Diagnosis and Management of Aortic Poppet Embolism

Transcription

1 Diagnosis and Management of Aortic Poppet Embolism B. Eugene Berry, M.D., Patrick F. Sheedy, M.D., and Dwight C. McGoon, M.D. ABSTRACT Evidence indicates that a lower incidence of ball variance has resulted from the use of Silastic poppets manufactured since For patients in whom poppet embolization is the first indication of variance, the diagnosis must first be suspected and then confirmed by physical findings and plain roentgenography or, in the case of radiolucent poppets, possibly aortography. Immediate operation with poppet replacement and then embolectomy is indicated. Only 2 patients have so far undergone surgical correction of poppet embolism, and neither has survived. The details of 1 of these patients are presented to emphasize considerations relating to this problem. Although one must retain a guarded outlook, an aggressive approach to the management of these patients is advisable. P oppet embolism is a manifestation of ball variance, a complication of the Silastic balls used in cardiac valve prostheses. The embolus may be poppet fragments [5] or may involve the intact poppet [l, 6, 12, 15, 161. Embolization of the entire poppet is usually an acute and catastrophic event. We could find only one previous report of a patient who underwent operative correction of this complication [2]. A recent experience, which has given us a guarded outlook but has shown the necessity of an aggressive approach to the management of these patients, has prompted this review. A 50-year-old man who had undergone mitral and aortic valve replacement elsewhere in 1965 for rheumatic valvular disease was first seen at the Mayo Clinic in November, He had done well until approximately 9:30 A.M. on the day of admission, when, while hunting, he noticed shortness of breath followed by numbness and weakness of the legs. Because of bilaterally absent femoral and lower extremity pulses, the diagnosis of a saddle embolus was made. The patient was given morphine and referred to the Mayo Clinic. On arrival at 11:OO A.M., he was somewhat irrational and restless, although he responded to questions, and was obviously in acute distress. He could not move his legs and complained of low back and abdominal pain. From the Mavo Clinic and Mavo Foundation. Rochester. Minn. Accepted for publication Sept. 26, Address reprint requests to Dr. Berry,. c/o. Section of Publications, Mayo Clinic, 200 First St. S.W., Rochester, Miin THE ANNALS OF THORACIC SURGERY

2 CASE REPORT: Aortic Poppet Embolism. His blood pressure was approximately 70/0 mm. Hg. There was no significant dyspnea. Both lower extremities showed mottling, which gradually progressed upward to the area of the umbilicus. Rhonchi were heard in both lungs, but there was no evidence of pulmonary edema. Cardiac auscultation revealed an irregular rhythm and the sounds of a single prosthetic valve but no murmurs. No pulses were palpable from the common femoral artery distally on either side, although a weak femoral pulse could be felt intermittently on one side or the other. The chest roentgenogram showed enlargement of the heart, and the mitral and aortic prostheses were in their usual positions. The balls in the prostheses were not radiopaque. The electrocardiogram verified atrial fibrillation and indicated loss of anterior forces compatible with anteroseptal infarction. Abdominal examination revealed nothing abnormal. The initial clinical impression was of aortic obstruction secondary to aortic dissection or poppet embolism. To establish the diagnosis, aortography was performed. A Teflon catheter (No. 7F) was inserted into the left femoral artery by a modified Seldinger technique and passed through the left iliac vessels to the level of the aortic bifurcation, where obstruction to further proximal passage of the catheter was encountered. A small test injection then revealed complete obstruction of the distal aorta with poor runoff. An attempt was made to advance the catheter gently above the obstruction with the aid of a curved guide wire. With moderate pressure the guide and catheter passed through the obstruction up into the aortic root. At this point an aortogram with biplane filming was obtained (Fig. 1). The catheter was FIG. 1. Anteroposterior (A) and lateral (B) thoracic aortograms taken after injection of contrast medium into aortic root. Gross aortic valvular incompetence, poor left ventricular contractility, absence of radiolucent aortic poppet, and presence of mitral poppet (arrows) are evident.

3 BERRY, SHEEDY, AND MC GOON FIG. 2. Anteroposterior (A) and lateral (B) abdominal aortograms reueal complete obstruction of aortic bifurcation (arrows) by intact radiolucent embolized poppet. withdrawn into the abdominal aorta, and a second injection of contrast medium was followed by biplane filming (Fig. 2). This study clearly demonstrated the absence of the poppet from the aortic valve prosthesis, gross aortic insufficiency, and obstruction of the abdominal aortic bifurcation by the intact poppet. During the course of these studies, information about the patient s cardiac operation in 1965, and particularly the sizes of the prostheses inserted, was obtained by telephone from the appropriate hospital in another city. Immediately thereafter operation was begun. Cardiopulmonary bypass was instituted through a median sternotomy. Because the patient s condition deteriorated rapidly during induction of anesthesia, the aorta and right ventricle were quickly cannulated, use of these sites being necessitated by adhesions from the previous operation. After the old aortotomy had been opened, the empty but otherwise intact prosthetic cage was inspected. A new Starr-Edwards ball (No. 9) was easily inserted into the cage. The aortotomy was closed and bypass discontinued. Caudal extension of the sternotomy incision permitted entry into the abdomen, and the poppet was readily removed from the distal aorta (Fig. 3). Hypotension persisted after bypass was discontinued. The prolonged preoperative period of hypotension and ischemia of the lower part of the body contributed to severe metabolic derangement. Blood, isoproterenol, and sodium bicarbonate were administered. After operation the systolic blood pressure ranged from 80 to 100 mm. 506 THE ANNALS OF THORACIC SURGERY

4 CASE REPORT: Aortic Poppet Embolism FIG. 3. Gross appearance of poppet. Note disfortion of poppet and numerous cracks. Hg, and this required continuous support with vasopressors or inotropic drugs, or both. Despite these measures, renal failure ensued, and the patient died thirty-six hours after operation. Postmortem examination showed that both aortic and mitral prostheses were intact. There was no aortic perivalvular leak, and the mitral poppet showed no variance. Failure to recover an adequate cardiac output postoperatively was explained by the presence of a massive acute myocardial infarction associated with atheromatous stenosis (95y0 complete) of the right and left anterior descending coronary arteries. An old posterior infarction was also demonstrated. Comment Ball variance can be defined as valvular malfunction resulting from physical and chemical alterations in the Silastic poppets of cardiac valve prostheses [8]. Its incidence, as reported in the literature [2-4, 71, varies considerably. Ball variance has been rarely encountered in valves manufactured since the latter part of 1965, although the incidence of variance in aortic prostheses used earlier than this was as high as 75%. This problem has been studied exhaustively [8, 11, 13, 191. The lower incidence in currently available prostheses with Silastic poppets has been achieved by decreasing both the time and the temperature of the process of curing the Silastic rubber; this results in delayed accumulation of lipid products within the Silastic [8]. Poppet embolism is, fortunately, an uncommon complication, but it may occur more frequently in the future because large numbers of prostheses with Silastic poppets have been used. Although previous case reports have reflected the rapid demise of most patients following poppet embolism [l, 6, 12, 151, survival up to 12 hours has been reported. This occurred in a patient of Bonnabeau and Lillehei [2], apparently the only other patient besides ours who was operated upon. Their patient also died, 18 hours after operation. Even though neither of these patients survived, we believe that the technical aspects of ball replacement and poppet embolectomy are not

5 BERRY, SHEEDY, AND MC GOON excessively formidable and that an operative procedure, if done early enough, could result in complete recovery of these patients. Ideally, it would be better for elective ball replacement to be made possible by early diagnosis of variance using one of the noninvasive techniques [9-11, 141. If this option is excluded by the occurrence of ball embolism, early diagnosis and treatment are required. Indeed, a clinical diagnosis should now be possible in most cases; this would greatly facilitate early operative intervention. Sufficient information to make the diagnosis would consist of absence of the appropriate prosthetic sounds, absence of pulses typical of an aortic saddle embolus, and absence of the radiopaque poppet from its usual location as seen on a plain chest roentgenogram or visualization of the poppet on a plain roentgenogram of the abdomen. Our patient caused concern in that mitral valve prosthetic sounds were present, and the back pain with cyanosis extending to the umbilicus caused suspicion of aortic dissection. If one is uncertain as to the diagnosis, particularly if the poppet has not been impregnated with barium, aortography can provide definitive information. Treatment other than restoration of normal prosthetic function and poppet embolectomy is inadequate. The aortic valve is approached first with the patient on cardiopulmonary bypass. If a large periprosthetic leak or thrombosis of the cage is encountered, total replacement of the prosthesis will be required. If the prosthesis is found to be seated well, with normal struts and smooth surfaces, a new poppet may simply be inserted, as has been shown to be effective for nonembolic variant poppets [7, 17, 191. To ensure proper replacement of the poppet, the size and model of the previous prosthesis should be ascertained: if possible, this should be done before operation. The technique of poppet embolectomy depends on the location of the poppet. Bonnabeau and Lillehei [2] used femoral artery cannulation, driving the poppet retrograde to the arch where it was retrieved. In the case of our patient, because we knew that the poppet had impinged on the aortic bifurcation, we felt more secure in leaving it there and cannulating the ascending aorta. Embolectomy was performed easily following laparotomy and a distal aortotomy. For patients who have severely reduced cardiac output and who require emergency open-heart operation, however, the value of peripheral cannulation and institution of cardiopulmonary bypass prior to induction of anesthesia has been established. The rapid deterioration of our patient after induction of anesthesia, followed by a significant period of hypoperfusion before cannulation was accomplished, was undoubtedly detrimental. Perhaps femoral vein and axillary artery cannulation, under local anesthesia, would be a preferred method in the future. Prolonged occlusion of the aortic bifurcation results in ischemia of the lower extremities, with acidosis, vasodilation, release of vasoactive agents, and loss of intravascular volume r18]. Restoration of flow to the legs following poppet embolectomy from the distal aorta could thus cause severe systemic 508 THE ANNALS OF THORACIC SURGERY

6 CASE REPORT: Aortic Poppet Embolism acidosis, hypovolemia, and shock. Measures which might be used to counter these effects include intermittent release of the aortic clamp, administration of vasopressors, and expansion of the blood volume. References Ablaza, S. G. G., Blanco, G., Maranhao, V., and Goldberg, H. Fatal extrusion of the ball from a Starr-Edwards aortic valve prosthesis: Report of a case. J. Thorac. Cardiovasc. Surg. 50:401, Bonnabeau, R. C., Jr., and Lillehei, C. W. Mechanical ball failure in Starr-Edwards prosthetic valves: A report of three cases. J. Thorac. Cardionasc. Surg. 56:258, Delman, A. J. Aortic ball variance. Am. Heart J. 83:291, Duvoisin, G. E., and McGoon, D. C. Aortic valve replacement with ballvalve prosthesis. Arch. Surg. 99:684, Fiegenberg, D. S., DeColli, J. A., and Lisan, P. R. Fracture of a Starr- Edwards aortic ball valve with systemic embolism of ball fragments. Am. J. Cardiol. 23:458, Hairston, P., Summerall, C. P., and Muller, W. H., Jr. Embolization of Silastic ball from Starr-Edwards prosthesis: Case report and comments. Ann. Surg. 166:817, Herr, R. H., Kloster, F. E., Sezai, Y., and Starr, A. Diagnosis and management of ball variance following aortic valve replacement (Abstract). Circulation (Suppl. 11): 141, Hylen, J. C., Hodam, R. P., and Kloster, F. E. Changes in the durability of silicone rubber in ball-valve prostheses. Ann. Thorac. Surg. 13:324, Hylen, J. C., Judkins, M. P., Herr, R. H., and Starr, A. Radiographic diagnosis of aortic-ball variance. J.A.M.A. 207: 1120, Hylen, j. C., Kloster, F. E., Herr, R. H., Starr, A., and Griswold, H. E. Sound spectrographic diagnosis of aortic ball variance. Circulation 39:849, Hylen, J. C., Kloster, F. E., Starr, A., and Griswold, H. E. Aortic ball variance: Diagnosis and treatment. Ann. Intern. Med. 72:1, Mackenzie, J. W., and Almond, C. H. Expulsion of ball from aortic valve prosthesis. Ann. Thorac. Surg. 2:435, McHenry, M. M., Smeloff, E. A., Fong, W. Y., Miller, G. E., Jr., and Ryan, P. M. Critical obstruction of prosthetic heart valves due to lipid absorption by Silastic. J. Thorac. Cardiovasc. Surg. 59:413, Murphy, G. W., Kramer, D. H., and DeWeese, J. A. Detection of aortic ball variance by a simple radiographic technique: Report of a case, J. Thorac. Cardiovasc. Surg. 60:253, Newman, M. M., Hoffman, M. S., and Gesink, M. H. Mechanical failure of Starr-Edwards aortic prosthesis due to ball fracture. J. Thorac. Cardiovasc. Surg. 53:398, Roberts, W. C., and Morrow, A. G. Fatal degeneration of the silicone rubber ball of Starr-Edwards prosthetic aortic valve. Am. J. Cardiol. 22: Scalabrini, B. Y., Rader, B., Milano, A., and Clauss, R. H. Successful replacement of defective ball of a prosthetic aortic valve. J.A.M.A. 203:333, Spencer, F. C. Peripheral Arterial Disease. In S. I. Schwartz (Ed.), Principles of Surgery. New York: McGraw-Hill, P Starr, A., Pierie, W. R., Raible, D. A., Edwards, M. L., Siposs, G. G., and Hancock, W. D. Cardiac valve replacement: Experience with the durability of silicone rubber. Circulation 33 (Suppl. I): 115, 1966.