Asian Cardiovasc Thorac Ann 2000;8:361-363
© 2000 Asia Publishing EXchange Pte Ltd
Iatrogenic Aortic Dissection Complicating Cardiac Surgery
Sin Yoong Kong, FRCS,
Sriram Shankar, FRCS
Department of Cardiothoracic Surgery
National Heart Centre
Singapore, Republic of Singapore
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For reprint information contact: Sriram Shankar, FRCS Tel: 65 436 7581 Fax: 65 224 3632 Department of Cardiothoracic Surgery, National Heart Centre, 17 Third Hospital Avenue, Mistri Wing, Singapore 168572, Republic of Singapore.
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Abstract
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Two consecutive cases of iatrogenic aortic dissection complicating coronary artery bypass surgery were successfully repaired by interposition graft replacement of the ascending aorta. Both patients had an uncomplicated postoperative recovery. Follow-up imaging showed no residual abnormality. Prompt recognition and repair are essential elements in the management of this potentially lethal complication.
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Introduction
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Iatrogenic aortic dissection is a rare complication of cardiac surgical procedures with potentially serious consequences. Murphy and colleagues1 in 1983 reported an incidence of 0.35% among 6,943 cardiac surgical procedures performed at Emory University Hospitals over a 10-year period. A decade later, Still and colleagues2 reviewed 14,877 sur-gical procedures utilizing cardiopulmonary bypass at Massachusetts General Hospital and Mt. Auburn Hospital over a similar length of time and found an incidence of 0.16%. Mortality rates ranged from 20% to 33% in patients diagnosed intraoperatively and 50% to 78% in those recognized postoperatively.1,2 Various techniques of repair have been advocated, including direct suture, interposition graft, or a patch in patients with intraoperative recogni-tion.1–3 Pappas and colleagues4 described 2 patients diagnosed postoperatively who were successfully managed with extraanatomic bypass of the lower extremities. These patients presented with lower limb ischemia with no other organ involvement and represent a fortuitous but un-common subgroup. We encountered 2 cases of cannulation-site dissection in the practice of a single surgeon, giving an incidence of 0.2%. Both patients were diagnosed intraoperatively and underwent immediate repair.
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Case Reports
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Patient 1
A 60-year-old man with a background of hypertension, hyperlipidemia, and smoking, presented with recurrent angina after a successful angioplasty to the left anterior descending coronary artery 3 years previously. Coronary angiography showed triple-vessel disease with a left ventricular ejection fraction of 30%. During surgery, the ascending aorta appeared normal and cardiopulmonary bypass was established with a 24F aortic cannula without difficulty. However, an extensive adventitial hematoma was noted around the aortic cannulation site shortly after commencement of cardiopulmonary bypass. The aorta was crossclamped and antegrade, followed by retrograde, blood cardioplegia was delivered. On completion of the distal coronary anastomoses, the aortic crossclamp was removed and the ascending aorta was found to have become dissected.
Patient 2
A 65-year-old man with no significant past medical history except for smoking, presented with stable angina. Coronary angiography showed triple-vessel disease and a left ventricular ejection fraction of 45%. He underwent elective coronary artery bypass grafting utilizing the left internal mammary artery and 3 saphenous vein grafts with intermittent antegrade and retrograde blood cardio-plegia for myocardial protection. A 24F aortic cannula was used during the procedure with no difficulty in cannulation. After completion of the distal and proximal anastomoses, the right coronary vein graft was found to be under tension and the proximal end was repositioned. Upon termination of cardiopulmonary bypass, a large adventitial hematoma and dissection of the cannulation site were discovered.
The left common femoral artery and the superior vena cava were cannulated and the cardiopulmonary bypass circuit was prepared for retrograde cerebral perfusion. The patient was cooled to 18°C, the crossclamp was reapplied and cardioplegia was delivered through the coronary ostium directly as well as through the vein grafts. A segment of the ascending aorta including the cannulation site was resected and replaced with an interposition graft with the distal anastomosis performed under hypothermic circulatory arrest and retrograde cerebral perfusion (at a perfusion pressure of 30 mm Hg). The proximal saphenous vein grafts were connected to the Dacron graft using brief periods of circulatory arrest in the first patient; in the second patient, the grafts were connected using side clamps while rewarming was taking place. Total aortic crossclamp and circulatory arrest times were 44 minutes and 42 minutes, respectively, for patient 1, and 104 and 22 minutes, respectively, for patient 2. Both patients were extubated the next day and recovered with no further complication. Histological examination of the aortic wall showed no abnormality except for intimal thickening. Follow-up computed tomography scans and echocardiography showed a normal thoracic aorta and preserved left ventricular function.
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Discussion
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Spontaneous acute dissection is a fearsome condition which, untreated, is associated with a 38% mortality within one day and 70% within one week.5 With improved management, the operative mortality has fallen from as high as 25% to 5%.6 However, iatrogenic dissection still presents a tremendous surgical challenge with a reported operative mortality of 78% if the diagnosis is delayed.1 Strategies used to avoid such a disaster include control of systolic blood pressure to below 100 mm Hg before cannulation, cannulating away from aortic plaques, use of deep partial or full-thickness pursestring sutures, careful attention when applying or removing clamps, and reducing pump flow during such applications.
Intraoperative recognition requires a high index of suspicion. In the cases presented, the aorta appeared normal and cannulation was uneventful. The first patient likely suffered dissection immediately after cardio-pulmonary bypass was commenced, despite taking the precautions outlined above, and the second was only discovered at the end of what appeared to be a routine procedure. No difficulties were encountered in clamp placement and in both cases, the cannula appeared to be in the true lumen. Recognition is often based on the distinction between an all too common subadventitial hematoma that tends to be localized, slowly enlarging, and easily decompressed, compared to a dissection which rapidly involves the entire aorta and is tense, dilated, and bleeds copiously on decompression. Intraoperative trans-esophageal echocardiography may be employed where there is doubt.7
Upon recognition, treatment is prompt control of blood pressure and immediate surgical repair that can be either by direct suture or with a Dacron patch if the dissection is small and localized, or by replacement of the ascending aorta under hypothermic circulatory arrest. Use of retrograde cerebral perfusion as an adjunct has been reported to reduce the incidence of cerebral complications associated with circulatory arrest.8 Direct repair can be attempted if the lesion is amenable as it incurs a short bypass time and avoids aortic crossclamping. However, there is the possibility of failure if the extent of dissection is underestimated and the intimal tear not fully in-corporated in the repair.
Open repair with an interposition graft allows direct visualization and definitive repair and it should be employed if there is an element of doubt in the efficacy of lesser procedures. Although this involves a longer operating time and a potentially higher morbidity, expeditious surgery combined with meticulous attention to myocardial and cerebral protection are key elements in ensuring a favorable patient outcome in what would otherwise be a salvage procedure. Our preference is towards open repair as the definitive approach; we feel that most iatrogenic dissections are usually too extensive for a lesser procedure which may be associated with an increased risk of persistent or recurrent dissection and consequently a poor patient outcome.
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References
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Murphy DA, Craver JM, Jones EL, Bone DK, Guyton RA, Hatcher CR Jr. Recognition and management of ascending aortic dissection complicating cardiac surgical operations. J Thorac Cardiovasc Surg 1983;85:247–56.[Abstract]
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Still RJ, Hilgenberg AD, Akins CW, Daggett WM, Buckley MJ. Intraoperative aortic dissection. Ann Thorac Surg 1992;53:374–80.[Abstract]
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Sabri MN, Henry D, Wechsler AS, DiSciasco G, Vetrovec GW. Late complications involving the ascending aorta after cardiac surgery: recognition and management. Am Heart J 1991;121:1779–83.[Medline]
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Pappas D, Hines GL, Gennaro M, Hartman A. Delayed iatrogenic aortic dissection from coronary bypass managed with extraanatomic bypass. J Thorac Cardiovasc Surg 1998;115:947–9.[Free Full Text]
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Anagnostopoulos CE, Prabhakar MJS, Kittle CF. Aortic dissections and dissecting aneurysms. Am J Cardiol 1972;30:263–73.[Medline]
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Svensson LG, Crawford ES, Hess KR, Coselli JS, Safi HJ. Dissection of the aorta and dissecting aortic aneurysms: improving early and long-term surgical results. Circulation 1990;82(Suppl IV):24–38.
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Andersen C, Joyce FS, Tingleff J, Arendrup H. Aortic dissection after cardiopulmonary bypass detected by intraoperative transesophageal echocardiography. Acta Anaes Scand 1997;41:1227–8.
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Lytle BW, McCarthy PM, Meaney KM, Stewart RW, Cosgrove DM III. Systemic hypothermia and circulatory arrest combined with arterial perfusion of the superior vena cava. Effective intraoperative cerebral protection. J Thorac Cardiovasc Surg 1995;109:738–43.[Abstract/Free Full Text]
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Abstract
Introduction
