Ann Thorac Surg 2000;69:940-942
© 2000 The Society of Thoracic Surgeons
Case Reports
Systemic-to-pulmonary shunt in a patient with isolation of the subclavian artery
Makoto Takeda, MDa,
Akira Furuse, MDa,
Shinichi Takamoto, MDa
a Department of Cardiothoracic Surgery, University of Tokyo, Tokyo, Japan
Address reprint requests to Dr Takeda, Division of Cardiovascular Surgery, Yokohama Rosai Hospital, 3211, Kozukue, Kouhoku-ku, Yokohama, Kanagawa 222-0036, Japan
e-mail: takedam-ind{at}umin.ac.jp
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Abstract
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A surgical procedure is described that was carried out to treat an 18-month-old boy with tetralogy of Fallot, right aortic arch, and isolation of the left subclavian artery. The patient underwent a descending aorta-right pulmonary artery shunt using a polytetrafluoroethylene graft, as a systemic-pulmonary shunt. The effectiveness of this procedure in patients with some special conditions is discussed.
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Introduction
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We describe a surgical procedure performed on a patient with isolation of the left subclavian artery, right aortic arch, and tetralogy of Fallot (TOF). As an alternative to a Blalock-Taussig shunt, our patient underwent a descending aorta-right pulmonary artery shunt using an expanded polytetrafluoroethylene (EPTFE) graft.
The patient, a young boy, was diagnosed as having TOF. When he was 18-months-old, the frequency of anoxic spells increased and palliative systemic-to-pulmonary shunt was considered necessary before radical repair of the TOF. A preoperative cineaortogram showed right aortic arch, isolation of the left subclavian artery, and no obvious ductus arteriosus (Fig 1). No arterial distortion progressed in either of the pulmonary branches. He showed no other general anomaly.
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Fig 1. The left carotid artery branched first from the arch, and the origins of right carotid and subclavian arteries were separate (A). The proximal segment of the left subclavian artery connected to the arch was absent. The right vertebral artery branching from the subclavian artery was large (B). (LCCA = left common carotid artery; RCCA = right common carotid artery; RSCA = right subclavian artery; RVA = right vertebral artery.)
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A posterolateral skin incision was made and the right thoracic cage was entered via the fourth intercostal space. Dissecting the great vessels, the right subclavian artery, which was only 3 mm in external diameter, was found to be inadequate to use as the proximal anastomosis for the modified Blalock-Taussig shunt, as it would not obtain sufficient blood flow. Although it would have been possible to use the large subclavian artery proximal to the vertebral artery for the anastomosis, occluding the right vertebral artery during the anastomosis might cause cerebral ischemia, because the left vertebral artery was perfused only in reverse and the right one was very large. It was, therefore, decided not to perform a Blalock-Taussig shunt, and a descending aorta-right pulmonary artery shunt was performed instead. An EPTFE graft, 4 mm in diameter, was inserted between the right pulmonary artery and the descending aorta, using a continuous 6-0 polypropylene suture. To make ligation in the subsequent operation easier, the graft was curved towards the front in an inverted U shape, to bring it closer to the sternum (Fig 2). A black silk suture was placed around the graft and its end was fixed to the adventitia of the ascending aorta as a marker for the later dissection. Postoperative angiography showed good engraftment.
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Fig 2. Surgical procedure. (RPA = right pulmonary artery; G = EPTFE graft; S = a silk suture as a marker.)
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Anoxic spells disappeared after this procedure and the patient improved considerably. Ten months later, intracardiac repair for the TOF was performed. After median sternotomy, the end of the suture placed around the graft could be located next to the ascending aorta, and the anterior part of the graft was easily exposed. Ligation of the graft and intracardiac repair for TOF could be performed uneventfully. The patient has been followed up in our unit and continues to improve, with no cerebrovascular events.
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Comment
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The isolation of subclavian artery is a relatively rare anomaly [1–3]. The mechanism responsible for isolation of the subclavian artery has been explained previously on the basis of Edward’s embryological model of malformation of the aortic arch system [4], and Victorica and associates classified left subclavian isolation into three categories based on their hypothesis for the double arch system [5]. This anomaly is observed on the opposite side of the aortic arch, and isolation of the left subclavian artery with the right aortic arch is seen more frequently than the reverse [6]. The only clinical symptom that can be caused by this anomaly is subclavian steal syndrome, which is quite uncommon in childhood [7, 8]. It is important to recognize this anomaly before surgical intervention for associated cardiac abnormalities that reduce the pulmonary blood flow, because Blalock-Taussig shunt unilateral to the isolated subclavian artery is impossible, and the opposite side should be selected.
Our patient was classified as Victorica type II, associated with TOF and closed ductus. Blalock-Taussig shunt was given up because of his small right subclavian artery. A central shunt via this posterolateral approach is technically difficult. A Waterstone shunt or a Potts shunt are rarely performed nowadays due to the risk of excessive pulmonary blood flow and late pulmonary artery distortion. These types of shunt are also difficult to perform and difficult to close later. A descending aorta-pulmonary artery shunt using an EPTFE graft was selected in this case as an alternative option. As excessive pulmonary flow may occur after the descending aorta and pulmonary artery are connected, and as it is often difficult to close the shunt later via the median incision, the surgical procedure was modified as follows: (a) the interposing graft was made long enough to control the flow of blood through it; (b) the graft was curved towards the front to bring it closer to the anterior chest wall and make the later dissection easier; and (c) a silk suture was placed around the graft as a marker for the dissection. As a result of these modifications, the patient’s pulmonary blood flow could be increased to within an adequate range, and the dissection and closure of the graft in the later operation could be performed without difficulty. As some symptoms due to subclavian steal may appear as he grows older, this patient needs to be monitored very closely.
In conclusion, the surgical technique described here could provide a beneficial and safe option for patients with abnormalities similar to those of our case.
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References
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Stewart J.R., Kincaid O.W., Edwards J.E. Malformations with left aortic arch (group 2). "Isolation" of the right subclavian artery from aorta. In: Stewart J.R., ed. An atlas of vascular rings and related malformations of the aortic arch system, 1st ed. Springfield, IL: Charles C. Thomas, 1964:76-79.
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Nath P.H., Castaneda-Zuniga W., Zollikofer C., et al. Isolation of a subclavian artery. Am J Roentgenol 1981;137:683-688.[Abstract/Free Full Text]
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Mulay A.V., Watterson K.G. Isolated right subclavian artery, interrupted aortic arch, and ventricular septal defect. Ann Thorac Surg 1997;63:1163-1165.[Abstract/Free Full Text]
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Edwards J.E. Anomalies of the aortic arch system. Birth Defects 1977;13:47-63.
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Victorica B.E., Van Mierop L.H.S., Elliott L.P. Right aortic arch associated with contralateral congenital subclavian steal syndrome. Am J Roentgenol 1970;108:582-590.[Abstract]
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Rodriguez L., Ikuzawa T., Moes C.A.F., et al. Surgical implication of right aortic arch with isolation of left subclavian artery. Br Heart J 1975;37:931-936.[Abstract/Free Full Text]
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Lansing A.M., Murphy J. Origin of the left subclavian artery from the pulmonary artery with congenital subclavian steal. Surgical implications in cyanotic patients. Ann Thorac Surg 1968;5:146-152.
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Baudet E., Roques X.F., Guibaud J.P., Laborde N., Choussat A. Isolation of the right subclavian artery. Ann Thorac Surg 1992;53:501-503.[Abstract]
Accepted for publication July 14, 1999.
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Abstract
Introduction
