Dear Editor,
I read with great interest the article by Li and colleagues [1] entitled ‘Successful Embolization of a Direct Carotid Cavernous Fistula Under Gadolinium-Based Angiography.’ To facilitate a more effective discussion of Li et al.’s [1] study and to assist in the design of future research, I would like to emphasize several key points and discuss them in conjunction with the relevant data presented in the literature. I intend to establish a foundation for future investigations and inspire new studies. In the study by Li et al. [1], the authors analyzed the use of gadolinium in a patient with a history of severe allergic reactions, mild renal insufficiency, and a direct carotid-cavernous fistula resulting from a ruptured internal carotid artery aneurysm. The aneurysm was successfully treated using the balloon-assisted coiling method during gadolinium-enhanced digital subtraction angiography (DSA) [1].
Off-label intra-arterial use of gadolinium for DSA or endovascular treatment has been reported in numerous cases [1-3]. For patients experiencing an undifferentiated type of contrast reaction, it is advisable to switch from an iodinated contrast medium to cyclic gadolinium chelates [4]. This strategy reduces the likelihood of subsequent contrast reactions [1]. The incidence of moderate to severe allergic reactions to gadolinium compounds is less than 0.04% [2,3]. If necessary, gadolinium can be effectively removed from the body through hemodialysis [3]. Measuring the estimated glomerular filtration rate before the DSA examination is not mandatory when administering intra-arterial cyclic gadolinium chelates [4]. However, the safe amount of contrast medium that can be administered to a specific patient with renal insufficiency remains uncertain [3].
Various doses of gadolinium-based agents have been documented in the literature [3]. Gadolinium can be utilized in both pure and diluted forms, as noted in the article by Li et al. [1]. Additionally, gadolinium can be employed in dual-energy and photon-counting computed tomography examinations [1,3,5]. The costs of contrast material-enhanced magnetic resonance exams may be reduced if the contrast-enhanced images are obtained after DSA. At the same time, there is still a sufficient level of circulating contrast medium in patients who undergo DSA or embolization with a gadolinium-based contrast agent [2].
Woven EndoBridgeTM (WEB; MicroVention) devices have been extensively utilized in treating intracranial aneurysms and offer numerous advantages [6,7]. In selected cases, the WEB device may be used for direct-type carotid-cavernous fistulas with reduced contrast material in a shorter exam time than balloon-assisted coiling, similar to WEB-assisted arteriovenous fistula or aneurysm embolization [8].
In conclusion, the properties of gadolinium contrast agents differ from those of iodine, and further investigation is needed to determine the optimal kilovoltage, milliamperage, infusion rates, intra-arterial dosage, dilution ratios, and frame rates. Using macrocyclic contrast agents and WEB-assisted embolization for treating direct carotid-cavernous fistulas resulting from aneurysm rupture may be effective in selected patients with moderate to severe allergic reactions or renal failure. New studies are necessary to address the issues highlighted above.
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