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Ann Thorac Surg 1997;63:445-448
© 1997 The Society of Thoracic Surgeons

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Original Article: Cardiovascular

Intraoperative Ultrasonographic Troubleshooting After the Arterial Switch Operation

Heart Unit, Birmingham Children's Hospital, Birmingham, United Kingdom

Accepted for publication August 30, 1996.

	Abstract

Top Footnotes Abstract Introduction Material and Methods Case Reports Comment Acknowledgments References

 
Background. Less than perfect coronary artery translocation accounts for the majority of perioperative deaths after the arterial switch procedure for transposition of the great arteries. Some types of coronary arterial anatomy are associated with a higher risk of death.

Methods. Prospective epicardial ultrasound examination of all neonates with failing left ventricle or difficulty in weaning off cardiopulmonary bypass was performed after completion of the arterial switch operation during a 2-year period from March 1994 to February 1996. The aim was to identify any mechanical, and potentially remediable, factors accounting for ventricular failure.

Results. Four neonates fulfilling the above criteria were identified during a 2-year period when epicardial echocardiography was routinely applied. In 2 patients coronary arterial problems in the form of kinking of the proximal left coronary artery (1 patient) and extrinsic compression of the artery by the neo-pulmonary trunk (1 patient) were identified and successfully corrected. In 2 other patients, supravalvar aortic stenosis was recognized, leading to prompt revision.

Conclusions. Epicardial echocardiography has an important "troubleshooting" role in the subgroup of patients with a suboptimal hemodynamic result after the arterial switch operation. Patients with unusual coronary anatomy should routinely be candidates for such studies.

	Introduction

Top Footnotes Abstract Introduction Material and Methods Case Reports Comment Acknowledgments References

 
The success of the arterial switch operation largely depends on the provision of unobstructed coronary flow and an unrestricted pathway into the great arteries. The factors affecting the relocation of the coronary arteries to its new position in the neo-aorta include the location of the coronary ostia and the course of the arteries. Particular care must be exercised in relocating coronary arteries with an intramural course [1–3] and especially those that fall into the type 2 pattern described by Serraf and associates [4], where one or both coronary arteries course between the great vessels. Coronary artery obstruction in these patients is sometimes dynamic in nature, and external compression of the relocated coronary artery by the anteriorly translocated pulmonary artery must be borne in mind [5]. There is also a small risk of obstruction in the great arteries along suture lines or the cannulation site. Intraoperative assessment of the coronary, aortic or pulmonary pathways using epicardial ultrasonography will help elucidate the cause of poor cardiac action after the repair and assist in their prompt and adequate correction. The following report includes 4 patients who benefited from the use of epicardial ultrasonography during the conduct of the arterial switch operation. Over the last 7 years, 272 arterial switch operations for all forms of D-transposition of the great arteries have been performed at our institution, with an operative mortality (up to 30 days after repair) of 5%. The operative deaths have predominantly been attributed to coronary artery injury (n = 3) or obstruction (n = 2), and have not been related to any specific type of coronary artery anatomy. On the basis of this evidence we have over the past 2 years prospectively undertaken intraoperative epicardial echocardiography in a subset of patients undergoing the arterial switch procedure in whom there was difficulty in weaning the patient off cardiopulmonary bypass or where the integrity of the repair was in doubt.

	Material and Methods

Top Footnotes Abstract Introduction Material and Methods Case Reports Comment Acknowledgments References

 
Intraoperative epicardial echocardiography was undertaken in a routine manner after repair [6, 7]. A standard 7.5-MHz or 5-MHz phased array transducer connected to a Hewlett-Packard Sonos 500 ultrasound system was used for epicardial studies. The epicardial approach was favored over transesophageal imaging, as it allows an unrestricted number of imaging planes, which is particularly useful in the intraoperative setting and after complex surgical procedures. The transducer was packed in a sterile plastic sleeve and delivered to the operating field. Warm normal saline solution was used to irrigate the pericardium and allow good contact between the transducer and the heart. All ultrasound studies were then performed by an experienced cardiologist and assessed in real time by the cardiologist and surgeon conducting the operation. All studies were also continuously recorded on videotape for off-line analysis. Ultrasound studies were repeated after surgical revision of any problems identified by the original study, to confirm a satisfactory repair. The average time required for each study was 5 minutes, and there were no arrhythmic or infective complications associated with any study.

	Case Reports

Top Footnotes Abstract Introduction Material and Methods Case Reports Comment Acknowledgments References

 
Patient 1
A 6-day-old neonate weighing 3.5 kg presented on the first day of life with transposition of the great arteries with an intact ventricular septum. He underwent a balloon atrial septostomy and came forward for an elective repair. At operation the aorta was directly anterior to the pulmonary artery. The left and the right coronary arteries arose very close to the commissure posteriorly from sinus 2 (the left facing sinus). The left coronary artery passed intramurally to the left side for a considerable distance before emerging to give rise to the anterior descending and circumflex coronary arteries. The right coronary artery passed from its rather posterior origin around the aorta into the normal coronary anatomy of the right coronary artery. There was a good-sized arterial duct.

On cardiopulmonary bypass, cooling to 18°C, the aorta was cross-clamped and the heart was arrested with a single dose of cold crystalloid cardioplegia. The duct was doubly ligated and divided. The aorta was transected and the aortic valve was dissected off the posterior aspect of the aorta to free a large patch, which included both orifices [8]. The pulmonary artery was then divided and the upper edge of the coronary artery patch was anastomosed to the anterior upper edge of the pulmonary artery. Bovine pericardium was sutured over the coronary arteries to create an anterior pouch. The Lecompte maneuver [9] was undertaken and the rest of the procedure completed in a routine fashion with reconstruction of the neo-pulmonary artery using a piece of autologus pericardium.

Once bypass was discontinued, the heart initially beat vigorously but the patient soon had low systemic arterial pressure and fluctuating left atrial pressures. An epicardial echocardiogram was then undertaken and demonstrated compression of the anterior part of the aorta bearing the coronary arteries, by the pulmonary artery. This was associated with regional left ventricular dysfunction occurring predominantly in the distribution of the left anterior descending coronary artery system. The main pulmonary artery was therefore suspended to the posterior aspect of the sternal periosteum. In addition, small tucks were taken in the pericardium on the lateral aspects of the neo-pulmonary artery to elevate the pericardium off the coronary arteries. At the completion of the operation, a repeat epicardial echocardiogram showed good left ventricular function without regional wall motion abnormalities. The patient made an uncomplicated recovery and is asymptomatic and well 22 months into follow-up, with no evidence of myocardial ischemia or dysfunction on electrograms and echocardiography.

Patient 2
A 5-week-old, 4-kg infant came forward for elective repair of transposition of the great arteries with a perimembranous ventricular septal defect. The operation was undertaken in a routine fashion with Dacron patch closure of the ventricular septal defect. Cardiopulmonary bypass was terminated with the patient in sinus rhythm. It soon became apparent that the cardiac action appeared unsatisfactory. An epicardial echocardiogram showed supravalvar aortic stenosis related to the aortic suture line (Fig 1). The calculated Doppler peak instantaneous gradient across the suture line was 46 mm Hg. Bypass was reinstituted, and on take down of the aortic suture line, it became clear that the anterior aortic wall had been gathered up excessively along the suture line. Reconstruction of the ascending aorta was completed with a piece of bovine pericardium along the anterior suture line, and the operation concluded uneventfully thereafter. The infant was discharged on the 11th postoperative day, and an echocardiogram at discharge showed good left ventricular function and no residual outflow obstruction in the ascending aorta.

View larger version (161K): [in this window] [in a new window]   Fig 1. . Postbypass epicardial echocardiogram, equivalent to a parasternal short-axis view, demonstrating supravalvar stenosis of the aorta (arrow) in patient 2. The calculated peak Doppler gradient was 46 mm Hg. (AO = neo-aorta; PT = pulmonary trunk; RV = right ventricle.)

Patient 4
A 10-day-old, 4-kg neonate with a preoperative diagnosis of intramural left coronary artery made on echocardiography (Fig 2) came forward for an elective repair. At operation, the right coronary artery arose from the central portion of sinus 2 (the left facing sinus). The left coronary artery ran intramurally from an origin close to the commissure in sinus 1 through to sinus 2 before emerging from the sinus and dividing into the anterior descending and circumflex coronary arteries. The aorta was transected and a complete flap of the posterior aortic wall including the left and right coronary ostia was cut out [8]. The left coronary ostium was opened as far out as possible, thereby unroofing it. The two ostia were then separated, and relocated to medially hinged flaps in the old pulmonary artery. The old pulmonary artery was quite short at operation. The rest of the operation was completed in a routine manner using the Lecompte maneuver and reconstructing the pulmonary artery with native pericardium. On discontinuation of cardiopulmonary bypass, the heart initially beat quite vigorously and then failed. Bypass was reinstituted and an epicardial echocardiogram showed obstruction of the left coronary artery at its proximal course (Fig 3). This was related to pulling the ostium too far backward. A piece of bovine pericardium was then used to augment the trap door to help make the ostium face more laterally. On cessation of bypass, the heart failed again. The anterior pulmonary artery wall appeared tight, and this was then augmented with a piece of bovine pericardium. Bypass was then terminated successfully and the patient returned to the intensive care unit with the chest left open. The chest was formally closed in the intensive care unit 48 hours postoperatively. The neonate made an uneventful recovery and was discharged on the sixteenth postoperative day.

View larger version (119K): [in this window] [in a new window]   Fig 2. . Preoperative transthoracic echocardiogram in patient 4, demonstrating an intramural course of the left coronary artery (arrows show the "tramline" appearance of the coronary artery within the wall of the aorta). (A = anterior; AO = aorta; L = left; P = posterior; PA = pulmonary trunk; R = right.) posterior; /L/R = left-right for image orientation.

View larger version (75K): [in this window] [in a new window]   Fig 3. . Postbypass color Doppler echocardiogram in patient 4, showing kinking of the origin of the translocated left coronary artery (arrow) associated with flow variance, indicating turbulent flow in the proximal left coronary artery (LCA). The proximal right coronary artery (RCA) demonstrates laminar flow. (AO = neo-aorta; PT = pulmonary trunk.)

	Comment

Top Footnotes Abstract Introduction Material and Methods Case Reports Comment Acknowledgments References

Successful translocation of the intramural coronary artery represents a major surgical challenge [1], and in some instances surgeons have opted for an atrial repair when faced with intramural coronary artery [3]. We have adopted a policy of primary arterial switch repair regardless of the coronary anatomy. Increasingly, it has also become possible to identify an intramural course of one of the coronary arteries by standard preoperative transthoracic echocardiography [10]. Typically, a posterior intramural course of either coronary artery creates a "tramline" appearance within the posterior aortic wall between the great arteries. Prior knowledge of an intramural course of either coronary artery should in turn diminish the risk of inadvertent transection of the artery during the arterial switch procedure. Two mechanisms of compromised coronary flow were identified by epicardial echocardiography: extrinsic compression by the pulmonary trunk in patient 1 and kinking of the orifice of the translocated left coronary artery in patient 4. In each case, specific revision was facilitated by the epicardial echocardiographic findings.

Although we have only selectively used epicardial echocardiography in the setting of the arterial switch operation, our experience with the 2 patients described here does raise some important questions about the potential role of this technique for monitoring the adequacy of coronary perfusion, and identifying the mechanisms by which this may be compromised in patients who cannot be weaned off cardiopulmonary bypass. Clearly it may not be possible to visualize the course of both coronary arteries for any great distance from the anastomotic site. It is also not possible to assess coronary flow quantitatively in neonates with any of the echocardiographic techniques currently available. Abnormalities in the takeoff and proximal course of either coronary artery from its anastomotic site can, however, be recognized. In conjunction with evidence of regional ventricular dyskinesia in the distribution of that vessel, a strong case can be made for revision of the coronary arterial anastomosis.

Systemic outflow obstruction of any significant degree is poorly tolerated after bypass. It is well established that the neo-aorta grows appropriately with somatic growth at follow-up [11]. Supravalvar aortic stenosis therefore is probably not acquired with time, but most likely occurs during the original arterial switch procedure. It is possible to interrogate both arterial trunks in exquisite detail by epicardial echocardiography. This in turn should diminish the incidence of stenoses at the arterial anastomotic sites after the arterial switch procedure.

The epicardial echocardiogram helped elucidate the problem in all 4 patients and contributed to a successful revision of the operation. On the basis of this experience, we would recommend intraoperative echocardiography whenever difficulty is encountered in weaning the patient off bypass, to identify residual mechanical problems that may contribute to poor myocardial function. There should also be a lower threshold for performing these studies postoperatively in patients with unusual coronary anatomy. Epicardial echocardiography is preferred over transesophageal echocardiography in view of the small size of the neonate undergoing arterial switch operation, which may restrict the applicability of transesophageal imaging, and because of the multiple planes of imaging offered by epicardial echocardiography.

	Acknowledgments

Top Footnotes Abstract Introduction Material and Methods Case Reports Comment Acknowledgments References

 
We gratefully acknowledge the assistance of Drs Eric D. Silove, John G. C. Wright, and Joseph V. deGiovanni, who assisted in the clinical care of the patients during their in-hospital stay.

	Footnotes

Top Footnotes Abstract Introduction Material and Methods Case Reports Comment Acknowledgments References

 
Address reprint requests to Dr Sreeram, Heart Unit, Birmingham Children's Hospital, Ladywood Middleway, Birmingham B16 8ET, United Kingdom.

	References

Top Footnotes Abstract Introduction Material and Methods Case Reports Comment Acknowledgments References

 

1. Kirklin JW, Blackstone EH, Tchervenkov CI, Castañeda AR. Clinical outcomes after the arterial switch operation for transposition: patient, support, procedural, and institutional risk factors. Circulation 1992;86:1501–15.
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3. Mayer JE, Sanders SP, Jonas RA, Castañeda AR, Wernovsky G. Coronary artery pattern and outcome of arterial switch operation for transposition of the great arteries. Circulation 1990;82(Suppl 4):139–45.
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5. Quaegebeur J, van Daele M, Stümper O, Suntherland GR. Intraoperative ultrasonographic identification of coronary artery compression after an arterial switch procedure. J Thorac Cardiovasc Surg 1991;102:837–40.[Abstract]
6. Sreeram N, Sutherland GR, Stümper O, et al. Epicardial echocardiography in subaortic obstruction. Ann Thorac Surg 1990;50:579–85.[Abstract]
7. Sreeram N, Jagtap R, Silove ED, Brawn WJ, Sethia B. Intraoperative epicardial echocardiography in assessing pulmonary artery banding procedures. Ann Thorac Surg 1995;60:1778–82.[Abstract/Free Full Text]
8. Asou T, Karl TR, Pawade A, Mee RBB. Arterial switch: translocation of the intramural coronary artery. Ann Thorac Surg 1994;57:461–5.[Abstract]
9. Lecompte Y, Zannini L, Hazan E, et al. Anatomic correction of transposition of the great arteries. New technique without use of a prosthetic conduit. J Thorac Cardiovasc Surg 1981;82:629–31.[Abstract]
10. Pasquini L, Parness IA, Colan SD, Wernovsky G, Mayer JE, Sanders SP. Diagnosis of intramural coronary artery in transposition of the great arteries using two-dimensional echocardiography. Circulation 1993;88:1136–41.[Abstract/Free Full Text]
11. Hourihan M, Colan SD, Wernovsky G, Maheswari U, Mayer JE, Sanders SP. Growth of the aortic anastomosis, annulus, and root after the arterial switch procedure performed in infancy. Circulation 1993;88:615–20.[Abstract/Free Full Text]

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This Article Abstract 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): Narayanswami Sreeram Babulal Sethia Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Shankar, S. Articles by Sethia, B. Search for Related Content PubMed PubMed Citation Articles by Shankar, S. Articles by Sethia, B.