Nasolacrimal duct coronary stent recanalization as a possible alternative to dacryocystorhinostomy

External dacryocystorhinostomy (DCR) for treatment of primary acquired nasolacrimal duct obstruction (PANDO) was described by Addeo Toti in 1904 and was modified later with the addition of mucosal anastomosis by Dupuy-Dutemps and Bourget.[1,2] Since then, the basic principle of the surgery has remained the same with minor changes over the years. The introduction of endoscopic endonasal DCR in the year 1893 by Caldwell revolutionized the surgery and further modifications reduced morbidity with similar outcomes minus the surgical scar.[3] DCR involves creation of a bony window and establishment of a bypass passage between the lacrimal sac and nasal cavity.[1–3] In an attempt to preserve the natural anatomy of the lacrimal drainage pathway with minimally-invasive approach, nasolacrimal duct (NLD) recanalization using probing, trephination, endoluminal drilling, intubation, and balloon dacryoplasty have been attempted in the past with lesser than expected outcomes.[4–11] Each technique utilized for NLD recanalization either resulted in a recoil closure or created a raw area that can be susceptible to restenosis. Hypothesis Drug eluting chromium-cobalt alloy coronary stent in the nasolacrimal duct following multi modal NLD recanalization can be an alternative to the traditional dacryocystorhinostomy. Evaluation of Hypothesis Coronary angioplasty balloons in dacryology The incorporation of coronary angioplasty balloons (CABs) in routine dacryology practice was initiated in the year 2019 by Bothra et al.[12] for the management of congenital NLD obstructions. The physical properties of the CAB were comparable to the traditional dacryoplasty balloons, such as having an ultra-low profile and a narrow tip with a guide-wire, thereby making the insertion into the lacrimal system easy. Unlike the traditional balloons, a spectrum of desirable balloon diameters and lengths are available with CAB, making it amenable to use in customized situations, according to the need. The compliant and semi-compliant models make CAB safer and help in achieving a precise dilatation. The burst pressures of coronary balloons are very high, hence a higher safety margin. The low cost of CAB in comparison to the traditional dacryoplasty balloons allows for a widespread usage.[12] These advantages enabled the coronary balloons to be explored in other disorders like punctal stenosis or in cases of revision endoscopic dacryocystorhinostomies with good outcomes.[13,14] It is now known that CABs are cost-effective, simple to use, and effective in the lacrimal system. The next logical step would be to assess their use for acquired NLD obstructions. Balloon dacryoplasty for acquired complete NLD obstructions using the traditional balloons have been carried out in the past with varying results (mean success rate: 37%).[15] The causes for failure have been acute recoil and fibrosis of the mucosal surfaces. Silicone stents for acute recoil have shown better results but complications like undue damage to the proximal lacrimal drainage systems and biofilm formation inciting rebound inflammation have been cited as reasons for failure.[16] Thus, to keep the NLD patent, the necessity is to keep the mucosal surfaces of the NLD separated for longer durations, prevent acute recoil and fibrosis, and have minimal biofilm formation preventing any rebound inflammation. Drug-eluting coronary stents for NLD obstructions: Technique of NCR Coronary stents and drug-eluting stents have been used in coronary and peripheral vessel angioplasty for decades and have helped to maintain a dilated lumen and prevent acute recoil. Besides, the drug elution helps prevents restenosis and fibrosis. A similar sirolimus-eluting coronary stent (Yukon Choice Flex R, Translumina Therapeutics LLP, Uttarakhand, India), a cobalt-chromium alloy with a polyamide balloon on the tip available in 8mm and 12 mm lengths and 2 mm width which corresponds to the NLD length [Fig. 1] were used in fresh cadavers to assess their feasibility, deliverability, and procedural complications.[16] The safety profile of the coronary balloons in the lacrimal drainage system is already known,[12] making this procedure more reliable. Platinum-iridium radio-opaque markers are present to indicate the balloon position intraoperatively. The procedure included punctal and canalicular dilatation followed by a standard coronary balloon dacryoplasty protocols under endoscopy guidance using a 2.75 × 10 mm coronary balloon. The drug-eluting stent mounted on a balloon catheter [Figs. 1 and 2] was introduced into the NLD under endoscopic guidance. After ensuring its accurate location, the stent-mounted balloon was inflated beyond the nominal pressure (12 mmHg) but far less than the rate burst pressure. This allowed the stent to spring open and lock itself in the desired position [Fig. 3]. Uniformly wide dilatation and good anatomical integration with the NLD wall was confirmed by dacryoendoscopy. The integrity of the bony NLD remained intact. The stent could not be pushed downwards and towards the NLD opening after it was locked. The stent then stayed in situ in the NLD to keep the lumen wide open and dilated [Fig. 3].Figure 1: External image of a coronary catheter showing the stent (red arrow) mounted on an uninflated balloonFigure 2: High-magnification image of the sirolimus-coated cobalt-chromium alloy stent. Note the complex stent structure is in an unlocked and unopened positionFigure 3: Cadaveric end-on image of the nasolacrimal duct demonstrating the opened-up stent with locked springs (black arrow)Current challenges and consequences of the hypothesis At this stage, the procedure appears very promising as it does not allow the raw surfaces of the NLD to come in contact with each other after recanalization: theoretically, this will prevent re-obstruction. The stent will keep the NLD permanently dilated and widely open, allowing the passage of tears safely into the inferior meatus. The challenges are that our study has been done only on human cadavers and needs to be validated in living patients. The feasibility and the ease of insertion and removal, in case needed, in vivo needs to be determined. The NLD obstruction must be overcome initially by probing followed by balloon dilatation of the fibrosed segment. The fibrous obstruction at the NLD and the length of NLD that has undergone fibrosis will determine the outcomes by influencing the ease of probing and the possibility of creation of a false passage. Conclusion The establishment of coronary balloon dacryoplasty in various lacrimal drainage disorders and the cadaveric evidence of feasibility of implanting drug-eluting chromium-cobalt alloy coronary stents open exiting possibilities of having a minimally invasive alternative to standard DCR.

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