Occlusion of the Modified Blalock?Taussig Shunt: Unique Methods of Treatment and Review of Catheter-based Intervention

Catheter Intervention for Flow Regulatory Clips on Palliative Shunts and Conduits in Patients with Congenital Heart Disease

Catheter intervention (CI) for a Blalock-Taussig shunt (BTS) or a ventricle-to-pulmonary artery conduit (VPC) is often required after a palliative surgery for congenital heart disease. Flow regulatory clips help improve interstage mortality; their use necessitates CIs to prevent cyanosis. To study the CI outcomes in patients who underwent palliative surgery with either BTSs or VPCs with flow regulatory clips. This single-center retrospective study evaluated demographic characteristics and interventional outcomes of 49 consecutive pediatric patients who required CI for BTS (BTS group) or VPC (VPC group) between January 2008 and September 2018. Overall, 34 and 18 procedures were performed in the BTS and VPC groups, respectively. Moreover, 19/32 (59.3%) and 12/17 (70.1%) patients from the BTS and VPC groups had flow regulatory clips, respectively. All clips were unclipped successfully; one patient in each group underwent staged unclipping. A higher proportion of "clipped patients" underwent CI due to desaturation [clipped vs. non-clipped: BTS, 10/20 (50.0%) vs. 3/14 (21.4%), p = 0.092; VPC, 9/13 (69.2%) vs. 1/5 (20.0%), p = 0.060]. Most clipped patients successfully progressed to the next stage [BTS, 19/20 (95.0%); VPC, 12/13 (92.3%)]. Severe adverse events (SAEs) were more frequent in the VPC group than in the BTS group [3/13 (23.1%) vs. 0/20 (0%), p = 0.024]. Two patients developed an atrioventricular block (requiring an atropine infusion), while one died due to pulmonary overcirculation. While the indication of CI was cyanosis for a higher proportion of clipped patients, all clips were unclipped successfully. The incidence of CI-related SAEs was higher in the VPC group than in the BTS group.

Case Report: Catheter-based mechanical thrombectomy using the Indigo aspiration system in a case of systemic-to-pulmonary shunt thrombosis

A 53-day-old girl with absent right atrioventricular (AV) connection, malposed great vessels, and pulmonary atresia underwent placement of a central shunt on the sixth day of her life. Her postoperative course was complicated by progressive desaturation, and computed tomographic angiography (CTA) demonstrated near-complete occlusion of her left pulmonary artery (LPA). Angiography demonstrated a nonocclusive thrombus in the distal central shunt and a thrombus with complete occlusion of the LPA. The Indigo aspiration system (Penumbra) was used to remove the thrombus from the central shunt and LPA, allowing placement of a stent in the narrowed LPA. Subsequent angiography showed a wide patient central shunt and LPA. The Indigo aspiration system (Penumbra) provides a viable option for removing thrombus in a patients refractory to other methods.

Percutaneous stent implantation for occluded central shunts in adults: A case report and review of current evidence

Background

Patients with cyanotic complex congenital heart defects (CHDs) commonly undergo palliation with interposition of systemic-to-pulmonary shunts (SPSs). These palliative shunts are rarely found in adults with CHDs and can be complicated with progressive obstruction or total occlusion during follow-up. The best treatment option for shunt re-permeabilization is challenging and case-oriented because most patients are high risk candidates for redo surgeries. We aimed to review the current evidence on percutaneous stent implantation to treat failed SPSs.

Methods

We performed a comprehensive literature review on percutaneous stent implantation to treat failed and occluded SPSs. We also reported the case of a 33-year-old man with cyanotic CHD and a occluded central aorto-pulmonary shunt, who was successfully treated with percutaneous balloon dilatation and subsequently stent implantation at our institution.

Result

We identified and included 31 articles reporting on 150 patients and 165 stent implantations in failed SPSs. The age of patients at the time of stent implantation ranged from 6 days to 47 years. The time between the surgical shunt creation and transcatheter intervention ranged from 1 day to 17 years. Overall, 161/165 (97.5%) stent implantations were successful. The most common clinical presentation was cyanosis and decreased atrial oxygen saturations and the indication for stent implantation was shunt obstruction and stenosis.

Conclusion

This review highlights the benefits of endovascular stenting to permeabilize failed SPSs in children and adults with complex CHD who are classified as poor candidates for re-surgical repair.

Successful coil embolisation for an arterio-bronchial fistula in a child presenting catastrophic haemoptysis

We report the case of a 2-year-old girl who developed catastrophic haemoptysis due to an arterio-bronchial fistula after transcatheter balloon dilatation for a narrowing aortopulmonary shunt. We embolised the fistula while haemoptysis was controlled with the left bronchial block ventilation and haemostatic balloon occlusion of the left subclavian artery. An arterio-bronchial fistula is an extremely rare complication for balloon dilatation of an aortopulmonary shunt.

Catheter-induced acute Blalock-Taussig shunt thrombosis and bailout

Modified Blalock-Taussig shunt thrombosis is a life-threatening event. We describe an extremely rare catheter-induced shunt thrombosis in an infant with complex CHD and its successful treatment utilising a single low dose of local recombinant tissue plasminogen activator in conjunction with balloon angioplasty.

Post-operative Catheterization Interventions at the Site of Surgery: An Application of the CRISP Scoring System

Catheter-based interventions in the early post-operative period are performed with caution due to concerns for increased procedural risk, particularly across fresh suture lines. The recently published CRISP scoring system provides prospective risk stratification based on pre-procedural criterion. In an effort to refine the assessment of risk in patients undergoing post-operative catheter-based interventions, the predicted risk of an adverse event based on CRISP scores was compared to actual adverse event rates. A single-center, retrospective review of patients undergoing catheterization interventions within 6 weeks of cardiac surgery was conducted between Jan 2004 and Dec 2014. Patients who underwent dilation interventions across fresh suture lines (group 1) were compared to patients who underwent interventional procedures at other sites (group 2), and a CRISP score was calculated for all patients. Patients receiving only surveillance biopsies were excluded. Sixty-eight patients underwent 100 interventional procedures. Group 1 was composed of 44 patients receiving 64 interventions, while group 2 had 24 patients who underwent 36 interventions. Group 1 was comprised significantly more single ventricles and patients were smaller/younger. Group 1 had a significantly higher median CRISP score, but both groups were within Category 4. The rates of adverse events were similar between groups and comparable to predicted rates with the CRISP scoring system. Catheter-based interventions in the early post-operative period can be performed with no significant increase in the risk of serious adverse events when intervening across fresh suture lines. The CRISP scoring system can be a valuable tool in pre-procedural counseling of high-risk post-operative patients.

Percutaneous intervention for central shunts: new routes, new strategies

Introduction In traditional locations, the standard Blalock-Taussig shunt presents numerous technical difficulties for percutaneous intervention. We changed our strategy to a central type shunt (Laks-type) with end-to-side pulmonary and side-to-side aortic anastomosis. The aim of this study was to determine whether this modified strategy would allow easier percutaneous manipulation in patients with small pulmonary arteries. Methods All children with a stretchable central vascular graft who required any form of percutaneous intervention were prospectively enrolled in the study. Results Eleven infants were evaluated a median time of 3 months (range 0.9-4.4) following initial shunt placement; the median weight at intervention was 5.7 kg (range: 4.0 - 10.0). All shunts (100%) were easily and swiftly entered without the need for special catheters or co-axial systems. In four patients other interventions in distal pulmonary arteries were first performed: cutting balloon treatment in three and balloon angioplasty of peripheral pulmonary artery stenosis in one. The shunts were then augmented with a stent with a diameter increasing from 3.5 ± 0.4 mm to 4.7 ± 0.8 mm and saturation increasing from 76% (range: 69-88) to 84% (range: 77-88) (P < 0.05). Several months later, two children required further interventions that could easily be performed via the stented shunts. No complications were observed. Conclusions The Laks-type shunt provides easy access for percutaneous procedures of the distal pulmonary arteries including cutting balloons; this shunt can predictably be expanded to augment pulmonary flow. This study highlights how co-operation between the interventionalist and the surgeon can improve strategies to manage these difficult patients.

Systemic thrombolysis with recombinant tissue plasminogen activator for acute life-threatening Blalock-Taussig shunt obstruction

Modified Blalock-Taussig shunt (mBTS) obstruction can be life-threatening, especially when it represents the only source of pulmonary blood flow. Current therapeutic options to reverse obstruction include surgical shunt revision/replacement, interventional endovascular procedures including balloon angioplasty and/or stent placement, and a combination of local and systemic thrombolytic therapy. We report two cases of acute mBTS thrombosis successfully treated with systemic recombinant tissue plasminogen activator in infants convalescing after cardiac surgery when the clinical status and resources precluded traditionally described rescue therapies.

Bleeding and Thrombosis in Pediatric Cardiac Intensive Care

OBJECTIVES

The objective of this article is to review the particular tendencies as well as specific concerns of bleeding and clotting in children with critical cardiac disease.

DATA SOURCE

MEDLINE and PubMed.

CONCLUSION

Children with critical heart disease are at particular risk for bleeding and clotting secondary to intrinsic as well as extrinsic factors. We hope that this review will aid the clinician in managing the unique challenges of bleeding and clotting in this patient population, and serve as a springboard for much needed research in this area.

Catheter-based interventions for modified Blalock-Taussig shunt obstruction: a 20-year experience

Thrombotic occlusion of a modified Blalock-Taussig (BT) shunt is rare, leading to life-threatening hypoxemia. Rescue percutaneous interventions may allow recanalization of the systemic-to-pulmonary shunt but data on large patients' scales are lacking. We aimed to describe safety and effectiveness of catheter-based interventions to restore modified BT shunt patency. All patients who attempted transcatheter intervention for thrombotic occlusion of a modified BT shunt at our Institution from 1994 to 2014 were reviewed. Characteristics, management, and outcomes of the 28 identified patients were analyzed. Thirty-three procedures were performed at a median age of 0.6 years old (range 0.03-32.1 years) and a median weight of 5.8 kg (range 2.2-82 kg). Percutaneous intervention consisted in 33 balloon angioplasty (100 %) and 14 stent implantations (42.4 %). Thrombolytic agents were also used in 6.1 % cases. No peri-procedural death occurred but complications were observed in five patients (15.2 %), including one catheter-induced transient complete atrioventricular block, one cardiac tamponade, and one massive thrombo-embolic stroke. Early procedural success was obtained in 28 patients (84.8 %) and remained long-lasting in 26 patients (78.8 %). A young age and a low body-weight at the time of the procedure were significantly associated with procedural failure (p = 0.0364 and p = 0.0247, respectively). Although technically challenging and carrying potential major complications, transcatheter intervention can be considered as an efficient rescue strategy to restore patency in case of thrombotic obstruction of a modified BT shunt.

Stenting for curved lesions using a novel curved balloon: Preliminary experimental study

BACKGROUND

Stenting may be a compelling approach to dilating curved lesions in congenital heart diseases. However, balloon-expandable stents, which are commonly used for congenital heart diseases, are usually deployed in a straight orientation. In this study, we evaluated the effect of stenting with a novel curved balloon considered to provide better conformability to the curved-angled lesion.

MATERIALS AND METHODS

In vitro experiments: A Palmaz Genesis(®) stent (Johnson & Johnson, Cordis Co, Bridgewater, NJ, USA) mounted on the Goku(®) curve (Tokai Medical Co. Nagoya, Japan) was dilated in vitro to observe directly the behavior of the stent and balloon assembly during expansion. Animal experiment: A short Express(®) Vascular SD (Boston Scientific Co, Marlborough, MA, USA) stent and a long Express(®) Vascular LD stent (Boston Scientific) mounted on the curved balloon were deployed in the curved vessel of a pig to observe the effect of stenting in vivo.

RESULTS

In vitro experiments: Although the stent was dilated in a curved fashion, stent and balloon assembly also rotated conjointly during expansion of its curved portion.

ANIMAL EXPERIMENT

In the primary stenting of the short stent, the stent was dilated with rotation of the curved portion. The excised stent conformed to the curved vessel. As the long stent could not be negotiated across the mid-portion with the balloon in expansion when it started curving, the mid-portion of the stent failed to expand fully. Furthermore, the balloon, which became entangled with the stent strut, could not be retrieved even after complete deflation.

CONCLUSION

This novel curved balloon catheter might be used for implantation of the short stent in a curved lesion; however, it should not be used for primary stenting of the long stent. Post-dilation to conform the stent to the angled vessel would be safer than primary stenting irrespective of stent length.

Initial use of endothelial progenitor cells capturing stents in paediatric congenital heart disease

INTRODUCTION

Stenosis, mediated by neointimal hyperplasia and thrombosis, is a major limiting factor in successful stent implantation. The introduction of a stent, coated in its endoluminal surface by antihuman CD34 antibodies with endothelial progenitor cell-capturing properties, opens the possibility of promoting a rapid and normal functioning coverage by endothelium and thus avoids both an excessive cell proliferation within stent and the need for long-term dual antiplatelet therapy. These stents, developed for adult coronary artery disease, have not yet been implanted in children or in those with congenital heart disease.

OBJECTIVE AND METHODS

In this paper, we describe the implantation of Genous® stents in three children with cyanotic congenital heart disease and obstructed systemic-to-pulmonary shunts. We describe the use of this stent and address its potential feasibility in paediatric congenital heart disease.

RESULTS

To maintain the patency of two modified Blalock-Taussig shunts and one ductus arteriosus, four Genous® stents were implanted in three infants with cyanotic heart disease. All procedures were immediately successful, with resolution of stenosis and improvement in transcutaneous oxygen saturation from 66% ± 3.6% to 92% ± 2.6%. In the follow-up, one stent had no occlusion; however, the remaining two had partial occlusion after 5 and 5.5 months, which were successfully managed with balloon dilatation preceding elective definitive surgical correction.

CONCLUSION

In our preliminary experience, we demonstrated that Genous® stent implantation was feasible in infants with complex congenital heart disease. Additional studies with larger samples and longer follow-up are required to confirm the potential benefits of this technology in this clinical setting.

Novel curved balloon catheter for dilating postoperative angled lesions associated with congenital heart disease

OBJECTIVES

This study aimed to analyze the surface stress generated by a novel curved balloon and assess its efficacy for treating angular lesions associated with congenital heart disease.

BACKGROUND

Obstructions at the anastomosis of aortopulmonary shunts and cavopulmonary connections may occur postoperatively. Catheter interventions are often performed for such lesions; however, acute angulation may cause balloon slippage or inappropriate stress on the vessel wall.

METHODS

We dilated the curved balloon in a curved vessel model and measured the resultant wall stress and its distribution. Clinical evaluations were performed using this balloon in angled lesions.

RESULTS

In the curved vessel model, curved balloons generated uniform stress on the lesser and greater curvatures (curved type, lesser/greater = 0.343 MPa/0.327 MPa; P = 0.61), whereas straight balloons caused disproportionate stress (straight type, lesser/greater = 0.358 MPa/0.254 MPa; P = 0.19). However, the difference in average stress was not statistically significant. Furthermore, the stress was uniform along the entire length of the curved balloon, but differed between the mid and end portions of the straight balloon. Curved balloon dilations were performed for 10 lesions in 7 patients. The curved balloon conformed well to the angulated lesion without slipping. The median percent change in the minimal lumen diameter (MLD) was 64% (range, 0-206%). In 5 lesions, MLD increased by ≥50%. Oxygen saturation increased by 5% (0-9%).

CONCLUSIONS

Although further clinical evaluation is necessary, this novel curved balloon may be a reasonable alternative in angled lesions, providing better conformability and preventing excessive stress to the vessel wall adjacent to the stenosis.

Prevention of arteriovenous shunt occlusion using microbubble and ultrasound mediated thromboprophylaxis

Background

Palliative shunts in congenital heart disease patients are vulnerable to thrombotic occlusion. High mechanical index (MI) impulses from a modified diagnostic ultrasound (US) transducer during a systemic microbubble (MB) infusion have been used to dissolve intravascular thrombi without anticoagulation, and we sought to determine whether this technique could be used prophylactically to reduce thrombus burden and prevent occlusion of surgically placed extracardiac shunts.

Methods and Results

Heparin‐bonded ePTFE tubular vascular shunts of 4 mm×2.5 cm (Propaten; W.L Gore) were surgically placed in 18 pigs: a right‐sided side‐to‐side arteriovenous (AV, carotid‐jugular) shunt, and a left‐sided arterio‐arterial (AA, carotid‐carotid) interposition shunt in each animal. After shunt implantation, animals were randomly assigned to one of 3 groups. Transcutaneous, weekly 30‐minute treatments (total of 4 treatments) of either guided high MI US+MB (Group 1; n=6) using a 3% MRX‐801 MB infusion, or US alone (Group 2; n=6) were given separately to each shunt. The third group of 6 pigs received no treatments. The shunts were explanted after 4 weeks and analyzed by histopathology to quantify luminal thrombus area (mm²) for the length of each shunt. No pigs received antiplatelet agents or anticoagulants during the treatment period. The median overall thrombus burden in the 3 groups for AV shunts was 5.10 mm² compared with 4.05 mm² in AA (P=0.199). Group 1 pigs had significantly less thrombus burden in the AV shunts (median 2.5 mm²) compared with Group 2 (median 5.6 mm²) and Group 3 (median 7.5 mm²) pigs (P=0.006). No difference in thrombus burden was seen between groups for AA shunts.

Conclusion

Transcutaneous US with intravenous MB is capable of preventing thrombus accumulation in arteriovenous shunts without the need for antiplatelet agents, and may be a method of preventing progressive occlusion of palliative shunts.

Complete Blalock-Taussig shunt obstruction in < 24 hours post-operative period in a neonate treated emergently using transcatheter angioplasty and low dose local recombinant TPA

A 12-day-old infant with pulmonary atresia, intact ventricular septum, and pulmonary blood flow through a ductus arteriosus developed complete shunt obstruction within 12 hr of creation of a modified Blalock-Taussig shunt. Low dose recombinant tissue plasminogen activator was administered locally as two 0.03 mg/kg bolus injections and was followed by balloon angioplasty. This resulted in complete recanalization of the shunt without any hemorrhagic complications.

Hypoplastic left heart syndrome: current considerations and expectations

In the recent era, no congenital heart defect has undergone a more dramatic change in diagnostic approach, management, and outcomes than hypoplastic left heart syndrome (HLHS). During this time, survival to the age of 5 years (including Fontan) has ranged from 50% to 69%, but current expectations are that 70% of newborns born today with HLHS may reach adulthood. Although the 3-stage treatment approach to HLHS is now well founded, there is significant variation among centers. In this white paper, we present the current state of the art in our understanding and treatment of HLHS during the stages of care: 1) pre-Stage I: fetal and neonatal assessment and management; 2) Stage I: perioperative care, interstage monitoring, and management strategies; 3) Stage II: surgeries; 4) Stage III: Fontan surgery; and 5) long-term follow-up. Issues surrounding the genetics of HLHS, developmental outcomes, and quality of life are addressed in addition to the many other considerations for caring for this group of complex patients.

Techniques for transcatheter recanalization of completely occluded vessels and pathways in patients with congenital heart disease

Occlusions of major vessels in patients with congenital heart disease may occur due to a variety of factors. These occlusions are often felt to be best addressed surgically; however, we and others have been successful in recanalizing most of these vessels in the catheterization laboratory. Most of these patients will require multiple procedures in the catheterization laboratory to ensure vessel patency and to facilitate vessel growth. Physicians performing the procedure should have a thorough understanding of the anatomic considerations for the intended procedure and have access to a variety of devices and equipment to optimize the result of the procedure. In this article, we review some of the technical aspects that are vital for the success of the procedure.

Stent expansion of stretch Gore-Tex grafts in children with congenital heart lesions

OBJECTIVE

To evaluate the efficacy and safety of expanding vascular shunt grafts beyond original nominal diameter using stents.

METHODS

Bench testing confirmed the expandability of 3.5 mm and 4.0 mm vascular Gore-Tex stretch grafts. A retrospective analysis included eleven systemic to pulmonary artery shunts with diminished flow which were stented with the aim of increasing the original nominal diameter of the shunts.

RESULTS

During bench testing, the grafts could be expanded to 4.5 mm and 5.8 mm, respectively. Fourteen stents were implanted in 11 stretch grafts a median of 18.9 months (3.2; 21.6 months) after shunt surgery. There was a median increase in diameter of 1.4 mm (0.9; 1.7 mm) [P = 0.001, 95% CI: 0.47; 1.7) from original nominal to final stented diameter of the shunts with a median gain of 28%. A simultaneous improvement in saturations from a median of 73% (66; 77%) to 87% (84; 89%) [P = 0.015; 95% CI: 3; 22] was observed. No complications were experienced during the procedures.

CONCLUSION

In our limited experience, stretch Gore-Tex vascular grafts can be safely expanded beyond nominal diameters using high pressure vascular stents. This leads to improvement in saturation and pulmonary blood flow. It allows the clinician to tailor pulmonary flow in relation to pulmonary artery size and growth, ensuring best possible timing for the next surgical procedure.

Acute and late obstruction of a modified Blalock-Taussig shunt: a two-center experience in different catheter-based methods of treatment

Modified Blalock-Taussig (B-T) shunt occlusion results in a sudden reduction of pulmonary vascular perfusion, causing dramatic saturation drop and cyanosis which pose a direct hazard to a child's life. The results of percutaneous local r-tpa infusion, balloon angioplasty and additionally stent implantation in obstructed modified B-T shunts were studied to assess their role as an alternative to a re-do surgery. We outline two pediatric centers' experience (period 2004-2008) regarding the effectiveness of various emergency treatment methods for occlusion or critical stenosis of systemic-to-pulmonary arterial shunts in 23 children. Local r-tpa infusion via catheter was performed in 12/23 patients, balloon angioplasty in 22/23 and additionally stent implantation in 3/23 children. Procedures were successful in 22/23 patients (96%), with an increase in arterial saturation [average: 30%; standard deviation (S.D.) 15%; Shapiro-Wilk test; dependent t-test-P<0.01]. Unrestricted contrast flow was achieved in 18 patients, reduced central flow in three and minimal flow in one child. Neither local nor systemic complications occurred. Our experience demonstrates the possibility of successful early shunt recanalization with the use of local thrombolytic therapy combined with the balloon angioplasty. The presence of old fixed thrombus with neointimal hypertrophy in the shunt constitutes an indication for endovascular stent implantation.