To the Editor,

Growing evidence supports the use of percutaneous sclerotherapy for the management of retro-bulbar low flow venolymphatic malformations (LFVM) with good efficacy and low complication rates [1, 2]. Whilst the most significant complication is intralesional/retro-bulbar haemorrhage, we wish to share our experiences of a previously unreported but clinically significant complication during retro-bulbar sclerotherapy with bleomycin—the oculocardiac reflex (OCR).

The reflex occurs in response to activation of stretch receptors within the periorbital and ocular tissues stimulating a vagal response (Fig. 1). This commonly manifests with bradycardia but may cause significant arrhythmias, hypotension and in severe cases, asystole [3]. The OCR is most associated with traction of the extraocular muscles during strabismus surgery and more common in younger patients. Other associations include raised orbital pressures, retro-bulbar haematoma, and orbital trauma particularly with entrapment of extraocular muscles [3,4,5]. Management involves terminating the underlying stimulus which triggered the reflex as well as treatment of the vagal response with atropine and anti-arrhythmics [5].

Fig. 1
figure 1

Demonstrates the afferent (the ophthalmic nerve-V1 branch of the trigeminal nerve) and efferent (vagus nerve) pathways of the oculocardiac reflex. (Courtesy of Mrs Haya Wheatley)

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We encountered the OCR in a 31-year-old male undergoing bleomycin sclerotherapy for a congenital right retro-bulbar LFVM which also involved the right eyelid and cheek. He had had two significant episodes of retro-bulbar haemorrhage in the past, the most recent was 16 years prior to presentation to our service. This was his second treatment, the first performed under general anaesthetic without any complications 20 months prior (repeat treatment delayed due to the COVID-19 pandemic).

The patient was anaesthetised without any concerns. Under direct ultrasound guidance, a 23-gauge needle was advanced through the medial eyelid, avoiding the globe and into the retro-bulbar LFVM. Contrast injection via this needle directly into the malformation confirmed the absence of any intracranial venous drainage.

Bleomycin was injected into the LFVM under ultrasound guidance and visualised diffusing through the malformation. Immediately following injection of 1500 international units (IU) of bleomycin, significant bradycardia developed to a heart rate of 30 beats per minute (from a baseline of 70–80 bpm). Administration of intravenous atropine rapidly normalised the heart rate. On repeated attempts at bleomycin injection, the patient again developed significant bradycardia without any associated arrhythmia. Alongside the use of further doses of atropine, cessation of the injection helped normalise the heart rate. A total of 2500 international IU of bleomycin (volume of 2.5 mls-equivalent to 2.5–3.3 United States Pharmacopoeia units) was injected into the retro-bulbar LFVM.

The patient recovered well from anaesthesia and was discharged home the same day. He experienced mild pain and swelling as expected in the subsequent weeks post-procedure but reported no significant complications. He has had excellent response on imaging (Fig. 2) and clinically: his proptosis, discomfort and entropion have resolved. Also, his self-esteem is higher due to the change in his appearance.

Fig. 2
figure 2

Axial T1 post-contrast MR images with fat saturation. a pre-procedure MRI demonstrates the lobulated retro-bulbar intraconal component of the LFVM, with relative proptosis of the right eye. b Following two sessions of percutaneous sclerotherapy with bleomycin, reduction in bulk and enhancement of the lesion are seen

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Percutaneous sclerotherapy is a safe and effective treatment for retro-bulbar LFVMs, which given its minimally invasive nature is becoming the first-line treatment option for these patients. Whilst rare in the context of percutaneous sclerotherapy, operators should still be mindful of the OCR. Certain risk factors such as prior surgery, scarring and orbital trauma increase the likelihood of developing such a complication. In this patient, who had prior episodes of intralesional haemorrhage, retro-bulbar scarring was palpable in the tactile feedback from needle insertion into the intraconal space. The reflex is also more prominent in younger patients and given many LFVM present in childhood, it is important that the OCR is considered and anticipated during sclerotherapy, particularly in children. Interventional radiologists as well as our anaesthetic colleagues should be aware of and prepared to manage this potentially significant cardiovascular complication.