Surgical Treatment in Pulmonary Hypertension

Abstract

Pulmonary hypertension (PH) is a medical condition with complex physiopathology due to several diseases involving heart, lung, connective tissue, or multifactorial. This chapter analyzes the main surgical procedures used in PH, starting with lung transplantation, pulmonary endarterectomy for chronic thromboembolism, mechanical circulatory support, and right-to-left shunts as palliative procedures. The indications for surgery, donor organ procurement, and preservation techniques are also reviewed.

1. Introduction

Pulmonary hypertension (PH) is a manifestation of high pulmonary artery pressure, which targets pulmonary artery vasculature by stimulating pathological transformations ending with increasing pulmonary vascular resistance and right heart failure. Pulmonary hypertension definition means a mean pulmonary artery pressure equal to or higher than 20 mm Hg at rest [1].

The clinical classification of PH incorporates five distinctive categories, group 1, pulmonary arterial hypertension (PAH). Group 2, PH associated with left heart disease (LHDPH). Group 3, PH associated with lung disease (LDPH). Group 4, PH related to thromboembolic obstruction of pulmonary arteries (CTEPH), and group 5 with unclear or multifactorial mechanism.

Pulmonary hypertension is very common in group 2, common in group 3, and rare in groups 1, 4, and 5 [1]. The main therapeutic, surgical procedure for PH is lung transplantation, mainly for group 1 and for group 3 in selected cases, and pulmonary artery endarterectomy is dedicated to group 4, including CTEPH [1]. Other surgical procedures as temporary mechanical circulatory support or shunt palliations can also be used as bridge to transplantation.

2. Lung transplantation

Is the procedure used to end-stage damage of pulmonary vasculature in group 1 (PAH) and for group 3 (LDPH), when there is recommendation to refer the patients for lung transplant evaluation and listing [1].

2.1 Indication for lung transplantation (LT)

Pulmonary arterial hypertension treatment for idiopathic, heritable, drug associated, and connective tissue disorders on risk 4 strata and intermediate and high risk recommends prostacyclin analog and evaluate for lung transplantation, class IIa [1].

For group 3 (LDPH) for pulmonary hypertension associated with hypoxia, it is recommended to send the qualified patients to lung transplant evaluation (class Ic) [1].

A 2014 consensus document for the selection of lung transplant candidates [2] mentioned end-stage lung disease general criteria:

1. High (>50%) risk of death from lung disease within two years if LT is not performed.

2. High (>80%) likelihood of surviving at least 90 days after lung transplantation.

3. High (80%) likelihood of 5-year posttransplant survival from a general medical perspective if adequate graft function exists.

Pulmonary hypertension secondary to congenital heart disease is common and responsive to curative surgery, but on severe PAH, lung transplantation can be used when medical therapy is futile. Contraindications for lung transplantation [3] are a recent history of malignancy (less< than 5 years), sepsis, severe organ dysfunction such as liver failure, heart failure, kidney failure, bleeding, severe obesity, severe chest wall deformity, no social support, psychiatric disease, drugs, alcohol intake, nonadherence to medical therapy, and no social support. For severe cases of PAH is preferable to bilateral lung transplantation [4]; for interstitial lung disease, single lung transplantation (SLT) or double lung transplantation (DLT) could be both options. In COPD, it depends on age if they are older SLT if they are younger BLT [4]. Patients with septic or infected lungs should have a DLT [4].

2.2 Donor lung selection, evaluation, procurement, and transportation

2.2.1 Donor lung selection and evaluation

Donor selection considers history, cause of death, clinical data, bronchoscopy findings, arterial blood gases evaluation, and other clinical tests such as chest X-Ray, CT thorax linked with intraoperative lung examination (organ inspection, color, absence of nodules, compliance, atelectatic areas, recruitable or not, pneumonia signs, trauma). Extended donor criteria are important for increasing the number of transplants and reducing the declining rate of organs. We try to accept older donors with secretions on bronchoscopy, recruitable atelectasis, or even with limited pneumonia (Table 1) [4].

Standard donor lung selection criteria	Extended lung selection criteria
Age < 55	Age > 55
Smoking history < 20 pack-years	Smoking history
P/F ratio > 300 on FIO2 100% and PEEP 5	P/F ratio < 300
No chest trauma	Unilateral lung infiltrate in double lung transplantation
No aspiration	Chest X-Ray abnormalities
No prior cardiothoracic surgery	EVLP
No infection	DCD
No purulent secretions on bronchoscopy
Clear chest X-ray

Table 1.

Donor allocation criteria [4].

Donation after cardiac death (DCD), usually in Maastricht category III, [4] has been successfully used in the last years with the purpose of donor pool extension. DCD donation exposes the organs to higher ischemic risk but can be used for lung retrieval. Ex vivo lung perfusion (EVLP) is a method of lungs preservation outside the body, focusing on lung repair, and evaluation (by gas analysis, and other blood criteria and repeat bronchoscopy) if they are qualified to be implanted.

2.2.2 Donor lung procurement (harvesting)

2.2.2.1 Lung procurement in DBD

The ideal lung donor may be less than 55 years old, a nonsmoker, and without infections. Additionally, the lungs may have the same size, size matching being very important in ruling out the organ [5]. Oversizing is accepted, but under-sizing is forbidden. The height, weight, and predicted total lung capacity are considered for sizing. A single lung transplantation assessment requires selective gases from each pulmonary vein [5]. Bronchoscopy is done prior to surgery; the tracheobronchial tree is analyzed, and samples for microbiology are taken. Cautious bronchial inspection and lavage are performed to improve the quality of the lungs. The surgical technique starts with opening the chest through median sternotomy, entering pleural cavities, and lung examination. The organs are inspected carefully and palpated to identify eventual masses, nodules, and recruitment maneuvers are performed on the atelectatic areas. If suspicious nodules are identified, a biopsy and the tissue will be sent to pathology [5]. The donor receives heparin, and when all teams are ready, the pulmonary trunk is cannulated, and the prostaglandin is given; the IVC is divided, the left atrial appendage is open for heart venting, and 3–4 liters of lung preservation solution Perfadex is administered antegrade in main pulmonary artery. The heart is explanted maintaining a good cuff around both right and left pulmonary veins to be used in both heart and lung transplantation. If the heart is not harvested for transplantation, an extensive atrial cuff is taken in favor of the lung, which is taken as a double lung block [5]. After the left atrial incision, IVC and SVC are cut, and aorta and pulmonary trunk are divided, and the heart is removed. Lung harvest begins with pulmonary ligament division, parallel with the esophagus on both sides, detaching the adjacent tissues on the left side until we reach the aorta, which is transversally cut at the site of the distal arch and on the right until the azygos vein, which is divided as well. The trachea is then freed from surrounding tissues and divided between two stapled lines, with the lungs semi-inflated at FIO₂ 70% under a Valsalva maneuver. The lungs are examined on the back table, and 1 liter of Perfadex is administered retrogradely throughout the pulmonary vein’s ostia sequentially. The last step is lung separation, by section with a stapler of the left bronchus and packing in three bags. Each lung’s first bag contains a preservation solution, and the other two with ice, and the lungs are ready for cold preservation and transportation.

2.2.2.2 Lung procurement in DCD donors

Withdrawal of life support is made in ICU when all the circulatory support and inotropic medication are stopped. Systemic heparin is necessary to prevent thrombosis of the donor organs, and warm ischemic time is starting. This agonal status usually cannot be longer than 60 minutes for lungs, and it varies between 30 and 180 minutes with ex vivo lung perfusion in experienced centers [4]. Once the death is confirmed by asystole, there is a no-touch period between 2 and 10 minutes (usually 5 minutes) to exclude the spontaneous return of circulation [4]. Then the surgical team proceeds to harvest the organs, and a skin incision is made. The patient is reintubated at 15 minutes from cardiac arrest, the aorta is clamped in the thorax, the arch vessels are clamped to prevent brain reperfusion, the pulmonary trunk or right ventricular outflow tract is cannulated, and preservation solution delivery is started [4]. The bronchoscopy can be performed at this moment, and the lungs are recruited. The PEEP is maintained at 5 and FIO₂ 50% and tidal volume 6–8 cc/kg. The heart is excised as usual, and for the lungs, the pulmonary ligament is incised, and dissection is prolonged at the margin of the esophagus until the aorta on the left and azygos on the right. Then a stapler is applied to the carina, and with lungs inflated at 60%, the trachea is stapled and divided. The lungs are removed from the chest, and retrograde pneumoplegia 250 ml on each pulmonary vein is given.

2.2.3 Donor lung preservation and transportation

The lungs are separated by dividing the mediastinal tissue, the atrial cuff and pulmonary artery cuff split into two equal pieces, and the left main bronchus is divided between two stapler lines applied on the proximal half of the left main bronchus far from the carina. They are placed in three sterile transport bags, first with Perfadex solution, tied securely, and in additional two plastic bags with cold saline. The bags are placed in separate containers with ice for transportation [5]. Donor lung preservation is commonly used in cold storage, and low temperature minimizes cellular damage and oxygen consumption by reducing cellular metabolism [5]. Another procurement strategy for DCD donors is by in situ thoracoabdominal normothermic regional perfusion (TA-NRP) for cardiothoracic organs recovery [6], and this method uses extracorporeal membrane oxygenation as a delivery pump (see Figure 1). Cannulation uses ascending aorta and right atrium (on central ECMO) or femoral vessels for peripheral approach. Extracorporeal circulation starts, and reperfusion time could extend to 90 minutes. Afterward, the assessment, retrieval, and preservation are identical as in DBD donors [6].

Figure 1.

Veno-arterial extracorporeal membrane oxigenation. From Ref. [7] Open Access: This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source =, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third-party material in this article are included in the article’s Creative Commons license unless indicated otherwise in a credit line to the material.

Another lung preservation and repair technique is the ex vivo lung perfusion technique, developed by the Toronto group when lungs are ventilated and perfused outside the body to recondition and extend the preservation time [5]. There are three EVLP protocols, Toronto, Lund, and organ care system (OCS) Transmedics [8].

Toronto EVLP technique is a lung support system for lung ventilation, a modified ECMO circuit that offers perfusion. The perfusate is Steen solution, a solution based on dextran and albumin. The method uses lung perfusion and ventilation, during a rewarming process, at 30 degrees and 37 degrees, gradually increasing the perfusion flow. Lung assessment is performed hourly for a minimum of 3 hours, and pulmonary veins gases are analyzed. If the lung’s gases are improving and PO₂ is more than 350 mm Hg, and the pulmonary artery pressures are stable or improving and stable or improving airway pressures and compliance after 4–6 hours of EVLP, the lungs can be used for LT [8].

2.3 Implantation technique

2.3.1 Bilateral sequential lung transplantation (DLT)

The chest entry (see Figure 2) approach is a clamshell incision (bilateral thoracotomy with transverse sternotomy with ligation of mammary arteries [10]. Separate bilateral thoracotomy or sternotomy are other options. Clamshell incision offers the best lung and heart exposure when cardiopulmonary bypass or central ECMO is necessary.

Figure 2.

The clamshell incision for double lung transplantation. From Ref. [9] Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third-party material in this article are included in the article’s Creative Commons license unless indicated otherwise in a credit line to the material. Suppose the material is not included in the article’s Creative Commons license, and your intended use is not permitted by statutory regulation or exceeds the permitted use. In that case, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

Intubation requires a left-sided double-lumen tube for unilateral ventilation because lung transplant is done sequentially. Usually, the most affected lung is transplanted first. The pneumonectomy and preparation of the hilum vasculature by stapling the pulmonary artery and pulmonary veins are followed by bronchus division and the lung removal from the chest. The donor’s lung is transported with cold storage and is prepared for implantation by careful dissection on the back table. Microbiological samples are taken from the bronchus after trimming the excess tissue and resizing [10]. After positioning in the chest, implantation began with the bronchus running suture on the membranous part and interrupted stitches on the cartilaginous part.

The pulmonary artery is sutured next with running 5/0 Prolene and the left atrial cuff with 4–0 Prolene running everting suture (see Figure 3). Deairing is the next step, followed by clamp removal from the pulmonary artery and veins. Ventilation is started on a protective mode and is recommended 10 minutes of controlled reperfusion time with partial compression on the pulmonary artery [10] to avoid volume overload of the lung. Then the second lung is explanted in the same fashion, and implantation follows the same rules. Bilateral pleural drainage is inserted, and the incision is closed in anatomical layers.

Figure 3.

The bronchial, pulmonary artery, and left atrial cuff anastomosis. From Ref. [9] Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third-party material in this article are included in the article’s Creative Commons license unless indicated otherwise in a credit line to the material. Suppose the material is not included in the article’s Creative Commons license, and your intended use is not permitted by statutory regulation or exceeds the permitted use. In that case, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

2.3.2 Extracorporeal support

Patients with severe pulmonary hypertension with high pulmonary artery pressures or patients who are desaturating or becoming unstable during transplant are not tolerating manipulations and pulmonary artery clamping. Veno-arterial ECMO can be inserted by peripheral or central cannulation and used intraoperatively during lung implantation and can be prolonged early after surgery in severe primary graft dysfunction. Cardiopulmonary bypass is another technique for extracorporeal support, which tend to be less used today because of full heparinization and increased risk of bleeding [10].

2.3.3 Size-reducing lung transplantation

Lung transplantation size-mismatch as oversizing is frequent, and until 20% is not a major problem. There are some size-reducing techniques as a nonanatomical wedge resection. When the over-sizing is more, a lobar reduction may be performed, usually the right middle lobe or a lobar resection, which can be performed on the back table after the dissection of interlobar vessels in the fissure [10].

2.3.4 Single lung transplantation

Single lung transplantation is not usually indicated in PT secondary pulmonary fibrosis and chronic obstructive pulmonary disease only in selected cases and is the operation of choice for frail patients with other comorbidities, offering the advantage of having an increased number of transplants in the benefit of very sick patients. Preoperative evaluation of the heart function is important to identify PH. Quantitively V/Q scan is important to determine which lung is less perfused and is a candidate for a single lung transplant. The left side has more space for lung hyperinflation than the right, as the liver is an obstacle on the right side. The position of the patient for a single lung transplant is on full lateral decubitus for posterolateral thoracotomy or for anterolateral for an antero-axillary approach. Single lung ventilation with a left-sided double-lumen endotracheal tube is used for SLT. Pneumonectomy is done in a usual manner by dissecting the hilum elements. The technique for pneumonectomy and implantation is similar to that presented for DLT.

2.3.5 Lobar lung transplantation from living donors (LDLLT)

In the condition of pediatric patients severely ill, with the scarcity of donors for this age group, living lung donation of one lobe (from two living donors) was practiced in Japan when a DBD donation was not legally approved. Nakajima and Date [11] showed that survival after 5 and 10 years in very specialized centers is 79% and 64.6%. Standard LDLLT involves three surgical teams because there are two living donors for harvesting one lobe (usually inferior) and one on the back table. In this way, the ischemic time and duration of surgery are maximally shortened. LDLLT is indicated in critical patients who cannot survive until a DBD donor is available, as in pediatrics or in adults where graft mismatch is possible when the donor’s lower lobes are too small for the recipient’s requirements. The surgical procedure involves two lobar grafts (lower lobes), and implantation is done on ECMO as routine. CPB is used only if there is a cardiac anomaly that may be corrected at the same time [11]. If the transplant is done in children and there is important oversizing single lobar transplant can be performed [11]. Functional size matching uses a formula developed by Nakajima and Date [11], and if the graft FVC is >45% or 50% for pulmonary hypertension, it can be used for lobar transplantation. Anatomical size matching uses 3D computed tomography volumetry; the upper limit of graft volume accepted to the recipient’s chest is 200% [11]. If the lower lobes are too small, the upper lobes of the recipient can be preserved (native upper lung-sparing procedure) to increase the lung parenchyma, or in children can be used adult lower lobes, which are oversized for the same reason.

Two right lower lobes from two living donors implanted, one to the right, and the other one inverted as a left lung, can be used to increase the lung volume when the lobes are two small, but the implantation technique is more demanding (see Figure 4).

Figure 4.

Right single lung transplantation using an inverted left donor lung. From Ref. [12] Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article unless otherwise stated.

3. Heart and lung en bloc transplantation (HLT)

3.1 Indication of heart and lung en bloc transplantation

Primary pulmonary hypertension with right ventricular failure and congenital heart disease with severe cardiomyopathy (Eisenmenger syndrome) is the most frequent indications for HLT. Also, patients with end-stage lung disease and complex cardiac disease with multiple surgeries are qualified for the same procedure [4].

3.2 Heart and lung en bloc procurement and transportation

The donor is approached by a longitudinal incision over the chest and abdomen. Both thoracic and abdominal teams expose the target organs. Both heart and lungs will be dissected, and the aorta and pulmonary trunk will be cannulated after systemic heparinization. Prostaglandin is given in the pulmonary trunk before retrieval. After SVC ligation and transection of IVC, 500 mcg of PGE-1 are administered in the pulmonary artery, the aorta is vented, and both cardioplegia and pulmoplegia are delivered. Next, the aorta, pulmonary artery, IVC, and SVC are transected. The lung ventilation is continued until the trachea is clamped. Trachea is divided between stapler lines, SVC and IVC are transected, and the heart and lungs are removed from the thorax [10]. Transportation of en bloc heart and lung can be on cold storage, in Perfadex solution, or by using the Paragonix transportation system. This has the advantage of maintaining a constant temperature preventing the freezing of the organs as in the cold ice storage technique.

3.3 Heart and lung en bloc transplantation-implantation technique

The heart and lungs bloc are removed from the transport container, and the trachea is transected one ring above the carina. Median sternotomy or clamshell are currently used for chest openings. The most important is to preserve the important nerves as phrenic, vagal, and laryngeal recurrent. Systemic heparinization and cardiopulmonary bypass with two cava veins are necessary, and the heart is clamped and arrested with cardioplegia. The heart is explanted by transecting the two cava veins, aorta, and pulmonary trunk, and only the left atrium remains attached by the posterior wall. Then the left atrium is divided between the pulmonary veins and mobilized together with the pulmonary artery and bronchus after the transaction of these structures in the same way. The lungs are sequentially removed from the thorax. The heart and lungs bloc implant begins with tracheal anastomosis, followed by IVC and SVC anastomosis, and lastly, the ascending aortic anastomosis to the donor aorta. The aorta and pulmonary are desired, and the aortic clamp is removed [10].

4. Pulmonary artery endarterectomy (PEA)

4.1 Introduction

Chronic thromboembolic pulmonary hypertension (CTEPH) is defined as a thrombus in pulmonary arteries and branches due to acute embolism with fibrotic changing or chronic persistent embolism. CTEPH is precapillary pulmonary hypertension with mean pulmonary artery pressure > 20 mm Hg at rest, a pulmonary vascular resistance (PVR) > 3 Wood units, and a wedge pressure < 15 mm Hg [13]. CTEPH is from group 4 of the functional classification of PH. Usually, acute embolism resolves by clot lysis and restoring normal hemodynamics. In the situation that part of the clots is still persistent at 3 months after the embolic episode will determine a flow restriction and increase in PVR secondary to an increase in pulmonary artery pressures and right heart failure [14]. Inflammation, infection, coagulation abnormalities, abnormal platelet function, or cancer are some of the predisposing causes of CTEPH. The surgical procedure for CTEPH is pulmonary artery endarterectomy (PEA).

4.2 Surgical technique in PEA

The goal of PEA is to remove all the obstructive lesions from pulmonary arteries and their branches to facilitate remodeling and decrease PVR with a secondary reduction of the workload of the right ventricle. The approach in PEA is median sternotomy and uses cardiopulmonary bypass with two cava veins drainage, with 20-degree Celsius cooling and a period of deep hypothermic circulatory arrest (DHCA). Indications for pulmonary endarterectomy are presented in Table 2 [14].

Mean PAP > 30 mm Hg PVR > 300 dyneseccm-5 NYHA class >/= III The embolus is in the proximal part of the pulmonary artery (central type).

Table 2.

Indication for PEA [14].

DHCA offers a bloodless field mandatory for pulmonary artery endarterectomy, and it will be on short periods of 10 minutes time for brain protection [15]. Both pulmonary arteries are open, and the embolic material is removed until the very distal segmental and subsegmental branches. The key to the endarterectomy is the correct plane between the intima and media of pulmonary arteries [16].

For these techniques, special instruments for endarterectomy are used to help with emboli removal as special dual action forceps or suction and dissection devices [16]. After completing the endarterectomy, the pulmonary arteries are sutured, CPB restored, and the patient is rewarmed to normothermia and weaned from bypass.

5. Balloon pulmonary angioplasty (BPA)

Is addressed to CTEPH patients considered “inoperable” by risk and benefit evaluation for PEA, or the lesions are too distal (see Table 2) by the European Society of Cardiology/European Respiratory Society guidelines (class IIb recommendation, level C), [17]. The vascular access is percutaneous through the femoral or internal jugular vein, and a long catheter is placed in the pulmonary trunk and branches. The main important stenosis is treated first, and the right lower lobe is usually targeted after because it contains more blood flow [17]. After the catheter is positioned into the lesion, the balloon is inflated and expanded to 5–8 atmosphere. Repeat dilatations may be performed with bigger balloons to attain a good result [17]. The distal vascular bed anatomy is important in the success of the procedure. The main complications are reperfusion pulmonary edema, vascular injury, and vessel rupture. Indications for BPA are presented in Table 3.

Difficulty in performing PEA or residual PH after PEA Insufficient response to medical treatment: NYHA class more than III or PAP pressure more than 30 mm Hg. The patient wishes to use BPA after being fully informed of their medical condition and the BPA risks and benefits. Exclusion criteria as multiorgan failure or renal dysfunction.

Table 3.

Indications for BPA [14].

Usually, three to ten sessions are recommended, depending on how many lesions each session focuses on the segmental artery of one lobe. BPA can be used in patients who have surgical indications, but the risk for open surgery is too high, or BPA can be combined with PEA in some circumstances [17].

6. Mechanical assist devices as a bridge for lung transplantation

6.1 Extracorporeal membrane oxygenation (ECMO)

Extracorporeal membrane oxygenation is a device used as support for the heart and lungs when they are fully compromised, or medical therapy is not helpful until a donor for lung transplantation is available (bridging therapy). The procedure has many complications (bleeding, infections, and multiorgan dysfunction) because of long-term mechanical support [18]. The most common ECMO configuration is veno-arterial (can be venovenous as well) and can be implanted centrally (using for cannulation right atrium and ascending aorta) or most often peripherally using femoral vein and artery.

Special circumstances require different techniques as awake implantation on local anesthesia, which is useful and can be done safely [18]. Peripheral artery cannulation is performed through a prosthetic graft, which is anastomosed to the femoral artery and for the femoral vein in preferred direct venous cannulation. There are other approaches using the internal jugular vein and carotid artery for patients estimated to be on a long time on ECMO. This type of cannulation allows walking and keeps the patient active. There are three methods of ECMO implantation surgical, percutaneous, or combined [19].

Surgical implantation uses an inflow or drainage cannula inserted in the right ventricle or right atrium and a return or outflow cannula in the femoral artery. The percutaneous method uses the classical Seldinger method to cannulate the right internal jugular vein or inferior vena cava and femoral artery. Mixed implantation surgery is used to surgically insert the femoral artery cannula inside a prosthesis (femoral artery), and the Seldinger method is used for internal jugular vein cannulation.

6.2 Right ventricular assist devices (RVAD)

Right ventricular assist devices are used in severe PH when the right ventricle fails, and other devices such as Veno-arterial ECMO show no benefit. Mechanical assistance of the right ventricle improves contractility and can be used as a bridge or destination therapy [19]. RVAD decreases RV loading, improves septal motion and contractility of the right ventricle, and helps the left ventricle improve stroke volume and aortic pressure. RVAD can use both the right atrium and right ventricle as inflow blood sources, and outflow cannula ends in the pulmonary trunk, usually throughout a prosthesis [19]. The main categories of mechanical circulatory support and main approaches are presented in Figure 5.

Figure 5.

Classification of mechanical circulatory support devices. BIVAD, biventricular assist device, LVAD, left ventricular assist device, RVAD, right ventricular assist device. From Ref. [20] Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article unless otherwise stated.

Impella RP heart pump is a device that uses a peripheral vein approach, and a pump is inserted in the right ventricle, a pulmonary artery trunk that can give 4.5 liters of flow. Aria CV PH system is a new device that uses a balloon that inflates and deflates in the pulmonary trunk synchronized with the cardiac cycle (inflates in diastole and deflates in systole), reducing the RV workload and increasing the output [17]. The balloon is introduced in the pulmonary trunk and positioned by a stent and uses a gas that assures inflation and deflation. There is no external power supply; the approach is through a subclavian vein [19].

7. Right-to-left shunting

Are palliative methods used in children with severe pulmonary hypertension unresponsive to medical therapy? To decrease the proper ventricle pressures, right-to-left shunts are helpful by increasing the left ventricle preload and increasing the systemic blood flow [19]. Atrial septostomy (AS) is a percutaneous method that makes or enlarges an atrial septal defect using balloon dilatation to generate a right-to-left shunt when the pressures in the pulmonary artery are supra-systemic as can be performed surgically or transcatheter with a balloon used to increase the septal orifice. Stacey [19] reported mean duration of survival was 63.1 months [19]. Severe desaturation (<90%) or low cardiac output with mean right atrial pressures of more than 20 mm Hg are considered contraindications of the procedure [19].

Another method is a surgical systemic-to-pulmonary shunt, as Potts shunt (anastomosis between descending aorta and left pulmonary artery) or modified Potts when a prosthesis with unidirectional valve is used for the same purpose. The Potts shunt is recommended for severe idiopathic PAH in children and seems to have better oxygen saturation for the brain and heart [19]. The condition for Potts shunt is to have supra systemic pulmonary artery pressures and good right heart valves. To avoid flow reversal in the shunt, a unidirectional valve can be created as a modified Potts shunt, but still, the long-term results on larger groups are necessary [19].

8. Conclusions

Double lung transplantation is the main surgical therapeutic option for severe pulmonary arterial hypertension. Some circumstances as congenital heart disease, in which severe PAH in children may need atrial septostomy or Potts shunt to create Eisenmenger circulation, can extend life until donor organs are available. Lobar lung transplantation is an alternative for pediatric patients, but technically more demanding and might be performed in centers with experience. Extracorporeal support with ECMO or right ventricular assistance can provide survival until the transplant, but many complications can occur. There are many techniques for lung reservation, the cold storage and transportation are still most used. The normothermic perfusion for lung recovery in DCD patients has gained more interest and ex vivo lung perfusion has spread now in many centers because increases preservation time and assures good assessment, assistance, and repair for the lung.