Balloon-occluded Retrograde Transvenous Obliteration Procedure Research Articles

Balloon-occluded retrograde transvenous obliteration with lauromacrogol sclerosant foam for gastric varices

ObjectivesTo evaluate the safety and efficacy of balloon-occluded retrograde transvenous obliteration (BRTO) using lauromacrogol sclerosant foam for gastric varices (GVs) with gastrorenal venous shunts. MethodsData of GV patients treated with BRTO using lauromacrogol sclerosant foam in 2016–2020 were retrospectively analyzed along with procedural success rate, complications, and follow-up efficacy. ResultsA total of 31 patients were treated with BRTO. The sclerosant foam was prepared by mixing iodinated oil, lauromacrogol, and air at a 1:2:3 ratio. The BRTO procedure was successfully completed in 93.5% of patients. One patient was allergic to the lauromacrogol injection. A mild postoperative fever occurred in three patients. One patient experienced grand mal seizures after the procedure. There was no significant difference in the median Child-Turcotte-Pugh scores before versus after BRTO. Complete GV resolution was observed in 93.1% of patients. One patient underwent endoscopic treatment for the development of high-risk esophageal varices. Another patient underwent transjugular intrahepatic portosystemic shunt placement for the aggravation of ascites. ConclusionsLauromacrogol sclerosant foam is safe and effective in patients undergoing BRTO for GV.

Role of Interventional Radiology in Complications of Portal Hypertension.

Portal hypertension, a consequence of end-stage liver disease and liver cirrhosis can lead to significant morbidity and mortality for patients through abnormal fluid accumulation as well as the formation of portosystemic shunts and varices. Treatment of the sequelae of portal hypertension can be achieved through endovascular management by referral to an interventional radiologist on an outpatient or emergent basis as required. Current techniques include the placement of peritoneovenous shunts and tunneled peritoneal drains, the creation of transjugular intrahepatic portosystemic shunts, or the obliteration of shunts via balloon-occluded retrograde transvenous obliteration (BRTO). In addition, newer procedural techniques utilizing vascular plugs and coils have reduced risks of the traditional BRTO procedure. Modified-BRTO procedures, known as plug-assisted and coil-assisted retrograde transvenous obliteration (PARTO and CARTO, respectively) have become the standard of care at many institutions for the treatment of gastric varices and portosystemic shunt-induced hepatic encephalopathy. This review examines the most recent literature of the management of portal hypertension by interventional radiologists, evaluating treatment options as well as the clinical and technical outcomes of TIPS, peritoneovenous shunts, tunneled peritoneal drains, BRTOs, and modified-BRTOs as well as future directions in the development of procedural techniques.

Measurement of Inferior Vena Cava to Shunt Distance in Deciding Access Route for Balloon-Occluded Retrograde Transvenous Obliteration Procedure: A Pilot Study

Purpose: Why and how to decide whether femoral or jugular approach should be used for shunt catheterization for a successful balloon-occluded retrograde transvenous obliteration (BRTO) procedure. Materials and Methods: Sixteen patients had undergone BRTO for variceal bleeding (11 cases) and encephalopathy (5 cases) with the femoral (13) and jugular approach (5). In two patients, both femoral and jugular approaches were used. There were four failed shunt catheterizations with the femoral or jugular approach two each. In all patients, the inferior vena cava (IVC) to shunt distance (ISD) was measured on the reformatted coronal computed tomography image. Results: The IVC to shunt distance (ISD) was between 2.0 and 3.5 cm in 13 patients and >3.5 cm in five. Two patients were having both proximal gastrorenal and distal splenorenal shunts. The ISD was >3.5 cm in two patients with failed initial femoral approach and < 3.5 cm in two other patients with failed initial jugular approach. In each of the four failures, the alternative approach resulted in obtaining a successful BRTO. Conclusion: The femoral approach is recommended for catheterization of the gastrorenal shunt for BRTO when the shunt joins the renal vein within 3.5 cm from the IVC. However, when the shunt is farther than 3.5 cm from the IVC, the jugular approach is suitable for a BRTO procedure.

Spontaneous thrombosis of large splenorenal shunt during balloon-occluded retrograde transvenous obliteration in a patient with chronic persistent hepatic encephalopathy. Is this catheter assisted trans-venous occlusion?

Large spontaneous portosystemic shunts in cirrhosis are implicated in recurrent and/or chronic persistent hepatic encephalopathy. In long standing cases, these shunts lead to portal vein thrombosis and hepatic dysfunction. Balloon-occluded retrograde transvenous obliteration (BRTO) is an endovascular technique that is usually employed for shunt closure in the patients manifesting the features of chronic hepatic encephalopathy. There are several reports documenting systemic and portal vein thrombosis as a part of the procedure. We report first time a patient in whom the difficult and partial BRTO procedure led to the extensive thrombosis of the large splenorenal shunt itself without sclerosant instillation.

An Algorithm for Management After Transjugular Intrahepatic Portosystemic Shunt Placement According to Clinical Manifestations.

We propose an algorithm for management after transjugular intrahepatic portosystemic shunt (TIPS) placement according to clinical manifestations. For patients with an initial good clinical response, surveillance Doppler ultrasound is recommended to detect stenosis or occlusion. A TIPS revision can be performed using basic or advanced techniques to treat stenosis or occlusion. In patients with an initial poor clinical response, a TIPS venogram with pressure measurements should be performed to assess shunt patency. The creation of a parallel TIPS may also be required if the patient is symptomatic and the portal pressure remains high after TIPS revision. Additional procedures may also be necessary, such as peritoneovenous shunt (Denver shunt) placement for refractory ascites, tunneled pleural catheter for hepatic hydrothorax, and balloon-occluded retrograde transvenous obliteration procedure for gastric variceal bleeding. A TIPS reduction procedure can also be performed in patients with uncontrolled hepatic encephalopathy or hepatic failure.

Retrograde venography during balloon-occluded retrograde transvenous obliteration of gastric varices

Purpose: The purpose of this study was to evaluate changes in thrombosis in gastric varices.Material and methods: Fourteen patients were studied who underwent balloon-occluded retrograde transvenous obliteration (B-RTO) for gastric varices with a gastrorenal shunt. The B-RTO catheter was retained overnight in all patients. Balloon-occluded retrograde venography (B-RTV) was performed to evaluate the degree of thrombus formation. This evaluation was done twice during the overnight B-RTO procedure: A few hours after the procedure and on the following day. Investigated were the degree of thrombus formation observed by the first and second B-RTV, change in the degree of thrombus between the first and second B-RTV, and whether and how much sclerosing agent was administered on the second day.Results: The first B-RTV showed entire or partial enhancement of the gastric varix in seven (50%) cases and complete or almost complete lack of enhancement in the remaining seven cases. In four of the former seven cases, the second B-RTV showed entire or partial enhancement of the gastric varix, and the sclerosing agent was added. However, in the remaining ten cases, enhancement was almost or completely lacking.Conclusion: When complete thrombosis is shown on B-RTV obtained a few hours after B-RTO, the addition of a sclerotic agent would be unnecessary.

Balloon‐occluded retrograde transvenous obliteration using a microballoon catheter for intractable gastric fundal varices

Balloon-occluded retrograde transvenous obliteration (B-RTO) is recognized as the standard therapy for patients with gastric fundal varices in Japan; however, the procedure is difficult when drainage veins other than the gastrorenal shunt developed. The efficacy and safety of B-RTO using a microballoon catheter for such patients were evaluated. The subjects were 99 patients with gastric fundal varices who fulfilled the criteria for receiving endoscopic and/or interventional therapies. Among these, 95 patients underwent B-RTO. Of the 95 patients, 14 were treated with the use of microballoon catheters, including nine in whom the left inferior phrenic vein was found as a secondary drainage vein in addition to the gastrorenal shunt, and five in whom a gastrorenal shunt was absent. The B-RTO procedure performed using a microballoon catheter inserted through the left inferior phrenic vein in 13 patients, and through the pericardiophrenic vein in one patient. The B-RTO procedure using microballoon catheters was successful in 13 of the 14 patients (93%), while in the remaining one patient, multiple drainage veins were visualized on venography. Complete obliteration of the varices was achieved in all the 13 patients by injection of 5% ethanolamine oleate iopamidol at a median volume of 25 mL (range, 11 to 40 mL) through the catheters. None of the patients showed injuries of the drainage veins or any systemic complications. B-RTO using a microballoon catheter is useful for the treatment of gastric fundal varices in which drainage veins other than the gastrorenal shunt developed.

Short-Term Rebleeding Rates for Isolated Gastric Varices Managed by Transjugular Intrahepatic Portosystemic Shunt versus Balloon-Occluded Retrograde Transvenous Obliteration

PurposeTo assess the short-term rebleeding rate associated with the use of a transjugular intrahepatic portosystemic shunt (TIPS) compared with balloon-occluded retrograde transvenous obliteration (BRTO) for management of gastric varices (GV). Materials and MethodsA single-center retrospective comparison of 50 patients with bleeding from GV treated with a TIPS or BRTO was performed. Of 50 patients, 27 (17 men and 10 women; median age, 55 y; range, 31–79 y) received a TIPS with covered stents, and 23 (12 men and 11 women; median age, 52 y; range, 23–83 y) underwent a BRTO procedure with a foam sclerosant. All study subjects had clinical and endoscopic evidence of isolated bleeding GV and were hemodynamically stable at the time of the procedure. Clinical and endoscopic follow-up was performed. Kaplan-Meier analysis was used to evaluate rebleeding rates from the GV. ResultsThe technical success rate was 100% in the TIPS group and 91% in the BRTO group (P = .21). Major complications occurred in 4% of the patients receiving TIPS and 9% of patients the undergoing BRTO (P = .344). Encephalopathy was reported in 4 of 27 (15%) patients in the TIPS group and in none of the patients in the BRTO group (0%; P = .12). At 12 months, the incidence of rebleeding from a GV source was 11% in the TIPS group and 0% in the BRTO group (P = .25). ConclusionsBRTO appears to be equivalent to TIPS in the short-term for management of bleeding GV. Further comparative studies are warranted to determine optimal management strategies in individual patients.

Vascular Anatomy and the Morphologic and Hemodynamic Classifications of Gastric Varices and Spontaneous Portosystemic Shunts Relevant to the BRTO Procedure

The pathologic anatomy and hemodynamics of the left-sided portal circulation that is associated with gastric varices (GVs) are complex and highly variable. Understanding the pathologic anatomy and hemodynamics associated with GVs is important for clinical management decisions and for the technical descriptive details of the balloon-occluded retrograde transvenous obliteration (BRTO) and balloon-occluded antegrade transvenous obliteration procedures. A reflection of the considerable variability in anatomy, pathology, and hemodynamics is the numerous descriptive and categorical classifications that have been described in the past 2 decades. This article reviews the detailed descriptive gross anatomy, radiographic anatomy, and portosystemic venous hemodynamics that are associated with GVs and that can be encountered during the BRTO or balloon-occluded antegrade transvenous obliteration procedure(s) or both. Definitions are also set to clarify this detailed anatomy that received limited description in the prior literature. Moreover, all the classifications that have been described (to the best of the author's knowledge) that are relevant to the BRTO procedure are detailed in the article.

Optimizing Logistics for Balloon-Occluded Retrograde Transvenous Obliteration (BRTO) of Gastric Varices by Doing Away With the Indwelling Balloon: Concept and Techniques

Since the conception of balloon-occluded retrograde transvenous obliteration (BRTO) of gastric varices 25 years ago, the placement of an indwelling balloon for hours has been central to the BRTO procedure. Numerous variables and variations of the BRTO procedure have been described, including methods to reduce sclerosant, combining percutaneous transhepatic obliteration, varying sclerosant, and using multiple sclerosants within the same procedure. However, the consistent feature of BRTO has always remained the indwelling balloon. Placing an indwelling balloon over hours for the BRTO procedure is a logistical burden that taxes the interventional radiology team and hospital resources. Substituting the balloon with hardware (coils or Amplatzer vascular plugs [AVPs] or both) is technically feasible and its risks most likely correlate with gastrorenal shunt (GRS) size. The current authors use packed 0.018- or 0.035-in coils or both for small gastric variceal systems (GRS size A and B) and AVPs for GRS sizes up to size E (from size A-E). The current authors recommend an indwelling balloon (no hardware substitute) for very large gastric variceal system (GRS size F). Substituting the indwelling balloon for hardware in size F and potentially size E GRS can also be risky. The current article describes the techniques of placing up to 16-mm AVPs through balloon occlusion guide catheters and then deflating the balloon once it has been substituted with the AVPs. In addition, 22-mm AVPs can be placed through sheaths once the balloon occlusion catheters are removed to further augment the 16-mm Amplatzer occlusion. To date, there are no studies describing, let alone evaluating, the clinical feasibility of performing BRTO without indwelling balloons. The described techniques have been successfully performed by the current authors. However, the long-term safety and effectiveness of these techniques is yet to be determined.

The Conventional Balloon-Occluded Retrograde Transvenous Obliteration Procedure: Indications, Contraindications, and Technical Applications

Transvenous obliteration of gastric varices can be performed from the systemic venous side (draining veins or shunts) or from the portal venous side (portal afferent feeders). Balloon-occluded transvenous obliteration from the systemic veins is referred to as balloon-occluded retrograde transvenous obliteration (BRTO) and balloon-occluded transvenous obliteration from the portal veins is referred to as balloon-occluded antegrade (anterograde) transvenous obliteration (BATO). BRTO is the conventional balloon-occluded transvenous obliteration procedure and BATO is considered an alternative or adjunctive approach. This is because, from a technical standpoint, the least invasive choice of access or approach for balloon-occluded transvenous obliteration of gastric varices is the traditional or conventional transrenal route. The objective of BRTO or BATO or both is complete obliteration of the gastric varices with preservation of the anatomical hepatopetal flow of the splenoportal circulation. This article reviews the indications, contraindications, and technical considerations of the conventional BRTO procedure. The indications of concomitant portal venous modulators such as splenic embolization or the creation of a transjugular intrahepatic portosystemic shunt or both are also discussed.

The Role of Divided Injections of a Sclerotic Agent over Two Days in Balloon-Occluded Retrograde Transvenous Obliteration for Large Gastric Varices

ObjectiveTo determine the safety and usefulness of a two-tiered approach to balloon-occluded retrograde transvenous obliteration (B-RTO) as a treatment for large gastric varices after portal hypertension.Materials and Methods50 patients were studied who underwent B-RTO for gastric varices between October 2004 and October 2011 in our institution. The B-RTO procedure was performed from the right femoral vein and the B-RTO catheter was retained until the following morning. Distribution of sclerotic agents in the gastric varices on fluoroscopy was evaluated in all patients on days 1 and 2. When distribution of sclerotic agents in the gastric varices on day 1 had been none or very scanty even though the volume of the sclerotic agent infused was above the acceptable level, a second infusion was administered on day 2. When distribution was satisfactory, the B-RTO catheter was removed.ResultsIn 8 (16%) patients, little or no sclerotic agent infused on day 1 was distributed in the gastric varices. However, on day 2, sclerotic agents were distributed in all gastric varices. Mean volume of ethanolamine oleate-iopamidol infused on day 1 was 24.6 mL and was 19.4 mL on day 2. Gastric varices were well obliterated with no recurrence. Complications caused by the sclerotic agent such as pulmonary edema or renal insufficiencies were not seen.ConclusionWhen gastric varices are very large, a strategy involving thrombosis of only the drainage vein on the first day followed by infusing the sclerotic agent on the following day might be effective and feasible.

Pre– and Post–Balloon-Occluded Retrograde Transvenous Obliteration Clinical Evaluation, Management, and Imaging: Indications, Management Protocols, and Follow-up

Patients with gastric variceal bleeding require a multidisciplinary team approach, which includes hepatologists, endoscopists, diagnostic radiologists, and interventional radiologists. Upper gastrointestinal endoscopy is the first-line diagnosis and management tool for bleeding gastric varices (GVs) as it is with all upper gastrointestinal bleeding scenarios. Traditionally, in the United States, when endoscopy fails to control gastric variceal bleeding, a transjugular intrahepatic portosystemic shunt (TIPS) is performed along the classic teachings of decompressing the portal circulation. However, TIPS has shown inconsistent effectiveness in controlling gastric variceal bleeding. Conversely, the balloon-occluded retrograde transvenous obliteration (BRTO) procedure has become common practice in Asia for the management of GVs. The BRTO procedure is gaining popularity in the United States. BRTO has shown to be effective in controlling gastric variceal bleeding with low gastric variceal rebleed rates. Regardless of the endovascular management (TIPS vs BRTO vs both), a multidisciplinary team with adequate preprocedural clinical assessment and management and endoscopic and imaging evaluation is required before and after the endovascular procedure. The article discusses the pre- and post-BRTO clinical evaluation and management, as well as endoscopic and imaging evaluation. Moreover, the article proposes indications, contraindications, and management protocols for the management of GVs.

Development of Thrombus in a Systemic Vein after Balloon-Occluded Retrograde Transvenous Obliteration of Gastric Varices

ObjectiveTo retrospectively evaluate the frequency and risk factors for developing thrombus in a systemic vein such as the infrarenal inferior vena cava or the iliac vein, in which a balloon-occluded retrograde transvenous obliteration (B-RTO) catheter was indwelled.Materials and MethodsForty-nine patients who underwent B-RTO for gastric varices were included in this study. The B-RTO procedure was performed from the right femoral vein, and the B-RTO catheter was retained overnight in all patients. Pre- and post-procedural CT scans were retrospectively compared in order to evaluate the development of thrombus in the systemic vein in which the catheter was indwelled. Additionally, several variables were analyzed to assess risk factors for thrombus in a systemic vein.ResultsIn all 49 patients (100%), B-RTO was technically successful, and in 46 patients (94%), complete thrombosis of the gastric varices was achieved. In 6 patients (12%), thrombus developed in the infrarenal inferior vena cava or the right common-external iliac vein. All thrombi lay longitudinally on the right side of the inferior vena cava or the right iliac vein. One of the aforementioned 6 patients required anticoagulation therapy. No symptoms suggestive of pulmonary embolism were observed. Prothrombin time-international normalized ratio and the addition of 5% ethanolamine oleate iopamidol, on the second day, were related to the development of thrombus.ConclusionDevelopment of a thrombus in a systemic vein such as the inferior vena cava or iliac vein, caused by indwelling of the B-RTO catheter, is relatively frequent. Physicians should be aware of the possibility of pulmonary embolism due to iliocaval thrombosis.

Balloon-occluded Retrograde Transvenous Obliteration (BRTO): Preprocedural Evaluation and Imaging

Patients undergoing balloon retrograde transvenous obliteration (BRTO) are mostly decompensated cirrhotic with either bleeding gastric varices (GV) or hepatic encephalopathy. It is crucial that clinicians are up-to-date with the assessments needed prior to BRTO to anticipate and prevent complications, and to deliver critical quality care. These patients will require preprocedural assessments and management, including endoscopic, clinical, laboratory, and imaging evaluation. Endoscopic evaluation is mandatory prior to BRTO, and it is highly recommended that it be performed at the same institution where BRTO will be performed. It is essential that clinicians are aware of the potential benefits and complications that may result from BRTO. These complications should be anticipated and prevented when possible. For GV bleeders, there should be consideration of a transvenous intrahepatic portosystemic shunt (TIPS) during or before BRTO in patients with refractory ascites or pleural effusion, as well as endoscopic banding or a TIPS in patients with high-risk esophageal varices. Patients undergoing BRTO are usually complicated and require a team approach. In this article, the authors address these assessment and preparatory management and planning procedures prior to the BRTO procedure as well as expected outcomes and potential complications.

The Prevalence, Risk Factors, and Clinical Outcome of Balloon Rupture in Balloon-occluded Retrograde Transvenous Obliteration of Gastric Varices

To evaluate the prevalence, risk factors, and clinical outcome after balloon rupture during balloon-occluded retrograde transvenous obliteration (BRTO). Sixty-nine patients who underwent the BRTO procedure from August 1999 to January 2009 were analyzed retrospectively. The occurrence of balloon rupture was recorded by a review of medical records and imaging studies. The chi(2) test was used to analyze risk factors for balloon rupture including balloon type and size, amount of sclerosant, and the use of microcatheters. The influence of balloon rupture on migration of the sclerosant and in-hospital mortality was analyzed with the Fisher exact test. The prevalence of balloon rupture was 8.7% (six of 69 patients). No significant risk factor for balloon rupture was identified because of the small number of balloon rupture cases. Migration of the sclerosant occurred in three patients with early balloon rupture within 1 hour. One of these patients died of recurrent gastric variceal bleeding and another experienced dyspnea and died of fungal sepsis. Among the 63 patients without rupture, no migration of the sclerosant was noted, and one patient died of sepsis caused by liver abscess. Incidences of sclerosant migration and in-hospital mortality were significantly higher in patients with balloon rupture versus patients without balloon rupture (P = .018 and P < .001, respectively). Balloon rupture during BRTO occurred in 8.7% of patients. Balloon rupture may cause rapid migration of sclerosant, pulmonary embolism, and recurrent gastric variceal bleeding.

Septic Complication After Balloon-Occluded Retrograde Transvenous Obliteration of Duodenal Variceal Bleeding

We report a 64-year-old woman with duodenal varices who underwent balloon-occluded retrograde transvenous obliteration (B-RTO) complicated by intraprocedural variceal rupture. The patient developed shivering and a fever higher than 40°C 3 days after the B-RTO procedure. A blood culture grew Entereobacter cloacoe. This case represents a rare septic complication of B-RTO for duodenal varices.

Long‐term follow up of esophageal varices after balloon‐occluded retrograde transvenous obliteration for gastric varices

Because the procedure of balloon-occluded retrograde transvenous obliteration (B-RTO) causes extensive thrombosis of the major shunt that connects the spleen and gastric/renal venous systems, an increase in portal pressure is unavoidable. The aim of the present study was to assess the long-term outcome of B-RTO, including changes in esophageal varices. B-RTO was conducted in 22 patients with gastric varices, who were divided according to the severity of esophageal varices at baseline; there were no esophageal varices (n = 7), F(1) varices (n = 11), and F(2) varices (n = 4). The outcome measures included the development/worsening of esophageal varices after B-RTO and survival rates. The cumulative bleeding-free probability for all 22 patients at 3 years after B-RTO was 100%. The overall 3-year survival was 94.4%. Seven patients who had no esophageal varices prior to B-RTO did not develop any after the procedure. Seven (63.6%) of the 11 patients with stage F(1) esophageal varices prior to B-RTO showed no changes in the varices after B-RTO, while two patients progressed to F(2) varices and two developed F(3) varices. The cumulative treatment-free probability of the esophageal varices at 24 months after B-RTO was 100% for patients without esophageal varices at baseline, 80.8% for patients with pre-existing F(1) varices, and 75% for those with pre-existing F(2) varices. Although the B-RTO procedure is considered useful for the treatment of gastric varices, changes in hemodynamics due to obliteration of this major shunt must be taken into account and observed closely.

Gastric ulcer after prophylactic balloon-occluded retrograde transvenous obliteration

A 74-year-old man with compensated hepatitis C virus-related liver cirrhosis was admitted for the treatment of small hepatocellular carcinoma (HCC) by radiofrequency ablation therapy (RFA). As a routine pretreatment examination, gastrointestinal endoscopy was performed, and large nodular varices were observed in the gastric fornix, with telangiectasia on top of the varices. As soon as the RFA was completed, prophylactic balloon-occluded retrograde transvenous obliteration (B-RTO) was performed. Seven days after the B-RTO, the patient complicated of upper abdominal pain. Gastrointestinal endoscopy was performed, and a deep ulcer, located at the top of the tumor-shaped gastric varices, was found. The ulcer showed rapid healing after 1-week administration of a proton pump inhibitor (PPI). A severe ulcer after a B-RTO procedure, is extremely rare, because sclerosing agents rarely flow into the gastric mucosa. The ulcer in this patient was deep and large, and it may have been due to direct mucosal damage caused by the sclerosing agent, because mucosal telangiectasia on top of the varices was observed before the B-RTO. It is likely that, in this patient, the mucosal vessels communicated with the submucosal large varices, and ethanolamine oleate (EOI) flowed into the gastric mucosa via this communication. Based on our experience, we recommend periodic follow-up endoscopy.

“Downgrading” of Gastric Varices with Multiple Collateral Veins in Balloon-occluded Retrograde Transvenous Obliteration

The efficacy of a "downgrading" method for treatment of gastric varices (GVs) was evaluated in 15 patients who had undergone balloon-occluded retrograde transvenous obliteration (B-RTO) of GVs with multiple collateral veins. Downgrading in this study was meant to transform high-grade GVs into GVs with a low-grade architecture more amenable to treatment. Success was defined as gastrorenal shunt occlusion at the proximal site with a 6-F balloon catheter advanced over a microcatheter and without opacification of large collateral vessels. Thirteen of 15 patients with grade 3/4 GVs had their GVs successfully downgraded. The procedure is thought to be safe and effective in the initial B-RTO procedure.