Pulmonary endarterectomy

The pulmonary hypertension (lung overpressure) is a group of diseases with increased pressure in the so-called small circulation, i.e. in the circulation between the right and the left heart. As the blood is only traveling a short distance to absorb oxygen in the lung a six times lower pressure is already sufficient compared to the body circulation, namely about 20/8 mmHg. As pulmonary hypertension a status is described, in which the medium pressure in the lung artery amounts more than 25 mmHg.

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  Schematic representation of the pulmonary arterial thromboses and their distance

If a pulmonary hypertension is diagnosed, it first of all has to be excluded that there is a disease of the left heart and the lungs, as in these cases the treatment of the main disease prevails. Then it is mainly about the distinction of the pulmonary arterial hypertension (PAH) and the chronic thromboembolic pulmonary hypertension (CTEPH), as the latter requires a surgical therapy  which might heals the disease.  The most important symptom in PAH patients is the idiopathic pulmonary arterial hypertension (IPAH), formerly named primary pulmonary hypertension (PPH). But the PAH can also be connected with certain risk factors such as connective tissue diseases, heart defects, liver cirrhosis, HIV infection or former appetite suppressant intake. This can be discussed in detail in the consultation hours for pulmonary hypertension. Pulmonary hypertension (PPH)

In case of suspicion of a CTEPH the patient should  be informed about the possibility of a surgery during the thoracic surgery consultation hours.

Causes
The causes of a CTPEH are still unknown. The fact that the acute leg vein thrombosis and the acute lung embolism are today often summarized as venous thromboembolism (VTE) - in the USA about 300.000 to 500.000 estimated cases per year - is in a startling contrast to the relatively low occurrence of CTEPH. Thereby it has to be considered, as always for the pulmonary hypertension, that in many cases the diagnosis not made or only very late. Until recently it has been estimated that only on of 10.000 patients develops a CTEPH after an acute VTE. More studies however showed a frequency of up to 5%.

After an acute VTE in most cases a dissolution of the blood cloth in the lung circulation takes place. This process happens under blood thinning over a timespan of 3 to 4 weeks. In case of undissolved blood cloths the blood might also finds its way through the cloth. In about 20% of the patients there is only a partial dissolution of the vessel blockage, so that also after 3 to 4 months still one or more of the lung sections are not supplied with blood. These areas are pictured in the so-called lung perfusion scintigraphy as a triangular missing defect (Fig. 1). Thereby the lung tissue is not dying off, as the lung is also supplied with blood over the body circulation, which means over the so-called bronchial arteries.

It is interesting that in CTEPH cases about the half of all patients never had an acute VTE, but that the clinical picture like the PAH became visible with slowly increasing respiratory distress. Furthermore in most cases no other risk factors typical for VTE or known coagulation abnormalities can be determined.

Clinical picture of CTEPH 

The symptoms and the clinical findings of CTEPH are comparable with those from PAH. As with pulmonary hypertension in general the main problem is that first of all the symptoms are very uncharacteristic and secondly that the examination results are often overlooked and thirdly that the clinical picture is not very well-known due to its rare occurrence. In the following constellation it always has to be thought about a pulmonary hypertension:

1. Increasing respiratory distress during exercise
2. Regular pulmonary function test
3. Regular X-ray of the lungs

Unfortunately the symptom of respiratory distress is often only weakly described. Some patients complain about overall fatigue, weakness in the legs or simply about depressive symptoms. Often also dull chest pains, which are wrongly interpreted as heart diseases, or vertigo and attacks of unconsciousness occur, which let physicians search for disturbances of the nervous system. Dry cough or hemoptysis as well as hoarseness are rather rare. In advanced cases weight gain as well as an increase of abdominal girth and swellings of legs occur due to the accumulation of water in the body.

Often it takes more than two years from the first sign of the illness to the diagnosis. If the suspicion of a pulmonary hypertension exists the further process of evaluation is given. An echocardiography (cardiac ultrasound examination ) confirms the diagnosis.

Then by means of a so-called lung perfusion scintigraphy, at which a low number of radioactive, microscopic small pieces is injected into the vein. Thereby the blood supply of the lungs can be examined and it an be clearly distinguished between a CTEPH with the triangular missing supply of lung tissue and a IPAH with the nearly normal scintigraphy.

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  Fig. 1: Perfusion scintigraphy 

Then in all patients a right-heart catheter examination should be performed for clear definition of the pressure in the lung artery. In case of a CTEPH then for planning the further proceeding also a so-called pulmonalis angiography, that means a catheter-technical examination of the lung arteries (Fig. 2), needs to be performed. It is important that both examinations take place in an experienced center, ideally in the center where the surgery will also be performed.

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   Fig.2: Pulmonalis angiography

Treatment options of CTEPH

The conservative, that means non-surgical, treatment options of CTEPH are limited and only indicated if a surgery is no option.
Thus all patients should first be informed about the possibility of surgery (see below). This is the only really effective therapy of CTEPH. This is justified by the fact that it is mainly a "mechanic" problem that also should be repaired "mechanically". A medical therapy should only be considered in cases in which a pulmonalis angiography showed that a surgery is impossible. Also in this respect  patients  can be adviced during the consultation hours for pulmonary hypertension.  

Pulmonary endarterectomy (PEA)

A surgery technique exists for over 30 years now, which can lead in the ideal case to a healing of pulmonary hypertension. It is the so-called pulmonary endarteriectomy (PEA), formerly also called pulmonary "thrombendarteriectomy". The word "thromb" is today not used anymore, as the lung arteries are in cases of CTEPH not clothed by embolisms but scarred over the time, why mainly alterations of the vascular walls prevail.

During the surgery the vascular wall is opened with a small cut after opening the rip cage in the area of the sternum in the middle of the main stem of the lung artery (Fig. 3). Then the three-parted artery wall is separated on the right side entirely from its inner and middle layer. Then the surgeon is working along this layer of the vascular wall to the second or third division of the right lung artery. This is very tricky, as the sight is clearly very limited and the surgeon has to rely on his anatomical knowledge and experience. If the layer is lost too early the lung artery is opened insufficiently or in the worst case the vascular wall can even rupture. 

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 Fig.3: Peeling of the material

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Fig. 4: Endarteriectomy of the right pulmonary artery

But in most cases the surgeon is successful in working up to the third division of the lung artery or even further and to finally extract a so to say drain of the entire arterial tree including the inner part of the arterial wall (Fig. 5). It is important to note than the surgeon is not only extracting the cloth from the lung artery but also the inner part of the arterial wall.

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  Fig.5: Removed arterial tree including arterial wall

As like mentioned above the lung is also supplied by the body circulation and the returning blood flow from this circulation into the lung artery would hinder the surgeon's sight enormously, the operation needs to be performed with total circulatory arrest. This is performed at the heart-lung machine, whereas the body of the patient is cooled down to a temperature of 18°C. Additionally also the head is cooled from the outside. Then shortly before the cut in the lung artery is performed the heart is suspended and finally also the heart-lung machine is turned off, which means that a total circulatory arrest is generated. The described surgery takes on average about 20 to 30 minutes. Then for a short while the circulation is restored again and then the left lung artery is operated in the same way (Fig. 6). Afterwards the circulation is restored and the body of the patient is slowly warmed up. Whereas the endarterectomy takes two times twenty minutes the complete surgery including preparation of the artificial circulation, cooling, circulatory arrest and warming up of the patient takes about eight hours.

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 Fig.6: Endarterectomy of the right pulmonary artery

The PEA is a complicated and complex surgery. During the surgery up to 10% of the patients die. The globally most experienced surgeons reach today a mortality rate of less than 5%. The most important cause of death are acute bleedings, for example at ruptures of the lung artery during the preparation of the vascular wall, and the so-called reperfusion edema. It is an accumulation of liquid in the lungs after the surgery due to increased blood supply of the lung areas which haven't been supplied from the circulation before. Whereas the first complication is hard to control the reperfusion edema can be influenced after several days of ventilation. Other direct postoperative problems are acute kidney failure and confusion syndromes in about 5 to 10% of the patients. If the surgery is free of complications the patient can be weaned from artificial ventilation after one or two days and can leave the hospital after two to three weeks. In most cases then a two to three week rehabilitation stay is planned.

The PEA allows most patients a nearly normal performance. Of course there is a relatively strong lack of fitness due to the often rather long course of disease until the PEA is performed. In about 10 to 20% of the cases the lung pressure can't be completely normalized by a PEA, why then also the performance level is limited - but not to the extent as before the surgery. Some patients need a medical therapy after the surgery.

The pre-clarifications (cardiac ultrasound, walking test, pulmonary function test, pulmonalis angiography, CT perfusion scintigram, right- and left-heart catheter) are arranged in cooperation with the consultation hours for pulmonary hypertension and the documents are interdisciplinarily discussed. Thereby in particular the pulmonalis angiography and the computer tomography are analyzed concerning the distribution and surgical reachability of the alterations. In this way the following can be evaluated: 1) if a surgery is even possible, 2) how well the alterations can be reached by the surgeon, this means how complicated the PEA and this the perioperative risk will be and 3) what are the chances that most of the alterations can be extracted or rather what is the approximate prognosis concerning the improvement of performance after the surgery.

Then we organize another meeting in the CTEPH consultation hours, where we inform you about your situation in detail. A consultation is also valuable if you don't consider a surgery! Neither the information nor such a communication define anything in advance. You can decide on your on independently after the conversation. Thus we recommend all our patients to let the clarifications be performed, independent from their personal attitude. There is also the possibility to talk with a patient who already had a PEA.

 

Personnel in  the CTEPH program:

​Department of Thoracic Surgery

Director:
Prof. Dr. W. Weder

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Prof.Dr. I. Schmitt-Opitz

​Department of Pneumology

Direktor:
Prof. Dr. M. Kohler

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PD Dr. S. Ulrich
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PD Dr. l .Huber


 

​Institute for Cardiac Anesthesia

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PD Dr. D. Bettex
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Dr. T. Horisberger

​Intensive care medicine

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PD Dr. R. Schüpbach

​Institute for Radiology

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​PD Dr. T. Frauenfelder

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​Prof. Dr. T. Pfammatter

 


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