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Alterations in the lungs of sheep after implantation of the Akutsu total artificial heart
Alterations in the lungs of sheep after implantation of the Akutsu total artificial heart Edmond C. Henson, Ph.D.,* Hisateru Takano, M.D.,** Hiroyuki Takagi, M.D.,** Tetsuzo Akutsu, M.D.,** and Joel G. Brunson, M.D.,* Jackson, Miss.
Since the implantation of the first total artificial heart in 1958, much progress has been made in artificial heart research. 1 The above studies produced a maximum survival of 2 hours in dogs. Later studies with a water-driven two-chambered device in 1963 resulted in an increased survival time up to 51h hours in dogs." The main pathologic alterations produced in the latter animals were marked pulmonary edema and hemorrhage, with pooling of blood in the mesentery, intestine, and liver. In 1969 there was a report of the first implantation of separate left and right ventricular pumping units into a human subject. 3 The patient received a heart allograft 3 days after implantation but died 3 days later. The main pathologic alterations noted at autopsy were confluent necrotizing bronchopneumonia of both lungs with tubular necrosis and edema of both kidneys. The first detailed descriptions concerning morphologic alterations after implantation of a total artificial heart in experimental aniFrom the University of Mississippi Medical Center Jackson, Miss. 39216. Supported in part by U.S. Public Health Contract No. NIH-69-2185 and U.S. Public Health, National Institutes of Health Grant HE-06943-08. Received for publication Dec. 5, 1972. 'Department of Pathology. •• Department of Surgery.
mals were recently reported.' The latter studies employed the implantation of the four-chambered Akutsu total artificial heart in sheep. Maximum survival time obtained was 60 hours. The causes of death were generally irreversible hypotension and respiratory failure. Findings at necropsy revealed severe alterations of all major organ systems. The use of anti-shock therapy in the second phase of the above studies was found to minimize many of the changes seen in all organs except for those in the lungs. The lungs in all animals studied showed many severe alterations too complex in nature to be described in a single paper concerning general systemic alterations. The purpose of the present report is to describe in detail, with illustrations, the various types of alterations produced in the lungs of sheep after implantation of a total artificial heart. Materials and methods
The Akutsu total artificial heart was implanted in 16 adult sheep of both sexes, weighing 70 to 80 kilograms. The surgical techniques and mode of clinical management used in these animals were described in earlier reports." 6 At the immediate time of death, as determined by the absence of neurologic reflexes, the animals were 629
630
The Journal of Thoracic and Card iovascular Surgery
Henson et al.
Upon opening the tracheobronchial tree, we noted an abundance of bloody, viscous, mucoid material. In certain of the animals the tracheobronchial tree was almost totally occluded by the mucoid material. Microscopic examination revealed massive, diffuse congestion with hemorrhage , interstitial edema, interstitial pneumonitis, and atelectasis (Fig. 2). Certain areas mainly had congestion with intra-alveolar hemorrhage (Fig . 3). Other areas showed infarctions, some of which were hemorrhagic. There were numerous zones with bronchiolar obstruction due to the presence of fibrinopurulent material and mucous (Fig. 4) .
Fig. 1. Lungs removed from sheep at time of death approximatel y 40 hours after being implanted with the total artificial heart. Note the presence of dark color suggestive of marked congestion. Numerous small areas of hemorrhage are also present.
necropsied. After gross examination, tissue sections were taken from the lungs and other organs and processed and stained with hematoxylin and eosin in the usual fashion for studies by light microscopy. Additional sections were taken and processed for study by electron microscopy by use of methods previously described. ' Results
The length of survival in the sheep after implantation with the Akutsu total artificial heart varied from 8 to 60 hours . The causes of death in all animals were respiratory failure and irreversible hypotension. At the time of death, the pleural cavities of all animals that were necropsied contained marked pleural effusion consisting of a dark pink fluid. Further examination revealed the lungs to be dark red to blue in color, wet, severely congested, and markedly hemorrhagic (Fig. 1). The lungs were quite heavy and distended , suggesting consolidation. Gross cut sectioning showed severe congestion, edema , and pneumonia with consolidation. There were also areas of atelectasis.
Ultrastructural studies revealed marked congestion with edema , leukocytic plugging of capillaries, disruption of alveolar septal walls, and inflammatory exudate in interstitial and alveolar areas (Fig. 5) . Other areas showed primarily congestion with degeneration of endothelial lining of capillaries and disruption of the basement membrane due to pressure exerted by the large amount of blood flow entering the pulmonary circulation (Fig. 6) . These changes in the pulmonary microcirculation led to diffuse hemorrhage. The morphologic alterations described above are compatible with a clinical course of severe respiratory failure. Discussion
The results of the present studies suggest that the lungs of sheep are severely altered after implantation of a total artificial heart. There are no other detailed studies of animals with total artificial hearts in the literature . However, some reports briefly described such factors as pulmonary edema and disseminated intravascular coagulation as the main causes of death in animals with implanted artificial hearts." 8 In the present studies, death resulted from respiratory failure followed by irreversible hypotension. Only 1 of the animals studied in the present experiments showed evidence of thromboembolism. The morphologic alterations produced in the lungs of sheep after implantation of the
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Fig. 2. Section of lung shows disruption of normal alveolar structure with atelectasis, extreme congestion, hemorrhage, interstitial edema, and interstitial pneumonitis. (Hematoxylin and eosin; original magnification x l OO.)
Fig. 3. Section of lung shows marked intraalveolar hemorrhage. Note retention of alveolar pattern even though marked hemorrhage is present. (Hematoxylin and eosin; original magnification x200. )
Akutsu total artificial heart are expressed by a diversity of patterns. There are certain areas which predominantly show congestion. Other areas mainly show interstitial pneumonitis. Still other areas mainly have interstitial edema and atelectasis. However, the generalized predominant pattern is a combination of congestion, interstitial edema,
hemorrhage, interstitial pneumonitis, and variable degrees of atelectasis. The etiologic factors leading to the above morphologic alterations are multiple . One important cause for pulmonary congestion , hemorrhage, and edema is a state of acute pulmonary hypertension which occurs immediately after implantation. It was noted
The Journol of
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Fig. 4. Section of lung shows bronchiole filled with mucous and inflammatory exudate. (Hematoxylin and eosin; original magnification x200.)
Fig. 5. Electron micrograph of lung section shows marked congestion with plugging of pulmonary capillary by degenerating leukocytes, platelets, and other inflammatory debris. There is also the presence of marked interestitial edema, areas of disrupted alveolar wall, and marked inflammatory exudate (x3,600).
Surgery
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Fig. 6. High magnification view by electron microscopy shows early disruption of both endothelial lining and basement membrane due to pressure by an erythrocyte in a severely congested pulmonary capillary. These changes led to marked hemorrhage throughout the pulmonary microcirculation (x46,OOO).
that although the mean pulmonary arterial pressure was 20 mm. Hg, the peak pulmonary arterial pressure during systole reached as high as 80 mm. Hg. This extremely high pulmonary arterial pressure in an acute situation causes blood to flow into the pulmonary microcirculation under a higher pressure than can be accommodated. The pulmonary microcirculation is unlike that in any other part of the body in that the terminal pulmonary arterioles have no muscular walls and therefore cannot produce resistance against a large blood flow. As a result, acute pulmonary hypertension brings about massive congestion, hemorrhage, and edema in the microcirculation (i.e., terminal arterioles and capillaries) of
the lungs. Sympathetic stimulation which occurs in this state causes constriction of the small postcapillary veins, which further contributes to the massive pooling of blood within the pulmonary circulation. The causes of the acute pulmonary hypertension in these studies were as follows: a high peak pressure during systole produced by the right ventricular pumping chamber; massive sympathetic stimulation which occurs after implantation due to stress and other factors; and possibly sepsis due to gram-negative bacteria. The artificial heart used in the present studies causes acute pulmonary hypertension because of the high mechanical pumping force of its right ventricle. Massive sympathetic stimulation due to stress after
The Journol of
634
Henson et al.
Thoracic ond Cardiovascular Surgery
implantation and to other factors contributes to acute pulmonary hypertension by the vasoconstrictive effect on the pulmonary arteries. Endotoxin shock from gram-negative bacteria has been documented as a cause of acute pulmonary hypertension in sheep." Therefore gram-negative sepsis may have contributed to the acute pulmonary hypertension observed in the present studies. Pneumonitis in the sheep used in the present experiments was most likely due to three possible sources: (l) generalized sepsis; (2) infection from around openings for chest tubes; and (3) depressed function of the reticuloendothelial system associated with stress factors, which may have caused inability to prevent infection from bacteria present in the upper and lower respiratory tracts. One study previously showed that extracorporeal pumping for maintenance of circulation caused depressed reticuloendothelial function in rats.?" The latter decrease in resistance was presumably due to the production of stress. One final significant alteration noted in almost all the above sheep was plugging of bronchioles with a thick, mucoid, often bloody material. An earlier report noted that sheep under a general anesthesia are very susceptible to respiratory failure due to plugging of the tracheobronchial tree from massive secretions by the salivary glands." The origin of the fluid material in the tracheobronchial tree in the present studies was not determined with certainty, but is thought to be from both salivary glands and bronchial glands. Clearly, the lungs are extremely vulnerable to severe insults in animals with implanted total artificial hearts. As noted in the present studies, these insults may be extreme enough to cause alterations leading to respiratory failure and death. We wish to thank Judy Fenter for technical assistance and Brenda Watts and Kathy Windham for assistance in the preparation of the manuscript.
REFERENCES Akutsu, T., and Kolff, W. J.: Permanent Substitutes for Valves and Hearts, Trans. Am. Soc. Artif. Intern. Organs 4: 230, 1958. 2 Atsumi, K., Hori, M., Ibeda, S., Sakurai, Y., Fujimori, Y., and Kimoto, S.: Artificial Heart Incorporated in the Chest, Trans. Am. Soc. Artif. Intern. Organs 9: 292, 1963. 3 Cooley, D. A, Liotta, D., Hallman, G. L., Bloodwell, R. D., Leachman, R. D., and Milam, J. D.: First Human Implantation of Cardiac Prosthesis for Staged Total Replacement of the Heart, Trans. Am. Soc. Artif. Intern. Organs 15: 252, 1969. 4 Henson, E. c., Weaver, D. Q., Lockard, V. G., Takano, H., Takagi, H., Akutsu, T., Arhelger, R. B., and Brunson, J. G.: Morphologic Alterations in Sheep After Implantation of the Akutsu Total Artificial Heart, Am. J. Pathol. 66: 331, 1972. 5 Akutsu, T., Takagi, H., and Takano, H.: Total Artificial Hearts With Built-In Valves, Trans. Am. Soc. Artif. Intern. Organs 16: 392, 1970. 6 Takano, H., Takagi, H., Turner, M. D., Henson, E. C., Crowell, J. W., and Akutsu, T.: Problems in Total Artificial Heart, Trans. Am. Soc. Artif. Intern. Organs 27: 449, 1971. 7 Boler, R. K., Bibighaus, A. J., and Brunson, J. G.: Ultrastructural Alterations of Dog Livers During Endotoxin Shock, Lab. Invest. 17: 527, 1967. 8 Kwan-Gett, C., Bakeman, D. K., Donovan, F. M., Jr., Eastwood, N., Foote, J. L., Kawai, J. L., Van Kampen, K. R., Wong, H. K., Zwartl, H. H. J., and Kolff, W. J.: Artifical Heart With Hemispherical Ventricles and Disseminated Intravascular Coagulation, Trans. Am. Soc. Artif. Intern. Organs 17: 474, 1971. 9 Halmagyi, D. F. J., Starzecki, B., and Horner, J.: Mechanisms and Pharmacology of Endotoxin Shock in Sheep, J. Appl, Physiol, 18: 544, 1963. 10 Subramanian, V., Lande, A. J., Gans, H., Lowman, J. T., and Lillehei, C. W.: Depression of Host-Defense Mechanism Following Extracorporeal Circulation, Trans. Am. Soc. Artif. Intern. Organs 15: 165, 1969. 11 Phillipson, A T., and Thomson, W.: The sheep, in Lane-Petter, W., Worden, A. N., Hill, B. F., Paterson, 1. S., and Vevers, H. G., editors: The VFAW Handbook on the Care and Management of Laboratory Animals. Baltimore, 1967, The Williams & Wilkins Company, p. 604.
Since the implantation of the first total artificial heart in 1958, much progress has been made in artificial heart research. 1 The above studies produced a maximum survival of 2 hours in dogs. Later studies with a water-driven two-chambered device in 1963 resulted in an increased survival time up to 51h hours in dogs." The main pathologic alterations produced in the latter animals were marked pulmonary edema and hemorrhage, with pooling of blood in the mesentery, intestine, and liver. In 1969 there was a report of the first implantation of separate left and right ventricular pumping units into a human subject. 3 The patient received a heart allograft 3 days after implantation but died 3 days later. The main pathologic alterations noted at autopsy were confluent necrotizing bronchopneumonia of both lungs with tubular necrosis and edema of both kidneys. The first detailed descriptions concerning morphologic alterations after implantation of a total artificial heart in experimental aniFrom the University of Mississippi Medical Center Jackson, Miss. 39216. Supported in part by U.S. Public Health Contract No. NIH-69-2185 and U.S. Public Health, National Institutes of Health Grant HE-06943-08. Received for publication Dec. 5, 1972. 'Department of Pathology. •• Department of Surgery.
mals were recently reported.' The latter studies employed the implantation of the four-chambered Akutsu total artificial heart in sheep. Maximum survival time obtained was 60 hours. The causes of death were generally irreversible hypotension and respiratory failure. Findings at necropsy revealed severe alterations of all major organ systems. The use of anti-shock therapy in the second phase of the above studies was found to minimize many of the changes seen in all organs except for those in the lungs. The lungs in all animals studied showed many severe alterations too complex in nature to be described in a single paper concerning general systemic alterations. The purpose of the present report is to describe in detail, with illustrations, the various types of alterations produced in the lungs of sheep after implantation of a total artificial heart. Materials and methods
The Akutsu total artificial heart was implanted in 16 adult sheep of both sexes, weighing 70 to 80 kilograms. The surgical techniques and mode of clinical management used in these animals were described in earlier reports." 6 At the immediate time of death, as determined by the absence of neurologic reflexes, the animals were 629
630
The Journal of Thoracic and Card iovascular Surgery
Henson et al.
Upon opening the tracheobronchial tree, we noted an abundance of bloody, viscous, mucoid material. In certain of the animals the tracheobronchial tree was almost totally occluded by the mucoid material. Microscopic examination revealed massive, diffuse congestion with hemorrhage , interstitial edema, interstitial pneumonitis, and atelectasis (Fig. 2). Certain areas mainly had congestion with intra-alveolar hemorrhage (Fig . 3). Other areas showed infarctions, some of which were hemorrhagic. There were numerous zones with bronchiolar obstruction due to the presence of fibrinopurulent material and mucous (Fig. 4) .
Fig. 1. Lungs removed from sheep at time of death approximatel y 40 hours after being implanted with the total artificial heart. Note the presence of dark color suggestive of marked congestion. Numerous small areas of hemorrhage are also present.
necropsied. After gross examination, tissue sections were taken from the lungs and other organs and processed and stained with hematoxylin and eosin in the usual fashion for studies by light microscopy. Additional sections were taken and processed for study by electron microscopy by use of methods previously described. ' Results
The length of survival in the sheep after implantation with the Akutsu total artificial heart varied from 8 to 60 hours . The causes of death in all animals were respiratory failure and irreversible hypotension. At the time of death, the pleural cavities of all animals that were necropsied contained marked pleural effusion consisting of a dark pink fluid. Further examination revealed the lungs to be dark red to blue in color, wet, severely congested, and markedly hemorrhagic (Fig. 1). The lungs were quite heavy and distended , suggesting consolidation. Gross cut sectioning showed severe congestion, edema , and pneumonia with consolidation. There were also areas of atelectasis.
Ultrastructural studies revealed marked congestion with edema , leukocytic plugging of capillaries, disruption of alveolar septal walls, and inflammatory exudate in interstitial and alveolar areas (Fig. 5) . Other areas showed primarily congestion with degeneration of endothelial lining of capillaries and disruption of the basement membrane due to pressure exerted by the large amount of blood flow entering the pulmonary circulation (Fig. 6) . These changes in the pulmonary microcirculation led to diffuse hemorrhage. The morphologic alterations described above are compatible with a clinical course of severe respiratory failure. Discussion
The results of the present studies suggest that the lungs of sheep are severely altered after implantation of a total artificial heart. There are no other detailed studies of animals with total artificial hearts in the literature . However, some reports briefly described such factors as pulmonary edema and disseminated intravascular coagulation as the main causes of death in animals with implanted artificial hearts." 8 In the present studies, death resulted from respiratory failure followed by irreversible hypotension. Only 1 of the animals studied in the present experiments showed evidence of thromboembolism. The morphologic alterations produced in the lungs of sheep after implantation of the
Volume 65 Number 4 April, 1973
Akutsu total artificial heart
631
Fig. 2. Section of lung shows disruption of normal alveolar structure with atelectasis, extreme congestion, hemorrhage, interstitial edema, and interstitial pneumonitis. (Hematoxylin and eosin; original magnification x l OO.)
Fig. 3. Section of lung shows marked intraalveolar hemorrhage. Note retention of alveolar pattern even though marked hemorrhage is present. (Hematoxylin and eosin; original magnification x200. )
Akutsu total artificial heart are expressed by a diversity of patterns. There are certain areas which predominantly show congestion. Other areas mainly show interstitial pneumonitis. Still other areas mainly have interstitial edema and atelectasis. However, the generalized predominant pattern is a combination of congestion, interstitial edema,
hemorrhage, interstitial pneumonitis, and variable degrees of atelectasis. The etiologic factors leading to the above morphologic alterations are multiple . One important cause for pulmonary congestion , hemorrhage, and edema is a state of acute pulmonary hypertension which occurs immediately after implantation. It was noted
The Journol of
632
Henson et al.
Thoracic and Cardiavascular
Fig. 4. Section of lung shows bronchiole filled with mucous and inflammatory exudate. (Hematoxylin and eosin; original magnification x200.)
Fig. 5. Electron micrograph of lung section shows marked congestion with plugging of pulmonary capillary by degenerating leukocytes, platelets, and other inflammatory debris. There is also the presence of marked interestitial edema, areas of disrupted alveolar wall, and marked inflammatory exudate (x3,600).
Surgery
Volume 65 Number 4 April, 1973
Akutsu total artificial heart
633
Fig. 6. High magnification view by electron microscopy shows early disruption of both endothelial lining and basement membrane due to pressure by an erythrocyte in a severely congested pulmonary capillary. These changes led to marked hemorrhage throughout the pulmonary microcirculation (x46,OOO).
that although the mean pulmonary arterial pressure was 20 mm. Hg, the peak pulmonary arterial pressure during systole reached as high as 80 mm. Hg. This extremely high pulmonary arterial pressure in an acute situation causes blood to flow into the pulmonary microcirculation under a higher pressure than can be accommodated. The pulmonary microcirculation is unlike that in any other part of the body in that the terminal pulmonary arterioles have no muscular walls and therefore cannot produce resistance against a large blood flow. As a result, acute pulmonary hypertension brings about massive congestion, hemorrhage, and edema in the microcirculation (i.e., terminal arterioles and capillaries) of
the lungs. Sympathetic stimulation which occurs in this state causes constriction of the small postcapillary veins, which further contributes to the massive pooling of blood within the pulmonary circulation. The causes of the acute pulmonary hypertension in these studies were as follows: a high peak pressure during systole produced by the right ventricular pumping chamber; massive sympathetic stimulation which occurs after implantation due to stress and other factors; and possibly sepsis due to gram-negative bacteria. The artificial heart used in the present studies causes acute pulmonary hypertension because of the high mechanical pumping force of its right ventricle. Massive sympathetic stimulation due to stress after
The Journol of
634
Henson et al.
Thoracic ond Cardiovascular Surgery
implantation and to other factors contributes to acute pulmonary hypertension by the vasoconstrictive effect on the pulmonary arteries. Endotoxin shock from gram-negative bacteria has been documented as a cause of acute pulmonary hypertension in sheep." Therefore gram-negative sepsis may have contributed to the acute pulmonary hypertension observed in the present studies. Pneumonitis in the sheep used in the present experiments was most likely due to three possible sources: (l) generalized sepsis; (2) infection from around openings for chest tubes; and (3) depressed function of the reticuloendothelial system associated with stress factors, which may have caused inability to prevent infection from bacteria present in the upper and lower respiratory tracts. One study previously showed that extracorporeal pumping for maintenance of circulation caused depressed reticuloendothelial function in rats.?" The latter decrease in resistance was presumably due to the production of stress. One final significant alteration noted in almost all the above sheep was plugging of bronchioles with a thick, mucoid, often bloody material. An earlier report noted that sheep under a general anesthesia are very susceptible to respiratory failure due to plugging of the tracheobronchial tree from massive secretions by the salivary glands." The origin of the fluid material in the tracheobronchial tree in the present studies was not determined with certainty, but is thought to be from both salivary glands and bronchial glands. Clearly, the lungs are extremely vulnerable to severe insults in animals with implanted total artificial hearts. As noted in the present studies, these insults may be extreme enough to cause alterations leading to respiratory failure and death. We wish to thank Judy Fenter for technical assistance and Brenda Watts and Kathy Windham for assistance in the preparation of the manuscript.
REFERENCES Akutsu, T., and Kolff, W. J.: Permanent Substitutes for Valves and Hearts, Trans. Am. Soc. Artif. Intern. Organs 4: 230, 1958. 2 Atsumi, K., Hori, M., Ibeda, S., Sakurai, Y., Fujimori, Y., and Kimoto, S.: Artificial Heart Incorporated in the Chest, Trans. Am. Soc. Artif. Intern. Organs 9: 292, 1963. 3 Cooley, D. A, Liotta, D., Hallman, G. L., Bloodwell, R. D., Leachman, R. D., and Milam, J. D.: First Human Implantation of Cardiac Prosthesis for Staged Total Replacement of the Heart, Trans. Am. Soc. Artif. Intern. Organs 15: 252, 1969. 4 Henson, E. c., Weaver, D. Q., Lockard, V. G., Takano, H., Takagi, H., Akutsu, T., Arhelger, R. B., and Brunson, J. G.: Morphologic Alterations in Sheep After Implantation of the Akutsu Total Artificial Heart, Am. J. Pathol. 66: 331, 1972. 5 Akutsu, T., Takagi, H., and Takano, H.: Total Artificial Hearts With Built-In Valves, Trans. Am. Soc. Artif. Intern. Organs 16: 392, 1970. 6 Takano, H., Takagi, H., Turner, M. D., Henson, E. C., Crowell, J. W., and Akutsu, T.: Problems in Total Artificial Heart, Trans. Am. Soc. Artif. Intern. Organs 27: 449, 1971. 7 Boler, R. K., Bibighaus, A. J., and Brunson, J. G.: Ultrastructural Alterations of Dog Livers During Endotoxin Shock, Lab. Invest. 17: 527, 1967. 8 Kwan-Gett, C., Bakeman, D. K., Donovan, F. M., Jr., Eastwood, N., Foote, J. L., Kawai, J. L., Van Kampen, K. R., Wong, H. K., Zwartl, H. H. J., and Kolff, W. J.: Artifical Heart With Hemispherical Ventricles and Disseminated Intravascular Coagulation, Trans. Am. Soc. Artif. Intern. Organs 17: 474, 1971. 9 Halmagyi, D. F. J., Starzecki, B., and Horner, J.: Mechanisms and Pharmacology of Endotoxin Shock in Sheep, J. Appl, Physiol, 18: 544, 1963. 10 Subramanian, V., Lande, A. J., Gans, H., Lowman, J. T., and Lillehei, C. W.: Depression of Host-Defense Mechanism Following Extracorporeal Circulation, Trans. Am. Soc. Artif. Intern. Organs 15: 165, 1969. 11 Phillipson, A T., and Thomson, W.: The sheep, in Lane-Petter, W., Worden, A. N., Hill, B. F., Paterson, 1. S., and Vevers, H. G., editors: The VFAW Handbook on the Care and Management of Laboratory Animals. Baltimore, 1967, The Williams & Wilkins Company, p. 604.