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Fracture and embolization of a Björk-Shiley disc
Fracture and embolization of a Bjork-Shiley disc Fatal failure of a prosthetic mitral valve A case offracture of the disc occluder of a Bjork-Shiley mitral prosthesis with embolization of the disc fragments to distal aorta is presented. The possibility of valve dysfunction and the diagnostic value of echocardiography should be considered whenever acute heart failure occurs in a patient with an artificial valve.
David D. Norenberg, M.D.,* Roger W. Evans, M.D., F.A.C.C.,* A. Erik Gundersen, M.D., F.A.C.S.,** and R. Mario Abellera, M.D., F.C.A.P.,***
La Crosse, Wis.
T
he Bjork-Shiley tilting disc valve has gained wide favor as an aortic and mitral replacement because of its low gradient, central laminar flow, and its low incidence of thrombotic and peripheral embolic complications. The design of the prosthesis, with the ability of the disc to rotate, allows for minimal stress and wear to the disc and excellent durability. 1 Since its introduction in 1969, more than 135,000 of these valves have been distributed for implantation around the world. This communication reports the previously unobserved occurrence of disc fracture with embolization of the fragments to the distal aorta.
Case report In March of 1976, a 49-year-old man underwent mitral valve replacement because of severe mitral insufficiency and congestive failure secondary to past inferior wall infarction with posterior papillary muscle dysfunction. At operation a gas-sterilized No. 31 Bjork-Shiley prosthesis (with pyrolytic carbon disc) was implanted and aorta-coronary grafting to the distal right coronary artery also was done to bypass complete proximal obstruction in that vessel. Prior to his discharge From the Departments of Medicine, Surgery, and Pathology, Gundersen Clinic La Crosse, Wis. Received for publication May 2, 1977. Accepted for publication July IS, 1977. Address for reprints: David D. Norenberg, M.D., Department of Medicine, Gundersen Clinic, La Crosse, Wis. 54601. *Department of Medicine. **Department of Surgery. ***Department of Pathology.
from the hospital, a postoperative echocardiogram demonstrated normal motion of the mitral valve prosthesis. In the following months the patient was normotensive, his heart size returned to normal, auscultation found normal valve opening and closing sounds without insufficiency murmur, and all signs of congestive failure resolved. Continuing digoxin and warfarin, he returned to full-time administrative work, feeling well. On Oct. I, 1976, during moderate exertion, he was stricken with chest and upper abdominal pain, shortness of breath, and weakness. He was returned to the hospital coronary care unit, and he was diaphoretic, dyspneic, and hypotensive. Heart sounds were faint with a muffled first sound. No murmur was detected by multiple examiners. Electrocardiogram showed a sinus tachycardia with anterior ischemic STsegment depression. Chest roentgenogram demonstrated pulmonary edema, and an upper-normal heart size with the radiopaque prosthetic valve ring appearing to be in normal position. The initial impression was acute myocardial infarction with cardiogenic shock. Hemodynamic monitoring with a double-lumen thermistor pulmonary artery catheter and a transfemoral distal aortic catheter recorded initial pulmonary artery end-diastolic pressure of 18 mrn. Hg, systolic aortic pressure of 50 mm. Hg , and cardiac index of 1.3 L. per minute per square meter. Intensive medical therapy was unsuccessful, progressive deterioration continued, and the patient died 7 hours after admission. At postmortem examination the pyrolytic carbon disc of the Bjork-Shiley mitral valve prosthesis was found to have fractured into nearly equal halves (Fig. I), with embolization of both segments to the bifurcation of the aorta. Inspection of the fractured disc revealed no defect or deformity other than the sharp clean edges of the break. The surfaces were smooth and free of thrombi. The prosthetic ring in the mitral position was intact, with good endothelialization of the sewing fabric and no evidence of pannus formation, leak, or deformity. The
925
The Journal of Thoracic and Cardiovascular Surgery
926 Norenberg et al.
Fig. 1. The fractured Bjork-Shiley disc removed from the bifurcation of aorta at autopsy.
metal struts were in normal configuration and stable, without any evidence of damage or thrombus formation. The valve and disc fragments were returned to Shiley Laboratories for detailed measurements and testing.
Discussion Artificial heart valves of all types are subject to mechanical dysfunction of various causes, including thrombus and pannus formation, dehiscene with peri valvular leak , occluder variance, occluder entrapment against ventricular walls , and disruption of the valve structure."?" Acute heart failure appearing in any patient with an artificial valve should be considered to be a result of such mechanical impairment until proved otherwise. Echocardiography may be of great value in early diagnosis of prosthetic dysfunction, particularly if a base-line echocardiogram has been obtained in the early postoperative period to confirm proper function and to serve for future comparison .P11-13 The echocardiographic characteristics of normally functioning and malfunctioning Bjork-Shiley valves have been described. 11-13 In the case reported here, the diagnosis of disc embolization would have been apparent if an echocardiogram had been done, and emergency surgery might have been undertaken. In the catastrophic event of mitral valve disruption with loss of the occluder, the patient may live for more than several hours, allowing time for valve assessment and successful reoperation.":" Escape of an aortic valve occluder appears to be more rapidly fatal," although survival for almost 12 hours was observed in one instance.! Loss of the disc from a Bjork-Shiley mitral valve has been reported in the literature previously. 8 In that case
the disc was made of Delrin and was deformed, probably as a result of steam-heat sterilization. The discs now are made of pyrolytic carbon and are unaffected by steam autoclaving.' Intraoperative disc escape from an aortic Bjork-Shiley prosthesis, due to a bent strut, has been described also . 10 Several other instances of intraoperative and postoperative disc embolization have been reported to Shiley Laboratories. Causes have included strut distortion (probably at the time of implantation by use of a surgical clamp to align the disc, rather than the valve holder designed for that purpose), Delrin disc deformity from heat sterilization, and disc dislodgment by transvalvular catheter placement. * In the present case the valve had been gas sterilized before implantation. Postmortem investigations at this institution and at Shiley Laboratories have confirmed that the supporting ring and struts had been constructed properly and that no distortion had occurred. At the time of manufacture, the dimensions, silicone-content, and coating microhardness of the disc all were within specification limits. Other than the fracture line, there was no distortion or variance of the disc . Continuous polished wear marks, present on the bottom of the disc well, indicated that it had rotated freely during implantation. Scanning electron microscopy demonstrated four tiny chipped areas directly on the fracture edge and two minor cracks on the surface of the disc well , contiguous with the fracture edge. Pyrolytic carbon is very brittle, and it is not known if these were related causally to the fracture or, more likely, if they were a result of it. The disc fracture remains unexplained .
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REFERENCES Brawley, R. K., Donahoo, 1. S., and Gott, V. L.: Current Status of the Beall, Bjork-Shiley, Braunwald-Cutter, Lillehei-Kaster and Smeloff-Cutter Cardiac Valve Prostheses, Am. J. Cardio\. 35: 855, 1975. Burch, G. E., and Giles, T. D.: Clinical Evaluation of Aortic and Mitral Valve Prostheses, Am. Heart J . 92: 245, 1976. Keen, G.: Late Death Due to Escape of Ball From Mitral Valve Prosthesis, J. THORAc. CARDJOVASC. SURG. 67: 202, 1974. Bonnabeau, R. C. J., and Lillehei, C. W.: Mechanical Ball Failure in Starr-Edwards Prosthetic Valves, J. THORAC . CARDJOVASC. SURG. 56: 258, 1968. Hughes, D. A., Leatherman, L. L., Norman, J. C., et al.: Late Embolization of Prosthetic Mitral Valve Occluder With Survival Following Reoperation, Ann. Thorac. Surg. 19: 212, 1975. Roberts, A. K., Lambert, C. J., and Mitchel, B. F.:
*Personal communication, Shiley Laboratories, Santa Barbara, Calif.
Volume 74 Number 6
Bjork-Shiley mitral prosthesis
927
December, 19n
Embolization of Disc Occluder of a Wada-Cutter Mitral Prosthesis With Survival, Ann. Thorac. Surg. 21: 361,
1976. 7 Ansbro, J., Clark, R., and Gerbode, F.: Successful Surgical Correction of an Embolized Prosthetic Valve Poppet, J. THORAC. CARDIOVASC. SURG. 72: 130, 1976. 8 Measmer, B. J., Rothlin, M., and Senning, A..: Early Disc Dislodgment. An Unusual Complication After Insertion of a Bjork-Shiley Mitral Valve Prosthesis, J. THORAC. CARDIOVASC. SURG. 65: 386, 1973. 9 Maronas, J. M., Rufilanchas, J. J., Villagra, F., et aI.: Reoperation for Dysfunction of the Bjork-Shiley Mitral Disc Prosthesis: Report of Eight Cases, Am. Heart J. 93:
316, 1977.
10 Mulder, G. A.: Discussion of Bjork, V. 0., Henze, A., and Holmgren, A.: Five Years' Experience With the Bjork-Shiley Tilting-disc Valve in Isolated Aortic Valvular Disease, J. THORAC. CARDIOVASC. SURG. 68: 403,
1974. 11. Douglas, J. E., and Williams, G. D.: Echocardiographic Evaluation of the Bjork-Shiley Prosthetic Valve, Circulation 50: 52, 1974. 12 Chandraratna, P., Lopez, J. M., Hildner, F. J., et aI.: Diagnosis of Bjork-Shiley Aortic Valve Dysfunction by Echocardiography, Am. Heart J. 91: 318, 1976. 13 Srivastava, T. N., Hussain, M., Gray, L. A. J., et aI.: Echocardiographic Diagnosis of a Stuck Bjork-Shiley Aortic Valve Prosthesis, Chest 70: 94, 1976.
David D. Norenberg, M.D.,* Roger W. Evans, M.D., F.A.C.C.,* A. Erik Gundersen, M.D., F.A.C.S.,** and R. Mario Abellera, M.D., F.C.A.P.,***
La Crosse, Wis.
T
he Bjork-Shiley tilting disc valve has gained wide favor as an aortic and mitral replacement because of its low gradient, central laminar flow, and its low incidence of thrombotic and peripheral embolic complications. The design of the prosthesis, with the ability of the disc to rotate, allows for minimal stress and wear to the disc and excellent durability. 1 Since its introduction in 1969, more than 135,000 of these valves have been distributed for implantation around the world. This communication reports the previously unobserved occurrence of disc fracture with embolization of the fragments to the distal aorta.
Case report In March of 1976, a 49-year-old man underwent mitral valve replacement because of severe mitral insufficiency and congestive failure secondary to past inferior wall infarction with posterior papillary muscle dysfunction. At operation a gas-sterilized No. 31 Bjork-Shiley prosthesis (with pyrolytic carbon disc) was implanted and aorta-coronary grafting to the distal right coronary artery also was done to bypass complete proximal obstruction in that vessel. Prior to his discharge From the Departments of Medicine, Surgery, and Pathology, Gundersen Clinic La Crosse, Wis. Received for publication May 2, 1977. Accepted for publication July IS, 1977. Address for reprints: David D. Norenberg, M.D., Department of Medicine, Gundersen Clinic, La Crosse, Wis. 54601. *Department of Medicine. **Department of Surgery. ***Department of Pathology.
from the hospital, a postoperative echocardiogram demonstrated normal motion of the mitral valve prosthesis. In the following months the patient was normotensive, his heart size returned to normal, auscultation found normal valve opening and closing sounds without insufficiency murmur, and all signs of congestive failure resolved. Continuing digoxin and warfarin, he returned to full-time administrative work, feeling well. On Oct. I, 1976, during moderate exertion, he was stricken with chest and upper abdominal pain, shortness of breath, and weakness. He was returned to the hospital coronary care unit, and he was diaphoretic, dyspneic, and hypotensive. Heart sounds were faint with a muffled first sound. No murmur was detected by multiple examiners. Electrocardiogram showed a sinus tachycardia with anterior ischemic STsegment depression. Chest roentgenogram demonstrated pulmonary edema, and an upper-normal heart size with the radiopaque prosthetic valve ring appearing to be in normal position. The initial impression was acute myocardial infarction with cardiogenic shock. Hemodynamic monitoring with a double-lumen thermistor pulmonary artery catheter and a transfemoral distal aortic catheter recorded initial pulmonary artery end-diastolic pressure of 18 mrn. Hg, systolic aortic pressure of 50 mm. Hg , and cardiac index of 1.3 L. per minute per square meter. Intensive medical therapy was unsuccessful, progressive deterioration continued, and the patient died 7 hours after admission. At postmortem examination the pyrolytic carbon disc of the Bjork-Shiley mitral valve prosthesis was found to have fractured into nearly equal halves (Fig. I), with embolization of both segments to the bifurcation of the aorta. Inspection of the fractured disc revealed no defect or deformity other than the sharp clean edges of the break. The surfaces were smooth and free of thrombi. The prosthetic ring in the mitral position was intact, with good endothelialization of the sewing fabric and no evidence of pannus formation, leak, or deformity. The
925
The Journal of Thoracic and Cardiovascular Surgery
926 Norenberg et al.
Fig. 1. The fractured Bjork-Shiley disc removed from the bifurcation of aorta at autopsy.
metal struts were in normal configuration and stable, without any evidence of damage or thrombus formation. The valve and disc fragments were returned to Shiley Laboratories for detailed measurements and testing.
Discussion Artificial heart valves of all types are subject to mechanical dysfunction of various causes, including thrombus and pannus formation, dehiscene with peri valvular leak , occluder variance, occluder entrapment against ventricular walls , and disruption of the valve structure."?" Acute heart failure appearing in any patient with an artificial valve should be considered to be a result of such mechanical impairment until proved otherwise. Echocardiography may be of great value in early diagnosis of prosthetic dysfunction, particularly if a base-line echocardiogram has been obtained in the early postoperative period to confirm proper function and to serve for future comparison .P11-13 The echocardiographic characteristics of normally functioning and malfunctioning Bjork-Shiley valves have been described. 11-13 In the case reported here, the diagnosis of disc embolization would have been apparent if an echocardiogram had been done, and emergency surgery might have been undertaken. In the catastrophic event of mitral valve disruption with loss of the occluder, the patient may live for more than several hours, allowing time for valve assessment and successful reoperation.":" Escape of an aortic valve occluder appears to be more rapidly fatal," although survival for almost 12 hours was observed in one instance.! Loss of the disc from a Bjork-Shiley mitral valve has been reported in the literature previously. 8 In that case
the disc was made of Delrin and was deformed, probably as a result of steam-heat sterilization. The discs now are made of pyrolytic carbon and are unaffected by steam autoclaving.' Intraoperative disc escape from an aortic Bjork-Shiley prosthesis, due to a bent strut, has been described also . 10 Several other instances of intraoperative and postoperative disc embolization have been reported to Shiley Laboratories. Causes have included strut distortion (probably at the time of implantation by use of a surgical clamp to align the disc, rather than the valve holder designed for that purpose), Delrin disc deformity from heat sterilization, and disc dislodgment by transvalvular catheter placement. * In the present case the valve had been gas sterilized before implantation. Postmortem investigations at this institution and at Shiley Laboratories have confirmed that the supporting ring and struts had been constructed properly and that no distortion had occurred. At the time of manufacture, the dimensions, silicone-content, and coating microhardness of the disc all were within specification limits. Other than the fracture line, there was no distortion or variance of the disc . Continuous polished wear marks, present on the bottom of the disc well, indicated that it had rotated freely during implantation. Scanning electron microscopy demonstrated four tiny chipped areas directly on the fracture edge and two minor cracks on the surface of the disc well , contiguous with the fracture edge. Pyrolytic carbon is very brittle, and it is not known if these were related causally to the fracture or, more likely, if they were a result of it. The disc fracture remains unexplained .
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REFERENCES Brawley, R. K., Donahoo, 1. S., and Gott, V. L.: Current Status of the Beall, Bjork-Shiley, Braunwald-Cutter, Lillehei-Kaster and Smeloff-Cutter Cardiac Valve Prostheses, Am. J. Cardio\. 35: 855, 1975. Burch, G. E., and Giles, T. D.: Clinical Evaluation of Aortic and Mitral Valve Prostheses, Am. Heart J . 92: 245, 1976. Keen, G.: Late Death Due to Escape of Ball From Mitral Valve Prosthesis, J. THORAc. CARDJOVASC. SURG. 67: 202, 1974. Bonnabeau, R. C. J., and Lillehei, C. W.: Mechanical Ball Failure in Starr-Edwards Prosthetic Valves, J. THORAC . CARDJOVASC. SURG. 56: 258, 1968. Hughes, D. A., Leatherman, L. L., Norman, J. C., et al.: Late Embolization of Prosthetic Mitral Valve Occluder With Survival Following Reoperation, Ann. Thorac. Surg. 19: 212, 1975. Roberts, A. K., Lambert, C. J., and Mitchel, B. F.:
*Personal communication, Shiley Laboratories, Santa Barbara, Calif.
Volume 74 Number 6
Bjork-Shiley mitral prosthesis
927
December, 19n
Embolization of Disc Occluder of a Wada-Cutter Mitral Prosthesis With Survival, Ann. Thorac. Surg. 21: 361,
1976. 7 Ansbro, J., Clark, R., and Gerbode, F.: Successful Surgical Correction of an Embolized Prosthetic Valve Poppet, J. THORAC. CARDIOVASC. SURG. 72: 130, 1976. 8 Measmer, B. J., Rothlin, M., and Senning, A..: Early Disc Dislodgment. An Unusual Complication After Insertion of a Bjork-Shiley Mitral Valve Prosthesis, J. THORAC. CARDIOVASC. SURG. 65: 386, 1973. 9 Maronas, J. M., Rufilanchas, J. J., Villagra, F., et aI.: Reoperation for Dysfunction of the Bjork-Shiley Mitral Disc Prosthesis: Report of Eight Cases, Am. Heart J. 93:
316, 1977.
10 Mulder, G. A.: Discussion of Bjork, V. 0., Henze, A., and Holmgren, A.: Five Years' Experience With the Bjork-Shiley Tilting-disc Valve in Isolated Aortic Valvular Disease, J. THORAC. CARDIOVASC. SURG. 68: 403,
1974. 11. Douglas, J. E., and Williams, G. D.: Echocardiographic Evaluation of the Bjork-Shiley Prosthetic Valve, Circulation 50: 52, 1974. 12 Chandraratna, P., Lopez, J. M., Hildner, F. J., et aI.: Diagnosis of Bjork-Shiley Aortic Valve Dysfunction by Echocardiography, Am. Heart J. 91: 318, 1976. 13 Srivastava, T. N., Hussain, M., Gray, L. A. J., et aI.: Echocardiographic Diagnosis of a Stuck Bjork-Shiley Aortic Valve Prosthesis, Chest 70: 94, 1976.