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Vascular and Interventional Radiology |
1 From the Dotter Interventional Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd, L-342, Portland, OR 97201 (H.H., S.L.W., B.D.P.); and Department of Angiography, Portland Veterans Administration Medical Center, Portland, Ore (B.D.P.). Received December 25, 2006; revision requested March 1, 2007; revision received April 29; final version accepted June 18. H.H. supported by the Swiss National Foundation (SSMBS), Novartis Foundation Switzerland, and the Swiss Radiology Society. Address correspondence to H.H. (e-mail: hanno.hoppe{at}web.de).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSION ADVANCE IN KNOWLEDGE IMPLICATION FOR PATIENT CARE...References |
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Materials and Methods: Institutional Review Board approval for this retrospective HIPAA-compliant study was obtained with waiver of informed consent. DIPS was created in 18 men and one woman (median age, 54 years; range, 45–65 years) by using nitinol polytetrafluoroethylene (PTFE)-covered stent-grafts. The primary indications were intractable ascites (n = 14), acute variceal bleeding (n = 3), and hydrothorax (n = 2). Follow-up included Doppler ultrasonography at 1, 6, and 12 months and venography with manometry at 6-month intervals after the procedure. Shunt patency and cumulative survival were evaluated by using the Kaplan-Meier method and survival curves were plotted. Differences in mean portosystemic gradients (PSGs) were evaluated by using the Student t test. Multiple regression analysis for survival and DIPS patency were performed for the following parameters: Child-Pugh class, model of end-stage liver disease score, pre- and post-DIPS PSGs, pre-DIPS liver function tests, and pre-DIPS creatinine levels.
Results: DIPS creation was successful in all patients. Effective portal decompression and free antegrade shunt flow was achieved in all patients. Intraperitoneal bleeding occurred in one patient during the procedure and was controlled during the same procedure by placing a second nitinol stent-graft. The primary patency rate was 100% at all times during the follow-up period (range, 2 days to 30 months; mean, 256 days; median, 160 days). Flow restrictors were deployed in two (11%) of 19 patients. The 1-year mortality rate was 37% (seven of 19).
Conclusion: Patency after DIPS creation with the nitinol PTFE-covered stent-graft was superior to that after TIPS with the nitinol stent-graft.
© RSNA, 2008
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSION ADVANCE IN KNOWLEDGE IMPLICATION FOR PATIENT CARE...References |
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A previous study demonstrated the advantage of polytetrafluoroethylene (PTFE)-covered stent-grafts over bare stents for use with TIPS, reducing the rates of bile leak and of parenchymal tract stenosis (4–6). In our initial series performed with a homemade PTFE-covered stent-graft, the primary patency of DIPS was greater than that of conventional TIPS performed with bare stents and equal to that of TIPS performed with a PTFE-covered stent-graft (7). Recently, the nitinol PTFE-covered stent-graft (Viatorr, W.L. Gore and Associates, Flagstaff, Ariz) became commercially available.
As stated in this device's instructions for use and the official Food and Drug Administration approval letter dated December 6, 2004, the Viatorr endoprosthesis "is indicated for use in the de novo and revision treatment of portal hypertension and its complications such as variceal bleeding, gastropathy, refractory ascites, and/or hepatic hydrothorax," including TIPS and DIPS procedures. The advantages of using this stent-graft with TIPS have been reported, and its use in a larger clinical series demonstrated increased shunt patency, contributing to lower repeat intervention and bleeding rates (5,8–10). Thus, the purpose of our study was to retrospectively evaluate the midterm patency rate of the Viatorr stent-graft for use with DIPS.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSION ADVANCE IN KNOWLEDGE IMPLICATION FOR PATIENT CARE...References |
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The mean patient age ± standard deviation was 53.8 years ± 4.9 (median age, 54 years; range 45–60 years). The etiology of the liver disease included hepatitis C and ethanol abuse (n = 11), hepatitis C alone (n = 6), and idiopathic cirrhosis (n = 2). One patient underwent liver transplantation before the DIPS procedure in 2001. Two patients were classified as Child-Pugh A, seven as Child-Pugh B, and 10 as Child-Pugh C liver disease. The model of end-stage liver disease United Network for Organ Sharing classification scores ranged from nine to 19 (mean ± 4). Hepatic encephalopathy was clinically evaluated by the referring hepatologic or liver transplant physician and was classified as no, mild (hypersomnia), moderate (somnolence), or severe (stupor or coma) encephalopathy.
No psychometric tests were performed. Before DIPS, 10 patients had no encephalopathy, seven had mild encephalopathy, and two had moderate encephalopathy. Encephalopathy is a relative contraindication to the TIPS/DIPS procedure. The two patients with moderate encephalopathy had debilitating ascites with weekly or biweekly paracentesis and a reasonable remaining synthetic liver function. The bleak outlook of these procedures and their inherent long-term risks were judged by the referring team of specialists to outweigh the relative risk of worsening encephalopathy. Family counsel and input from the caregivers to these patients also influenced the decision to proceed with the DIPS procedure.
The primary indications for the procedure were intractable ascites (n = 14), acute variceal bleeding (n = 3), and hydrothorax (n = 2). A previous TIPS procedure at an outside institution failed in two patients. In one of these, failure occurred owing to a large right hydrothorax and distorted normal anatomy; in the other, the hepatic vein had an unsuitable angle, rendering TIPS creation difficult. At the time of the DIPS procedure, all 19 patients were hemodynamically stable.
Each patient was evaluated by the liver transplant service prior to referral for DIPS. All patients were deemed by the referring services to be suitable candidates who would gain reasonable benefit in palliation of their symptoms, with acceptable risks of complications. These 19 patients represent all patients with DIPS during the study period; no patient was excluded. All DIPS procedures were performed by the same radiologist (B.D.P., with 13 and 4 years respective experience with interventional radiology and DIPS).
Before the procedure, patients underwent abdominal computed tomography (CT) or US examinations to evaluate the patency of the PV. No patient was excluded due to PV occlusion or distortion of normal anatomy.
Nitinol Stent-Graft
The Viatorr nitinol stent-graft has been described in detail elsewhere (10). The 2-cm uncovered part on the portal side facilitates blood flow to side branches of the PV. The covered part on the portal side is coated with expanded PTFE on the inside. The size of the delivery sheaths was 10 F. The noncovered portion of the stent-graft is released by unsheathing; the covered portion is released by pulling a suture line. The stent-graft is available in 8-, 10-, and 12-mm diameters. The covered portion is available in 4–8-cm-long sizes.
DIPS Procedure
The technique used for DIPS creation has been described in detail (7,11). Briefly, an intravascular US probe is advanced from the right common femoral vein to the intrahepatic IVC. A modified Rosch-Uchida liver access set (RUPS-100; Cook, Bloomington, Ind) is introduced into the IVC by using a transjugular approach. Intravascular US is then used to guide a needle puncture from the IVC into the PV near its bifurcation via the caudate lobe of the liver.
The applied intravascular US system consists of a variable 5–10-MHz catheter (Acu-Nav; Acuson, Mountain View, Calif) coupled with a US system (Sequoia; Acuson). The catheter produces 90° "side-fire" sector images with respect to the catheter in the sagittal plane. These images are more analogous to those created with standard 5-MHz transabdominal sector transducers than with other intravascular US systems. The catheter allows detailed real-time visualization of the needle puncture tract from the IVC to the PV. This technique helps prevent potential kinking of the sheath owing to an acute transition to the IVC.
After puncture of the PV, a 5-F pigtail catheter was advanced into the PV and portography was performed. The pigtail catheter was then removed and a 6-mm-diameter, 6-cm-long angioplasty balloon catheter (Opta 5; Cordis, Miami Lakes, Fla) was positioned in the tract between the IVC and PV and partially inflated. A spot radiograph of the partially inflated balloon catheter was performed to guide the stent-graft placement. The distal waist of the balloon marked the PV wall and the proximal waist marked the IVC wall. The distance between both waists was measured as the lengths of the hepatic parenchymal tract between the PV and IVC, the minimum length of the covered portion of the stent-graft required to connect these structures.
The balloon angioplasty catheter was fully inflated to predilitate the tract and a 10-F sheath was advanced into the PV. The direct shunt was completed with a nitinol stent-graft. Stent-graft deployment was monitored by using fluoroscopy and intravascular US. Twenty-three 10-mm-diameter stent-grafts were inserted in 19 patients. Fifteen patients received one stent-graft each, with a covered segment length of 4 cm in four patients, of 5 cm in eight patients, and of 6 cm in three patients. In one patient, the main PV was partially occluded prior to the DIPS procedure; in another, the right PV was occluded; and in a third, intraperitoneal bleeding occurred during the procedure and was controlled.
In four patients, two overlapping stent-grafts were necessary to cover the shunt tract and therefore the tract lengths varied considerably (Fig 1). In three of these patients, the first stent ended before reaching the IVC, with the end occluded by hepatic parenchyma. In one patient, the initial stent deployment was not deep enough. In the patients who required placement of a second stent-graft, there was no instance of stent-graft migration. All of the additional stent-grafts were placed at the initial time of DIPS creation to extend completely into the IVC.
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The portosystemic gradient (PSG) was then measured between the main PV and IVC. If the initial gradient was higher than 15 mm Hg, the shunt was sequentially dilated with a larger balloon in 1-mm increments until the gradient was 15 mm Hg or lower. For dilation, an 8-mm-diameter balloon was used in 12 patients, a 9-mm-diameter balloon in two, and a 10-mm-diameter balloon in five. Final portography was performed. Three patients with variceal bleeding underwent embolization. Technical and hemodynamic successes of the DIPS procedure were recorded (H.H.).
For follow-up venography, all patients underwent right internal jugular vein cannulation with placement of a 10-F sheath in the IVC. The shunt was then catheterized with a 5-F diagnostic catheter and exchanged for a 5-F pigtail catheter, which was placed in the main PV near the confluence with the superior mesenteric vein. Simultaneous pressure measurements were then obtained through the 10-F sheath and 5-F pigtail catheter, followed by venography.
At the beginning of the procedure, all patients were given 1 g intravenous cefotaxime (Hoechst-Roussel, Somerville, NJ). A dose of 3000 IU heparin (American Pharmaceutical Partners, Los Angeles, Calif) was administered to patients without coagulation disorders after the PV was punctured successfully and it was established that no injury to the liver capsule had occurred. The IVC puncture site, needle track in the liver, and PV puncture site were visualized by using direct intravascular US imaging. There was no evidence of subcapsular hematoma, liver capsule injury, or intrahepatic hematoma. When the procedure was performed in patients with acute bleeding, no heparin was given. During follow-up, no further anticoagulation therapy or platelet inhibitors were given.
Follow-up Examination
Patients were followed up with Doppler US examinations at 1, 6, and 12 months postoperatively, and venography and manometry at 6-month intervals postoperative. US criteria for a patent shunt are described elsewhere (12). With the stent-graft, it was not possible to perform a 24-hour baseline US examination. Immediately after stent-graft insertion, the expanded PTFE material still contains many air bubbles, severely limiting the use of US imaging. These air bubbles usually resolve in 2–4 days. If there was clinical or US-based suspicion of shunt insufficiency, shunt venograms and manometry were obtained. The same radiologist (B.D.P.) who participated in the primary intervention performed venograms and US.
Liver function parameters and bilirubin levels were measured at each examination and the clinical situation of the patient was evaluated with regard to overt hepatic encephalopathy. US follow-up of DIPS is remarkably unreliable owing to the deep location of the shunt and the necessary angles of Doppler interrogation (7,11). In general, US readings tend to overcall stenosis or occlusion of the shunt; in the early days of DIPS, this led to many unnecessary venographic studies. We have since learned to realistically evaluate the velocities generated in the US studies and follow up our patients clinically. If there is any concern regarding the patency of the shunt, we proceed directly to venography with pressure measurements.
Study End Points and Definitions
In all patients, the PV target was situated at the PV bifurcation or the main PV segment just below the bifurcation, which was believed to represent a safe intrahepatic segment on the basis of intravascular US assessment. The main right and left PV branches were not individually targeted. Technical success was defined as the ability to correctly place the stent-graft between the IVC and PV (main or bifurcation).
Hemodynamic success was defined as a reduction of the PSG to 15 mm Hg or lower. Shunt stenosis was defined as a 50% or greater narrowing of the stent-graft lumen and/or an increase in the PSG above 15 mm Hg, as determined by using portography with manometry. Shunt occlusion was defined as the absence of flow through the shunt as determined by using venography.
The primary patency period was defined as the time from DIPS creation to the first intervention to treat a shunt stenosis, or until the study end point (see below). If a revision or intervention was performed to treat a shunt stenosis, the time period thereafter until the study end point was defined as the secondary patency period. If an elective intervention was performed to enlarge an already mainly patent shunt to treat persistent ascites by further decreasing the PSG, DIPS was considered to remain primarily patent, provided that there was no significant stenosis and the PSG remained below 15 mm Hg.
Clinical success was defined as the resolution of indications (see above) for which DIPS was created, namely improvement of ascites (n = 14), cessation of bleeding in patients with variceal bleeding (n = 3), or hydrothorax (n = 2). Because ascites is often multifactorial and may not entirely resolve after a portal decompression procedure, we regarded improvement rather than complete resolution of ascites as a successful clinical result. Refractory ascites was defined as recurrent tense ascites not improved by using diuretic medication and sodium restriction or ascites requiring frequent paracentesis or frequent hospitalizations for control (13). All patients were monitored clinically for the presence and level of encephalopathy by the referring medical team before the procedure and then followed up longitudinally.
Procedural complications, including stent malpositioning, liver trauma, hemoperitoneum, hemobilia, entry site complications, renal failure, and acute or worsening encephalopathy were recorded (S.L.W.), as were 30-day morbidities, including liver failure and death (14). The repeat intervention rate was also recorded. End points of this study were liver transplantation, patient death, or occlusion of the shunt in which patency could not be restored by percutaneous means.
Statistical Analysis
Shunt patency and cumulative survival were evaluated by using the Kaplan-Meier method, and survival curves were plotted (15). Censored events included liver transplantation, patient death, or termination of follow-up. Differences in mean PSG were evaluated by using the Student t test. Multiple regression analysis for survival and DIPS patency was performed for the following parameters: Child-Pugh class, model of end-stage liver disease score, pre- and post-DIPS PSG, pre-DIPS liver function tests (total bilirubin level, albumin level, and international normalized ratio), and pre-DIPS creatinine levels.
A P value of less than .05 indicated a significant difference. Analysis was performed (H.H.) with statistical software (Prism, version 4.01, and InStat, version 3.0; GraphPad Software, San Diego, Calif).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSION ADVANCE IN KNOWLEDGE IMPLICATION FOR PATIENT CARE...References |
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Hemodynamic Success
Effective portal decompression and free antegrade shunt flow was achieved in all patients. The mean portal pressure gradient decreased significantly (P <.001) from 23.2 mm Hg ± 5.1 (95% confidence interval: 20.7, 25.6) before DIPS creation to 8.2 mm Hg ± 3 (95% confidence interval: 6.8, 9.7) after.
Clinical Success
Eight patients died and one patient underwent liver transplantation during the follow-up period, which ranged from 2 days to 30 months (mean, 256 days; median, 160 days). One patient underwent liver transplantation 2 months after DIPS creation. Three patients underwent DIPS creation and variceal embolization for the primary indication of acute upper gastrointestinal tract bleeding. During the follow-up period, no further upper gastrointestinal bleeding occurred.
Fourteen patients with ascites (n = 13) or hydrothorax (n = 1) as the primary indication for DIPS survived the 1-month follow-up examination. Four patients did not undergo follow-up studies at 1 month. Eight patients experienced reduction in their ascites; however, ascites redeveloped in one patient. Hydrothorax declined in one patient after DIPS creation.
Four of 19 patients experienced acute liver failure with encephalopathy and hepatic coma ultimately leading to death. In another four patients with mild (n = 2) or moderate (n = 2) encephalopathy at baseline, encephalopathy worsened after DIPS creation. The rate of increased encephalopathy was 42% (eight of 19).
DIPS Patency
The follow-up period ranged from 2 days to 30 months (mean, 256 days; median, 160 days). Two patients died of acute liver failure after DIPS creation and were excluded from follow-up. Of the remaining 17 patients, DIPS patency was confirmed in eight at 1 month by using US. Intravenous contrast material–enhanced CT was performed in one patient and revealed a patent shunt. A venogram was obtained in another patient, demonstrating a patent shunt with a PSG of 9 mm Hg. Six patients did not undergo follow-up US at 1 month. One of these patients underwent liver transplantation 2 months after DIPS creation and the shunt patency was documented by direct inspection at the time of surgery; the patency at 1 month could therefore be inferred.
Five patients died of acute liver failure prior to the 6-month follow-up (at days 41, 48, 62, 93, and 162, respectively). In the 12 remaining patients, DIPS patency was confirmed by using US in two patients and CT in one patient. A venogram in two patients demonstrated a PSG of 6 and 7 mm Hg. One patient underwent liver transplantation 2 months after DIPS creation and the patency of his shunt was documented by direct inspection at the time of surgery. Five patients did not undergo follow-up imaging studies at 6 months. In the remaining 11 patients, DIPS patency was confirmed by using US in two and CT in two; in two patients, venograms demonstrated PSGs of 5 and 15 mm Hg (Fig 2).
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Six other patients died of acute liver failure on days 21, 41, 48, 62, 93, and 162. DIPS revision was successfully performed in another patient on day 2 after DIPS creation with placement of a 5-mm flow restrictor, increasing the patient's PSG from 9 to 14 mm Hg (Fig 4). The repeat intervention rate in this study was 11% (two of 19). No shunt stenosis or occlusion occurred. No liver trauma, hemobilia, renal failure, or entry site complications occurred. One patient developed hepatoma after DIPS. The 30-day mortality rate in this series was 11% (two of 19); the overall mortality rate was 37% (seven of 19).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSION ADVANCE IN KNOWLEDGE IMPLICATION FOR PATIENT CARE...References |
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For successful DIPS creation, a covered stent-graft is necessary because deployment of a bare stent at an extrahepatic PV puncture site could cause intraperitoneal bleeding. In recent animal studies, evaluation of different stent-graft materials, including PTFE, silicon, Dacron (synthetic polyester), and polyester revealed that PTFE-covered stent-grafts have superior patency when used with TIPS creation and related procedures (16–20).
The commercially available Viatorr TIPS stent-graft used for DIPS creation in our study is a U.S. Food and Drug Administation–approved, PTFE-covered, self-expanding nitinol stent-graft designed for use in TIPS and related procedures. It has a smooth surface which permits a higher initial flow rate than a noncovered stent and effectively prevents protrusion of liver tissue into the hepatic parenchymal tract as well as biliary leaks (10). Its professional manufacture guarantees better and more uniform quality and stability than does the homemade PTFE-covered stent-graft, reducing the risk of shunt occlusion due to technical failure. Moreover, its delivery system precludes inadvertent uncovering of the stent due to rolling back of the PTFE covering, a contingency of our homemade stent-graft delivery systems.
Use of the stent-graft in TIPS procedures has been documented in several studies. In one of the earliest studies (9) the researchers reported an 80% primary patency rate and a 100% secondary patency rate. In a study by Rossi et al (21), a primary patency rate of 83% over a minimum follow-up of 9 months was reported. In another study (22), in-graft patency was 100% in 10 of 16 patients with follow-up, but additional stent-graft placement for revision was required in 10 patients who developed hepatic vein stenosis in portions of the outflow tract not covered by the initial stent-graft.
The likelihood of developing hepatic vein stenosis may be reduced by extending the stent-graft completely through the hepatic vein to the IVC. Hausegger et al (10) recently reported primary patency rates of 87% at 6 months and 81% at 12 months in a series of 71 patients, but venographic follow-up at 12 months was performed in only 20% of patients.
In our series of 19 patients, we achieved a primary patency rate of 100% for as long as 30 months. This patency rate is greater than the reported patency rates for TIPS with the stent-graft. It is also better than our prior experience with DIPS by using homemade PTFE-covered stent-grafts, which had a primary patency rate of 75% 1 year after DIPS creation (7). This improved patency suggests that the use of a nitinol stent-graft in DIPS may result in greater patency than its use in TIPS. This improved patency of the nitinol stent-grafts over the homemade grafts in DIPS is probably a function of the superior delivery system and construction of the commercially available stent-grafts.
In one (6%) of our patients, hemoperitoneum occurred after the DIPS procedure owing to extrahepatic PV puncture. This rate is greater than the 1% hemoperitoneum rate suggested by the Society of Cardiovascular and Interventional Radiology Quality Improvement Guidelines (14). The hemoperitoneum in our patient was not related to extrahepatic puncture but resulted from initial stent malpositioning consequent to deployment of the bare part of the stent outside of the extrahepatic PV. Bleeding was controlled by placing an overlapping stent during the same procedure.
The blind PV puncture is the critical step of the TIPS procedure and has the highest potential for procedural complications and patient morbidity. In the DIPS procedure, the Acu-Nav transducer and the coaxial sheath method are used, which routinely allow for direct IVC-to-PV puncture in one needle pass (7). Furthermore, intravascular US has proved extremely helpful in guiding stent-graft placement, contributing to reduced fluoroscopy time. Intravascular US-guided DIPS offers a potentially safer and more efficient alternative to the traditional blind TIPS approach.
The balance between minimizing encephalopathy and preventing the recurrence of bleeding or ascites is mainly determined by the diameter of the stent-graft. Given the stent-graft's smooth surface, higher initial flow rates, diminished pseudointimal hyperplasia, and exclusion of hepatic parenchyma within the stent, the hepatic encephalopathy rate could potentially be worse with stent-grafts versus bare stents (10). The rate of increased encephalopathy after DIPS in our study was 42%, which is similar to the encephalopathy rates reported in other studies (10,23–26). Thus, the Viatorr stent-graft does not lead to an increase in hepatic encephalopathy after DIPS creation compared with traditional TIPS.
The 1-year mortality rate in our study was low (37%) compared with that in other studies (27,28). Angermayr et al (29) reported that the survival rate after TIPS was higher for patients receiving PTFE-covered stent-grafts than for patients undergoing TIPS creation with bare stents. This finding was also supported by Hausegger et al (10), who reported a remarkably low mortality rate after TIPS creation with Viatorr stent-grafts. The recurrent bleeding rate in our study was also lower than that in previous reports (23).
Our study had limitations and there are disadvantages to the DIPS procedure. First, it requires an additional femoral vein puncture. Second, DIPS performed with a Viatorr stent-graft entails additional cost, primarily associated with the intravascular US catheter and the stent-graft itself. It must be said, though, that the cost of both devices is still lower than the cost of multiple revision procedures often associated with traditional TIPS.
Third, although DIPS can be performed in patients with liver vein occlusion, it requires a longer segment of patent intrahepatic IVC than does TIPS. Fourth, experience with the intravascular US-guided puncture may have an effect on patient outcome. We were able to avoid this disadvantage by having an interventionalist (B.D.P., with 4 years extensive experience with DIPS technique) perform all of the procedures. Last, the study design is retrospective and therefore was not controlled for selection bias, detection of events, and data collection, and the small number of patients limited the statistical power.
In conclusion, our results demonstrate that use of the stent-graft for shunt creation improves DIPS patency. Furthermore, our findings indicate that patency may be even greater after DIPS than after TIPS by using Viatorr stent-grafts. The recurrent bleeding and mortality rates reported here are consistent with our previous DIPS experience and lower than those in previous TIPS studies.
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ADVANCE IN KNOWLEDGE |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSION ADVANCE IN KNOWLEDGE IMPLICATION FOR PATIENT CARE...References |
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IMPLICATION FOR PATIENT CARE |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSION ADVANCE IN KNOWLEDGE IMPLICATION FOR PATIENT CARE...References |
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FOOTNOTES |
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Abbreviations: DIPS = direct intrahepatic portocaval shunt • IVC = inferior vena cava • PSG = portosystemic gradient • PTFE = polytetrafluoroethylene • PV = portal vein • TIPS = transjugular intrahepatic portosystemic shunt
Guarantor of integrity of entire study, H.H.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approved, all authors; literature research, H.H., S.L.W.; clinical studies, all authors; statistical analysis, H.H., S.L.W.; and manuscript editing, all authors
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