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Ann Thorac Surg 1997;63:1451-1452
© 1997 The Society of Thoracic Surgeons
Division of Pneumology, Department of Internal Medicine, and Departments of Thoracic and Cardiovascular Surgery, and Radiology, University Hospital, Basel, Switzerland
Accepted for publication November 16, 1996.
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Abstract |
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Introduction |
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A 70-year-old man with a long history of smoking (200 pack-years) presented with an episode of cough with purulent and bloody sputum. A chest roentgenogram and computed tomographic scan disclosed a tumor of 4 cm in diameter between the lateral and the medial segmental bronchi of the middle lobe without enlarged mediastinal lymph nodes. The patient was referred to our hospital.
The patient was in good general health and physical examination was normal, apart from an arterial hypertension of 200/100 mm Hg. Bronchoscopy revealed an atypically vascularized mucosal area in the right middle lobe, at the carina between medial and lateral segment. Transbronchial needle aspiration cytology of this segmental carina allowed the diagnosis of an undifferentiated non–small cell carcinoma. Needle aspiration cytologic examination of the mediastinal lymph node locations was negative, as was the cytologic examination of bronchial washings.
Blood tests were within normal levels, with the exception of lactate dehydrogenase and uric acid, which were twofold increased. Lung function tests and arterial blood gas analysis were within normal limits. A bone scan, a magnetic resonance image of the liver and adrenal glands, and a magnetic resonance image of the head were negative for distant metastases. With a diagnosis of clinical stage T2 N0 M0, a resection by lobectomy of the middle lobe was planned.
Upon thoracotomy a firm tumor in the middle lobe, in close contact with the lower lobe was found. A positive lymph node with a diameter of 2 cm was situated at the origin of the middle lobe bronchus. Another positive lymph node was found ventral to the right stem bronchus, 2 cm distal to the main bronchus. Therefore, a right pneumonectomy with lymphadenectomy had to be performed. Histologic evaluation revealed an undifferentiated large cell carcinoma with areas of small cells, maximal diameter 5.3 cm, staged pT2 pN2 G3. The patient was discharged with a normal blood gas analysis on the 10th postoperative day.
Radiation therapy with 25 MeV linear accelerator was started 6 weeks postoperatively. One week later the patient complained of increasing dyspnea, productive cough with white sputum, and no fever. An arterial blood gas analysis showed a mild hypoxemia with normal partial pressure of carbon dioxide. Radiologically there was no infiltrate in the remaining left lung. A normal radionuclide ventilation–perfusion scan excluded pulmonary embolism. Bacteriologic examination of the sputum revealed gram-negative rods and gram-positive cocci. The patient improved with antibiotics, steroids, and physiotherapy and was discharged after 10 days. Radiotherapy was continued.
Another 3 weeks later he had to be hospitalized again because of increasing dyspnea on exertion with severe hypoxemia and hypocapnia at rest. Spirometry showed a restrictive defect compatible with pneumonectomy but no airway obstruction. Diffusion capacity could not be measured. Again a radionuclide ventilation–perfusion scan excluded pulmonary embolism. A computed tomographic scan revealed normal lung parenchyma on the left side. No pneumonitis, no obvious mediastinal or hilar tumor recurrence, no arteriovenous malformation could be seen. Oxygen titration was indicative of a severe right-to-left shunting. Transthoracic echocardiography was technically difficult because of the distorted anatomy of the mediastinal structures. The four heart chambers were of normal size and wall thickness. There was no sign of increased right atrial pressure. Pulmonary arteriography revealed a ligated right pulmonary artery, and no intrapulmonary arteriovenous shunt. Mean pulmonary artery pressure was 12 mm Hg. The further examination showed a right-to-left connection at the atrial level with a pressure of 6 mm Hg in the right atrium and 4 mm Hg in the left atrium. The shunt was calculated to be approximately 25% of the cardiac output. After this examination the patient was referred to the intensive care unit for controlled fluid substitution. In the supine position the patient had a normal oxygen saturation measured with pulse oximetry. In this position he was not dyspneic. Lifting his head from the pillow was enough of a Valsalva maneuver to cause right-to-left shunting with a decrease in saturation to 78%. Transesophageal echo cardiography revealed a prolapse of the atrial septum into the left atrium, with a right-to-left jet pattern at the caudal end of the prolapse. A further assessment of the morphology by cardiac magnetic resonance was not possible because of problems with electrocardiogram triggering the magnetic resonance signals in this patient with atrial fibrillation.
At operation an aneurysm of the interatrial septum was found in the dorsocaudal part, in addition to a residual Chiari network, close to the entrance of the vena cava inferior. In the cranial part of this aneurysm was a large opening into the left atrium; therefore, not an open foramen ovale but a true septum secundum defect was responsible for the right-to-left shunt. The septal defect was closed and the aneurysm tightened, which resulted in a negative transesophageal echocardiographic bubble test at the end of the operation.
The day after the operation the arterial blood gas analysis was within normal limits and the patient felt quite well. The postoperative course was complicated by the occurrence of atrial tachyarrhythmia on day 8, treated successfully with verapamil. The patient left the hospital with a normal blood gas analysis on the 10th day after operation.
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Comment |
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In all reported cases three characteristic observations were made. First, nearly all patients had an asymptomatic interval after lung resection. Second, dyspnea and degree of right-to-left shunting depended on body position with increased dyspnea and shunting in the upright as compared to the recumbent position. This phenomenon is called platypnea [4, 5]. Third, there seems to be a certain volume dependency of the shunt, with an increased shunt fraction with relative hypovolemia. All three characteristics were seen in our patient as well.
It remains unclear why this atrial septal defect became manifest only after pneumonectomy, and why not immediately but only 2 months after the operation. "Probe patency," or an incomplete seal of foramen ovale, occurs in about 25% of adults. It is conceivable, therefore, that right-to-left shunting through an open foramen ovale may occur more frequently in pneumonectomy patients, but in a less severe, clinically not obvious form.
The right-to-left shunt after pneumonectomy was documented in all reported patients without elevated right atrial pressures. This led to the hypothesis that a postoperatively changed anatomy between inferior and superior caval vein (orifice) and the atrial septum may lead to a preferential blood flow through the aperture directly into the left atrium, even at similar pressures in both atria.
Right-to-left shunting at an atrial level needs to be considered in the differential diagnosis of hypoxemia after pneumonectomy. The simplest diagnostic test is arterial blood gas analysis while breathing 100% oxygen.
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J. M. Alvarez Dyspnea After Pneumonectomy: The Result of an Atrial Septal Defect Ann. Thorac. Surg., December 1, 1997; 64(6): 1872 - 1872. [Full Text]
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