Use of Intravascular Stents for Superior Vena Caval Obstruction After the Mustard Operation. d-tga =dextrotransposition ofthe great arteries

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1 Case Report Use of Intravascular Stents for Superior Vena Caval Obstruction After the Mustard Operation SUSAN G. MACLELLAN-ToBERT, M.D.,* FRANK CETTA, M.D.,t AND DONALD J. HAGLER, M.D. Obstruction of the systemic venous pathway is a complication in patients who have undergone the Mustard operation for complete transposition of the great arteries. In this report, we discuss intravascular stent placement in three patients for relief of superior vena caval obstruction after the Mustard operation. The clinical history, cardiac catheterization data, and echocardiographic data before and after stent placement are presented for each patient. Overall, four stents were placed. The mean gradients from the superior vena cava to the right atrium before stent placement were 10, 8, and 6 mm Hg, and they decreased to 3, 0, and 1 mm Hg immediately after stent placement. No complications occurred. Doppler echocardiographic assessment of mean gradients before and after stent placement correlated with the mean gradients determined by cardiac catheterization. Intravascular stent placement is effective for relief of baffle obstruction after the Mustard operation. Serial Doppler assessments of the gradient across the stent offer a noninvasive method for followup of these patients. (Mayo Clin Proc 1996; 71: ) d-tga =dextrotransposition ofthe great arteries Systemic venous baffle obstruction is a common complication in patients who have undergone the Mustard operation for dextrotransposition of the great arteries (d-tga). Obstruction of the atrial pathways has been reported to occur in 10 to 40% of patients and may be more common in patients operated on before 1 year of age.':' Symptoms are most likely to occur in patients with obstruction of both the superior and the inferior systemic venous pathways and may include superior vena cava syndrome, chylothorax, and protein-losing enteropathy.v" Obstruction of the pulmonary venous pathway has also been reported." Historically, reoperation with revision of the baffle has been recommended;'? however, mortality due to reoperation may be as high as 20%.0 More recently, balloon dilation of both systemic and pulmonary venous pathway stenoses has been used as an alternative to surgical therapy, although stenoses may recur.!':" Restenosis rates after balloon dilation are reported to range from 30% in incomplete venous obstructions to as high as 100% in occluded or newly createdvenous channels.":" Additional therapeutic alternatives include in- From the Section of Pediatric Cardiology, Mayo Clinic Rochester, Rochester, Minnesota, *Current address: Covenant Medical Center, Waterloo, Iowa, tcurrent address: Loyola University Medical Center, Maywood, Illinois, Address reprint requests to Dr. D, J. Hagler, Section of Pediatric Cardiology, Mayo Clinic Rochester, 200 First Street SW, Rochester, MN 55905, travascular stent placement when balloon angioplasty alone is ineffective for maintaining a patent pathway.":" Intravascular stent placement may offer permanent relief of obstruction without the risk associated with surgical revision. Experience with intravascular stent placement in patients with systemic venous pathway obstruction after the Mustard or Senning operation is limited. To our knowledge, seven cases of intravascular stent placement for baffle obstruction have been previously reported in the literature.":" In those reports, restenosis did not seem to be a major complication of stent placement. Herein we discuss three additional cases in which superior vena caval obstruction was successfully relieved with balloon angioplasty and subsequent stent placement. PATIENTS AND METHODS Study Subjects.-Between August 1994 and January 1995, three patients, ages 8, 17, and 26 years, had clinical evidence of systemic baffle obstruction. Clinical assessment, chest radiography, and echocardiography were performed in each patient before cardiac catheterization and endovascular stent placement. Echocardiography.-Echocardiography, either transthoracic or transesophageal, was used to identify patients with evidence of baffle obstruction. Indications of obstruction included two-dimensional evidence of severe narrowing, color flow acceleration in the region of the narrowing, and MayoClinProc 1996; 71: /996 Mayo Foundation for Medical Education and Research For personal use, Mass reproduce only with permission from Mayo Clinic Proceedings.

2 1072 STENTS FOR OBSTRUCTION AFTER MUSTARD OPERATION Mayo Clio Proc, November 1996, Vol 71 abnormal continuous flow with increased velocity as determined by Doppler assessment. Although pulsed wave Doppler interrogation was used to localize the site of maximal velocity, the mean gradient across the narrowed area was determined by continuous wave Doppler assessment. Tracing the flow signal over several cardiac cycles yields an estimate of mean gradient. This technique has an advantage over pulsed wave interrogation in that it includes all velocities that may occur over a length of stenosis. Although care must be taken to avoid including extraneous flow velocities, the Nyquist limit will not be exceeded in severe stenoses if continuous wave Doppler assessment is used. If the echocardiographic findings suggested severe obstruction, the patient was referred for cardiac catheterization and consideration of stent placement. Severe obstruction was defined as a mean gradient across the obstruction of at least 4 mm Hg. In one patient (case 2), angiography demonstrated pronounced decompression by way of the azygos vein, and this occurrence may have lessened the measured gradient. Cardiac Catheterization.-Cardiac catheterization was performed while the patient was sedated or with use of general anesthesia. Vascular access was through the femoral or internal jugular route. Routine saturation and hemodynamic data were collected during right heart catheterization. The degree of obstruction was determined by measurement of the mean gradient and by angiocardiography. Next, an end-hole catheter was positioned, with the tip across the stenosis, and a super stiff exchange guidewire (Meditech, Boston Scientific Corp., Watertown, Massachusetts) was placed through the catheter into the superior vena cava. In one patient (case 2), an internal jugular route was used, and the wire was passed into the inferior vena cava. Each stenosis was predilated with use of a high-pressure 17-atm balloon (Meditech, Boston Scientific Corp.) to ensure complete elimination of the waist. Subsequently, an 11 F long transseptal sheath (Mullins) was placed across the area of stenosis. The intravascular stent (Palmaz, Johnson and Johnson Interventional Systems, Somerville, New Jer- sey) was mounted on a lower pressure balloon catheter (Z Med, Braun, Bethlehem, Pennsylvania) and advanced into position across the stenosis. The long sheath was withdrawn, and the balloon and stent were inflated into position across the obstruction. REPORT OF CASES Case 1.-An 8-year-old boy with d-tga had undergone a Mustard procedure at 2 years of age (Table 1). Because of intermittent complete heart block, an atrial pacemaker with epicardial leads was also placed. On examination of the patient 6 years postoperatively, subtle symptoms of the superior vena cava syndrome were noted. Echocardiography revealed severe narrowing of the superior vena caval pathway with decompression by way of a dilated azygos vein. The continuous wave Doppler mean gradient was 7 mmhg. During cardiac catheterization, cineangiography demonstrated severe narrowing of the superior vena cava at its connection to the atrial baffle. The narrowest diameter was 4 mm, and the mean gradient was 8 mm Hg. Balloon angioplasty of the narrowed connection was performed, and a 3-cm Palmaz stent was placed with subsequent balloon expansion to a final stent diameter of 12 mm. At the end of the procedure, no measurable gradient was present. The patient was dismissed from the hospital the next day and was taking 50 mg of dipyridamole, three times daily, and 81 mg of aspirin, once daily. Follow-up echocardiography performed 3 months and 12 months after the procedure revealed a widely patent superior vena caval pathway with a mean gradient of I mm Hg (Fig. 1). Symptoms of superior vena cava syndrome were no longer noted. Use of dipyridamole was discontinued 3 months after stent placement, but the patient continued to take 81 mg of aspirin once daily until I year after the procedure. Case 2.-A 26-year-old woman sought medical attention because of abdominal distention. When she was 2 days old, a Blalock-Hanlon atrial septostomy had been performed. At the age of 5 years, she had undergone a Mustard procedure Table I.-Characteristics of Patients Before and After Stent Placement* Mean gradient Catheterization Doppler assessment Before After Before After Age (yr) Site of stent stent stent stent Case and sex obstruction (mm Hg) (mmhg) (mmhg) (mmhg) 1 8M SVC F SVC F SVC IVC *IVC =inferior vena cava; SVC =superior vena cava.

3 Mayo Clio Proc, November 1996, Vol 71 STENTS FOR OBSTRUCTION AFTER MUSTARD OPERATION 1073 Fig. 1 (case 1). Continuous wavedoppler tracing, demonstrating superior venacavalflow in 8-year-old boy 1day afterstentplacement. Systolic anddiastolic velocities were0.3 mls and 0.6 tuls, respectively. Meangradient, traced over threecardiac cycles(between arrows), was 0.5 mmhg. for d-tga (Table 1). The patient had done well until 1 year before the current assessment when she experienced abdominal bloating and nausea. Cardiac catheterization at that time revealed severe superior vena caval obstruction. She underwent surgical baffle revision, after which obstruction recurred. Balloon angioplasty of the recurrent superior vena caval stenosis was performed at another institution; relief of symptoms was minimal. Transthoracic and transesophageal echocardiography revealed severe residual superior vena caval obstruction, with a mean gradient measured by continuous wave Doppler assessment of 5 mm Hg and narrowing of the superior vena caval pathway to a minimal diameter of5mm. On the basis of these findings, cardiac catheterization was performed with a 7-F internal jugular vein sheath after an unsuccessful attempt at femoral venous access. Angiography revealed interrupted inferior vena caval blood flow with azygos continuation to the superior vena cava. Severe superior vena caval obstruction was noted with decompression into the dilated azygos system. The hepatic veins drained into the floor of the right atrium and were incorporated into the inferior limb of the systemic venous baffle. The mean gradient across the superior vena caval pathway was 6 mm Hg. Balloon angioplasty of the superior vena caval pathway was performed, and two 3-cm Palmaz stents were placed across the length of the obstruction and dilated, by using an 18-mm, 4-cm length, 2-atm balloon, to a final diameter of 17 mm. At the end of the procedure, the mean gradient across the stent was 1 mm Hg. No complications occurred, and the patient was dismissed from the hospital the next day. She was taking 81 mg of aspirin once daily. Follow-up echocardiography performed 3 months after stent placement revealed a patent superior systemic venous pathway, with a mean gradient across the stent of 1 mm Hg. The abdominal bloating had resolved. Case 3.-A 17-year-old female adolescent who had undergone a Mustard procedure for d-tga had symptoms of superior vena caval obstruction, including facial edema, plethora, mild exophthalmos, and a jugular venous pressure increased at 10 em of water (Table 1). She had undergone balloon atrial septostomy at 6 days of age and a Blalock Hanlon operation at 1 month of age. A Mustard procedure was performed when she was 1 1 /4years old, and the systemic venous baffle was revised 6 months later because of superior vena caval obstruction. Facial edemarecurred when she was 7 years of age, and cardiac catheterization revealed obstruction of the superior limb of the systemic venous pathway. Her symptoms were managed medically with diuretic therapy until 8 months before the current assessment, when the facial edema worsened. Echocardiography disclosed evidence of both superior and inferior vena caval obstruction. The inferior vena caval stenosis was discrete at the connection to the atrial baffle and had a continuous wave Doppler mean gradient of 8 mm Hg, as measured over

4 1074 STENTS FOR OBSTRUCTION AFTER MUSTARD OPERATION Mayo Clio Proe, November 1996, Vol 71 Fig. 2 (case 3). Angiogram, demonstrating stenosis of superior vena caval baffle in 17-year-old female adolescent. Mean gradient was6mm Hg. several cardiac cycles. Similarly, the mean Doppler gradient across the superior vena caval connection was 6 mm Hg. Initial assessment during cardiac catheterization revealed a mean gradient of 10 mm Hg across the superior limb of the systemic venous baffle and a mean gradient of 7 mm Hg across the inferior limb of the baffle. Cineangiography demonstrated severe narrowing of the superior vena cava to a minimal diameter of 4 mm at the connection to the systemic venous atrium, with decompression by way of a dilated azygos vein (Fig. 2). The stenosis was dilated initially to a diameter of 6 mm and then to 12 mm. The second dilation simultaneously dilated the inferior vena caval pathway when the balloon was inflated in the superiorvena cava. After dilation, a 3-cm Palmaz stent was placed across the stenosis in the superior vena cava. After stent placement, cineangiography revealed a widely patent superior vena caval pathway that was 12 mm in diameter (Fig. 3 and 4) and minimal resolution of the inferior vena caval stenosis. The mean gradient across the stent was 3 mm Hg, and it was 6 mm Hg across the inferior systemic venous pathway. Because less flow was decompressing down the azygos vein and across the residual inferior stenosis, we elected not to place a stent in the inferior vena cava at that time. Close follow-up of the residual stenosis was planned, and future stent placement in the inferior vena cava will be considered if the stenotic area persists. The procedure was well tolerated. Two-dimensional echocardiographic assessment the next day indicated that the stent was widely patent. The mean gradient across the stent was 2 mm Hg, as measured by continuous wave Doppler assessment. The patient was dismissed and was taking 81 mg of aspirin once daily. Six months after stent placement, the patient reported complete resolution of the symptoms of superior vena cava syndrome. Doppler assessment revealed a mean gradient across the stent of 1 mm Hg and a mean gradient across the residual inferior vena caval stenosis of 6 mm Hg. Follow-up cardiac catheterization was planned for 1 year after the initial stent placement. DISCUSSION Stenosis of the atrial pathwaysafter the Mustardprocedure is a well-documented complication that occurs in 10 to 40% of patients. To date, experience is limited relative to use and Fig. 3 (case 3). Angiogram after balloon dilation and intravascular stent placement in superior venous pathway. Fig. 4 (case 3). Angiogram, showing widely patent superior vena caval baffle after stent placement. Mean gradient was I mm Hg.

5 Mayo Clio Proc, November 1996, Vol 71 long-term outcome of intravascular stents in such patients (Table 2) In the current report, we describe three patients who were followed up for 3 to 6 months after stent placement. In the past, surgical revision was the mainstay of therapy for baffle stenosis; however, stenosis can recur after surgical revision and can lead to recurrent symptoms, as in one of our patients (case 2). Balloon angioplasty has been somewhat successful, but after dilation, elastic recoil of the vena cava or baffle may result in continued narrowing. IS-I? Stent placement seems to prevent the immediate recoil of the baffle, facilitating long-term patency. This phenomenon of elastic recoil was observed in two of our patients (case 2 and 3) and led to a persistent gradient. In one of these patients (case 3), the inferior vena caval stenosis remained after dilation. Although some degree of decompression by way of the azygos vein into the widely patent superior vena cava should occur, the mean gradient was 6 mm Hg on her 6-month follow-up echocardiogram. Thus, stent placement in the stenotic inferior limb of the baffle is being considered. Use of intravascular stents for various systemic venous stenoses has been reported.":" The incidence of thrombosis is low, and neointima proliferates on the inner surface of the stent as soon as 2 months after implantation." Progressive neointimal hyperplasia may necessitate redilation of the stent. 20 Furthermore, antiplatelet therapy has been recommended during the first months after stent placement in an attempt to decrease the risk of thrombosis. 19 Each of our patients took "low-dose" aspirin (81 mg/day). Because one of our patients (case 1) was the first patient with baffle stenosis to undergo stent placement at Mayo Clinic Rochester, he was treated with dipyridamole and aspirin. Our current practice is to use only aspirin for 6 months to I year after stent placement. The technique of stent placement described in the current report is based on the experience of O'Laughlin and associates.v-" Although dilation without stent placement seems to be less effective for long-term relief of obstruction in comparison with intravascular stents," we believe that dilating the stenotic zone before stent placement to eliminate any waist is an important part of the procedure. Predilation of the stenosis has an important role in the decision to place a stent. If substantial balloon waisting remains at the site of stenosis, stent placement may not be advantageous. Predilation with a high-pressure (17-atm) balloon to eliminate the waist and subsequent stent placement with a lower pressure balloon was used in the current cases. Other investigators' experience with patients with similar conditions suggests that restenosis after stent placement is unusual.p-" In patients who have undergone the Mustard procedure, potential complications at the time of dilation and stent STENTS FOR OBSTRUCTION AFTER MUSTARD OPERATION 1075 Table 2.-Summary of Reported Cases of Stent Placement for Systemic Venous Pathway Obstruction* No. of patients Age Reference Follow-up (rna) Ward et al," 1995 Chatelain et al, Abdulhamed et al," 1994 O'Laughlin et al, ,8,16, (yr) NA NA *NA = not available. placement include vessel rupture and dissection in the area of stenosis, migration of the stent, and, possibly, pulmonary venous pathway obstruction after stent placement. Echocardiography is a noninvasive means for monitoring patients after stent placement. Continuous wave Doppler flow assessment of the superior and inferior vena caval pathways and the pulmonary venous pathway can provide valuable information. In two of our patients (case I and 2), mean gradients in the systemic venous pathways, determined echocardiographically, before and after stent placement correlated with those found at cardiac catheterization (Table 1). In the other patient (case 3), the measurements by catheterization and Doppler assessment across the inferior baffle also correlated. The presence of a catheter across the superior stenosis at the time of gradient measurement may have contributed to the increased gradient of 10 mm Hg in comparison with the Doppler-derived measurement of 6 mm Hg. The three current cases demonstrate the use of intravascular stents as an alternative to surgical revision of the Mustard baffle in patients with d-tga and baffle stenoses. Patients with superior or inferior systemic venous pathway stenoses should be considered for stent placement. Furthermore, stent placement may be associated with less morbidity and mortality than surgical revision or balloon dilation. Initial balloon dilation with subsequent stent placement is suggested because of a high incidence of restenosis after dilation alone due to elastic recoil of the tissues. Low-dose aspirin therapy for 6 months to 1 year after stent placement, during which time neointima is lining the inner surface of the stent, is recommended to help avoid thrombosis. Potential candidates for stent placement can be identified by echocardiography with use of two-dimensional and Doppler evaluation of the Mustard baffle. If transthoracic images are poor or Doppler findings are inconclusive relative to the presence or severity of stenosis, transesophageal echocardiography or, perhaps, magnetic resonance imaging may provide the necessary information. Continuous wave Doppler assessment of the mean gradient across the stent also offers a noninvasive method of follow-up in these patients.

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