Pressure-Directed Embolotherapy With Antireflux Catheters: Articles From the Official Show Daily for Synergy 2015

The primary intraprocedural goal of catheter-based hepatic artery embolotherapy of liver malignancies, whether bland embolization, chemoembolization, or radioembolization, is to maximize delivery of agent to tumor, avoid nontarget delivery to extrahepatic structures, and minimize delivery to nontumorous liver. Conventional delivery strategies with end-hole catheters have included peripheral delivery, coil occlusion of hepaticoenteric arteries, or exclusionary coil embolization of sacrificable hepatic artery branches that supply hepaticoenteric arteries. Recently, microcatheters with expandable balloons or dynamic one-way valves (Surefire Infusion System; Surefire Medical) have been deployed to prevent retrograde reflux to prevent upstream nontarget delivery.^1-3 

An important feature of antireflux catheters is that due to relative obstruction to antegrade blood flow, blood pressure in the downstream (antegrade) arterial vascular territory is significantly reduced relative to the blood pressure in the rest of the systemic arteries. Typical downstream blood pressure reduction is in the order of 15 mmHg to 20 mmHg.⁴ This differential blood pressure can be assessed by simultaneously measuring the blood pressure in a femoral artery vascular side arm sheath that is at least 1 Fr larger than the guide catheter, and through the lumen of the antireflex catheter. When the antireflex tip has been deployed, the systemic-hepatic arterial pressure differential (SHAPD) can be measured. 

The importance of the SHAPD is substantial for multiple reasons. Since the blood pressure in the targeted vascular territory is typically 20 mmHg lower than the rest of the body, blood flow in downstream hepaticoenteric arteries is made to flow hepatopedally with a pressure head of 20 mmHg. In addition to retrograde protection from reflux with nontarget arteries, a high degree of antegrade protection is afforded. This bidirectional protection largely eliminates the need for coil embolization. In patients who are candidates for Yttrium-90 (Y-90) resin microsphere radioembolization, significant savings in procedural time, radiation exposure, contrast material dose, and disposable supply costs may be realized.^5-6

In addition to SHAPD causing hepaticoenteric artery blood to flow hepatopedally, blood flows into the intrahepatic portions of the protected vascular territory from liver outside of the targeted vascular territory. Irie et al have demonstrated that when using temporary balloon occlusion of hepatic segmental arteries during the lipiodol chemoembolization, the lipiodol is flushed out of the nontumorous liver by inflow of blood from neighboring hepatic segments. Alternatively, lipiodol continues to accumulate within the tumor, presumably because the tumor is a different vascular compartment.³ A group from the University of Tennessee has demonstrated similar improvement in deposition of technetium 99m ((99m)Tc) macroaggregated albumin (MAA) into tumor, while decreasing activity in nontumorous liver when using the Surefire Infusion System.⁷ In summary, these antireflux devices appear to reduce the risk of nontarget delivery of agents both extrahepatically and intrahepatically and likely improve selective delivery of agent into tumor.

One caveat about the effect of SHAPD is that the phenomena of intersegmental inflow of arterial blood from neighboring hepatic segments likely results in effective shrinkage of the vascular territory from its peripheral margins. The practical importance is that “watershed” tumors that bridge vascular territories may not get adequate delivery of agent at the boundaries.⁸ 

The conventional endpoint for embolization is based on visual fluoroscopic cues of changes in blood flow velocity or direction. By their one-way valve nature, antireflux devices only permit antegrade blood flow, which is sluggish due to obstruction to forward flow. Since the usual fluoroscopic visual cues are compromised, over embolization is possible. It has been hypothesized that intraprocedural relative reduction in SHAPD is a reflection of the degree of vascular bed embolic saturation. 

In a series of 24 lobar drug-eluting bead chemoembolization procedures in 11 patients, intraprocedural interval measurement of SHAPD was used to determine the endpoint of chemoembolization.⁹ In 11 of 24 (46%) procedures, there was a significant reduction in SHAPD that led to early termination of dose administration. In these patients with Childs-Pugh A cirrhosis who underwent lobar DEB chemoembolization, liver toxicity was negligible. The mean change in CTCAE 90-day liver toxicity score was 0.16 over baseline. It appears that intraprocedural interval measurement of SHAPD is a potential useful endpoint for chemoembolization when using antireflux catheters. It is rare that SHAPD is reduced significantly when delivering either glass or resin Y-90 microspheres (Rose; unpublished data).

In summary, local hemodynamic changes caused by antireflux catheters are profound. In the hepatic artery circulation, these devices provide both retrograde and antegrade protection from nontarget embolization. Intrahepatically it appears that within the targeted vascular territory, agent delivery into the tumor is improved while delivery to the adjacent nontumorous liver is minimized. “Watershed” tumors potentially may present challenges to homogeneous agent delivery. It appears that the relative reduction in SHAPD may be a useful endpoint for chemoembolization procedures.  

Editor’s note: This article first appeared in the Synergy Daily conference newspaper, available to attendees of the Synergy Miami interventional oncology meeting, published November 7, 2015. This article did not undergo peer review. Dr. Rose reports no disclosures related to the content herein. 

Suggested citation: Rose SC. Pressure-directed embolotherapy with antireflux catheters: articles from the official show daily for Synergy 2015. Intervent Oncol 360. 2016;4(1):E1-E3. 

References

1. Nakamura H, Hashimoto T, Oi H, Sawada S, Furui S. Prevention of gastric complications in hepatic arterial chemoembolization. balloon catheter occlusion technique. Acta Radiol. 1991;32(1):81-82. 
2. Arepally A, Chomas J, Kraitchman D, Hong K. Quantification and reduction of reflux during embolotherapy using an antireflux catheter and tantalum microspheres: ex vivo analysis. J Vasc Interv Radiol. 2013;24(4):575-580.
3. Irie T, Kuramochi M, Takahashi N. Dense accumulation of lipiodol emulsion in hepatocellular carcinoma nodule during selective balloon-occluded transarterial chemoembolization: measurement of balloon-occluded arterial stump pressure. Cardiovasc Intervent Radiol. 2013;36(3):706-713.
4. Rose SC, Kikolski SG, Chomas JE. Downstream hepatic arterial blood pressure changes caused by deployment of the surefire antireflux expandable tip. Cardiovasc Intervent Radiol. 2013;36(5):1262-1269.
5. Morshedi MM, Bauman M, Rose SC, Kikolski SG. Yttrium-90 resin microsphere radioembolization using an antireflux catheter: an alternative to traditional coil embolization for nontarget protection. Cardiovasc Intervent Radiol. 2015;38(2):381-388.
6. Fischman AM, Ward TJ, Patel RS, Arepally A, Kim E, Nowakowski FS, Lookstein RA. Prospective, randomized study of coiling vs surefire infusion system during yttrium-90 radioembolization with resin microspheres. J Vasc Interv Radiol. 2014;25(11):1709-1716.
7. Pasciak AS, McElmurray JH, Bourgeois AC, Heidel RE, Bradley YC. The impact of an antireflux catheter on target volume particulate distribution in liver-directed embolotherapy: a pilot study. J Vasc Interv Radiol. 2015;26(5):660-669.
8. Kothary N, Takehana C, Mueller K, et al. Watershed hepatocellular carcinomas: the risk of incomplete response following transhepatic arterial chemoembolization. J Vasc Interv Radiol. 2015;26(8):1122-1129.
9. Rose SC, Kikolski SG, Morshedi MM, Narsinh KH. Feasibility of intraprocedural transluminal hepatic and femoral artery blood pressure measurements as an alternative embolization safety endpoint when antireflux devices are used during lobar chemoembolization. AJR Am J Roentgenol. 2015;205(1):196-202.