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Ann Thorac Surg 2005;80:1634-1640
© 2005 The Society of Thoracic Surgeons

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Original article: Cardiovascular

Coronary Reimplantation After Neoaortic Reconstruction Can Yield Better Result in Arterial Switch Operation: Comparison With Open Trap Door Technique

^a Department of Thoracic and Cardiovascular Surgery, Pusan National University Hospital, Seo-gu, Busan, South Korea
^b Department of Pediatrics, Pusan National University Hospital, Seo-gu, Busan, South Korea
^c Department of Thoracic and Cardiovascular Surgery, DongA University Hospital, Seo-gu, Busan, South Korea
^d Department of Pediatrics, DongA University Hospital, Seo-gu, Busan, South Korea

Accepted for publication April 26, 2005.

^_* Address correspondence to Dr Sung, Department of Thoracic and Cardiovascular Surgery, Pusan National University Hospital, 1-10, Ami-dong, Seo-gu, Busan, 602-061 South Korea (Email: scsung21{at}hanmail.net).

Presented at the Poster Session of the Forty-first Annual Meeting of The Society of Thoracic Surgeons, Tampa, FL, Jan 24–26, 2005.

	Abstract

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
BACKGROUND: Accurate coronary reimplantation is the most important component in the arterial switch operation. It is especially demanding for the less experienced surgeons. We compared the result of the technique of coronary reimplantation after neoaortic reconstruction with that of the open trap door technique.

METHODS: From March 1994 to June 2004, 103 consecutive patients underwent the arterial switch operation by one surgeon. Patients who underwent coronary artery transfer with other modified techniques were excluded. Diagnoses of 94 patients were transposition of the great arteries with intact ventricular septum (n = 50), transposition of the great arteries with ventricular septal defect (n = 26), and the Taussig-Bing anomaly (n = 18). An aortic arch anomaly was present in 13 patients. The median age of the patients was 12 days and the mean body weight was 3.5 kg. Coronary reimplantation after neoaortic reconstruction was applied to 34 patients (group I), and the open trap door technique was applied to the rest (group II).

RESULTS: Preoperative data were similar in both groups. Four patients in group II required intraoperative revision of a transferred coronary artery, and 1 patient with an intramural left coronary artery in group I had a conversion to free grafting using the left subclavian artery. Overall early mortality was 17.0% (16 of 94). Mortality in group I (1 of 34; 2.9%) was significantly lower than in group II (15 of 60; 25.0%) (p = 0.008). The leading cause of death in group II was low cardiac output (n = 9). During the follow-up, an aortic regurgitation of greater than mild was detected in 2 patients in group II.

CONCLUSIONS: Coronary reimplantation after neoaoartic reconstruction is an attractive method to minimize coronary artery transfer-related mortality or morbidity.

	Introduction

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Because of Jatene and colleagues' [1] initial success with the arterial switch operation (ASO) for transposition of the great arteries in 1975, numerous centers have contributed to improving the outcome for infants born with this defect [2–4]. Although some have achieved excellent results, overall success rate with respect to hospital survival after the ASO is still dependent on the experience of the surgeon. This is exaggerated in complicated cases such as the Taussig-Bing anomaly or in combination with an aortic arch anomaly. Survival in successful centers is claimed to be related to the ability of the surgeon to transfer the coronary artery without ischemic insult. This ability to reimplant the coronary artery without torsion or kinking has been enhanced over recent years by several technical contributions such as trap door [5], pericardial hood [6], aortocoronary flap [7], spiral reconstruction [8], and in situ coronary relocation [9]. These maneuvers are more useful in the presence of unusual coronary arteries and size discrepancy of the great arteries. Since September 2000, we have changed the coronary transfer method from the open coronary reimplantation technique into coronary reimplantation after neoaortic reconstruction in the repair of transposition complexes. We compared this method with the open coronary reimplantation technique in regard to postoperative mortality and morbidity.

	Material and Methods

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This study was conducted under the approval of the Institutional Review Board of the Pusan National University Hospital. We reviewed the records of all 103 patients who underwent arterial switch operations at the Pusan National and DongA University Hospitals from March 1994 to June 2004. The operations were done by one surgeon (SCS). Of these 103 patients, the patients who underwent coronary artery transfer with other modified techniques such as aortocoronary flap technique (n = 8) or coronary bypass grafting using left a subclavian artery free graft (n = 1) were excluded. All excluded patients had coronary arteries from a single aortic sinus, and there was only 1 operative death. Among the 94 patients included in our study, transposition of the great arteries with an intact ventricular septum was encountered in 50, transposition of the great arteries with a ventricular septal defect was encountered in 26, and the Taussig-Bing anomaly was encountered in 18. Age at operation varied between 3 and 143 days (median age, 12 days). The male to female ratio was 2.9:1. Mean body weight was 3.5 kg (range, 2.1 to 6.3 kg). A patient underwent rapid two-stage ASO with prior training of the left ventricle. Thirteen patients (13.8%) had coarctation of the aorta (n = 8) or interrupted aortic arch (n = 5), which were repaired before the ASO in 2 patients and simultaneously in 11.

The patients were divided into two groups according to the coronary transfer techniques; coronary reimplantation after neoaortic reconstruction was applied to 34 patients (group I), and an open coronary reimplantation technique was applied to the rest (group II). Coronary patterns were classified according to the Leiden convention. A usual coronary pattern was found in 67 patients (71.3%). A single sinus coronary artery was present in 7 patients (7.4%). Side-by-side great arteries were observed in 15 patients (16.0%). Patients' characteristics are summarized in Table 1 for the two different groups.

Surgical Technique
All operations were performed with a standard open heart surgery technique using high-flow perfusion (150 to 170 mL/kg/min) at 21°C to 23°C. Short-term period of circulatory arrest was used for the closure of interatrial communication if required. Myocardial protection was accomplished with intermittent infusion of 1:1 cold blood cardioplegic solution into the aortic root or coronary ostia every 20 to 30 minutes at the 20 mL/kg. In the cases of coarctation of the aorta or interrupted aortic arch, deep hypothermic circulatory arrest or regional cerebral perfusion was used for arch reconstruction.

The pulmonary artery was dissected beyond the upper lobe branching. The ascending aorta was divided at 5 to 7 mm distal to the sinotubular junction. The coronary artery buttons were excised from the aortic sinuses taking enough cuff tissues. The coronary arteries were then mobilized for some distance and allowed to be resided on the neoaortic root without torsion or tension. Intramural left coronary artery required partial take down of the anterior commissure and creation of separate coronary buttons. After creation of the coronary buttons, the main pulmonary artery (MPA) was cut at the site about 2 mm proximal to its bifurcation. Open trap door incisions (group II) (Fig 1) were made at the site of marking stitches, which was placed before cannulations, and the coronary buttons were implanted to the incisions using 8-0 non-absorbable monofilament sutures in running fashion. A Lecompte maneuver was performed in 89 patients. The aorta was reconstructed by an extended end-to-end or end-to-side anastomosis. A size discrepancy between the neoaortic root and the distal aorta was adjusted through reduction of proximal MPA diameter by excision of some tissue around the non-facing sinus in the wedge shape or through patch augmentation of the distal aorta, or both, with the excised MPA wall or autologous pericardium.

View larger version (28K): [in this window] [in a new window]   Fig 1. Open trap door technique (A–C).

View larger version (50K): [in this window] [in a new window]   Fig 2. Coronary reimplantation after neoaortic reconstruction (A–D).

Clinical follow-up was completed in all survivors with median follow-up of 39.7 months (range, 1.2 to 123.9 months). Echocardiographs were examined at discharge every 6 months for the first year, then yearly in our institution or by the referring cardiologist. Routine follow-up consisted of clinical assessment, electrocardiography, and two-dimensional echocardiography with Doppler study. Further investigations such as cardiac catheterization and coronary angiography or myocardial perfusion scan were performed as necessary.

Statistical Analysis
Continuous data were expressed as mean and standard deviation. Mean values of continuous variables were compared by means of the Student's t test. Fisher's exact test was used for the non-continuous variables between the groups. Those variables not following a normal distribution (ie, age and ventilation time) were expressed in terms of the median and compared by the Kolmogorov-Smirnov statistic. In the analysis of risk factor for operative death, variables with significant levels of 0.05 in univariate analysis were admitted to a multivariate logistic regression model. Factors with p values less than 0.05 were considered significantly related to early death. Long-term survival rates were calculated using the Kaplan-Meier method and statistical significance was calculated by the Breslow test.

Early mortality was defined as death during initial hospitalization or within 30 days of operation. Any deaths later were then defined as late mortality. In our series, all early deaths occurred during the initial hospitalization and all late deaths occurred after discharge from the initial hospitalization.

	Results

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Preoperative variables did not show significant differences between the two groups (Table 1). Overall early mortality was 16 of 94 (17.0%); mortality for group I (1 of 34; 2.9%) was significantly lower than group II (15 of 60; 25.0%) (p = 0.008) (Table 2).

Univariate logistic regression analysis showed that the risk factors for operative death were the open trap door technique (p = 0.023), preoperative mechanical ventilation (p = 0.0004), aortic arch anomaly (p = 0.001), and earlier date of operation (p = 0.003). Unusual pattern of coronary anatomy or single coronary artery, the presence of VSD, side-by-side great artery relation, aortic cross-clamp time, and cardiopulmonary bypass time had no influence. Multivariate analysis confirmed that the aortic arch anomaly was the only risk factor for early mortality in the entire series as well as in group II (Tables 3 and 4). After technical modification of the coronary artery transfer, the operative mortality fell to 1 of 34 (2.9%) with higher actuarial survival (p = 0.0015) (Fig 3).

View larger version (19K): [in this window] [in a new window]   Fig 3. (A) Actuarial survival by group with 95% confidence interval (p = 0.002; Breslow test). (B) Actuarial survival of entire series with 95% confidence interval.

The causes of early death were low cardiac output (n = 9), multiorgan failure (n = 3), postoperative bleeding (n = 1), and pulmonary hypertensive crisis (n = 1), intracranial hemorrhage (n = 1), and sepsis (n = 1). Two of these operative deaths were related to serious preoperative conditions. One patient who had preoperative cardiac arrest caused by severe tension pneumothorax underwent ASO 5 days after the event. He was found to have large intracranial hematoma and died 60 days after the operation. We suspected that the intracranial hematoma was related to the preoperative cardiac arrest. The other patients had congenital complete atrioventricular block and acute renal failure. The acute renal failure persisted postoperatively, and he died of sepsis 7 days after the operation. The only 1 operative death in group I occurred in the patient with the aortic arch anomaly. The patient died of multiorgan failure 53 days after the operation following persistent acute renal failure. His cardiac angiography showed left pulmonary artery compression by a large anterior neoaorta, but his coronary arteries were patent and his left ventricular function was normal.

Five patients, 1 in group I and 4 in group II (2.9 vs 6.7%; p = 0.650), required intraoperative revision of transferred coronary arteries (Table 2). The patients in group II underwent complete relocation (n = 2) or partial reposition of angled coronary arteries with traction sutures (n = 2). The patient in group I had intramural course of the left coronary artery and underwent left coronary artery bypass using the left subclavian free graft as a rescue procedure.

Cardiopulmonary bypass time was not significantly different between the two groups (p = 0.234), and aortic cross-clamping time was longer in group I (p = 0.020). A mechanical assist device was needed in 6 patients (all in group II) because of low cardiac output (p = 0.084), but it was successful in only 2 patients in salvaging their lives. The postoperative mechanical ventilation time was longer in group II (p = 0.043). However, the incidence of the open sternum was not different between the groups (p = 0.290). Operative and postoperative data including complications are listed in Table 2.

Late death occurred in 4 patients exclusively in group II. The causes of late death were chronic lung disease in 1 patient, neurologic problem in 1, and sudden death with unknown cause in 2. The overall actuarial survival at 30 days, 1 year, and 5 years were 85, 79, and 79%, respectively. Mortality is highest in the early postoperative period; the curve flattens down after the first months, and no patients died after 6 months (Fig 3).

Follow-Up Data
At the time of last follow-up, echocardiography revealed normal ventricular function and electrocardiogram showed sinus rhythm in all patients. Four patients (4 of 74; 5.4%) had pulmonary gradient of more than 30 mm Hg develop. Two patients had aortic regurgitation greater than mild in group II. Percutaneous balloon dilatation of pulmonary artery stenosis was done in 4 patients (1 in group I, 3 in group II).

Reoperations
Two patients underwent reoperations because of left ventricular outflow obstruction caused by abnormal chordae of mitral valve crossing subaortic area and pulmonary stenosis at multiple levels, respectively.

	Comment

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
The arterial switch operation is still a challenging operation for less experienced surgeons, even though it has been performed with very low mortality in many high-volume centers. Accurate transfer of the coronary artery is the key component to a successful ASO. Acute myocardial failure caused by inadequate coronary transfer has been known to be the most important cause of death after ASO.

The open trap door technique advocated by Yacoub and Radley-Smith [10] and Brawn and Mee [11] is regarded as a basic component of ASO and is used in many centers with low operative mortality. In this technique, marking stitches are made at the neoaorta to select accurate sites for the coronary arteries to be reimplanted. However, it is not easy for the less experienced surgeons to select the accurate sites for the coronary reimplantation, even if they make marking stitches on the neoaorta before cannulations. Many reports have shown a typical learning curve in which the operative result improved with increasing experience of the surgeon [12–14]. However, the operative mortality in our series was unacceptably high before the change of coronary transfer technique, even though the learning curve was taken into account. Moreover the date of operation in group II was not the risk factor for operative mortality in our series (Table 4). This means that the operative mortality is not solely related to the experience of the surgeon in our practice. Frankly, we were not confident about coronary artery transfer at that time. As a result, we changed the coronary transfer technique from open reimplantation into reimplatation after neoaortic anastomosis. The most concerning problem about the later technique was the possible damage to the neoaortic valve when creating openings at the neoaorta for coronary reimplantation. We have overcome this problem by making a marking stitch at the site of the anterior commissural attachment of the neoaorta as inserting needles from inside to outside using a double-armed fine suture (Fig 2A). This technique was very useful to locate the commissural site of the neoaorta from outside after neoaorta reconstruction. Since we adopted the technique, we have become very confident with coronary transfer and have not felt any difficulty even in the case with unusual coronary artery patterns. As our data shows, the operative mortality of the ASO significantly fell to the acceptable level after technical modification of the coronary transfer (Table 2).

The reduction of the operative mortality was more striking in the patient group with the aortic arch anomaly; 85.7% (6 of 7) in group II dramatically fell to 16.7% (1 of 6) in group I. The contribution of the technical modification to this improvement should be emphasized in regard to the fact that the aortic arch anomaly was the main risk factor in the entire series. Although the difference of the operative results between the two techniques in our series might be surgeon-dependent because many surgeons are using open trap door technique with excellent results, we strongly feel that the coronary reimplantation after neoaortic anastomosis may be easier and safer for the less experienced surgeon. We also think that this technique may be more effective in cases with aortic arch anomaly.

Brown and associates [13] reported similar results. They reported that imperfect coronary transfer ceased to be a significant risk factor for operative death after using the new technique. We know that the technique of coronary reimplantation after neoaortic reconstruction was advocated by Bove [15] in 1989 and is now widely being used. However there are few reports comparing results between these two different techniques.

Each technique has its own advantages and disadvantages. The main advantage of the open technique is avoiding neoaortic valve injury. However, this technique is somewhat difficult or inaccurate to select the most proper site of coronary transfer, because the incision is made with an arrested heart. The coronary artery button may be further distorted at the time of the neoaorta anastomosis, unless the geometry of the distal ascending aorta and proximal neoaorta is accurately aligned. On the other hand, the reimplatation technique after neoaortic anastomosis has its main advantage of selecting coronary transfer site easily and accurately with a distended aortic root. We think that this technique is more effective in the situations of significant size disparity between great vessels or malaligned facing commissure. It was amazing that there was a significant gap of the location of the coronary transfer site as compared with the previous open technique in some cases. The two coronary buttons were sometimes reimplanted around one neoaortic sinus. The only important disadvantage of this technique is a possible injury of the neoaortic valve, but there was no evidence of intraoperative neoaortic valve injury nor significant postoperative neoaortic valve regurgitation in our series. We think that the described maneuver (Fig 2A) in avoiding neoaortic valve injury is very effective.

It is very difficult to tell if one operative technique is better in terms of neoaortic regurgitation and pulmonary stenosis. Actually there was no statistical difference in their incidences, and the follow-up durations were quite different between groups.

We had 4 late deaths, all from group II. Among these patients, 2 sudden deaths were believed to be possibly related to the coronary problem even though the exact cause of death was not elucidated through autopsy.

We conclude that coronary reimplantation after neoaortic reconstruction is effective in reducing postoperative mortality or morbidity. We recommend this technique to the less experienced surgeons or the surgeons who do not have good results with the open coronary reimplantation technique.

There were a few study limitations. We have no autopsy data to clarify the causes of death. There might be some bias in making the conclusion that modification of the coronary transfer technique was the sole factor accounting for the improvement of the operative results, because not all operative deaths were related to the coronary problem, even though the majority of them were related. There was also lack of statistical or scientific data about the less experienced surgeon.

	Acknowledgments

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
We appreciate the efforts of Dr Hon Chi Suen in the preparation of this article.

	References

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 

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