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Silent, chronic, massive pulmonary thromboembolism masquerading as bronchogenic carcinoma
Silent, chronic, massive pulmonary thromboembolism masquerading as bronchogenic carcinoma A unique case is described of a 64-year-old white woman who had silent thromboembolic occlusion of the right pulmonary artery. Over the ensuing months, severe pulmonary hypertension developed, as manifested by marked dilatation and atherosclerosis of the right and left pulmonary arteries and severe right ventricular hypertrophy. Nevertheless, she remained fully ambulatory and felt generally well throughout this time. Eventually, however, the pulmonary arteries became so dilated that they compressed the recurrent laryngeal nerve as it looped under the aortic arch, and it was the resulting hoarseness that first caused the patient to seek medical attention. A work-up disclosed normal peripheral lung fields on x-ray study and a large dense right hilar mass. Accordingly, the patient was subjected to an exploratory thoracotomy on the reasonable but mistaken diagnosis of bronchogenic carcinoma. After the following operation, her condition deteriorated. She developed bronchopneumonia which, when superimposed on her already precariously reduced cardiopulmonary function, precipitated respiratory insufficiency. An independent stroke was the immediate cause of death.
Myron R. Schoenfeld, M . D . , * and John M. Budinger, M.D.,** Bronxville,
T
A. he catastrophic event known as massive pulmonary embolism is defined by various authors as involving occlusion of at least one third to one half of the pulmonary arterial bed. This occurrence is described as invariably resulting in a severe and often lethal compromise of cardiopulmonary function. This report describes the unique case history of a patient who is a striking exception to this rule. The woman was so free of cardiopulmonary symptoms and, in fact, generally felt so well that she walked casually into her physician's office to complain, not of dyspnea, but of hoarseness. When the chest x-ray film disclosed a dense hilar mass, she was subjected to chest surgery on From the Departments of Medicine and Pathology, Lawrence Hospital, Bronxville, N. Y. Received for publication April 22, 1976. Accepted for publication May 14, 1976. Address for reprints: Myron R. Schoenfeld, M. D., II Bronx River Road. Yonkers, N. Y. 10704. *Attending Cardiologist. Lawrence Hospital, Bronxville, New York, and Assistant Clinical Professor of Medicine (Cardiology), The Albert Einstein College of Medicine, Bronx, N. Y. **Attending Pathologist. Lawrence Hospital, Bronxville, N. Y., and Clinical Associate Professor of Pathology, College of Physicians and Surgeons. Columbia University, New York, N. Y.
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the reasonable (but mistaken) assumption that she was suffering from bronchogenic carcinoma. This case demonstrates that even such a serious disease as massive pulmonary embolism can be silent in onset, chronic in duration, and asymptomatic for months. To the best of our knowledge, this is the first such case reported.'~ 8 Case report G. M., a 67-year-old white woman, was admitted to our intensive care unit in acute respiratory distress. Until 3 months prior to admission, the patient always had been in good health, physically active, and without any cardiorespiratory symptoms. Several routine chest films had been taken over the years, the most recent 2 years prior to admission, and all were said to be normal. Initially, she noted the onset of intermittent hoarseness. Four weeks prior to admission, she casually consulted her physician because of this symptom. A chest x-ray film at that time showed a dense, well-circumscribed, right hilar mass, and examination with the laryngoscope revealed left vocal cord paralysis. She was admitted to another hospital with the presumptive diagnosis of bronchogenic carcinoma. Neither cyanosis nor dyspnea was noted prior to admission. Three weeks before her admission to Lawrence Hospital, an exploratory thoracotomy was performed. The surgical findings were unexpected. A tumor was not found, but both the right and left pulmonary arteries were markedly dilated. The heart and lungs were
58 1
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The Journal of Thoracic and Cardiovascular Surgery
Budinger
Y..
\
K Fig. 1. Chest x-ray film (posteroanterior view) taken one week after admission to Lawrence Hospital and 4 weeks after the thoracotomy. Note the large, dense, well-circumscribed, prominent right hilar mass caused by the enormously dilated and thrombosed right pulmonary artery. The appearance of the lung fields does not give any sign of massive right thromboembolism, however. The right lung is normal in size and lucency and has normal interstitial markings. The heart size perhaps is somewhat large for a person of asthenic build, but certainly it does not give a clue to the severity of the right ventricular hypertrophy. described as appearing normal. A diagnosis of "idiopathic pulmonary artery dilatation" was made, and hence no further procedures were done. Following 2 weeks of uneventful convalescence from the exploratory thoracotomy, the patient was discharged to her home, weak but ambulatory. On the day of her admission to Lawrence Hospital, she became acutely short of breath and came to our emergency room for treatment. Physical examination. She appeared undernourished and in severe respiratory distress, with marked dyspnea and moderate cyanosis. The temperature was 100.5° F., pulse 80 beats per minute and regular, blood pressure 104/82 mm. Hg, and respiration 28 breaths per minute and labored. The lung fields were clear. The heart was normal on examination: no murmurs, gallop, rub, or abnormal pulsations. Findings from the remainder of the physical examination were normal. There was no clubbing. Hospital course. Blood and urine cultures were negative. There was no leukocytosis, and the findings from urinalysis were normal. The chest x-ray film did not show any periphreal pulmonary infiltrate. Nevertheless, persistent fever of 101 to 102° F. during the first few days of hospitalization suggested that she probably had had aspiration pneumonia as
n?
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Fig. 2. Radioisotope lung scan (anteroposterior view), using 200 /aCi of macroaggregated serum albumin tagged with 1-131 and administered intravenously, showing total nonvisualization of the right lung field. The left lung field appears normal. a result of vocal chord paralysis. Accordingly, she was treated with oxygen and antibiotics, and her condition considerably improved. Repeated examination of the heart disclosed no significant murmurs. Serial electrocardiograms, however, showed persistent signs of right heart strain characterized by depressed ST segments, inverted T waves, and somewhat high voltage of the R wave over the right percordial leads. In addition, the chest x-ray film showed mild cardiomegaly and a dense, wellcircumscribed, prominent right hilar mass (Fig. 1). Tomograms of the right lung did not further define this mass. Isotopic lung scan showed complete absence of visualization of the entire right lung (Fig. 2). Multiple arterial blood gas studies showed marked hypoxemia (Po2 24 to 50 mm. Hg) which improved greatly with the administration of oxygen by nasal catheter at a rate of 5 L. per minute. (Po2 80 to 140 mm. Hg). At the same time, the cyanosis cleared. The hemoglobin value of 13 to 14 Gm. per 100 ml. seemed incongruous with her rather undernourished appearance and was suspected to represent a mild degree of erythrocytosis. Pulmonary arteriograms were planned but cancelled twice because of the patient's inability to cooperate. It was concluded that the patient had complete thromboembolic occlusion of the right main pulmonary artery and perhaps partial occlusion of the left pulmonary arterial tree as well. Laryngoscopic examination confirmed left vocal chord paralysis, which was attributed to compression of the recurrent laryngeal nerve by the dilated pulmonary arteries. In addition to the cardiopulmonary problem, she was noted to have a rather blank facies, dysphagia (primarily to fluids rather than solids), sagging of the soft palate, a weak gag reflex, and bilateral positive Babinski reflexes. The spinal
Volume 72 Number 4 October, 1976
fluid was normal. These neurologic findings were thought to be due to pseudobulbar palsy caused by diffuse cerebral arteriosclerosis. On the nineteenth hospital day, when she was in relatively good physical condition, a transient episode of acute hypotension suddenly developed. Thereafter, she remained comatose, had generalized seizures, and had a marked increase in the muscle tone of all four extremities. The patient failed to respond to supportive measures and died on the twenty-first hospital day. An autopsy was performed. Final premortem clinical diagnoses. The final clinical diagnoses were as follows: (1) thromboembolism with complete occlusion of the right main pulmonary artery and perhaps partial occlusion of the left pulmonary arterial tree, with resultant chronic cor pulmonale and hypoxemia; (2) diffuse cerebral arteriosclerosis with pseudobulbar palsy and terminal episode of an acute cerebral infarction; (3) aspiration pneumonia owing to paralysis of the left vocal chord; (4) paralysis of the left recurrent laryngeal nerve owing to compression by the dilated pulmonary artery. Postmorten examination. The abnormal findings were as follows: Cardiovascular system. The heart weighed 300 grams. The right ventricle was 1.0 cm. thick. It was extremely firm in consistency, and there was marked hypertrophy of the trabeculae carnae. The left ventricle was 0.8 cm. thick. The epicardium, endocardium, valves, and pericardium were normal. The aorta was moderately antherosclerotic, but the coronary arteries and other major aortic arch arteries were strikingly free of atherosclerosis. Respiratory system. The entire laryngotracheobronchial tree contained moderate amounts of frothy serous fluid. The main pulmonary artery was normal in diameter and was not atherosclerotic. The right lung weighed 510 grams. Its pleural surface and cut section appeared normal. The right pulmonary artery was completely occluded by a laminated, dark and light-red clot which propagated out into the lobar and lobular arteries. Beginning at the bifurcation of the main pulmonary artery, the right pulmonary artery and all of its lobar and lobular branches were very dilated, thin walled, and markedly atherosclerotic. Beyond the lobular branches, the arteries were grossly and microscopically normal. The right pulmonary veins were normal. The left lung weighed 480 grams. Its pleural and cut surfaces also appeared normal. The left pulmonary artery and its lobar and lobular branches were moderately atherosclerotic, but they were not dilated or thin walled. The alveoli and small arteries of both lungs were normal. Nervous system. The proximal portions of both internal carotid arteries were markedly atherosclerotic. The basilar artery was moderately atherosclerotic. Microscopically, the small cerebral arteries and arterioles showed marked sclerosis. The brain was normal except for small cysts in the left putamen, globus pallidus, and adjacent white matter. The right basal ganglia appeared normal. Final postmortem anatomic diagnoses. The final anatomic diagnoses were as follows: (1) severe bilateral pulmonary arteriosclerosis, with marked cor pulmonale, and normal pulmonary arterioles; (2) thromboembolism of the right pulmonary artery, with occlusive thrombus; (3) cerebral arteriosclerosis and arteriolosclerosis, with multiple small
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cystic necrotic foci, both recent and old, in the left basal ganglia; (4) minimal generalized arteriosclerosis. Discussion There can be no doubt that the thromboembolism which caused total occlusion of the patient's right pulmonary artery antedated her death by at least several months, and perhaps as long as 2 years; certainly, it was not a recent happening. This is proved by the severity of the right ventricular hypertrophy, by the marked pulmonary atherosclerosis, and by the extensive endothelialization of the blood clot itself. With confidence, then, we can term the occlusion chronic. The normal size, aeration, and interstitial markings of the right lung on chest roentgenogram were striking findings in this case. Apparently, collateral circulation via the bronchial arteries was sufficient to maintain viability of the substance and appearance of the entire lung. The surgical removal of a lung does not result in more than a mild increase in the pulmonary artery pressure. Therefore, the cause of the severe pulmonary hyptertension in the present case cannot be attributed to the absence of pulmonary arterial blood flow to one lung. This fact constitutes yet another and particularly striking piece of evidence that the cause of pulmonary hypertension in pulmonary thromboembolism largely is due to reflex9 and/or hormonal factors (eg., platelet serotonin) induced by the clot and affecting the entire pulmonary arteriolar bed bilaterally. This case adds a further dimension to the thesis that the pulmonary hypertension induced by a clot can be more than an acute episode: If the clot is not lysed, the pulmonary hypertension can be chronic and hence can induce pronounced cardiac hypertrophy. The severe dilatation of the thrombosed right pulmonary artery perhaps can be attributed to the following sequence of events: Thromboembolic occlusion of the right pulmonary artery causes local anoxia which, in turn, leads to progressive dilatation and increased branching of the bronchial arteries—the classic pattern of collateral vascularization in response to ischemia. The result is a sharp drop in the peripheral resistance and a striking increase in the volume of blood flow through the bronchial arterial tree. Via anastomoses between the bronchial and pulmonary arteries, a large volume of arterial blood at high systemic pressures now is being delivered into the pulmonary arterial tree of the right lung downstream from the occluding clot. The pulmonary artery, being relative thin walled and unaccustomed to such high pressure, responds by dilating. In addition, the thromboembolus prevents retrograde egress of this blood and the pulmonary arteriolar spasm
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slows the antegrade egress of the blood, so that the velocity of blood flow within the occluded right pulmonary artery is very low. As explained elsewhere, 10 Bernoulli's law then becomes operative: As the velocity of flow decreases, the lateral pressure on the vessel wall increases, so that vasodilation is enhanced still further. Under this scheme, progressive dilation of the right pulmonary artery would be expected to continue until the process was brought to a halt by antegrade thrombosis of the smaller pulmonary artery branches. The evidence suggests that the latter indeed did occur, and just in time to prevent the pulmonary artery from rupturing. Enormous dilatation of the left pulmonary artery was observed at the time of thoracotomy. The causes can be attributed to a different combination of factors: the necessity for the left pulmonary artery to accommodate twice its usual amount of blood and the pulmonary arteriolar spasm resulting in pulmonary hypertension. At death, of course, the small vessels in the thoracic and abdominal viscera lose their vasomotor tone and hence dilate, that the pulmonary circulation becomes decompressed. This accounts for the absence of dilatation of the left pulmonary artery when inspected at the time of autopsy. In contrast, the large clot prevented postmortem decompression of the right pulmonary artery. REFERENCES 1 Wenger, N. K., Stein, P., and Willis, P. W.: Massive Acute Pulmonary Embolism: The Deceivingly Nonspecific Manifestations, J. A. M. A. 220: 843, 1972.
The Journal of Thoracic and Cardiovascular Surgery
2 Cooperative Study Group: Urokinase Pulmonary Embolism Trial. Phase 1 Results, J. A. M. A. 214: 2163, 1970. 3 Wagner, H. N., Jr., Sabiston, D. C , Jr., McAfee, J. G., Tow, D., and Stern, H. S.: Diagnosis of Massive Pulmonary Embolism in Man by Radioisotope Scanning, N. Engl. J. Med. 271: 377, 1964. 4 Klein, E. W., McCarten, K., Dincheff, D. G., and Calvin, J. T.: Massive Pulmonary Emboli Diagnosed and Followed in Progress by Lung Imaging and Radionuclide Pulmonary Angiography, Circulation 50: 1260, 1974. 5 Mobin-Uddin, K., editor: Pulmonary Thromboembolism, Springfield, 111., 1975, Charles C Thomas, Publisher. 6 Alpert, J. S., Smith, R. E., Ockene, I. S., Askenasi, J., Dexter, L., and Dalen, J. E.: Treatment of Massive Pulmonary Embolism: The Role of Pulmonary Embolectomy, Am. Heart J. 89: 413, 1975. 7 Dalen, J. E., and Alpert, J. S.: Natural History of Pulmonary Embolism, Progr. Cardiovasc. Dis. 17: 259, 1975. 8 Kerr, I. H., Simon, G., and Sutton, G. C : The Value of the Plain Radiograph in Acute Massive Pulmonary Embolism, Br. J. Radiol. 44: 751, 1971. 9 Laks, M. M., Joviatsch, C. E., Garner, D., Beazell, M. S., and Criley, J. M.: Acute Pulmonary Artery Hypertension Produced by Distention of the Main Pulmonary Artery in the Conscious Dog, Chest 68: 807, 1975. 10 Schoenfeld, M. R., and Bernstein, R.: Hypernephroma, Marked Renal Vein Dilatation, and the Bernoulli Phenomenon, Am. J. Med. 50: 845, 1971.
Myron R. Schoenfeld, M . D . , * and John M. Budinger, M.D.,** Bronxville,
T
A. he catastrophic event known as massive pulmonary embolism is defined by various authors as involving occlusion of at least one third to one half of the pulmonary arterial bed. This occurrence is described as invariably resulting in a severe and often lethal compromise of cardiopulmonary function. This report describes the unique case history of a patient who is a striking exception to this rule. The woman was so free of cardiopulmonary symptoms and, in fact, generally felt so well that she walked casually into her physician's office to complain, not of dyspnea, but of hoarseness. When the chest x-ray film disclosed a dense hilar mass, she was subjected to chest surgery on From the Departments of Medicine and Pathology, Lawrence Hospital, Bronxville, N. Y. Received for publication April 22, 1976. Accepted for publication May 14, 1976. Address for reprints: Myron R. Schoenfeld, M. D., II Bronx River Road. Yonkers, N. Y. 10704. *Attending Cardiologist. Lawrence Hospital, Bronxville, New York, and Assistant Clinical Professor of Medicine (Cardiology), The Albert Einstein College of Medicine, Bronx, N. Y. **Attending Pathologist. Lawrence Hospital, Bronxville, N. Y., and Clinical Associate Professor of Pathology, College of Physicians and Surgeons. Columbia University, New York, N. Y.
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the reasonable (but mistaken) assumption that she was suffering from bronchogenic carcinoma. This case demonstrates that even such a serious disease as massive pulmonary embolism can be silent in onset, chronic in duration, and asymptomatic for months. To the best of our knowledge, this is the first such case reported.'~ 8 Case report G. M., a 67-year-old white woman, was admitted to our intensive care unit in acute respiratory distress. Until 3 months prior to admission, the patient always had been in good health, physically active, and without any cardiorespiratory symptoms. Several routine chest films had been taken over the years, the most recent 2 years prior to admission, and all were said to be normal. Initially, she noted the onset of intermittent hoarseness. Four weeks prior to admission, she casually consulted her physician because of this symptom. A chest x-ray film at that time showed a dense, well-circumscribed, right hilar mass, and examination with the laryngoscope revealed left vocal cord paralysis. She was admitted to another hospital with the presumptive diagnosis of bronchogenic carcinoma. Neither cyanosis nor dyspnea was noted prior to admission. Three weeks before her admission to Lawrence Hospital, an exploratory thoracotomy was performed. The surgical findings were unexpected. A tumor was not found, but both the right and left pulmonary arteries were markedly dilated. The heart and lungs were
58 1
582
Schoenfeld and
The Journal of Thoracic and Cardiovascular Surgery
Budinger
Y..
\
K Fig. 1. Chest x-ray film (posteroanterior view) taken one week after admission to Lawrence Hospital and 4 weeks after the thoracotomy. Note the large, dense, well-circumscribed, prominent right hilar mass caused by the enormously dilated and thrombosed right pulmonary artery. The appearance of the lung fields does not give any sign of massive right thromboembolism, however. The right lung is normal in size and lucency and has normal interstitial markings. The heart size perhaps is somewhat large for a person of asthenic build, but certainly it does not give a clue to the severity of the right ventricular hypertrophy. described as appearing normal. A diagnosis of "idiopathic pulmonary artery dilatation" was made, and hence no further procedures were done. Following 2 weeks of uneventful convalescence from the exploratory thoracotomy, the patient was discharged to her home, weak but ambulatory. On the day of her admission to Lawrence Hospital, she became acutely short of breath and came to our emergency room for treatment. Physical examination. She appeared undernourished and in severe respiratory distress, with marked dyspnea and moderate cyanosis. The temperature was 100.5° F., pulse 80 beats per minute and regular, blood pressure 104/82 mm. Hg, and respiration 28 breaths per minute and labored. The lung fields were clear. The heart was normal on examination: no murmurs, gallop, rub, or abnormal pulsations. Findings from the remainder of the physical examination were normal. There was no clubbing. Hospital course. Blood and urine cultures were negative. There was no leukocytosis, and the findings from urinalysis were normal. The chest x-ray film did not show any periphreal pulmonary infiltrate. Nevertheless, persistent fever of 101 to 102° F. during the first few days of hospitalization suggested that she probably had had aspiration pneumonia as
n?
L
Fig. 2. Radioisotope lung scan (anteroposterior view), using 200 /aCi of macroaggregated serum albumin tagged with 1-131 and administered intravenously, showing total nonvisualization of the right lung field. The left lung field appears normal. a result of vocal chord paralysis. Accordingly, she was treated with oxygen and antibiotics, and her condition considerably improved. Repeated examination of the heart disclosed no significant murmurs. Serial electrocardiograms, however, showed persistent signs of right heart strain characterized by depressed ST segments, inverted T waves, and somewhat high voltage of the R wave over the right percordial leads. In addition, the chest x-ray film showed mild cardiomegaly and a dense, wellcircumscribed, prominent right hilar mass (Fig. 1). Tomograms of the right lung did not further define this mass. Isotopic lung scan showed complete absence of visualization of the entire right lung (Fig. 2). Multiple arterial blood gas studies showed marked hypoxemia (Po2 24 to 50 mm. Hg) which improved greatly with the administration of oxygen by nasal catheter at a rate of 5 L. per minute. (Po2 80 to 140 mm. Hg). At the same time, the cyanosis cleared. The hemoglobin value of 13 to 14 Gm. per 100 ml. seemed incongruous with her rather undernourished appearance and was suspected to represent a mild degree of erythrocytosis. Pulmonary arteriograms were planned but cancelled twice because of the patient's inability to cooperate. It was concluded that the patient had complete thromboembolic occlusion of the right main pulmonary artery and perhaps partial occlusion of the left pulmonary arterial tree as well. Laryngoscopic examination confirmed left vocal chord paralysis, which was attributed to compression of the recurrent laryngeal nerve by the dilated pulmonary arteries. In addition to the cardiopulmonary problem, she was noted to have a rather blank facies, dysphagia (primarily to fluids rather than solids), sagging of the soft palate, a weak gag reflex, and bilateral positive Babinski reflexes. The spinal
Volume 72 Number 4 October, 1976
fluid was normal. These neurologic findings were thought to be due to pseudobulbar palsy caused by diffuse cerebral arteriosclerosis. On the nineteenth hospital day, when she was in relatively good physical condition, a transient episode of acute hypotension suddenly developed. Thereafter, she remained comatose, had generalized seizures, and had a marked increase in the muscle tone of all four extremities. The patient failed to respond to supportive measures and died on the twenty-first hospital day. An autopsy was performed. Final premortem clinical diagnoses. The final clinical diagnoses were as follows: (1) thromboembolism with complete occlusion of the right main pulmonary artery and perhaps partial occlusion of the left pulmonary arterial tree, with resultant chronic cor pulmonale and hypoxemia; (2) diffuse cerebral arteriosclerosis with pseudobulbar palsy and terminal episode of an acute cerebral infarction; (3) aspiration pneumonia owing to paralysis of the left vocal chord; (4) paralysis of the left recurrent laryngeal nerve owing to compression by the dilated pulmonary artery. Postmorten examination. The abnormal findings were as follows: Cardiovascular system. The heart weighed 300 grams. The right ventricle was 1.0 cm. thick. It was extremely firm in consistency, and there was marked hypertrophy of the trabeculae carnae. The left ventricle was 0.8 cm. thick. The epicardium, endocardium, valves, and pericardium were normal. The aorta was moderately antherosclerotic, but the coronary arteries and other major aortic arch arteries were strikingly free of atherosclerosis. Respiratory system. The entire laryngotracheobronchial tree contained moderate amounts of frothy serous fluid. The main pulmonary artery was normal in diameter and was not atherosclerotic. The right lung weighed 510 grams. Its pleural surface and cut section appeared normal. The right pulmonary artery was completely occluded by a laminated, dark and light-red clot which propagated out into the lobar and lobular arteries. Beginning at the bifurcation of the main pulmonary artery, the right pulmonary artery and all of its lobar and lobular branches were very dilated, thin walled, and markedly atherosclerotic. Beyond the lobular branches, the arteries were grossly and microscopically normal. The right pulmonary veins were normal. The left lung weighed 480 grams. Its pleural and cut surfaces also appeared normal. The left pulmonary artery and its lobar and lobular branches were moderately atherosclerotic, but they were not dilated or thin walled. The alveoli and small arteries of both lungs were normal. Nervous system. The proximal portions of both internal carotid arteries were markedly atherosclerotic. The basilar artery was moderately atherosclerotic. Microscopically, the small cerebral arteries and arterioles showed marked sclerosis. The brain was normal except for small cysts in the left putamen, globus pallidus, and adjacent white matter. The right basal ganglia appeared normal. Final postmortem anatomic diagnoses. The final anatomic diagnoses were as follows: (1) severe bilateral pulmonary arteriosclerosis, with marked cor pulmonale, and normal pulmonary arterioles; (2) thromboembolism of the right pulmonary artery, with occlusive thrombus; (3) cerebral arteriosclerosis and arteriolosclerosis, with multiple small
Pulmonary thromboembolism
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cystic necrotic foci, both recent and old, in the left basal ganglia; (4) minimal generalized arteriosclerosis. Discussion There can be no doubt that the thromboembolism which caused total occlusion of the patient's right pulmonary artery antedated her death by at least several months, and perhaps as long as 2 years; certainly, it was not a recent happening. This is proved by the severity of the right ventricular hypertrophy, by the marked pulmonary atherosclerosis, and by the extensive endothelialization of the blood clot itself. With confidence, then, we can term the occlusion chronic. The normal size, aeration, and interstitial markings of the right lung on chest roentgenogram were striking findings in this case. Apparently, collateral circulation via the bronchial arteries was sufficient to maintain viability of the substance and appearance of the entire lung. The surgical removal of a lung does not result in more than a mild increase in the pulmonary artery pressure. Therefore, the cause of the severe pulmonary hyptertension in the present case cannot be attributed to the absence of pulmonary arterial blood flow to one lung. This fact constitutes yet another and particularly striking piece of evidence that the cause of pulmonary hypertension in pulmonary thromboembolism largely is due to reflex9 and/or hormonal factors (eg., platelet serotonin) induced by the clot and affecting the entire pulmonary arteriolar bed bilaterally. This case adds a further dimension to the thesis that the pulmonary hypertension induced by a clot can be more than an acute episode: If the clot is not lysed, the pulmonary hypertension can be chronic and hence can induce pronounced cardiac hypertrophy. The severe dilatation of the thrombosed right pulmonary artery perhaps can be attributed to the following sequence of events: Thromboembolic occlusion of the right pulmonary artery causes local anoxia which, in turn, leads to progressive dilatation and increased branching of the bronchial arteries—the classic pattern of collateral vascularization in response to ischemia. The result is a sharp drop in the peripheral resistance and a striking increase in the volume of blood flow through the bronchial arterial tree. Via anastomoses between the bronchial and pulmonary arteries, a large volume of arterial blood at high systemic pressures now is being delivered into the pulmonary arterial tree of the right lung downstream from the occluding clot. The pulmonary artery, being relative thin walled and unaccustomed to such high pressure, responds by dilating. In addition, the thromboembolus prevents retrograde egress of this blood and the pulmonary arteriolar spasm
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slows the antegrade egress of the blood, so that the velocity of blood flow within the occluded right pulmonary artery is very low. As explained elsewhere, 10 Bernoulli's law then becomes operative: As the velocity of flow decreases, the lateral pressure on the vessel wall increases, so that vasodilation is enhanced still further. Under this scheme, progressive dilation of the right pulmonary artery would be expected to continue until the process was brought to a halt by antegrade thrombosis of the smaller pulmonary artery branches. The evidence suggests that the latter indeed did occur, and just in time to prevent the pulmonary artery from rupturing. Enormous dilatation of the left pulmonary artery was observed at the time of thoracotomy. The causes can be attributed to a different combination of factors: the necessity for the left pulmonary artery to accommodate twice its usual amount of blood and the pulmonary arteriolar spasm resulting in pulmonary hypertension. At death, of course, the small vessels in the thoracic and abdominal viscera lose their vasomotor tone and hence dilate, that the pulmonary circulation becomes decompressed. This accounts for the absence of dilatation of the left pulmonary artery when inspected at the time of autopsy. In contrast, the large clot prevented postmortem decompression of the right pulmonary artery. REFERENCES 1 Wenger, N. K., Stein, P., and Willis, P. W.: Massive Acute Pulmonary Embolism: The Deceivingly Nonspecific Manifestations, J. A. M. A. 220: 843, 1972.
The Journal of Thoracic and Cardiovascular Surgery
2 Cooperative Study Group: Urokinase Pulmonary Embolism Trial. Phase 1 Results, J. A. M. A. 214: 2163, 1970. 3 Wagner, H. N., Jr., Sabiston, D. C , Jr., McAfee, J. G., Tow, D., and Stern, H. S.: Diagnosis of Massive Pulmonary Embolism in Man by Radioisotope Scanning, N. Engl. J. Med. 271: 377, 1964. 4 Klein, E. W., McCarten, K., Dincheff, D. G., and Calvin, J. T.: Massive Pulmonary Emboli Diagnosed and Followed in Progress by Lung Imaging and Radionuclide Pulmonary Angiography, Circulation 50: 1260, 1974. 5 Mobin-Uddin, K., editor: Pulmonary Thromboembolism, Springfield, 111., 1975, Charles C Thomas, Publisher. 6 Alpert, J. S., Smith, R. E., Ockene, I. S., Askenasi, J., Dexter, L., and Dalen, J. E.: Treatment of Massive Pulmonary Embolism: The Role of Pulmonary Embolectomy, Am. Heart J. 89: 413, 1975. 7 Dalen, J. E., and Alpert, J. S.: Natural History of Pulmonary Embolism, Progr. Cardiovasc. Dis. 17: 259, 1975. 8 Kerr, I. H., Simon, G., and Sutton, G. C : The Value of the Plain Radiograph in Acute Massive Pulmonary Embolism, Br. J. Radiol. 44: 751, 1971. 9 Laks, M. M., Joviatsch, C. E., Garner, D., Beazell, M. S., and Criley, J. M.: Acute Pulmonary Artery Hypertension Produced by Distention of the Main Pulmonary Artery in the Conscious Dog, Chest 68: 807, 1975. 10 Schoenfeld, M. R., and Bernstein, R.: Hypernephroma, Marked Renal Vein Dilatation, and the Bernoulli Phenomenon, Am. J. Med. 50: 845, 1971.