Use of Endovascular Stents for the Treatment of Coarctation of the Aorta in Children and Adults: Immediate and Midterm Results

Coarctation of the aorta (CoA) accounts for 6–8% of all forms of congenital heart defects. In children and adults, balloon angioplasty has become the preferred treatment for patients with recurrent CoA.^1–5,6–18 The application of this technique for treatment of native coarctation is somewhat controversial due to the high incidence of recoarctation (5–10%) and the incidence of aneurysm formation (5–7%).⁷ There are few reports in the medical literature documenting the beneficial use of stent implantation for the treatment of CoA.^{2–5,8–10,19} Stent implantation results in less residual gradient across the coarctation site, improved diameter, decreased incidence of aneurysm formation and sustained hemodynamic benefit. In this paper, we report the immediate and midterm results of our experience in two centers by a single operator for percutaneous stent implantation in patients with native or recurrent CoA. Methods Successful outcome after stent implantation was defined as a reduction in the peak systolic gradient of more than 50% and/or more than 50% improvement in the diameter of the narrow area as evidenced by angiography or MRI/MRA. Patients. From May 1995 to February 2005, 44 patients (24 male, 20 female) with native (n = 28) or recurrent (n = 16) CoA underwent 44 procedures at two institutions by the same operator. The mean age of patients was 16.9 ± 1.8 years (range 3 months to 44 years), and 14 of these patients were 20 mmHg or had systemic hypertension in the presence of coarctation. The most common associated cardiac anomaly was a bicuspid aortic valve (BAV) in (n = 16). Eleven patients had undergone previous surgery for correction of other associated congenital heart defects other than CoA. Table 1 lists the demographic findings of the patients. This study was performed in compliance with the Health Information Privacy and Accountability Act (HIPAA). Data were collected on our patients through chart review. This retrospective study involved no testing on any of the subjects as part of the protocol. Patient confidentiality was maintained throughout the data collection and preparation of the manuscript. Technique of stent implantation. The stent implantation technique was similar to that described previously.³ Briefly, all procedures were performed under general endotracheal anesthesia. Vascular access was obtained percutaneously via the femoral artery and vein. In general, if a bare stent was implanted, the size of the delivery sheath was usually one French size larger than the shaft of the balloon. For covered stents, an 11 French (Fr) sheath was used. Anticoagulation to keep the activated clotting time over 200 seconds with heparin was maintained throughout the procedure. Routine hemodynamic evaluation was performed with measurement of the gradient across the coarctation site by catheter pullback. Biplane angiographic assessment of the arch was performed, and the appropriate measurements of the diameter at the site of coarctation, isthmus and the descending aorta at the level of the diaphragm were made. Calibration of the angiographic measurements was based on the presence of marker catheters of either 20 mm or 10 mm lengths. An extra-stiff guidewire was positioned in the ascending aorta or left subclavian artery. A Mullins-type sheath was positioned over the wire above the site of coarctation. The appropriate stent was mounted by hand crimping over the appropriately-sized high-pressure balloons (ZMED or BIB balloon catheters, NuMED, Inc., Hopkinton, New York) and introduced over the guidewire inside the delivery sheath until it reached the tip of the sheath. The diameter of the first balloon was chosen to be at least the same as the diameter of the isthmus above the coarctation. Repeated hand injections via the side arm of the sheath were performed to delineate the position of the stent. Once correct positioning was confirmed, the balloon was inflated until the stent was fully expanded. Next, the balloon was deflated and the sheath was advanced over the balloon inside the stent. Repeat measurement of the gradient across the stent was performed using either a Multitrack catheter (NuMED, Inc.) or by simultaneous measurement using a pigtail catheter above the stent and the side arm of the sheath below the stent. Repeat angiography was performed to assess the result. If the stent was not fully apposed to the wall of the isthmus, a larger balloon of a diameter similar to the isthmus was used to overexpand the proximal part of the stent. Due to the large size of the descending aorta, no attempts were made to overexpand the distal part of the stent to fully oppose the wall. The following day, chest radiograph, an echocardiogram with color Doppler and blood pressure in the arm and leg were performed. Patients were discharged home on 81mg of aspirin per day for 6 months. Patients were asked to observe bacterial endocarditis prophylaxis when appropriate for 6 months. Statistical analysis. Data are expressed as mean values ± SEM. Values obtained before and immediately after stent placement and at follow-up are compared with repeated measurement analysis of variance. A p-value of Follow-up. Retrospective chart review was used to evaluate follow-up of all subjects. The data obtained were clinical examinations including blood pressure, chest radiograph, echocardiographic results, magnetic resonance imaging, computed tomography scan and repeat cardiac catheterizations. Follow-up data were available on all surviving except for 1 patient. The mean follow-up time was 19.8 ± 3.5 months (0.1–117 months). Results Immediate results. During 44 primary procedures, a total of 52 stents were deployed. Two patients required 3 stents to be deployed before an adequate result was achieved secondary to stent migration during the procedure. Four patients required a second stenting procedure secondary to narrowing at the initial site. A total of 26 Palmaz 308 or 188 stents was used (Johnson & Johnson InterventionalSystems, Sommerville, New Jersey). Other commonly used stents were IT (n = 9) (Intratherapeutics, Minneapolis, Minnesota), Cheatham Platinum (n = 4) covered stent (NuMED, Inc.), P4010 stents (n = 4) (Figure 1), PG2510B stents (n = 4), PG2910B stents (n = 3), one P5010 stent, and one PG244B stent. The mean sheath size used was 9 ± 0.2 Fr (range 6–13 Fr). The stents were initially inflated to a mean diameter of 14 mm ± 2 (range 6–18 mm). Subsequently, larger balloons were used to expand the stent to its final diameter and to assist with dilation to allow for apposition of the stent to the proximal descending aorta (isthmus). Immediately after stent placement, significant relief of obstruction was observed in all 44 patients. The peak-to-peak gradient across the aortic arch prior to stent placement was 29.2 ± 1.9 mmHg versus 3.7 ± 0.7 mmHg (p-value 0.001). Following stent placement the gradient decreased to p-value Complications. A total of 9 complications were encountered in the 44 procedures (Table 2) There were no death-related or surgery requiring complications in any of the procedures. Of these complications, only dissection was considered to be a major complication. This occurred in 1 patient who had stent migration followed by a small dissection. This was managed with follow-up and no surgical intervention was required. Other minor complications included a small aneurysm, hypertension and decreased femoral pulses requiring heparin therapy overnight. Balloon rupture and stent migration occurred in 1 patient without any further complication. Two patients died several months later from complications unrelated to the procedure. Repeat catheterization and stent dilatation. Thirteen patients underwent repeat catheterization procedures. The mean time between the first catheterization and the repeat catheterization was 17.9 ± 2.4 months with a range from 1 day to 47.5 months. Restenosis occurred in 12/13 patients. The median residual gradient at the time of repeat catheterization was 20 mmHg, with a range from 0–59 mmHg. Eight of the patients who underwent recatheterization had re-expansion of the previously stented area with resolution of the gradient. Four of the patients who had recatheterization underwent a restenting procedure secondary to narrowing in the previously stented area (Figure 2). These patients required restenting procedures, rather than further expansion of the initial stent. This was done due to the phenomenon of recoil of the initial stent. The final patient who underwent a repeat catheterization had no intervention. This patient underwent his recatheterization 1 day after his initial procedure to assess stent migration. The stent was found not interfering with any vital blood vessel and the initial site where the stent was implanted was of adequate diameter with minimal gradient across the coarctation. Of the patients who underwent repeat catheterization or had additional dilatation or stenting procedures done, all experienced some relief in the gradient. The postintervention gradient was reduced to a mean of 7 mmHg, with a range from 0–14 mmHg. Of those patients who underwent repeat catheterization, none were found to have aneurysm formation, stent displacement or stent fracture. However, 1 patient who underwent Multidetector CT scan for follow-up after 9 years was found to have a large aneurysm at the distal site of the stent (Figure 3). He is awaiting surgical repair of the aneurysm. Fourteen patients in the study were Follow-up. The mean follow-up period was 19.8 ± 3.5 months (range 15 days to 117 months). Follow-up data were available on 40 of the 41 surviving patients. At the time of follow-up, only 14 patients were on antihypertensive medications and only 5 patients were noted on physical examinations to have abnormal pulses in the extremities. Follow-up blood pressure data were available for 32 of 40 patients. The difference between upper and lower systolic blood pressures decreased from a mean of 29 mmHg ± 1.9 pre-intervention, to a mean of 10 ± 2.4 at follow-up. No significant differences were identified between those patients with native or recurrent coarctation of the aorta. No significant difference in results was noted between patients based on age or weight. Discussion The ideal treatment for coarctation of the aorta has been a topic of controversy for many years. Over the last 15 years, surgical repair and balloon angioplasty have been used alternatively or together as the primary treatments.^1,4,7,12,17 However, depending on the anatomy of the CoA, different procedures are preferential. The effect of balloon angioplasty appears to be favorable in patients with a discrete type of CoA, but limited in those with diffuse stenosis involving the arch or those with isthmic hypoplasia.¹⁵ Both treatments have similar complications, primarily restenosis and aneurysm formation.² A comparative study conducted in the 1990s between surgery versus balloon angioplasty, suggested an overall incidence of recoarctation of 14% after surgery and 57% after balloon angioplasty alone. Other studies showed that surgery for aortic recoarctation has a recoarctation rate of 9–26%, whether a subclavian flap repair, patch aortoplasty, or end-to-end anastamosis repair has been performed.^5,7 While initial surgery for native coarctation does not carry a very high mortality rate, surgery for recoarctation does have substantially higher morbidity and mortality rates. Therefore, balloon dilatation has been recommended as the treatment of choice. It is generally successful and has low morbidity, though complications such as aneurysm formation may occur. In our patients, only 9 complications occurred, and of these, only 1 was a dissection. We also had 2 patients with aneurysm formation (1 that resolved without the need for surgical intervention; and the other 1 diagnosed by Multidetector CT scan after 9 years). It is not known if this aneurysm formed shortly after the stent or on long-term follow-up. This patient was seen for follow-up on a sporadic basis; however, echocardiography failed to identify the aneurysm. Our follow-up results show that 13 patients underwent repeat catheterization and in 12, repeat intervention was performed. However, it is interesting to see that most of the patients (8/13) required only redilatation of the stent that had already been placed. Thus, re-stenting was not commonly required up to 48 months from the initial procedure. In smaller patients, growth of the patient will certainly require that the stent be dilated further, but this is much less invasive than repeat surgery or even restenting. The application of this form of treatment demonstrates optimal results in adults and adolescents with severe coarctation, and often, no further re-expansion of the stent is needed. In neonates, infants and small children, progressive stent expansion as demanded by somatic growth will be required. Potential risks of redilatation after scar tissue has formed, as well as the fate of side branches and the management of transverse arch hypoplasia, are still unanswered questions and will require more trials and studies with further long-term results. In conclusion, our preliminary experience with dilatation of coarctation of the aorta and stent repair shows this treatment to be an alternative to surgery as the mainstay of treatment. In addition, the complications, while present, are low in gravity and occurrence. Large patients (> 25 kg) benefit from stenting, with subsequent redilatation corresponding to demand from somatic growth. While long-term results are still lacking, short-term and intermediate-term results are promising. Acknowledgment. The authors wish to thank Dr. Michael de Moor, from Massachusetts General Hospital, for providing follow-up and images on the patient with an aneurysm.

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