Pressure-Enabled Microcatheters Allow Complete Thyroid Embolization Through Inferior Arterial Access

A technical guide published in CVIR Endovascular details an inferior thyroid artery-first approach to thyroid artery embolization that utilizes pressure-enabled delivery microcatheters to achieve complete ipsilateral lobar devascularization. Authored by interventional radiologists Joe K. Khoury and Juan C. Camacho, the technical report outlines a standardized procedural workflow designed to eliminate the necessity of selectively catheterizing the superior thyroid artery. By exploiting naturally occurring intrathyroidal arterial anastomoses, the protocol aims to mitigate the inherent procedural risks of cerebral thromboembolism and reflux-related non-target embolization associated with navigating the carotid arterial system.

Thyroid artery embolization was first documented in 1985 as an intervention for invasive medullary thyroid carcinoma. In conventional practice, the procedure involves embolizing both superior thyroid arteries alongside a single inferior thyroid artery, deliberately sparing the contralateral inferior thyroid artery to preserve perfusion to the parathyroid glands and theoretically reduce the incidence of post-procedural hypoparathyroidism. However, the superior thyroid artery most frequently originates from the proximal external carotid artery, or less commonly from the common carotid artery or carotid bifurcation. Navigating catheters within these carotid territories introduces persistent hazards of particulate reflux and catheter-induced thromboemboli entering the cerebral circulation, which can lead to ischemic stroke.

To bypass carotid instrumentation, the pressure-enabled thyroid artery embolization technique relies on the TriNav microcatheter, manufactured by TriSalus Life Sciences. This specialized device incorporates SmartValve technology consisting of a self-expanding braided nitinol mesh positioned near the tip. During ventricular systole, the valve collapses inward to allow forward antegrade blood flow into the vessel. During ventricular diastole, the valve expands radially against the vessel wall, creating partial flow restriction without total vascular occlusion. This dynamic valve cycle reduces backward fluid reflux while generating modulated infusion pressure that drives embolic agents distally into the glandular capillary bed. The authors observe that while alternative anti-reflux microcatheters might theoretically perform similarly, the TriNav remains the only device currently described in the medical literature for this specific thyroid application.

Patient selection guidelines outlined in the report define appropriate candidates as individuals presenting with large benign thyroid nodules measuring greater than 30 milliliters, multinodular goiters exceeding 50 milliliters, toxic multinodular goiters, or substernal and retrosternal goiters. The therapy serves patients who are poor surgical candidates or those requiring pre-operative devascularization to alleviate compressive airway or neck symptoms. While thyroid embolization does not replace surgical intervention when surgery is indicated, it provides a minimally invasive palliative alternative. General angiographic relative contraindications apply, including pregnancy, severe renal impairment, and allergies to iodinated contrast media. Notably, candidates must have an inferior thyroid artery clearly visualizable on computed tomography angiography, as an absent or non-visualized inferior artery precludes this specific single-vessel technique.

Detailed pre-procedural anatomical assessment using head and neck computed tomography angiography is mandatory to map vascular variations before entering the angiography suite. Although the inferior thyroid artery typically originates from the thyrocervical trunk, operators must identify anatomical anomalies such as a thyroid ima artery arising directly from the aortic arch or brachiocephalic trunk, an absent inferior thyroid artery, or parasitized collateral supply from neighboring vessels such as the internal mammary artery. These anatomical variants occur with greater frequency in large substernal goiters extending into the mediastinum. Furthermore, patients with a history of cervical thermal ablation may have damaged internal collateral pathways, preventing embolic transit into the superior territory, while solitary nodules may rely on dominant independent superior arterial feeders rather than diffuse anastomoses.

Vascular access for the procedure can be secured via femoral or radial arterial routes, though the authors state a clear clinical preference for an ipsilateral radial approach. Radial access significantly decreases catheter traversal across the supra-aortic arch vessels, thereby lowering mechanical stroke hazards. For bilateral interventions, bilateral radial access is recommended to treat each thyroid lobe from its respective ipsilateral side. Systemic heparinization and continuous heparinized saline line flushes are maintained throughout catheter manipulation to prevent catheter-associated thrombus formation within the arterial system.

Catheter selection begins by cannulating the ipsilateral subclavian artery with a 5 French, 90 to 100 centimeter angled or reverse curve base catheter, followed by hand-injected digital subtraction angiography to locate the thyrocervical trunk. The authors categorize inferior thyroid artery morphologies into three distinct angiographic patterns: a cancer ribbon appearance, a candy cane configuration, and a diverging crossroads structure. Caliper measurements of the descending inferior thyroid artery determine microcatheter caliber: vessels measuring 3.5 millimeters or less receive a 2.4 French microcatheter, whereas larger vessels require a 2.9 French device. Larger microcatheters necessitate a guide catheter with an inner lumen of at least 0.047 inches, whereas smaller vessels can be accessed over a standard 0.014-inch microwire.

Precise anatomical positioning of the microcatheter tip is critical to prevent non-target delivery. The microcatheter is navigated over the microwire into the descending segment of the inferior thyroid artery, positioned distal to its primary arterial curvature but immediately proximal to intrathyroidal parenchymal branching. At this specific location, the catheter tip resides securely within the thyroid capsule, beyond the takeoff of dangerous extra-thyroidal branches including the ascending cervical and tracheoesophageal arteries. Operators are instructed to seat the microcatheter within a straight arterial segment to ensure the nitinol valve expands symmetrically without mechanical distortion that could impair pressure modulation.

Once stable position is achieved, power-injected digital subtraction angiography is performed using 8 milliliters of contrast delivered at 2 milliliters per second under 1000 to 1200 pounds per square inch to verify complete lobar enhancement and screen for reflux. Power injection is strictly avoided prior to seating the microcatheter within the inferior thyroid artery to minimize non-target air embolization risks. Subsequent intraprocedural cone-beam computed tomography utilizes a 22-milliliter contrast injection at 2 milliliters per second with a 5-second imaging delay during a 270-degree rotational acquisition lasting 5 to 6 seconds. The resulting cross-sectional data must be rigorously evaluated during the arterial parenchymal phase to rule out unintended perfusion of muscular, esophageal, or vertebral collateral vessels.

Embolic therapy utilizes calibrated Embosphere microspheres sized between 100 and 300 micrometers, manufactured by Merit Medical Systems. This size range is selected specifically to negotiate the intrathyroidal capillary and arteriolar anastomoses linking the superior and inferior thyroid circulations, which anatomically measure between 120 and 250 micrometers. Under optimized fluoroscopy, often involving contralateral head rotation to displace overlying osseous structures like the clavicle, embolic delivery proceeds. Contrast transit into the superior thyroid artery represents pressure-mediated collateral flow through microvascular channels rather than particulate reflux. If retrograde contrast enhancement is observed in the superior vessel, injection is briefly suspended to restore forward physiological flow before resuming particle delivery.

The procedural endpoint is reached when embolization produces a short column of contrast stasis accompanied by slight microcatheter kick-back, signaling elevated peripheral vascular resistance. Embolic distribution is subsequently verified using non-contrast cone-beam computed tomography to demonstrate diffuse, persistent parenchymal contrast retention. The authors explicitly advise against executing post-embolization digital subtraction angiography directly inside the inferior thyroid artery or thyrocervical trunk, as high-pressure contrast flushes can dislodge deposited particles and provoke catastrophic retrograde reflux. If confirmation of trunk patency is required, gentle completion angiography may only be performed remotely from within the subclavian artery.

Comprehensive peri-procedural pharmacotherapy is outlined to manage symptoms and physiological responses to acute ischemic devascularization. Oral propranolol at a dose of 20 milligrams is initiated one week prior to intervention and continued for four weeks post-procedure with an eventual taper to prevent transient hyperthyroidism and suppress peripheral conversion of thyroid hormones. Procedural discomfort is managed with 15 milligrams of intravenous ketorolac administered before and after embolization, supplemented by 1 gram of intravenous acetaminophen post-procedure. To suppress local glandular inflammation, 8 milligrams of intravenous dexamethasone is administered immediately following embolization, accompanied by clinical vigilance for transient perineal pruritus, followed by a discharge oral corticosteroid taper.

The authors emphasize that because pressure-enabled thyroid artery embolization remains an evolving interventional technique, current recommendations stem from initial clinical experience rather than large-scale randomized prospective investigations. Catheter manipulation must be aborted if cannulation of the thyrocervical trunk proves difficult, avoiding excessive catheter agitation adjacent to the vertebral artery. Prospective multicenter clinical trials are required to rigorously validate the procedural safety profile, clinical efficacy, and long-term durability of pressure-enabled embolization compared against conventional three-vessel thyroid artery embolization and standard surgical resection.

Subject of Research: Procedural technique and safety framework for pressure-enabled thyroid artery embolization using the inferior thyroid artery

Article Title: Pressure-enabled thyroid artery embolization: minimizing the risk of non-target embolization

Article References: Khoury, J. K., & Camacho, J. C. (2026). Pressure-enabled thyroid artery embolization: minimizing the risk of non-target embolization. CVIR Endovascular, 9(1), Article 142. https://doi.org/10.1186/s42155-026-00795-4

Image Credits: AI Generated

DOI: 10.1186/s42155-026-00795-4

Keywords: thyroid artery embolization, inferior thyroid artery, superior thyroid artery, pressure-enabled delivery, TriNav microcatheter, SmartValve technology, non-target embolization, cerebral thromboembolism, calibrated microspheres, cone-beam computed tomography, digital subtraction angiography, thyrocervical trunk, substernal goiter, intrathyroidal anastomoses, radial artery access, propranolol premedication, transient hyperthyroidism