Ann Thorac Surg 1998;66:1821-1823
© 1998 The Society of Thoracic Surgeons
How to Do It
Improved exposure of the pulmonary arteries for thromboendarterectomy
Gregor Zund, MDa,
René Prêtre, MDa,
Urs Niederhäuser, MDa,
Paul R. Vogt, MDa,
Marko I. Turina, MDa
a Clinic for Cardiovascular Surgery, University Hospital Zurich, Zurich, Switzerland
Address reprint requests to Dr Zund, Clinic for Cardiovascular Surgery, University Hospital Zurich, CH-8091 Zurich, Switzerland
Presented at the Poster Session of the Thirty-fourth Annual Meeting of The Society of Thoracic Surgeons, New Orleans, LA, Jan 26–28, 1998.
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Abstract
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Pulmonary thromboendarterectomy is a surgical technique for treating pulmonary hypertension caused by unresolved pulmonary embolism. It has been recommended to perform this procedure under deep hypothermic circulatory arrest. Here we describe two technical modifications: (1) improved exposure to the right pulmonary artery by division of the superior caval vein and (2) thromboendarterectomy in normothermic cardiopulmonary bypass, with beating heart or electrically induced ventricular fibrillation. These modifications allow complete endarterectomy of both pulmonary arteries under normothermic conditions, thus avoiding hypothermic circulatory arrest, which results in short cardiopulmonary bypass times and reduces the morbidity and mortality of this procedure.
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Introduction
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Pulmonary thromboendarterectomy is a surgical technique for treating pulmonary hypertension caused by unresolved pulmonary embolism [1–5[. Because of disturbing backflow, it has been recommended to perform the meticulous thromboendarterectomy under deep hypothermic circulatory arrest. This procedure involves a long cardiopulmonary bypass time and is often followed by delayed neurologic recovery, bleeding complications, and substantial postoperative morbidity and mortality. Improving the exposure of the pulmonary arteries allows a complete thromboendarterectomy under normothermic conditions without reducing pump flow or resorting to circulatory arrest.
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Technique
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The operation is performed through a median sternotomy. A pulmonary artery catheter is advanced into the right atrium only, and transesophageal echocardiography is performed to demonstrate the obstructing thrombi in pulmonary arteries and to assess the patency of the atrial septum with contrast echocardiography. Cardiopulmonary bypass is established by cannulating the ascending aorta and both caval veins. The cannula in the superior caval vein is placed high, close to the convergence of the innominate vein. In normothermic cardiopulmonary bypass the superior caval vein is transected below the cannulation site, leaving a generous cuff above the right atrium (Fig 1). This enhances the exposure of the right pulmonary artery, which can be easily followed into the hilum of the right lung. The left pulmonary artery is also dissected beyond the origin of the upper lobe artery, with both phrenic nerves carefully preserved. Working either on the beating heart (when the atrial septum is intact) or under electrically induced ventricular fibrillation (when the foramen ovale is patent), the surgeon places two incisions in the pulmonary artery to perform a bilateral thromboendarterectomy. The first incision starts in the main pulmonary artery and extends into the left pulmonary artery beyond the origin of the upper lobe artery. The second incision is placed in the right pulmonary artery, starting to the right of the aorta, and is also carried into the hilum (Fig 2). The endarterectomy is performed in the usual fashion, working from the main pulmonary artery toward the hilum of both lungs, with use of blunt dissection. By maintaining light tension on the thrombus it is usually possible to free all segmental branches, with thrombus tapering off into the periphery. After completion of the pulmonary endarterectomy, the right atrium and right ventricle are inspected for residual thrombus and the foramen ovale is closed, when patent. The previously placed pulmonary catheter is guided under direct vision from the right atrium into the right pulmonary artery, and the incisions in both pulmonary arteries are closed with running 4-0 polypropylene sutures. The superior caval vein is reconstructed with three interrupted running sutures. The heart is defibrillated and weaned off cardiopulmonary bypass.
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Fig 1. The cannula (a) in the superior caval vein is placed high, close to the convergence of the innominate vein (b). In normothermic cardiopulmonary bypass the superior caval vein is transected below the cannulation site, leaving a generous cuff above the right atrium (c). (d = pulmonary artery.)
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Fig 2. The incision is placed in the right pulmonary artery, starting to the right of the aorta, and is also carried into the hilum.
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Results
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Since November 1992, this modified exposure was performed on 4 patients (3 men and 1 woman) suffering from pulmonary hypertension caused by chronic pulmonary embolism. They were all dyspneic at rest, and their average pulmonary artery pressure ranged from 70 to 95 mm Hg. The preoperative echocardiography showed no additional thrombus in the heart, and the atrial septum was intact in all patients. Cardiopulmonary bypass time was 48, 62, 67, and 78 minutes. The endarterectomy of the pulmonary artery was considered to be complete in all patients. There were no perioperative complications, waking was prompt after the operation, and no patient suffered a neurologic complication. Postoperative bleeding was minimal, and no patient received foreign blood. These 4 patients were assessed in July 1997 (3, 39, 48, and 55 month after the operation) and were all in New York Heart Association class I or II. By transthoracic echocardiography, pulmonary artery pressure was estimated to be 22, 28, 35, and 40 mm Hg.
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Comment
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Thromboendarterectomy of the pulmonary arteries is an established treatment of pulmonary hypertension caused by chronic embolism [1–5]. The procedure is technically demanding because of the fragility of the pulmonary artery wall. It is recommended to perform the endarterectomy under hypothermic circulatory arrest [1, 6]. The procedure is long, involving cooling to 20°C and rewarming thereafter, resulting in a long overall operating time and requiring substantial amount of blood transfusions because of hypothermia-induced coagulopathy. Deep hypothermia and long cardiopulmonary bypass times lead to a homeostatic derangement, which in turn leads to organ dysfunction, especially of the lungs themselves [7–11]. By using normothermic cardiopulmonary bypass and improving the exposure of the right pulmonary artery it is possible to perform a complete endarterectomy under normothermic conditions, with rapid postoperative recovery and with a notable absence of usual complications common to this type of operation. In our patients backflow did not prevent us from extending the endarterectomy into segmental arteries. If excessive backflow is encountered, the left atrium can be vented, thereby reducing the blood return through the pulmonary artery.
The transection of the superior caval vein allows a long longitudinal incision of the pulmonary artery. Because of the wide exposure it provides, it is possible to work under good conditions and to perform a complete endarterectomy with careful inspection of the distal end of the endarterectomy cylinder. The repair of the superior caval vein did not pose special problems and is indeed a routine procedure when heart transplantation is performed with a bicaval anastomosis [12]. Our experience with this procedure has demonstrated the necessity of using three interrupted 4-0 polypropylene running sutures to avoid a pursestring effect that could create a stenosis.
In conclusion, by improving the exposure of the right pulmonary artery it is possible to perform a complete endarterectomy under normothermic conditions. This technique has the advantages of avoiding deep hypothermic circulatory arrest with its inherent complications.
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References
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Abstract
Introduction
