Asian Cardiovasc Thorac Ann 1998;6:66-67
© 1998 Asia Publishing EXchange Pte Ltd
Intraoperative Dissection of Aorta and Successful Repair
Nainar Madhu Sankar, PhD,
Kevin Lai, MBBS,
Kenneth Harrison, FANCZA1,
Peter Klineberg, FANCZA1,
William Meldrum Hanna, FRACS
Cardiothoracic Surgical Unit
1 Department of Anaesthesia Westmead Hospital Westmead, Australia
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For reprint information contact: Nainar Madhu Sankar, PhD Madras Medical Mission 4A, Dr. J. Jeyalalitha Nagar Mogappair Madras 600050, India Tel:91 44 625 9801 Fax:91 44 625 9920
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ABSTRACT
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A 67-year-old female undergoing coronary artery bypass grafting developed dissection of the ascending aorta during decannulation. It was diagnosed by intraoperative transesophageal echocardiography and she underwent a successful repair.
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INTRODUCTION
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Intraoperative ascending aortic dissection during open-heart surgical procedures is an unpredictable complication. Out of 14,877 patients operated over a period of 10 years, Still and colleagues1 reported 20 instances of aortic dissection. Unarguably, it is better to prevent the occurrence than to treat it. However, once the need for repair is realized, it is necessary to act quickly to limit the extent of dissection and the time on cardiopulmonary bypass. We describe a case of ascending aortic dissection during decannulation, diagnosed by intraoperative transesophageal echocardiography and repaired successfully.
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CASE REPORT
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A 67-year-old female with ischemic heart disease was admitted for coronary artery bypass graft surgery. She was a known hypertensive for 10 years and her coronary angiogram revealed occlusion of the left anterior descending coronary artery that was 80% diseased, with 75% disease in the left circumflex, and minor disease in the right coronary artery. She had no previous myocardial infarction and her left ventricular function was normal.
The left internal mammary artery and the long saphenous vein from the left thigh were harvested. Routine cardiopulmonary bypass was instituted with ascending aortic and right atrial cannulation. A saphenous vein graft was anastomosed to the obtuse marginal branch of the left circumflex artery. The left anterior descending coronary artery and the diagonal branch were not graftable, hence the left internal mammary artery was left alone. The patient was rewarmed and weaned off cardiopulmonary bypass. The aortic cross-clamp time was 16 minutes and the cardiopulmonary bypass time was 63 minutes. The intraoperative transesophageal echocardiogram showed good contraction of the left ventricle.
After aortic decannulation there was brisk bleeding from the aortic cannulation site, which could not be controlled and her blood pressure dropped to a mean of 40 mm Hg. Transesophageal echocardiography showed dissection of the ascending aorta extending into the arch and the descending aorta (Figure 1
). Femoral cannulation was performed and cardiopulmonary bypass was reinstituted. Antegrade cardioplegia was infused after aortic cross-clamping. The aorta was opened and two layers of aorta were identified with a tear starting from the cannulation site and ending at the sinotubular junction. The distal limit was unknown. The aorta was grafted with a 22-mm Teflon graft proximally, preserving the aortic valve. The patient was cooled to 18°C and the aortic clamp was removed. The dissected layer was glued to the distal site and open distal anastomosis was performed. After de-airing, the left internal mammary artery was anastamosed end-to-end to the venous graft. The patient was weaned off bypass with minimal inotropic support. The aortic cross-clamp time was 25 minutes and the cardiopulmonary bypass time was 116 minutes. There was generalized oozing so her chest wound was left open and she was returned to the intensive care unit. Delayed closure of the chest wound was carried out next day. The postoperative course was otherwise smooth and she was discharged on the 11th postoperative day.
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DISCUSSION
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Acute dissection of the ascending aorta occurring during cardiac procedures is a known but rare complication.2 In a series of 7000 cases operated over a period of 10 years, the incidence of intraoperative dissection was reported to be 0.3%.3 The predisposing factors include hypertension, advanced atherosclerotic lesions, cystic medial necrosis, and a dilated and thinned aorta. The sites of initial tearing include the aortic cannulation site, the cardioplegic cannula insertion site, the cross-clamping and partial clamping areas. The number of times a clamp is applied, the ratchet setting, the failure to maintain a normotensive state before clamping, and not reducing the flow during declamping are among the contributory factors.4,5 Once initiated, the dissection extends rapidly along the length of aorta and prompt recognition and repair may often save the patient from this otherwise fatal complication. Widespread use of transesophageal echocardiography, particularly in patients with high risk such as old age or hypertension, facilitates prompt recognition as in our case.
Replacement of the ascending aorta is preferred to local repair of the tear. The use of a glue is definitely helpful, reducing the risk of tearing the fragile tissues as well as hemorrhagic complications. The high early mortality of patients with acute aortic dissection, up to 83% during the acute phase and 1% to 3% per hour in the first 48 hours, mandates rapid diagnosis to allow adequate management.6 Transesophageal echocardiography is highly accurate in the diagnosis of aortic dissection. Sensitivity and specificity of nearly 100% for identification of aortic dissection and correct classification of the type of dissection in 96% of cases has been reported by Simon and colleagues.7 In a recent report, Cohn and colleagues8 concluded that with improvement of myocardial protection techniques, use of antifibrinolytic agents and collagen impregnated grafts, intraoperative transesophageal echocardiography and open distal anastomosis, the current risk for surgical repair is low regardless of the cause of the aneurysm.
The case described here illustrates the usefulness and efficacy of intraoperative transesophageal echocardiography as well as the possibility of saving the patient with prompt repair.
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REFERENCES
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Still RJ, Hilgenberg AD, Akins CW, et al. Intraoperative aortic dissection. Ann Thorac Surg
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Boruchow IB, Iyengar R, Jude JR. Injury to ascending aorta by partial occlusion clamp during aorta coronary bypass. J Thorac Cardiovasc Surg
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Hirst AE, Johns VJ, Kime SW. Dissecting aneurysm of the aorta; a review of 505 cases. Medicine (Baltimore)
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Simon P, Owen AN, Havel M, et al. Transesophageal echocardiography in the emergency surgical management of patients with aortic dissection. J Thorac Cardiovasc Surg
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Cohn LH, Rizzo RJ, Adams DH, et al. Reduced mortality and morbidity for ascending aortic aneurysm resection regardless of cause. Ann Thorac Surg
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ABSTRACT
INTRODUCTION
