Ann Thorac Surg 1998;65:1746-1750
© 1998 The Society of Thoracic Surgeons
Original articles: cardiovascular
Growth of the Subclavian Artery and the Anastomosis in Blalock-Taussig Shunt: Absorbable Versus Nonabsorbable Suture
Naoki Yoshimura, MDa,
Masahiro Yamaguchi, MDa,
Hidetaka Ohashi, MDa,
Yoshihiro Oshima, MDa,
Yoshiya Toyoda, MDa,
Hee-Nam Chung, MDb,
Kyoichi Ogawa, MDa
a Department of Cardiothoracic Surgery, Kobe Children’s Hospital, Kobe, Japan
b Department of Cardiology, Kobe Children’s Hospital, Kobe, Japan
Accepted for publication January 17, 1998.
Address reprint requests to Dr Yoshimura, Department of Cardiothoracic Surgery, Kobe Children’s Hospital, 1-1-1, Takakura-dai, Suma-ku, Kobe 654, Japan
e-mail: (y-naoki{at}za2.so-net.or.jp)
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Abstract
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Background. We evaluated the growth of Blalock-Taussig shunts placed with absorbable suture by cineangiographic findings and long-term results and compared them with those in an earlier group of patients in whom we used nonabsorbable suture.
Methods. Eighty-one patients had postoperative cineangiography 1 year or more after a Blalock-Taussig shunt procedure. From September 1985 to December 1994, 40 patients (group I) underwent a Blalock-Taussig shunt procedure with the use of absorbable polydioxanone suture, and from January 1980 to August 1989, 41 (group II) underwent the same operation with nonabsorbable polypropylene suture. Cineangiograms were reviewed to assess shunt patency and growth of the subclavian arteries and the subclavian artery–pulmonary artery anastomoses.
Results. At the Blalock-Taussig shunt operation, mean outer diameters of the subclavian artery and the anastomosis in group I were 3.8 ± 0.1 mm and 4.1 ± 0.1 mm, respectively and 3.9 ± 0.1 mm and 4.0 ± 0.1 mm in group II. The mean inner diameters of the subclavian artery and the anastomosis measured in postoperative cineangiograms were 7.9 ± 0.5 mm and 4.6 ± 0.2 mm, respectively in group I and 6.6 ± 0.4 mm and 3.1 ± 0.2 mm in group II. The diameters of both the subclavian artery (p < 0.05) and the anastomosis (p < 0.001) were significantly greater in group I than in group II. Five years after operation, 71.1% ± 7.4% of patients in group I and 54.8% ± 8.0% in group II had good palliation.
Conclusions. The use of absorbable polydioxanone suture has an advantage in terms of growth of the diameters of the subclavian artery and the anastomosis in a Blalock-Taussig shunt and may improve the long-term results after this shunt operation in infancy.
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Introduction
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The Blalock-Taussig shunt remains a major strategy in the treatment of patients with congenital cyanotic heart defects. The modified Blalock-Taussig shunt has become increasingly popular as an alternative to the classic Blalock-Taussig shunt. However, it is sometimes technically impossible to use a 5-mm graft, especially in neonates with very small systemic and pulmonary vessels. Although recent advances in pediatric cardiac surgery allow early primary definitive repair in many patients, some patients with complex cardiac anomalies still require a palliative shunt early in life and long-term palliation [1–3]. There is no universally accepted optimal shunt procedure for infants. We have performed the classic Blalock-Taussig shunt as the procedure of choice in neonates and infants because of the relatively disappointing palliation afforded by the 4-mm shunt [4, 5].
Several authors [6–9] have recommended the use of absorbable suture in pediatric cardiac operations to improve the long-term results. Although the theoretical advantages of absorbable suture are attractive, there have been very few reports on growth of the classic Blalock-Taussig shunt in large series. In recent years, we have routinely used a continuous polydioxanone monofilament suture to create the subclavian artery–pulmonary artery anastomosis. In this study, using cineangiographic findings and long-term results, we evaluated the growth of Blalock-Taussig shunts sewn with an absorbable suture and compared them with those in an earlier group of patients in whom we used a nonabsorbable suture.
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Patients and methods
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Patient population
Between January 1980 and December 1994, 116 infants less than 1 year of age received a classic Blalock-Taussig shunt. There were no early deaths, but 14 patients died late before postoperative cineangiography was performed. Of the remaining 102 patients, 81 underwent cineangiography 1 year or more after the shunt procedure.
Forty patients (group I) had a Blalock-Taussig shunt procedure with the use of absorbable polydioxanone suture (PDS II; Ethicon, Inc, Somerville, NJ) from September 1985 to December 1994, and 41 (group II) underwent the same procedure with nonabsorbable polypropylene suture (Prolene; Ethicon, Inc) from January 1980 to August 1989. Mean age at shunt operation was 1.8 months (range, 4 days to 7 months) in group I and 3.0 months (range, 6 days to 11 months) in group II. Mean body weight was 4.0 kg (range, 2.3 to 7.6 kg) in group I and 4.9 kg (range, 2.5 to 7.8 kg) in group II. The major diagnoses in each group are shown in Table 1. The groups were similar with respect to complexity of the intracardiac anomaly.
Operative technique
The side opposite the aortic arch was selected in 71 (87.7%) of the 81 patients. All shunts were constructed through a standard lateral thoracotomy. The subclavian and pulmonary arteries were identified. Heparin sodium (100 U/kg) was administered before ligation of the subclavian artery. The subclavian artery was transected at the level of its first branch and then brought through the loop of the recurrent nerve. The pulmonary artery was clamped proximally and snared distally, and then a small transverse incision was made. The end of the subclavian artery was anastomosed to this pulmonary arteriotomy. In group I, an everting running mattress technique was used posteriorly and a simple running technique anteriorly. In group II, on the other hand, the posterior wall anastomosis was performed with an everting running mattress suture and the anterior portion with interrupted sutures. Size 6-0 sutures and a tapered needle (BV-1; Ethicon, Inc) were used in 79 patients and 7-0 sutures, in the last 2 patients. Postoperatively, heparin was administered (480 U · kg-1 · day-1) for a few days and then was replaced by long-term anticoagulation therapy. Warfarin sodium (0.1 mg · kg-1 · day-1) was used to 1986; since then, ticlopidine hydrochloride (5 mg · kg-1 · day-1) has been used.
Postoperative cineangiographic studies
The mean interval between the Blalock-Taussig shunt operation and postoperative cardiac catheterization was 51.4 months (range, 12 to 86 months) in group I and 59.0 months (range, 14 to 111 months) in group II. Mean body weight at cardiac catheterization was 14.0 kg (range, 6.8 to 26.5 kg) in group I and 14.7 kg (range, 8.2 to 20.0 kg) in group II. Cineangiograms were reviewed to assess shunt patency and growth of the subclavian arteries and the subclavian artery–pulmonary artery anastomoses. From frontal views, the diameters of the subclavian arteries and the anastomoses were measured in the systolic phase (Fig 1). The subclavian arteries were measured just distal to their origin. The measured diameters were converted to true measurements by comparison with a 1-cm grid filmed with each cineangiogram.
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Fig 1. Postoperative cineangiogram made 83 months after Blalock-Taussig shunt operation with polydioxanone suture in a patient with pulmonary atresia. Outer diameters of the subclavian artery (SCA) and the subclavian artery–pulmonary artery (PA) anastomosis at operation were 4.5 mm and 4.0 mm, respectively, and inner diameters on postoperative cineangiograms were 13.8 mm and 6.3 mm. The subclavian artery and the subclavian artery–pulmonary artery anastomosis showed marked growth in this patient. (CCA = common carotid artery.)
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Patient follow-up
Follow-up was obtained for all patients through clinic visits. Mean follow-up was 108.3 months (range, 21 to 196 months), and the end of the study follow-up was June 30, 1997. The patient’s condition was considered palliated until he or she died before a corrective operation or until a second shunt operation became necessary. The decision to perform a second shunt procedure was based on the red blood cell count, the oxygen saturation in arterial blood, and the general condition of the patient.
Statistical analysis
Continuous data are expressed as the mean ± the standard error of the mean. Values were compared at the various times by analysis of variance with repeated measures, and differences at each comparison were tested by factorial analysis of variance. When the F ratio of the analysis of variance was significant, the differences were tested by Scheffé’s test. The Kaplan-Meier survival analysis and the generalized Wilcoxon test for comparison of survival curves were used to evaluate the freedom from shunt failure (cardiac-related death or repeat shunt operation) ratio in each group. Significance was tested at the 95% confidence level.
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Results
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Growth of subclavian artery and subclavian–pulmonary artery anastomosis
At the Blalock-Taussig shunt operation, sizes of the subclavian artery and the subclavian artery–pulmonary artery anastomosis were measured by the surgeon. Mean outer diameters of the subclavian artery and the anastomosis in group I were 3.8 ± 0.1 mm and 4.1 ± 0.1 mm, respectively, and 3.9 ± 0.1 mm and 4.0 ± 0.1 mm in group II. No significant differences were found between the two groups. Mean inner diameters of the subclavian artery and the anastomosis measured in postoperative cineangiograms were 7.9 ± 0.5 mm and 4.6 ± 0.2 mm, respectively, in group I and 6.6 ± 0.4 mm and 3.1 ± 0.2 mm in group II (Fig 2). The diameters of both the subclavian artery (p < 0.05) and the subclavian artery–pulmonary artery anastomosis (p < 0.001) were significantly greater in group I patients than in group II. There was no shunt occlusion in group I. On the other hand, two shunts in group II showed complete occlusion.
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Fig 2. Changes in diameters of (A) subclavian arteries and (B) anastomoses. No significant differences were found between the two groups at shunt operation. The diameters of the subclavian artery and the subclavian artery–pulmonary artery anastomosis measured on postoperative cineangiograms in group I patients were significantly greater than those in group II. (NS = not significant.)
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Long-term results
There were no late deaths in group I and two late deaths in group II before the corrective operation. Both patients died of congestive heart failure 22 months after the first Blalock-Taussig shunt operation. In group I, 12 patients required a second shunt operation (modified Blalock-Taussig, 11, and Glenn, 1) for inadequate shunt function manifested by increasing cyanosis. The mean interval between the two operations was 28.3 months (range, 6 to 67 months). Eighteen patients in group II underwent 22 additional shunt operations (classic Blalock-Taussig, 4; modified Blalock-Taussig, 15; unifocalization + modified Blalock-Taussig, 1; and Glenn, 2). The mean interval between the two shunt operations was 26.6 months (range, 6 to 61 months).
Twenty-five patients in group I and 37 in group II have undergone a corrective operation. Mean age at this operation was 80.6 months (range, 14 to 117 months) in group I and 86.5 months (range, 33 to 150 months) in group II. Seven patients in group I and 1 patient in group II are scheduled for a corrective operation in the near future.
Actuarial freedom from shunt failure is shown in Figure 3. Three years after the Blalock-Taussig shunt operation, 79.6% ± 6.4% of patients in group I and 65.8% ± 7.4% in group II remained well palliated. The difference was not significant.
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Fig 3. Actuarial freedom from shunt failure. The difference between the two groups did not reach significance.
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Red blood cell counts were analyzed to evaluate the effect of the Blalock-Taussig shunt in patients who remained well and free from further operation. Figure 4 illustrates the changes in red blood cell counts in each group. There were significant differences in the cell count between the two groups at 6 months, 1 year, 2 years, and 4 years after the Blalock-Taussig shunt operation.
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Fig 4. Changes in red blood cell counts in each group. There were significant differences between the two groups at 6 months, 1 year, 2 years, and 4 years after the Blalock-Taussig shunt operation. (*p < 0.05. **p < 0.01. ***p < 0.005.)
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Comment
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The trend in congenital heart surgery is toward earlier and earlier correction [1, 4], and most of the patients in this study would have had an earlier corrective operation today. However, a substantial number of patients require a Blalock-Taussig shunt soon after birth and also need long-term palliation. Prolonged patency and adequate growth of the shunt are necessary for long-term palliation. Clinical [6–10] and experimental [11, 12] investigations concerning the vascular anastomosis in growing vessels have been undertaken. Wilson and associates [10] reported that performing the anastomosis with interrupted sutures rather than continuous suture reduces the possibility of late pulmonary venous obstruction after repair of total anomalous pulmonary venous connection. Hawkins and colleagues [7] demonstrated that a continuous polydioxanone suture for repair of total anomalous pulmonary venous connection is associated with a low incidence of late pulmonary venous obstruction and good long-term results. Moreover, Ott and coworkers [9] and Myers and associates [6] suggested that the use of polydioxanone suture might allow for future growth of a Blalock-Taussig shunt.
In this study, we analyzed postoperative cineangiograms and evaluated the growth of Blalock-Taussig shunts in a large series. The diameters of both the subclavian artery and the subclavian artery–pulmonary artery anastomosis in patients who underwent a Blalock-Taussig shunt procedure with the use of continuous polydioxanone suture were significantly greater than those in patients who underwent the same procedure with interrupted polypropylene sutures. Because shunt flow is limited by the diameters of the subclavian artery and the anastomosis, better clinical results can be expected in group I, as evidenced by the lower postoperative red blood cell counts and the lower rate of late shunt failure.
Today, an increasing number of patients receive a Blalock-Taussig shunt early in life [1, 2, 4]. In the present study, mean age and mean weight at shunt operation were lower in group I than in group II because the indication for the classic Blalock-Taussig shunt has become limited to neonates and infants. Stewart and associates [3] reported that the mean duration of adequate shunt function in patients less than 1 month of age at shunt operation was shorter than that in patients older than 1 month. In our experience, however, the actuarial freedom from shunt failure was higher in group I than in group II during follow up, even though the Blalock-Taussig shunt operation was performed at an earlier age in group I.
It would be attractive to conclude from these results that the use of absorbable polydioxanone suture improves the long-term results after the Blalock-Taussig shunt operation, but the nature of a retrospective review with differing time periods makes this conclusion difficult to draw. Earlier experience, differences in anticoagulation therapy, and technical improvements may be more important factors than suture materials. However, the surgeon, operative technique, operative time, and early operative results were nearly identical during the period of this study. Moreover, we directly confirmed the better growth of the subclavian artery and the subclavian artery–pulmonary artery anastomosis in group I patients by analyzing postoperative cineangiograms.
In conclusion, the use of absorbable polydioxanone suture has an advantage in terms of growth of the diameters of the subclavian artery and the anastomosis in the Blalock-Taussig shunt and may improve the long-term results after a Blalock-Taussig shunt operation in infancy.
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References
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- Wilson W.R., Ilbawi M.N., DeLeon S.Y., et al. Technical modifications for improved results in total anomalous pulmonary venous drainage. J Thorac Cardiovasc Surg 1992;103:861-871.[Abstract]
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Abstract
Introduction
