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I thank Dr Woronow and colleagues for their letter to the Editor recognizing the absence of neurologic and cardiac adverse events (NCAEs) in my recently published case series regarding outcomes from 250 patients treated with Food and Drug Administration-approved polidocanol microfoam 1%.1Deak S.T. Retrograde administration of ultrasound-guided endovenous microfoam chemical ablation for the treatment of superficial venous insufficiency.J Vasc Surg Venous Lymphat Disord. 2018; 6: 477-484Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar The safety profile demonstrated in phase 3 clinical trials was the rationale for incorporating this treatment in my practice in place of physician-compounded foam (PCF). The analysis in Dr Woronow's letter revealed 23 leg vein sclerotherapy NCAE cases with use of PCF. NCAE cases are likely the result of gas emboli that occur in using foams made with room air that have a high nitrogen content. Polidocanol microfoam 1% has a low nitrogen content (<0.8%) to reduce the risk of neurologic complications. Before adopting polidocanol microfoam 1% in my practice, I refrained from using PCF because of the published reports of patients who suffered significant neurologic events after treatment, including stroke, seizure, and transient ischemic attack.2Asbjornsen C.B. Rogers C.D. Russell B.L. Middle cerebral air embolism after foam sclerotherapy.Phlebology. 2012; 27: 430-433Crossref PubMed Scopus (17) Google Scholar, 3Bush R.G. Derrick M. Manjoney D. Major neurological events following foam sclerotherapy.Phlebology. 2008; 23: 189-192Crossref PubMed Scopus (124) Google Scholar, 4Hill D.A. Neurological and chest symptoms following sclerotherapy: a single centre experience.Phlebology. 2014; 29: 619-627Crossref PubMed Scopus (12) Google Scholar, 5Parsi K. Paradoxical embolism, stroke and sclerotherapy.Phlebology. 2012; 27: 147-167Crossref PubMed Scopus (68) Google Scholar, 6Engelberger R.P. Ney B. Clair M. Dabiri A. Alatri A. Mazzolai L. et al.Myocardial infarction after ultrasound-guided foam sclerotherapy for varicose veins—a case report and review of the literature of a rare but serious adverse event.Vasa. 2016; 45: 255-258Crossref PubMed Scopus (8) Google Scholar, 7Malvehy M.A. Asbjornsen C. Transient neurologic event following administration of foam sclerotherapy.Phlebology. 2017; 32: 66-68Crossref PubMed Scopus (7) Google Scholar I also noted that the existence of a patent foramen ovale (PFO) may contribute to the increased risk of NCAE. In the analysis performed by Dr Woronow, more than half of the patients with NCAEs had a PFO. This incidence was similar to an analysis of 82 patients undergoing polidocanol microfoam 1% ablation of the great saphenous vein.8Wright D.D. Gibson K.D. Barclay J. Razumovsky A. Rush J. McCollum C.N. High prevalence of right-to-left shunt in patients with symptomatic great saphenous incompetence and varicose veins.J Vasc Surg. 2010; 51: 104-107Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar In that study, 61% of the patients were PFO positive. In another study, middle cerebral artery bubbles were detected during polidocanol microfoam 1% ablation in 89% of the PFO-positive patients and 29% of PFO-negative patients. No patients displayed evidence of cerebral or cardiac microinfarction 30 days after treatment, nor did they display any adverse neurologic signs or elevated cardiac troponin I.9Regan J.D. Gibson K.D. Rush J.E. Shortell C.K. Hirsch S.A. Wright D.D. Clinical significance of cerebrovascular gas emboli during polidocanol endovenous ultra-low nitrogen microfoam ablation and correlation with magnetic resonance imaging in patients with right-to-left shunt.J Vasc Surg. 2011; 53: 131-137Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar Therefore, if arterial bubble emboli are unavoidable during the injection of sclerosant foam, it is critical to select a Food and Drug Administration-approved formulation that minimizes risk to the patient. I have since treated 420 patients with polidocanol microfoam 1%. My patients continue to benefit from treatment, with no NCAEs reported. Regarding “Retrograde administration of ultrasound-guided endovenous microfoam chemical ablation for the treatment of superficial venous insufficiency”Journal of Vascular Surgery: Venous and Lymphatic DisordersVol. 7Issue 2PreviewWe read with interest Dr Deak's case series1 of 250 patients treated with U.S. Food and Drug Administration (FDA)-approved polidocanol microfoam 1% consisting of 65% oxygen and 35% carbon dioxide (O2CO2FS) containing <0.8% nitrogen. The absence of neurologic or cardiac adverse events (NCAEs) in Dr Deak's community practice case series is consistent with the absence of clinically important neurologic events in the Efficacy and Safety Study of Polidocanol Injectable Foam for the Treatment of Saphenofemoral Junction Incompetence (VANISH-1) and Polidocanol Endovenous Microfoam Versus Vehicle for the Treatment of Saphenofemoral Junction Incompetence (VANISH-2). Full-Text PDF