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Monday, August 20, 2018

Covered Stents in the Treatment of Pulmonary Arteriovenous Malformations


Summary


Pulmonary arteriovenous malformations (pAVM) are a unique problem that is seen most often in the rare population of patients afflicted with hereditary hemorrhagic telangiectasia. These patients often require multiple treatments throughout their lives and it is important to prioritize the preservation of normal lung tissue whenever possible. In some cases, this can be achieved with the use of covered stens. This study retrospectively reviews the cases of seven patients (8 total pAVM treatments) who were treated with covered stents at their institution (approximately 1.1% of all pAVM’s treated at the host institution from 2001-2017). The decision to use stent grafts was made based on the presence of a short neck, the inability to cross or enter an existing coil nest in a way that additional coils or plugs could be safely deployed, and the desire to preserve the normal downstream pulmonary vascular bed. No antiplatelet or anticoagulant medications were used due to issues with epistaxis in this patient population. Complete technical success was defined as exclusion of the pAVM with a covered stent while maintaining patency of the parent vessel which was achieved in 7 of 8 cases. In one patient the decision was made to sacrifice the parent vessel due to the presence of multiple feeders to the pAVM which were only seen after initial stent placement. Six of these patients had follow up imaging at a median of 8 months, all of which maintained stent patency without stent migration or deformation. In conclusion, the authors state that covered stents are a useful adjunct for treating select pAVM’s not well suited to coil and/or plug embolotherapy. Intermediate-term patency of this treatment was also favorable despite the small diameters of treated vessels (mean 6mm) and inability to use antiplatelet therapy and/or anticoagulants in this patient population.



Figure 1. (a) Selective right upper lobe pulmonary arteriogram shows PAVM before initial treatment. Note very short communication (arrowhead) between the pulmonary artery (containing catheter) and draining vein (arrow). Note also the large normal pulmonary vascular bed distal to PAVM. (b) Selective right upper lobe pulmonary arteriogram after coil embolization shows occlusion of PAVM. (c) Selective right upper lobe pulmonary arteriogram obtained at follow-up shows recanalized PAVM with prompt arteriovenous shunting (arrowhead shows draining vein). Note very short remaining vessel between catheter tip and coil nest (arrow). (d) Oblique view with catheter tip in the vessel that previously received embolization again shows pronounced shunting with prompt filling of draining vein (arrow). Digitally subtracted (e) and native (f) images after placement of a covered stent (arrows) show good position and exclusion of the feeding artery with no further flow into PAVM. The parent vessel is well preserved. (g) Coronally reformatted image from computed tomography arteriogram obtained 55 months after the procedure shows a patent covered stent with resolution of PAVM.

Commentary


This article demonstrates a novel approach to treating an uncommon entity (pAVM) of a rare disease (HHT) with an emphasis on the preservation of normal pulmonary vasculature in patients who often require multiple treatments throughout their lives. Interestingly, despite the small size of these vessels, the stents remained patient without the use of anticoagulant or antiplatelet medications. In one instance, a separate study reported patency at 120 months without recanalization or persistence of the treated AVM. Pulmonary AVMs are seen nearly entirely in patients with hereditary hemorrhagic telangiectasia and stent-graft exclusion of these lesions is an infrequent treatment approach, which explains the small sample size limitation of this study. However, the particular predilection of pAVMs for patients with HHT raises the question of whether or not their unique genetic makeup and biochemistry helps prevent stent occlusion. While confident use of stent grafts for this purpose requires additional research with long-term follow up, consideration may be given to using these more liberally as they are impermeable to flow and should theoretically eliminate the possibility of recanalization of the treated feeder vessels. They also carry the added benefit of easier follow-up with chest CTA as they do not produce any significant imaging artifact. Finally, a cost based analysis may be warranted to ascertain whether universal use of stent-grafts is financially feasible or should be reserved for complex interventions like those in this study.

Click here for abstract

Harrison X. Bai, MD, Reed E. Pyeritz, MD, and Scott O. Trerotola, MD. Covered Stents in the Treatment of Pulmonary Arteriovenous Malformations. J Vasc Interv Radiol 2018; 29:981–985

Post Author:
Caleb L. Mills, MD PGY-4
Department of Radiology
Wake Forest Baptist Medical Center
@WakeForest_IR

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