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Eur J Cardiothorac Surg 1998;14:449-452
© 1998 Elsevier Science NL

Acute ascending aortic dissection complicating open heart surgery: cerebral perfusion defines the outcome¹

Department of Cardiovascular Surgery, University Hospital Center, Lausanne, Switzerland

Received 30 November 1997; received in revised form 5 August 1998; accepted 11 August 1998.

Corresponding author. Service de Chirurgie Cardio-Vasculaire, Centre Hospitalier Universitaire Vaudois, rue du Bugnon 46, CH-1011 Lausanne, Switzerland. Tel.: +41 21 3142280; fax: +41 21 3142278; e-mail: patrick.ruchat@chuv.hospvd.ch

	Abstract

Top Abstract Introduction Method and patients Surgical results Discussion Conclusion References

 
Objective: This retrospective study was designed to assess the risks of acute ascending aorta dissection (AAD) as a rare but potentially fatal complication of open heart surgery. Method: Among 8624 cardiac surgical procedures under cardiopulmonary bypass (CPB) and cardioplegic myocardial protection from 1978 to 1997, 10 patients (0.12%) presented with a secondary or so called `iatrogenic' AAD. There were seven men and three women, mean age 64±9 years, ranging from 47 to 79. The original procedures involved five coronary artery bypass grafts (CABG), one repeat CABG, one aortic valve replacement (AVR), one AVR and CABG, one mitral valvuloplasty (MVP) and CABG and one ascending aorta replacement. We retrospectively analyzed their hospital records. Results: Group I consisted of seven patients with AAD intraoperatively and group II consisted of three patients who developed acute AAD 8–32 days after cardiac surgery. In group I, treatment consisted of the original procedure, plus grafting of the ascending aorta in six patients and closed plication and aortic wrapping in one. In group II, two patients received a dacron graft and one patient developed lethal tamponnade due to aortic rupture before surgery. Postoperatively, six patients responded well and three died (33%), two patients from group I on the 2nd postoperative day with severe post-anoxic encephalopathy, and one from group II with severe peroperative cardiogenic shock. Conclusion: Preventing AAD with the appropriate means remains standard practice in cardiac surgery. If AAD occurs, it requires prompt diagnosis and interposition graft to allow a better prognosis. Intraoperative AAD happens at the beginning of CPB jeopardizing perfusion of the supra-aortic arteries.

Key Words: Aortic dissection • Cardiopulmonary bypass • Surgical complication • Surgical treatment

	Introduction

Top Abstract Introduction Method and patients Surgical results Discussion Conclusion References

 
Canulating the ascending aorta for cardiopulmonary bypass was first proposed by Nunez and Bailey in 1959 [1]. Their technique became widely accepted only in the late 1960's. Retrograde aortic dissection, a frequent mortal complication of cardiac surgery, was well known with reports as high as 3% in femoral canulation or secondary to aortic crossclamping [2]. In 1974, Williams et al. [3] and Reinke et al. [4] reported the first successfully treated acute aortoiliac dissections resulting from aortic canulation. Since then, a few papers [5] [6] [7] [8] have reported this rare but potentially fatal complication, stating the importance of early diagnosis and prompt surgical repair. Current knowledge is based on conclusions of `ancient' publications from the pre-cardioplegic era and a few recent reports [9] [10] [11]. We reviewed our own cases since the introduction of cardioplegic myocardial protection and analysed the early and long-term results.

	Method and patients

Top Abstract Introduction Method and patients Surgical results Discussion Conclusion References

 
Among 8624 cardiac surgical procedures under cardiopulmonary bypass (CPB) and cardioplegic myocardial protection from January 1978 to March 1997, we found 10 patients (0.12%) having presented a secondary or so called `iatrogenic' acute ascending aorta dissection (AAD). The retrospective review of their hospital records is the basis of this report. Follow-up information on surviving patients was obtained from direct patients' interview. If death had occured, the cause was established by contacting referring physicians or the Swiss federal registry of deaths. The study cases are divided into two groups based on the time of presentation of AAD. Preoperative data are summarized in Table 1.

Group II consisted of three men (mean age 58±10 years, ranging from 47 to 68) where AAD appeared between the 8th and 32nd post-operative day (POD). Two patients were diagnosed with CAD and one with aortic regurgitation.

Eight patients had a history of hypertension, a well-known predisposing factor for dissection, who was directly responsible for dissection in two patients from group II.

The aortic diameter was clearly dilated in patient no. 7 at 58 mm with a thin wall. Patients nos. 6 and 9 were described as normal. The other patients had no conspicuous features.

Original operative procedures included coronary artery bypass grafting (CABG) in six, AVR and CABG in one, mitral valvuloplasty and CABG in one, aortic valve replacement (AVR) in one, and ascending aorta replacement in one.

Canulation and surgical technique
Canulation technique was fairly homogeneous throughout the years. It consisted in double concentric subadventitial purse-string 4–0 sutures; sufficient adventitia is excised in their centre; adequate intimo-medial incision is made with a No. 11 bistoury blade. Predilatation with a conical curved dilator is performed before gentle insertion of a curved-tip non-wire reinforced 8 mm Sarns' aortic canula. Arterial pressure is systematically lowered before cannulating the aorta. Aorta was always cross-clamped with the Fogarty hydrogrip aortic clamp. Myocardial protection was established by anterograde intermittent cristalloid Saint-Thomas' cardioplegia.

	Surgical results

Top Abstract Introduction Method and patients Surgical results Discussion Conclusion References

 
Intraoperative findings are summarized in Table 2.

No cardiogenic shock, no low output syndrome nor perioperative myocardial infarct occured in the first group. In two patients, despite an uneventful recovery from operation, we diagnosed a severe post-anoxic encephalopathy with classical EEG and CT scan pattern. Death occurred on POD 2 after medical support was stopped. In one patient impaired brain perfusion was suspected peroperatively due to a sudden drop in blood pressure at the left radial catheter while initiating bypass. In the other one there was absence of head cooling while installing general hypothermia. Autopsy revealed extended brain necrosis without carotid dissection.

Group II
Acute AAD happened 8th, 9th and 32nd day postoperatively, secondary to a hypertensive crisis in two patients. One patient died of cardiac tamponnade on ascending aorta rupture before surgical repair, an autopsy was performed. One patient did well after aortic graft with reimplantation of the saphenous vein. One died under CPB because of intractable cardiogenic shock.

Pathology
Histological examination of the aortic wall showed the presence of four cystic medial necrosis, three atherosclerosis and two described as normal.

Late results
Follow-up was complete in six hospital survivors. At a mean time of 54±33 (range 8–89) months, four patients were doing well and two are dead. The one patient with a closed plication presented an aortic rupture with cardiac tamponnade 8 months later. The second one suffered a recurrent myocardial infarction with ventricular fibrillation 79 months postoperatively.

	Discussion

Top Abstract Introduction Method and patients Surgical results Discussion Conclusion References

 
To avoid vascular complication associated with cardiopulmonary bypass we adopted, like each cardiac surgeon, preventive measures. Most injuries described in the literature were related to aortic canulation [3], aortic crossclamping [6], partial lateral occlusion [7], surgical intimal disruption like aortotomy and vein anastomosis [8]. Like in the study of Taylor et al. [12], all dissections in our group I were due to canulation. Dissections in group II involved surgical intimal disruption associated with hypertension.

Intra-operative recognition of aortic dissection requires a high index of suspicion and good clinical judgment. Diagnosis was made on appearance of a tense, circumferential dilatation with bluish discoloration of the exposed aorta, enlarging during CPB via the aortic canula.

Cross-sectional trans-esophageal echocardiography (TEE) introduced by Hanrath opened up a new tool to detect aortic dissection (see [13]). We routinely use it for every cardiac procedure since 1992. TEE is a valuable intraoperative tool like direct aortic peroperative echography to differentiate between dissection and subadventitial hematoma. The two most recent patients underwent these examinations, identifying the dissection and evaluating permeability and perfusion of the supra-aortic arteries.

As with acute dissections, generally, this complication carries a mortality of 90% when untreated. The most frequent cause of death is full thickness rupture with cardiac tamponade. This sudden death was encountered in patient no. 10 at the 32nd postoperative day before surgery could intervene.

Murphy et al. [14] attributed their 33% mortality rate to subsequent myocardial dysfunction due to prolongation of crossclamping time. Based on our experience in nine operated patients, only one died from myocardial dysfunction. We think that since introduction of routine myocardial protection, duration of crossclamping time might play a less important role in early mortality. Interposition graft has to be therefore performed.

Ohashi et al. recently reported cerebral malperfusion as a consequence of iatrogenic dissection [11]. Two patients in our series showed the same complication. Autopsy revealed no evidence of carotid dissection so the mechanism of malperfusion is likely to be blood flow in the false lumen with total occlusion of supra aortic trunks.

Morphological studies have shown that cystic medial necrosis, typical of connective tissue disorders, is only quantitatively different from the histopathologic features found in the normal aging aorta [15]. These features represent the morphologic expression of an interaction within the aortic wall of traumatizing and reparative processes due to hemodynamic impact. The high incidence of cystic media necrosis found in our histological studies of aortic wall is directly due to the high incidence of hypertension and the elevated mean age of our collective.

	Conclusion

Top Abstract Introduction Method and patients Surgical results Discussion Conclusion References

 
Preventing AAD with the appropriate means remains standard practice in Cardiac Surgery. If AAD occurs, it requires prompt diagnosis and interposition graft to allow a better prognosis. Intraoperative AAD reveals itself at the start of CPB jeopardizing perfusion of the supra-aortic arteries. We recommend to check routinely canulation site before starting CPB. If dissection is suspected, TEE will confirm if it is necessary to change the site of arterial canulation.

	Footnotes

 
Presented at the 11th Annual Meeting of the European Association for Cardio-thoracic Surgery, Copenhagen, Denmark, September 28 – October 1, 1997.

	References

Top Abstract Introduction Method and patients Surgical results Discussion Conclusion References

 

1. Nunez L.E., Bailey C.P. New method for systemic arterial perfusion in extracorporeal circulation. J Thorac Cardiovasc Surg 1959;37:707.
2. Black L.L., McComb R.J., Silver M.D. Vascular injury following heart valve replacement. Ann Thorac Surg 1973;16:19-29.[Medline]
3. Williams C.D., Suwansirikul S., Engelman R.M. Thoracic aortic dissection following cannulation for perfusion. Ann Thorac Surg 1974;18:300-304.[Medline]
4. Reinke R.T., Harris R.D., Klein A.J., Daily P.O. Aortoiliac dissection due to aortic cannulation. Ann Thorac Surg 1974;18:295-299.[Medline]
5. Kimbiris D., Dreifus L.S., Adam A., Blanco G., Linhart J.W. Dissection and rupture of the ascending aorta. Unusual complications of aortocoronary bypass surgery. Chest 1975;68:313-316.[Abstract/Free Full Text]
6. Litchford B., Okies J.E., Sugimura S., Starr A. Acute aortic dissection from cross-clamp injury. J Thorac Cardiovasc Surg 1976;72:709-713.[Abstract]
7. Boruchow I.B., Iyengar R., Jude J.R. Injury to ascending aorta by partial-occlusion clamp during aorta-coronary bypass. J Thorac Cardiovasc Surg 1977;73:303-305.[Abstract]
8. Nicholson W.J., Crawley I.S., Logue R.B., Dorney E.R., Cobbs B.W., Hatcher C.R., Jr. Aortic root dissection complicating coronary bypass surgery. Am J Cardiol 1978;41:103-107.[Medline]
9. Still R.J., Hilgenberg A.D., Akins C.W., Daggett W.M., Buckley M.J. Intraoperative aortic dissection. Ann Thorac Surg 1992;53:374-379.[Abstract]
10. Subramaniam P., Skillington P. Acute aortic dissection as a complication of coronary artery surgery. Aust New Zealand J Surg 1996;66:498-500.
11. Ohashi Y., Onishi Y., Akamatsu T., Maruyama K., Kuro M. Aortic dissection after weaning from extracorporeal circulation. Masui Jap J Anesth 1996;45:1281-1284.
12. Taylor P.C., Groves L.K., Loop F.D., Effler D. Cannulation of the ascending aorta for cardiopulmonary bypass. Experience with 9000 cases. J Thorac Cardiovasc Surg 1976;71:255-258.[Abstract]
13. Erbel R., Borner N., Steller D., et al. Detection of aortic dissection by transoesophageal echocardiography. Br Heart J 1987;58:45-51.[Abstract/Free Full Text]
14. Murphy D.A., Craver J.M., Jones E.L., Bone D.K., Guyton R.A., Hatcher C.R., Jr. Recognition and management of ascending aortic dissection complicating cardiac surgical operations. J Thorac Cardiovasc Surg 1983;85:247-256.[Abstract]
15. Schlatmann T.J., Becker A.E. Histologic changes in the normal aging aorta: implications for dissecting aortic aneurysm. Am J Cardiol 1977;39:13-20.[Medline]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Patrick Ruchat Michel Hurni Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ruchat, P. Articles by von Segesser, L. K. Search for Related Content PubMed PubMed Citation Articles by Ruchat, P. Articles by von Segesser, L. K.