Ann Thorac Surg 2001;72:1401-1402
© 2001 The Society of Thoracic Surgeons
How to do it
Isolation technique for stroke prevention in patients with a mobile atheroma
Norihiko Shiiya, MDa,
Takashi Kunihara, MDa,
Yasuhiro Kamikubo, MDa,
Keishu Yasuda, MDa
a Department of Cardiovascular Surgery, Hokkaido University Hospital, Kita-ku, Sapporo, Japan
Accepted for publication May 28, 2001.
Address reprint requests to Dr Shiiya, Department of Cardiovascular Surgery, Hokkaido University Hospital, N14W5, Kita-ku, Sapporo 060-8648, Japan
e-mail: shiyanor{at}med.hokudai.ac.jp
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Abstract
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Mobile atheroma in the proximal aorta is a risk factor for brain complication after cardiovascular operation. We report a new technique of replacing the ascending and transverse aorta by establishing selective hypothermic antegrade cerebral perfusion. After cooling, cerebral vessels are clamped and systemic perfusion is started. This technique was applied in 5 patients. All patients woke up normally and recovered without neurologic complication.
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Introduction
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Mobile atheroma in the proximal aorta is a risk factor for stroke after cardiopulmonary bypass [1]. Although endarterectomy or prosthetic replacement of the affected segments of aorta under circulatory arrest have been advocated as treatments of choice [2], the results have not always been reproducible [3] because atheroemboli may be generated before circulatory arrest by cannulating the atheromatous aorta, by the sandblasting effect of the arterial jet, or by retrograde perfusion through the diseased aorta. We report a new technique of operation (the isolation technique) to replace the ascending and transverse aorta, which is designed to prevent aortogenic brain embolism during the initial perfusion period.
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Technique
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Through a standard median sternotomy incision, the innominate vein and three arch vessels were dissected and encircled. The ascending aorta, proximal aortic arch, and three arch vessels were evaluated by epiaortic echography. After systemic heparinization, a pediatric arch cannula (3.8 mm Sarns [Terumo, Ann Arbor, MI] or 3.4 mm JMS [JMS, Hiroshima, Japan]) was inserted into the three arch vessels through a stab wound distally to the innominate vein (Fig 1A), where little atheromatous disease was found in the arteries. In 1 patient the right axillary artery was cannulated instead of the brachiocephalic trunk because diffuse intimal thickening was found. Then we started brain perfusion cooling using one or two roller pumps. When nasopharyngeal temperature reached 30°C, the bulldog clamps were placed to the three arch vessels proximally to the cannulas, so that brain circulation was isolated from the systemic one. At this stage, we cannulated the disease-free proximal part of the ascending aorta and started systemic perfusion cooling.
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Fig 1. Schematic drawing of the technique. (A) The method of cannulation and isolation: (1) brain perfusion cooling, (2) isolation of the branches, and (3) systemic perfusion cooling. (B) The completed result.
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The remaining part of the operation was performed as previously described [4]. When the bladder temperature reached 22°C, open distal aortic anastomosis was performed. A 4-arm arch graft (not commercially available in the United States) was used in all patients. Then systemic perfusion was resumed through the fourth sidearm and the patients were rewarmed. We reconstructed the three arch vessels after completion of the proximal aortic anastomosis, using the three side arms (Fig 1B).
The new technique was used in 5 male patients whose ages ranged from 67 to 75 years. It was initially introduced as a routine procedure for atherosclerotic aneurysms in June 1998, and was used in the first 2 patients. Subsequently, it was used in selected high-risk groups of patients, which was determined by epiaortic echography. One patient concomitantly underwent coronary artery bypass grafting with two vein grafts. All patients survived the operations without neurologic complication. They woke up normally and became alert 206 to 533 minutes (mean ± standard deviation; 350 ± 141 minutes) after the operation. They were extubated 360 to 1,107 minutes (mean ± standard deviation; 755 ± 272 minutes) after the operation.
To select the high-risk group of patients, we graded the findings of epiaortic echography into five groups according to Katz and colleagues [1], and patients with protruding or mobile atheromas (grade 4 and 5) were treated with the isolation technique. Until January 2001, 4 of 23 patients (17%) with atherosclerotic aortic arch aneurysms were found to have mobile atheromas (3 patients) or protruding atheromas (1 patient). In 1 of these patients, the isolation technique was not used because the surgical team was unavailable. This patient suffered from stroke.
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Comment
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During operations for atherosclerotic aortic arch aneurysms we have been using selective antegrade cerebral perfusion as a brain protection method. To prevent atheroembolism we make it a rule to isolate brain circulation from the systemic one before mobilizing the aorta by establishing selective cerebral perfusion during the perfusion cooling period. Our results have been satisfactory with the stroke rate of 4% [4]. After experience with a patient who had multiple embolic stroke that seemed to result from atheroembolism during the perfusion cooling period, however, we started modifying our technique in selected high-risk groups of patients to isolate brain circulation before systemic perfusion was initiated (ie, the isolation technique). This preliminary result shows the feasibility of the technique and supports our patient selection strategy.
Several other techniques including the use of alternate cannulation sites have been proposed to reduce the risk of atheroembolism. Among these, axillary or innominate artery perfusion seems promising, but turbulent flow in the proximal aortic arch may still dislodge the atheroma. Therefore, we believe that our technique is the most reliable to prevent embolic strokes.
There are several issues that need to be discussed. First, safety of selective cerebral perfusion under normothermia remains a concern. Under hypothermia, we have been using cerebral perfusion rates of 600 to 750 mL per minute according to the body size and perfusion pressure [4]. Under normothermia, however, the same flow management resulted in a drop of jugular venous oxygen saturation that suggested brain hypoperfusion. Therefore, we started brain perfusion cooling without clamping the three arch vessels so that blood flow from the native heart could accommodate cerebral blood flow to its demand. Brain circulation was isolated after the brain was cooled and jugular venous oxygen saturation became elevated.
The second issue is whether all three branches should be isolated and perfused. In the human being, the left vertebral artery is more important for blood supply to the occipital lobe, small brain, and the brain stem. Because embolic strokes after cardiopulmonary bypass have been reported to be distributed predominantly to the posterior part of the brain [5], we believe that the left subclavian artery should be isolated. Although Kazui and associates [6] have been using two-vessel perfusion with excellent results, its simple clamping may not always be safe in the isolation technique because the brain temperature is higher at the time of clamping. We thus believe that the left subclavian artery should be perfused.
The third issue is the possibility of atheroembolism to the lower torso. Although we have not experienced problems in this regard so far, further studies with larger groups of patients will be required.
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References
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Katz E.S., Tunick P.A., Rusinek H., Ribakove G., Spencer F.C., Kronzon I. Protruding aortic atheromas predict stroke in elderly patients undergoing cardiopulmonary bypass: experience with intraoperative transesophageal echocardiography. J Am Coll Cardiol 1992;20:70-77.[Medline]
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Rokkas C.K., Kouchoukos N.T. Surgical management of the severely atherosclerotic ascending aorta during cardiac operations. Semin Thorac Cardiovasc Surg 1998;10:240-246.[Medline]
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Stern A., Tunick P.A., Culliford A.T., et al. Protruding aortic arch atheromas: risk of stroke during heart surgery with and without aortic arch endarterectomy. Am Heart J 1999;138:746-752.[Medline]
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Shiiya N., Kunihara T., Imamura M., Murashita T., Matsui Y., Yasuda K. Surgical management of atherosclerotic aortic arch aneurysms using selective cerebral perfusion: 7-year experience in 52 patients. Eur J Cardiothorac Surg 2000;17:266-271.[Abstract/Free Full Text]
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Barbut D., Grassineau D., Lis E., Heier L., Hartman G.S., Isom O.W. Posterior distribution of infarcts in strokes related to cardiac operations. Ann Thorac Surg 1998;65:1656-1659.[Abstract/Free Full Text]
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Kazui T., Washiyama N., Muhammad B.A., et al. Total arch replacement using aortic arch branched grafts with the aid of antegrade selective cerebral perfusion. Ann Thorac Surg 2000;70:3-8.[Abstract/Free Full Text]
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Abstract
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