" and "Chronic thromboembolic pulmonary hypertension: Initial management and evaluation for pulmonary artery thromboendarterectomy", section on 'Pulmonary hypertension-specific therapy'.)