Transcatheter Retrieval and Repositioning of Embolized Stent from the Right Ventricle in an Infant

Abstract

Intracardiac stent embolization is a challenging complication in a small infant. A Palmaz stent was placed across the atrial septum in a 3-month-old boy to relieve symptoms of right-side heart failure. On routine chest radiography one week later, the stent was found to have embolized into the right ventricle. The stent was retrieved and repositioned by means of transcatheter technique, without subsequent complications. We found this method to be a viable alternative to surgery in a high-risk infant. To our knowledge, this is the first report of the successful transcatheter retrieval and repositioning of an expandable intravascular stent from an intraventricular position in an infant.

Stent placement is widely used to relieve hemodynamically significant stenosis in children and adults.¹ Several transcatheter techniques have been described for atrial septal stent implantation in patients with complex congenital heart disease.^2,3 Stent embolization is one of the challenging complications. A few case reports have documented the successful transcatheter retrieval of embolized stents from the pulmonary arteries (PAs) of adults,^4–7 and one stent was similarly retrieved from the right ventricle (RV) of a 9-year-old girl.⁸ We describe the retrieval and repositioning of an embolized stent from the RV of an infant.

Case Report

A 3-month-old, 5.8-kg boy was born in 2010 with a perimembranous ventricular septal defect, an atrial septal defect, patent ductus arteriosus, and left main stem bronchus compression caused by a deviated aortic root in relation to the ascending aorta. At one month of age, he underwent surgical closure of the cardiac lesions, bilateral PA patch angioplasty, and reimplantation of the right PA to the main PA by means of the Lecompte maneuver. Postoperatively, it was difficult to provide sufficient ventilation because of severe bronchomalacia that required tracheostomy. During the next month, cardiac catheterization disclosed systemic RV pressures with right-PA stenosis. The stenosis was treated with stent placement; however, the patient's systemic RV pressures did not improve. Computed tomography showed the left main stem bronchus to be trapped between the ascending and descending aorta, and bronchoscopy confirmed its total obstruction. Posterior left aortopexy was performed through a left thoracotomy. However, the patient's respiratory difficulties persisted, and he could not be weaned from ventilation. He displayed clinical signs and symptoms of right-side heart failure. An echocardiogram showed persistent suprasystemic RV pressures. Repeat cardiac catheterization was performed to attempt PA angioplasty, if indicated, and atrial decompression was performed for systemic RV pressures with stent placement. Hemodynamic evaluation revealed a substantially elevated mean right atrial pressure of 19 mmHg. The RV pressure was systemic; there was a gradient of 22 mmHg across the main PA, and mild left-PA stenosis. There was no evidence of restenosis in the previously placed right-PA stent.

We performed atrial septal stent placement to decompress the right side of the heart. Atrial septostomy was performed with use of a radiofrequency transseptal system. Under transthoracic echocardiographic guidance and using a 7F Mullins sheath, we deployed a Palmaz-Genesis XD™ 1910 stent (Cordis Corporation, a Johnson & Johnson company; Miami Lakes, Fla) across the atrial septum, over a 6-mm × 2-cm ATB® Advance® PTA Dilatation Catheter (Cook Medical, Inc.; Bloomington, Ind). However, after stent deployment, the balloon could not be withdrawn to the sheath, because part of the balloon was stuck to the distal stent: the asymmetric folding of the balloon might have displaced the stent slightly toward the right atrium. After careful partial repeat dilation while simultaneously advancing the sheath, we were able to withdraw the balloon into the sheath. The stent was thought to be in a reasonably stable position, as seen on chest radiography and echocardiography (Figs. 1A and 2A). There was no change in the patient's RV pressure or systemic saturation after atrial septal stent placement; however, he experienced substantial improvement in edema, hepatomegaly, and ventilation in the next 48 hours. One week later, routine chest radiography showed stent migration (Fig. 1B). Echocardiography confirmed stent embolization in the RV without evidence of thrombus formation (Fig. 2B). The patient remained hemodynamically stable without ventricular or atrial arrhythmias.

Fig. 1 Chest radiographs show A) the initial position of the stent in the atrial septum (arrow) and a stent in the right pulmonary artery (arrowhead). B) Anteroposterior view shows stent migration into the right ventricle (arrow), characterized by inferior displacement and altered orientation.

Fig. 2 Echocardiograms (4-chamber views) show the stent A) positioned in the atrial septum (arrow) before stent embolization and B) embolized in the right ventricle (arrow). Moderate tricuspid regurgitation is also apparent.

Our initial thought was to retrieve the stent surgically. However, in view of the patient's relatively stable condition, extensive surgical history, significant airway impediments, and pulmonary hypertension, we decided to attempt transcatheter stent retrieval and repositioning. Using a 7F sheath in the right femoral vein, we maneuvered a 6F Berman wedge catheter across the tricuspid valve (TV) into the RV, with the balloon inflated. We successfully advanced a 0.021-in Hi-Torque Flex-T™ guidewire (Tyco Healthcare; Gosport, UK)into the stent, ensuring a stent orientation parallel to the long axis of the RV. We then advanced a 6-mm × 2-cm Tyshak® II balloon catheter (B. Braun Medical Inc.; Bethlehem, Pa) over the wire and inflated the balloon gently to 2 atm of pressure, in order to latch onto the stent adequately. We were careful not to increase the stent size, because we anticipated difficulty in withdrawing the stent balloon unit across the TV to the relatively small-caliber inferior vena cava (IVC). We cautiously withdrew the stent-balloon catheter unit into the right atrium and farther back into the IVC below the hepatic veins, without any resistance across the TV (Fig. 3A). A final IVC angiogram showed stable positioning of the stent and no overlap with the hepatic or renal veins (Fig. 3B). There was no evidence of vessel injury. Echocardiography showed no change in the degree of tricuspid regurgitation and no pericardial effusion.

Fig. 3 A) Chest fluoroscopy (lateral view) shows retrieval of the embolized stent from the right ventricle into the junction of the right atrium and inferior vena cava. B) Angiogram shows the stent reimplanted in the suprarenal inferior vena cava and no overlap with the hepatic and renal veins.

The patient's hospital course was complicated by frequent airway problems that required prolonged mechanical ventilation. He died at 11 months of age because of chronic lung disease and ventilator-related pneumonia.

Discussion

To our knowledge, this is the first report of the successful retrieval and repositioning of an expandable intravascular stent in an infant from an intraventricular position by means of the transcatheter technique and without complications. Atrial septal stent placement to relieve atrial hypertension or to achieve adequate atrial mixing in patients who have a single-ventricle physiology has yielded better systemic cardiac output and saturation in infants beyond the neonatal period.^9,10 Accurate sizing of stents is not essential in these patients, because the goal is to create unrestrictive communication. In contrast, patients with severe pulmonary hypertension require the creation of an ideal atrial septal opening for adequate cardiac output and the decompression of right-side pressures. Too large an opening can increase the risk of death due to severe hypoxemia from excessive right-to-left shunting.² Therefore, atrial stenting could be preferable to conventional balloon septostomy and balloon dilation, because the conventional procedures can cause imprecise and variable atrial communication. Using standard techniques, we deployed the stent in an ideal and stable position. However, an asymmetric balloon fold prevented balloon withdrawal into the sheath and caused slight displacement of the stent toward the right atrium. Recto and colleagues¹¹ described a transcatheter technique to prevent stent displacement: partially re-inflating the dilation balloon within the stent and carefully advancing the sheath over the balloon as the balloon is slowly deflated and withdrawn into the sheath. We used a similar technique to withdraw the balloon without causing further displacement of the stent.

Although stent embolization is a major sequela of intravascular stent implantation, it has not been reported in association with atrial septal stent placement. Transcatheter techniques have been used to retrieve expanded endovascular stents from the RV and other vascular structures in adults and an older child.^4–8 Transcatheter techniques to remove an embolized Palmaz stent from the PA have been described in adults.⁵ Two venous stents that had embolized into the PA were withdrawn with use of a large sheath, snared, and removed.⁶ Entirely retrieving a stent from our small infant patient was not thought to be feasible without surgery. Hoyer and colleagues⁸ reported the case of a 9-year-old, 21-kg girl in whom an embolized Palmaz stent was successfully retrieved from the RV and repositioned in the IVC by means of a transcatheter technique. Our technique was similar, with minor modifications in retrieving the stent. Although our patient sustained no secondary injury associated with stent retrieval, the technique must be performed cautiously to avoid injuring the vessel walls and cardiac structures—especially the TV—with the free edges of the stent. The balloon catheter should be advanced through the stent over the guidewire, through the center of the TV and not through the valvular chordae. The stent should then be maneuvered to remain parallel to the long axis of the RV. The balloon should be slightly longer and larger in diameter than the stent, to be well engaged and have a “dog-bone” effect on either side of the stent: this is for safer withdrawal and also to protect the TV from being damaged by the stent struts.⁶ In contrast with techniques reported earlier, we underinflated the balloon in our patient to avoid further dilation of the stent, and the balloon's length was almost the same length as the stent because of the infant's small size and his relatively smaller IVC and RV.

Our encouraging experience with this infant, along with the earlier reports of successful stent retrieval in an older child and in adults, belies the fear of inherent catastrophic consequences from overzealous catheterization attempts at stent retrieval in an infant or small child. Nonetheless, we advise caution in considering transcatheter stent retrieval from the RV as a primary option in all infants and young children. If persistent technical difficulty is encountered when engaging the stent with the balloon catheter, or if any resistance is felt while withdrawing the balloon stent unit across the TV, surgery could be a more prudent method of stent retrieval in an infant. This choice entails less risk of substantial injury to adjacent cardiac structures, specifically the TV and the atrioventricular node.

Our case highlights the importance of using proper technique in deploying atrial septal stents. For inadvertent stent embolization into intraventricular chambers, we have described a feasible transcatheter technique that enabled us to retrieve and redeploy the stent from the RV to the IVC in an infant without causing secondary injury. This method provides a suitable option for interventional cardiologists before surgical retrieval is attempted in these high-risk patients.