Percutaneous Hydrogel Coil Embolization of Aneurysms and Coronary Artery Fistulae in Congenital Heart Disease

Impact of Specialized Electrophysiological Care on the Outcome of Catheter Ablation for Supraventricular Tachycardias in Adults with Congenital Heart Disease: Independent Risk Factors and Gender Aspects. Fischer AJ et al.

Heart Rhythm. 2021; 18:1852-1859.

Percutaneous Hydrogel Coil Embolization of Aneurysms and Coronary Artery Fistulae in Congenital Heart Disease.

Healan SJ, Nicholson G, Doyle T, Janssen D.Tex Heart Inst J. 2021 Jul 1;48(3):e207312. doi: 10.14503/THIJ-20-7312.PMID: 34347100.


Take Home Points:

  • Coils are commonly used for percutaneous embolization of vascular lesions (collaterals, fistulas) in patients with congenital heart disease.
  • Hydrogel based coils (Azur CX coils and Azur hydrogel coils, Terumo medical) have the advantage of a less reliant on clot formation due to the expanding hydrogel.
  • Azur hydrogel coils have a controlled electronic release mechanism designed to improve the precision of coil positioning, thus increasing procedural accuracy.
  • Although promising, long term prospective data is needed in congenital heart disease patients.

Commentary from Dr. Varun Aggarwal (Minneapolis, MN, USA), editor-in-chief and section editor of Congenital Heart Disease Interventions Journal Watch:

Patients with congenital heart disease often have collateral vessels, fistulas, aneurysms, pseudoaneurysms etc. that necessitate use of vascular occlusion devices like vascular occlusion coils and plugs. Use of bare metal (Ruby coil, Penumbra) or fibered coils (eg. MReye® Embolization Coil, Cook Medical; Concerto Versa™ detachable coil, Medtronic) is common in congenital catheterization laboratory. Historically these coils have served well. One of the drawbacks of these coils is the dependence on clot formation besides mechanical occlusion. Compaction of these coil over time has also been reported. Hydrogel based coils have been more commonly used in neurological and peripheral interventional laboratories and have been demonstrated to have an advantage over bare metal or fibered coils with higher packing density (1), lower rate of recurrence of intracranial aneurysms (2), lower rate of recanalization (3) without any increased risk of procedural complications (1).


Healan SJ et al (4) in this case series describe the use of hydrogel-based coils (Azur CX and Azur hydro coils, Terumo medical) in 5 patients with congenital heart disease. Azur CX coil is filled with hydrogel forming a solid core and the Azur hydrogel coil a hydrogel coating, which increases the effective diameter of the coil after expansion, providing a higher packing density and thereby making it suitable for packing aneurysms. They have the advantage of reduced incidence of coil compaction and recanalization over time. The authors describe the use of these coils in a multitude of lesions such as aortic pseudoaneurysm, pulmonary arterial pseudoaneurysm, coronary artery fistula (in 3 patients). All patients underwent successful closure of the intended lesion without any complications. Azur hydrogel coils also contain an electronic release mechanism that improves coil positioning precision, resulting in higher procedural accuracy and lower complication rates.


In our experience, these coils especially the Azur hydrocoils may be a little stiffer as compared to the bare platinum or fibered coils. This can make these coils more technically challenging especially when using for the first few times. Also, the Azur hydrocoils swell up after coming in contact with blood and therefore provide a 3-5 minute window to either deploy the coil or retract back in the catheter. Despite these technical limitations, these coils have benefit at lower recanalization, higher packing density and lower rate of recurrence. Future longitudinal studies are warranted to compare the outcomes in congenital heart disease patients.



Example of a bare platinum coil in Figure A showing residual flow of contrast (marked by red circle) despite densely packed coil mass in the proximal vessel in a child with aortopulmonary collateral vessels. Figure B demonstrates no residual flow through an aortopulmonary collateral vessel in a patient with Fontan circulation post embolization using Azur hydrogel coil.


1. Taschner CA, Chapot R, Costalat V, Machi P, Courtheoux P, Barreau X, et al. GREAT-a randomized controlled trial comparing HydroSoft/HydroFrame and bare platinum coils for endovascular aneurysm treatment: procedural safety and core-lab-assessedangiographic results. Neuroradiology. 2016;58(8):777-86.

2. Xue T, Chen Z, Lin W, Xu J, Shen X, Wang Z. Hydrogel coils versus bare platinum coils for the endovascular treatment of intracranial aneurysms: a meta-analysis of randomized controlled trials. BMC Neurol. 2018;18(1):167.

3. Fohlen A, Namur J, Ghegediban H, Laurent A, Wassef M, Pelage JP. Midterm Recanalization after Arterial Embolization Using Hydrogel-Coated Coils versus Fibered Coils in an Animal Model. J Vasc Interv Radiol. 2019;30(6):940-8.

4. Healan SJ, Nicholson G, Doyle T, Janssen D. Percutaneous Hydrogel Coil Embolization of Aneurysms and Coronary Artery Fistulae in Congenital Heart Disease. Tex Heart Inst J. 2021;48(3).