MMCTS
(June 12, 2009). doi:10.1510/mmcts.2008.003491
Copyright © 2009 European Association for Cardio-thoracic Surgery
Procedure
Pulmonary endarterectomy – an example of treatment of right ventricular after load failure
Marius Berman,
Evgeny Pavlushkov,
Essac Abraham,
John Dunning,
Steven Tsui,
Roger Hall,
Andrew Klein and
David P. Jenkins*
Papworth Hospital, Cambridge, CB23 3RE, UK
* Corresponding author: Tel.: +44-1480-364807; fax: +44-1480-364709. david.jenkins{at}papworth.nhs.uk
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Summary
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The treatment of choice for patients with chronic thromboembolic pulmonary hypertension is pulmonary endarterectomy to reduce pulmonary vascular resistance with significant symptomatic and prognostic benefit. The fundamental aim of the surgery is to perform a full endarterectomy (not embolectomy or thrombectomy) in both pulmonary arteries. The operation is performed via a median sternotomy with hypothermic cardiopulmonary bypass (CPB) at 20 °C. Pulmonary arteriotomies are performed within the pericardium and periods of circulatory arrest are necessary to reduce collateral blood flow from bronchial arteries and allow a clear field for dissection distally. The endarterectomy plane is raised carefully as it is essential the correct layer be identified. The dissection proceeds within the superficial media into all the affected segmental and sub-segmental vessels. A cast of the inner layer of the pulmonary arterial tree is then dissected free by eversion moving towards the periphery. After completion of the endarterectomies, and the patient is rewarmed slowly on full CPB. During weaning from CPB the right-sided filling pressures should be kept low, guided by invasive haemodynamic monitoring. Survival to hospital discharge is >95% in experienced centres with outcome dependent on the disease pattern and pulmonary vascular resistance pre- and post-surgery.
Key Words: Chronic thromboembolic pulmonary hypertension • Pulmonary endarterectomy • Right ventricular failure
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Introduction
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The pulmonary thromboendarterectomy (PTE) operation, as performed today, was mainly developed at the University of California in San Diego (UCSD) and this unit is the world leader having now completed well over 2000 procedures. A full summary of the world experience up to the year 2000 is provided by Jamieson and Kapelanski in a specialist monograph [1]. The largest series of patients published to date is also from UCSD [2], but important contributions have also been made from Europe [3]. Chronic thromboembolic pulmonary hypertension (CTEPH) has recently been reviewed in detail [4].
Typical examples of imaging techniques demonstrating CTEPH preoperation are shown in Photos 1234.
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Photo 1 CT-scan (sagittal view) of thorax demonstrating mosaic attenuation due to variation in perfusion in a patient with CTEPH.
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Photo 2 CT pulmonary angiogram demonstrating proximal laminated thrombus in the right main pulmonary artery.
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Photo 3 MRI pulmonary angiogram showing extensive right-sided chronic thromboembolic disease with webs in the upper and middle lobe segmental vessels (arrowed) and complete occlusion of the lower lobe.
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Photo 4 Conventional right pulmonary angiogram showing web formation and stenoses in the upper and lower lobes.
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The majority of patients accepted for PTE surgery have class III symptoms of breathlessness and a pulmonary vascular resistance (PVR) of >300 dynes·s·cm–5.
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Surgical technique
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General anaesthesia is induced as for standard cardiac surgery with care taken to avoid hypoxia. Monitoring lines are placed in the right radial and femoral arteries, and right internal jugular vein with a pulmonary artery catheter for haemodynamic monitoring. A transoesophageal echocardiograph probe is inserted. Nasopharyngeal and bladder thermometer probes are used for peripheral and central temperature monitoring. Near-infrared spectroscopy is used to monitor cerebral oxygenation (INVOS Cerebral Oximeter). A head cooling jacket is used during hypothermic bypass to aid cerebral cooling. An example of monitoring is seen in Photo 5.
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Photo 5 Snapshot of monitoring screen pre-CPB with radial arterial trace in red, femoral arterial trace in white, pulmonary artery trace in yellow, and right atrial trace in blue.
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The chest is opened with a standard median sternotomy, the right heart is often significantly dilated (Photo 6). Systemic heparin is administered to achieve an activated clotting time of >400 s. Cardiopulmonary bypass (CPB) is then established with venous drainage from two venous cannulae (one two-stage cannula inserted in the right atrial appendage and a straight 28 French superior vena caval cannula inserted through the body of the right atrium) and arterial return to the ascending aorta. The ascending aorta, main pulmonary artery, superior vena cava (SVC) are then isolated with tapes (Video 1). It is important that the heart is empty and well vented.
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Photo 6 View of heart from patient's head prior to cannulation demonstrating signs of severe chronic pulmonary hypertension.
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Video 1 View from patients head showing dilated right heart and CPB cannulae.
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Cooling is commenced to a core temperature of 20 °C using pH-stat management. Vents are placed in the main pulmonary artery and the left atrium via the right superior pulmonary vein before the heart fibrillates. A cardioplegia cannula is placed in the aortic root. A cooling water jacket is positioned over the right ventricle for additional myocardial protection (Video 2).
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Video 2 View from patient's head, on full CPB, showing white cooling jacket over anterior surface of heart.
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Once a core temperature of 20 °C is reached, the dissection begins with the surgeon standing on the patient's left side. A headlight is essential for good visualisation deep in the pulmonary artery. The right pulmonary artery is exposed between the ascending aorta and the fully mobilised SVC with a cerebellar type self-retaining retractor (Video 3). A longitudinal incision is made in the midline and extended beneath the SVC laterally as far as the origin of the middle lobe branch, but the incision remains within the pericardium and the pleura is not entered (Video 4). Care is taken to avoid denuding the artery of adventitial tissue to facilitate secure haemostasis during closure.
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Video 3 Mobilisation of SVC with diathermy to allow lateral retraction for full exposure to right PA.
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Video 4 Right PA exposed and opened with a longitudinal incision.
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The lumen of the right pulmonary arterial system is shown (Video 5) and initial inspection by the uninitiated may suggest no obvious thromboembolism. The appearances can be variable with extensive laminated thrombus visible proximally (Video 6). The yellow PA catheter is retracted with a stay suture and replaced prior to artery closure.
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Video 5 Internal view of right PA demonstrating origins of segmental vessels after institution of circulatory arrest.
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Video 6 Internal view of right PA in a different patient demonstrating extensive chronic laminated thrombus with calcification.
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The endarterectomy plane is raised posteriorly in the main right pulmonary artery using a long Beaver blade scalpel and Watson Cheyne dissector. The instruments are demonstrated in Photo 7. If proximal laminated thrombotic material is present it is removed at this stage to improve visualisation and reduce the bulk of the endarterectomy specimen to allow easier manipulation. The dissection proceeds within the superficial media of the artery wall, the correct plane recognised by the smooth pearly white appearance and ease of separation of the specimen (Video 7).
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Video 7 Demonstration of dissection plane in superficial media.
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By the use of a nerve hook, long Snowden forceps and a Jamieson sucker-dissector, the plane can be extended circumferentially and then distally by careful traction on the endarterectomy specimen using an eversion technique to push the remaining artery wall off the grasped specimen as far as possible with the intention of tracing the endarterectomy into all the affected segmental or sub-segmental vessels [5] (Video 8).
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Video 8 Delivery of segmental ‘tails’ and completion of more distal dissection.
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It is important that every sub-segmental branch is followed until it spontaneously separates in a feathered tail at its distal limit. The ease of dissection varies from patient to patient with some specimens being extremely adherent requiring considerable force and others being very fragile. The upper lobe is often the easiest to clear as it is more superficial and exposure is simple. The middle lobe can be challenging because of the angulation directly away from the surgeon.
Whilst the initial dissection can be performed with full CPB, once visualisation becomes compromised by return of bronchial collateral blood flow dissection cannot proceed safely. At this stage, the circulation needs to be arrested to give a completely clear field. A cross-clamp is placed on the ascending aorta and the heart arrested with 1 l cold blood cardioplegia. The circulation is then stopped and the patient exanguinated. This allows a safe period of up to 20 min that is usually adequate for completion of the remainder of the endarterectomy. If necessary a recovery period of 10 min full perfusion is used between arrest periods when more dissection time is required. The cerebral oxygenation trace (INVOS) is shown in Photo 8.
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Photo 8 Cerebral oximetry traces from right and left sides for duration of procedure, in this case with two periods of circulatory arrest for the right dissection and one for the left.
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An alternative technique suitable in some patients is partial circulatory arrest with continued cerebral perfusion [6]. When using the latter method an angled clamp is placed between the left common carotid and left subclavian arteries and a standard cross-clamp is placed on the ascending aorta proximal to the arterial inflow cannula (CPB flow is then confined to the brachiocephalic and left carotid arteries, and bronchial collateral blood flow is reduced) (Schematic 1). Full cerebral perfusion and partial circulatory arrest of the body can be maintained with approximately 1.0 l min-2 flow giving a perfusion pressure of 40–50 mmHg in the right radial artery for up to 50 min at 20 °C. During this time, femoral arterial pressure is usually between 10 and 15 mmHg (Photo 9). If at any stage during cerebral perfusion collateral flow remains excessive and interferes with safe surgical dissection, the strategy can be switched to complete circulatory arrest.
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Schematic 1 Diagram illustrating positions of cross clamps on aorta for continued brain perfusion and partial circulatory arrest (from Ref. [6]).
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Photo 9 Snapshot of monitoring screen during partial circulatory arrest with cerebral perfusion showing a mean pressure of 43 mmHg (red) in the right radial artery, reduced pressure of 18 mmHg (white) in the femoral artery, the heart is arrested in asystole.
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Once the endarterectomy is complete on the right side, the full CPB is recommenced and the right arteriotomy is closed (Video 9). The aortic cross-clamp is removed and the heart reperfused.
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Video 9 The right PA is closed with continuous 5/0 Prolene in two layers.
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The surgeon then moves to the patient's right side and the left pulmonary arteriotomy is extended from the vent insertion site in the main pulmonary artery into the left pulmonary artery trending inferiorly and laterally, but the pleura is not opened (Video 10). The left-sided endarterectomy can then be completed with the same surgical technique and perfusion strategy as for the right side. Care must be taken when dissecting the left lower lobe as the artery changes direction under the bronchus, and loss of integrity of the specimen in this region can render further dissection impossible, as it is difficult to regain the dissection plane beyond this point (Video 11). The artery is closed with continuous 5/0 Prolene in two layers and the aortic cross-clamp removed (Video 12).
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Video 10 Opening of the pulmonary trunk extending into main left PA.
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Video 11 View inside the PA showing web disease at origin of lower lobe segmental vessels.
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Video 12 Closure of the left PA with continuous 5/0 Prolene in two layers, leaving a vent in situ during rewarming on CPB.
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After completion of the endarterectomies, the patient is rewarmed slowly on full CPB flow to a core temperature of at least 36.5 °C, keeping the temperature gradient between periphery and core <6 °C. It is often possible to defibrillate the heart whilst the body temperature is <23 °C. Ventilation is commenced at this stage with 50% tidal volume. Any concomitant cardiothoracic surgical procedures can be completed during this phase of the operation. The patient is then weaned from CPB slowly keeping right-sided filling pressures low, guided by invasive haemodynamic monitoring. Atrial and ventricular pacing wires are inserted. If there are no pleural adhesions on the CT, the right pleura is opened widely and drains are placed in the pleura and two in the mediastinum anterior and posterior to the heart to reduce late pericardial collections. After thorough haemostasis the chest is closed in layers with standard techniques.
A typical example of the endarterectomy specimen is seen in Photo 10.
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Photo 10 Typical endarterectomy specimen, demonstrating type 1 disease on the right with extensive laminated thrombus and type 2 disease on the left with webs and stenoses. The segmental and sub-segmental ‘tails’ are shown.
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Results
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The centres with most experience (>300 procedures) now report in-hospital mortality of 5% following PTE [2]. The risk of PTE surgery increases with increasing PVR preoperation [3], and a residual PVR of >500 dynes·s·cm–5 following PTE is a risk factor for in-hospital mortality [2].
In the majority of patients recovery is similar to that after more routine cardiac surgery. There is a substantial early fall in pulmonary hypertension and PVR [2, 6, 7] (Graphs 1, 2). By 3 months post-surgery there is a significant improvement in functional class [7] (Graph 3). Patients who leave hospital following PTE surgery have an excellent survival of >90% at 5 years [7] (Graph 4).
The main complications are residual pulmonary hypertension secondary to ‘distal’ small vessel arteriopathy and reperfusion lung injury. These may coexist. Severe residual pulmonary hypertension leads to right heart failure secondary to after load resistance, with low cardiac output and poor oxygenation. Many of these factors interact in a vicious cycle of decompensation. In these rare circumstances it may not be possible to wean from CPB, or the patient develops very low cardiac output secondary to right heart failure in the first 24 h and the only possible support is veno-arterial extra corporeal membrane oxygenation (ECMO), usually with central cannulation, to provide full haemodynamic support and gas exchange (Photo 11) [8]. In this situation with right ventricular failure secondary to raised after load, ventricular assist devices are not helpful. For patients (up to 20%) who develop reperfusion lung injury at a later stage (typically 48–72 h post-PTE) with stable haemodynamics, supportive positive pressure ventilation is usually sufficient, but in severe cases with hypoxia, hypercapnoea and acidosis, peripheral veno-venous ECMO is feasible.
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Photo 11 ECMO circuit with (from right to left) Medos hollow fibre oxygenator, Levitronix Centrimag centrifugal pump, gas flow mixer, Levitronix controller, and hypo-hyperthermia unit.
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Despite widespread use of circulatory arrest for this procedure, significant neurological complications are rarely seen, but neuropsychological testing has not been reported.
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Discussion
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Pulmonary endarterectomy is a remarkably successful operation. Without treatment, patients with CTEPH, and a mean PA pressure of >50 mmHg, have a very poor prognosis, with 20% surviving 2 years [4]. PTE confers significant symptomatic and survival benefits, as seen above. The only alternative is heart/lung or lung transplantation, with the problems of donor availability, and complications related to immunosuppression (rejection and infection), making it an inferior option with survival of only 50% by 5 years.
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References
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- Jamieson SW, Kapelanski DP. Pulmonary endarterectomy. Curr Prob Surg 2000;37:165–252.[CrossRef][Medline]
- Jamieson SW, Kapelanski DP, Sakakibara N, Manecke GR, Thistlethwaite PA, Kerr KM, Channick RN, Fedullo PF, Auger WR. Pulmonary endarterectomy: experience and lessons learned in 1,500 cases. Ann Thorac Surg 2003;76:1457–1462.[Abstract/Free Full Text]
- Dartevelle P, Fadel E, Mussot S, Chapelier A, Hervé P, de Perrot M, Cerrina J, Ladurie FL, Lehouerou D, Humbert M, Sitbon O, Simonneau G. Chronic thromboembolic pulmonary hypertension. Eur Respir J 2004;23:637–648.[Abstract/Free Full Text]
- Hoeper MM, Mayer E, Simonneau G, Rubin LJ. Chronic thromboembolic pulmonary hypertension. Circulation 2006;113:2011–2020.[Free Full Text]
- Madani MM, Jamieson SW. Technical advances of pulmonary endarterectomy for chronic thromboembolic pulmonary hypertension. Semin Thorac Cardiovasc Surg 2006;18:243–249.[CrossRef][Medline]
- Thomson B, Tsui SSL, Dunning J, Goodwin A, Vuylsteke A, Latimer R, Pepke-Zaba J, Jenkins DP. Pulmonary endarterectomy is possible and effective without the use of complete circulatory arrest – the UK experience in over 150 patients. Eur J Cardiothoracic Surg 2008;33:157–163.[Abstract/Free Full Text]
- Freed DH, Thomson BM, Tsui SSL, Dunning JJ, Shears KK, Pepke-Zaba J, Jenkins DP. Functional and haemodynamic outcome 1 year after pulmonary thromboendarterectomy. Eur J Cardiothoracic Surg 2008;34:525–529.[Abstract/Free Full Text]
- Berman M, Tsui S, Vuylsteke A, Snell A, Colah S, Latimer R, Hall R, Arrowsmith JE, Kneeshaw J, Klein AA, Jenkins DP. Successful extracorporeal membrane oxygenation support after pulmonary thromboendarterectomy. Ann Thorac Surg 2008;86:1261–1267.[Abstract/Free Full Text]
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Summary
Introduction
