Retained microcatheter after onyx embolization of intracranial arteriovenous malformation

Bailouts During Neurointervention; Novel Techniques in Tackling Coil Migration and Premature Intravascular Detachment of Microcatheter Tip

BACKGROUND

Intracranial vascular malformations are increasingly being treated via the endovascular route. Though generally safe, a multitude of intraprocedural complications that potentially lead to disastrous clinical outcomes may arise. It is crucial for the operators to be well versed with the various techniques that are available to overcome any procedure-specific complications.

METHODS

We present 2 cases in which we encountered premature intravascular detachment of the microcatheter tip and coil migration while treating a dural arteriovenous fistula and aneurysm, respectively. We used a stentriever to remove the detached microcatheter tip and suction using the reperfusion catheter to remove the migrated coil, both techniques that have not been reported in the literature thus far.

RESULTS

Detached microcatheter tip and migrated coil were successfully retrieved using a stentriever and aspiration catheter.

CONCLUSIONS

These novel techniques could potentially reduce mortality and morbidity associated with neurointervention.

Delayed Fragmentation and Distal Embolization of Retained Microcatheter Causing Lower Limb Ischemia: Case Report and Review of the Literature

BACKGROUND

Endovascular microcatheter adherence and retention is an uncommon complication during brain arteriovenous malformation (AVM) embolization with glue or ethylene-vinyl alcohol copolymer that has previously reported, although there are sparse reports of symptomatic complications thereafter.

CASE DESCRIPTION

We present a unique complication 6 years after initial embolization of a cerebral AVM. The patient presented with acute lower limb insufficiency with computed tomography angiogram revealing fragmentation of the microcatheter and associated popliteal aneurysm. The patient underwent an emergency grafting and removal of the retained fragment and recovered without deficit postoperatively.

CONCLUSIONS

Fragmentation over retained microcatheters remains a concern that may be worth monitoring in the long term, although there are no recommendations for timing.

Offline impedance measurements for detection and mitigation of dangerous implant interactions: an RF safety prescreen

PURPOSE

The concept of a "radiofrequency safety prescreen" is investigated, wherein dangerous interactions between radiofrequency fields used in MRI, and conductive implants in patients are detected through impedance changes in the radiofrequency coil.

THEORY

The behavior of coupled oscillators is reviewed, and the resulting, observable impedance changes are discussed.

METHODS

A birdcage coil is loaded with a static head phantom and a wire phantom with a wire close to its resonant length, the shape, position, and orientation of which can be changed. Interactions are probed with a current sensor and network analyzer.

RESULTS

Impedance spectra show dramatic, unmistakable splitting in cases of strong coupling, and strong correlation is observed between induced current and scattering parameters.

CONCLUSIONS

The feasibility of a new, low-power prescreening technique has been demonstrated in a simple phantom experiment, which can unambiguously detect resonant interactions between an implanted wire and an imaging coil. A new technique has also been presented which can detect parallel transmit null modes for the wire.

Entrapment of a micro-guidewire during stenting of basilar stenosis

Entrapment of a microwire related to intracranial endovascular therapy is an uncommon complication. A 64-year-old man with symptomatic basilar artery stenosis was treated with stenting. A 300 cm Synchro microwire became trapped in the P1 segment of the left posterior cerebral artery during the procedure. The decision was made to leave the microwire in place, considering that aggressive retrieval procedures could cause injury to the cerebral vasculature. The entrapped microwire was later inadvertently dislocated and removed while pulling the microwire back into the femoral artery with a looped catheter from the left femoral access. This demonstrates that, although entrapment of a microwire during endovascular therapy is a rare event, an optimal salvage technique needs to be explored further.

Entrapment of a micro-guidewire during stenting of basilar stenosis

Entrapment of a microwire related to intracranial endovascular therapy is an uncommon complication. A 64-year-old man with symptomatic basilar artery stenosis was treated with stenting. A 300 cm Synchro microwire became trapped in the P1 segment of the left posterior cerebral artery during the procedure. The decision was made to leave the microwire in place, considering that aggressive retrieval procedures could cause injury to the cerebral vasculature. The entrapped microwire was later inadvertently dislocated and removed while pulling the microwire back into the femoral artery with a looped catheter from the left femoral access. This demonstrates that, although entrapment of a microwire during endovascular therapy is a rare event, an optimal salvage technique needs to be explored further.

Safety of retained microcatheters: an evaluation of radiofrequency heating in endovascular microcatheters with nitinol, tungsten, and polyetheretherketone braiding at 1.5 T and 3 T

BACKGROUND

The use of ethylene-vinyl alcohol copolymer for liquid embolization of cranial vascular lesions has resulted in microcatheter fragments entrapped in patients following endovascular procedures. Undergoing subsequent diagnostic MRI examinations poses a safety concern due to the possibility of radiofrequency heating of the metallic braid incorporated into the microcatheter. Heating of nitinol, tungsten, and polyetheretherketone (PEEK) braided microcatheters was assessed and compared using a phantom model.

METHODS

Microcatheters coupled with fluoroptic temperature probes were embedded in a polyacrylamide gel within a head and torso phantom. Experiments were performed at 1.5 T and 3 T, analyzing the effects of different catheter immersion lengths, specific absorption rate (SAR) levels, short clinical scans, long clinical scans, and microcatheter fragment lengths.

RESULTS

The maximal increase in temperature for the nitinol braided microcatheter during a 15 min scan was 3.06°C using the T1 fast spin echo sequence at 1.5 T and 0.45°C using the balanced steady state free precession sequence at 3 T. The same scans for fragment lengths of 9, 18, 36, and 72 cm produced maximal temperature rises of 0.68, 0.80, 1.70, and 1.07°C at 1.5 T, respectively. The temperature changes at 3 T for these fragment lengths were 0.66, 0.83, 1.07, and 0.72°C, respectively. The tungsten and PEEK braided microcatheters did not demonstrate heating.

CONCLUSIONS

Substantial heating of nitinol braided microcatheters occurred and was a function of SAR level and geometric considerations. SAR and time limitations on MR scanning are proposed for patients with this microcatheter entrapped in their vasculature. In contrast, tungsten and PEEK braided microcatheters showed potential safe use in MRI.