Ann Thorac Surg 2002;73:953-955
© 2002 The Society of Thoracic Surgeons
Case report
Successful repair of intraoperative aortic dissection detected by transesophageal echocardiography
David Varghese, MB, ChB*a,
Bernhard J.C.J. Riedel, FCAa,
S. Nicholas Fletcher, FRCAa,
Mohammed I. Al-Momatten, FRCSa,
Asghar Khaghani, FRCSa
a Department of Cardiothoracic Surgery and Anesthetics, Harefield Hospital, Middlesex, United Kingdom
Accepted for publication April 21, 2001.
* Address reprint requests to Dr Varghese, 20 Lytham Close, Thamesmead, London, England SE 28 8QH, UK
e-mail: david{at}varghese.freeserve.co.uk
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Abstract
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Aortic dissection is a rare but devastating complication of cardiac surgery. Early intraoperative diagnosis and management are essential for a favorable outcome. We describe the case of a 69-year-old man with worsening dyspnea who was admitted for mitral valve replacement having previously had a mitral valve repair. Pre-cardiopulmonary bypass transesophageal echocardiography confirmed mitral regurgitation and showed mild atherosclerotic changes in the descending aorta. Following successful replacement of the mitral valve, an attempt to wean from cardiopulmonary bypass failed. This was characterized by acute onset hypovolemia. The transesophageal echocardiography showed the presence of features of acute aortic dissection involving only the descending aorta without identifying the entry point. The tear was successfully repaired by direct suture within the lumen.
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Introduction
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Aortic dissection is a rare complication of open cardiac surgery that needs early recognition and repair. We report an unusual case of intraoperative aortic dissection with an intimal tear in the descending aorta and its diagnosis by transesophageal echocardiography.
A 69-year-old man who underwent mitral valve repair for posterior mitral valve leaflet prolapse 2 years previously presented with a short history of worsening dyspnea. He was admitted for mitral valve replacement. He had no history of peripheral vascular disease, hypertension, or hypercholesterolemia. On examination, he was noted to have long-standing atrial fibrillation, ankle edema, and reduced breath sounds on the right base. The preoperative chest radiograph showed cardiomegaly and a loculated pleural effusion on the right side. A transthoracic echocardiograph demonstrated moderate mitral regurgitation and mild tricuspid regurgitation, with good left ventricular ejection. The aortic root and valve were normal. His warfarin therapy was stopped 6 days previously and anticoagulation was maintained with a heparin infusion. Other regular medication included digoxin, amiloride, and bumetanide.
Anesthesia consisted of a balanced low dose opioid-volatile (fentanyl-isoflurane-propofol) general anesthetic technique. Monitoring was facilitated by a left radial artery cannula, a right internal jugular central venous catheter, pulmonary artery catheter, and a transesophageal echocardiograph (TEE). The precardiopulmonary bypass TEE examination revealed mobile mitral valve cusps with a moderately severe central regurgitant jet secondary to ruptured chordae. The left atrium was dilated (8.5 cm) with systolic pulmonary artery pressures estimated at 35 mm Hg. Left ventricular function was normal. The ascending aorta was normal but there were grade I-II atheromatous changes in the descending aorta.
Surgery was commenced through a median sternotomy. Cardiopulmonary bypass (CPB) was instituted through the ascending aorta and bicaval cannulation. The aortic line pressure was normal during the whole procedure. Left atrial and mitral annular dilatation were noted on inspection. The anterior mitral leaflet was found to be partially prolapsed with ruptured chordae. The mitral valve was replaced with a CarboMedics 31 mm type M (Sulzer Carbomedics Limited, UK). After the procedure, while still on CPB, TEE examination showed anterior displacement of the left atrium by the descending aorta (Figs 1, 2, 3)
and increased shadowing around the descending aorta from the level of the left subclavian artery to the level of the diaphragm. No intimal tear could be detected on TEE. In addition to echocardiographic findings, there was acute volume loss requiring extra volume to be added to the CPB reservoir repeatedly. There was also increasing abdominal distension, with anterior displacement of the mediastinum that coincided with an attempt to wean the patient off CPB. There were immediate signs of hypovolemia. Inspection of the mitral valve using color flow doppler indicated good valve function. There was no visible sign of ascending aortic involvement. A presumptive diagnosis of dissection of either the distal aortic arch or descending aorta was made. CPB was reinstituted by placing the arterial cannula in the left femoral artery. After cooling to 20°C, total circulatory arrest was established. Intermittent retrograde perfusion to the cerebral circulation was maintained through the superior vena cava line. The left pleura was opened, but no blood was found in the pleural cavity. A large hematoma was however palpated around the whole length of the descending aorta compatible with TEE findings (Fig 4).
Examination of the aortic cannulation site and ascending aorta up to the proximal arch revealed no abnormality or external signs of dissection. The ascending aorta was opened at the site of cannulation. A 2.5-cm transverse tear was found in the distal arch just opposite the origin of the left subclavian artery. The entry site was repaired from within the lumen with Teflon (Impra Inc., Subsidiary of L.R. Bard, Tempe, AZ) pledgetted interrupted Prolene (Ethicon, Somerville, NJ) sutures. The patient was rewarmed and successfully weaned from CPB. The cross-clamp time was 59 minutes, and the circulatory arrest time was 22 minutes. Residual hemodynamic instability precluded sternal closure at this time. The chest was stented and a delayed sternal closure was performed 3 days later.
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Fig 2. Horizontal plane of descending aorta showing compression of left atrium and appendage by hematoma.
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Immediately postoperatively, the patient had a computed tomographic scan. This showed an aortic dissection extending to the abdominal aorta involving both renal and mesenteric vessels with a large retroperitoneal hematoma. The early postoperative period was characterized by over 2 liters of drainage from the chest tubes without a decrease in hematocrit. The drainage was thought to be from the posterior mediastinum.
A computed tomographic scan prior to discharge showed no aortic luminal compromise, no intimal flap, and resolving mediastinal and retroperitoneal hematoma. The patient was discharged from hospital 32 days after surgery. He had no shortness of breath or neurologic deficit at the 6-week follow-up.
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Comment
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Intraoperative aortic dissection is a rare but catastrophic complication of cardiac surgery with a well-described pathophysiology. In one study, the frequency of iatrogenic aortic dissection was 0.16% [1]. The site of dissection as seen in our patient (descending aorta) is very rare.
There are two types of clinical presentations regarding iatrogenic aortic dissection [2]. Type I is that seen in our patient where the aortic dissection presents intraoperatively [2]. Type II are those patients who present with aortic dissections from any time during the postoperative period up to 20 years after cardiac surgery [2, 3].
There was evidence of grade I to II atherosclerosis in the descending aorta. Atherosclerosis is a known predisposing factor for development of aortic dissection [1]. We postulate that a jet of blood from the aortic cannula may have caused an intimal tear and subsequent dissection in the already atherosclerotic aorta as suggested by the transesophageal echocardiogram. In this case, the TEE findings were very helpful in suspecting the presence of acute dissection while still on CPB. Mortality increases with a delay in diagnosis. Still and colleagues, in a retrospective study of 14,877 operative procedures, showed mortality to be 20% for dissections discovered intraoperatively and 50% for dissections discovered postoperatively [1]. This confirms the value of routine preoperative TEE in cardiac surgery. Pericardiopulmonary bypass TEE would also greatly aid in the placement of aortic cannula away from sites of aortic plaques and avoidance of aortic cross-clamping at these sites. Once diagnosed, there are two types of repair: a conservative surgery with primary suture [1, 4] as done in our patient, or a patch-tube graft interpositioning. The extent and the location of the intimal tear determines the type of repair. It is relatively easy to repair ascending aortic dissections, but it becomes technically more challenging when the dissection is in the arch or descending aorta. In our patient, the tear was distal and the only simple way was to repair the tear from within the lumen by direct suture. The size of the periaortic hematoma was very extensive in this case, extending from the posterior mediastinum to the retroperitoneal area due to lack of reentry point. This could result in compression of aortic branches such as the mesenteric vessels, which may have been the cause of the acute pancreatitis in this case.
In conclusion, we suggest that in circumstances of acute aortic dissection due to a limited intimal tear, simple primary repair is the procedure of choice particularly when the access to the area is restricted. Also, TEE is a useful tool in the preoperative diagnosis of aortic dissection and guidance of cannula placement [5].
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References
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Still R.J, Hilgenburg A.D, Atkins C.W, Daggart W.M, Buckley M.J Intraoperative aortic dissection. Ann Thorac Surg 1992;53:374-380.[Abstract]
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Ruchat P., Hurni M., Stumpe F., Fischer A.P, von Segesser L.K Acute ascending aortic dissection complication open heart surgery: cerebral perfusion defines the outcome. Eur J Cardiothorac Surg 1998;14:449-452.[Abstract/Free Full Text]
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Orszulak T.A, Pluth J.R, Schaff H.V, Piehler J.M, Smith H.C, McGoon D.C Results of surgical treatment of ascending aortic dissections occurring late after cardiac operation. J Thorac Cardiovasc Surg 1982;83:538-545.[Abstract]
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Leclercq F., Albat B., Messner-Pellenc P., et al. Successful conservative surgery of acute ascending aortic dissection occurring during coronary angiography. J Cardiovasc Surg 2000;41:61-63.[Medline]
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Anderson C., Joyce F.S., Tingleff J., Arendrup H. Aortic dissection after cardiopulmonary bypass detected by intraoperative transesophageal echocardiography. Acta Anaesthesiol Scand 1997;41:1227-1228.[Medline]
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Abstract
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