William T Kuo

Stanford Medicine, Stanford, California, United States

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Publications (74)222.25 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Systemic thrombolysis for acute PE carries up to a 20% risk of major bleeding, including a 2-5% risk of hemorrhagic stroke. We evaluated the safety and effectiveness of catheter-directed therapy (CDT) as an alternative treatment for acute PE. One hundred one consecutive patients receiving CDT for acute PE were prospectively enrolled in a multicenter registry. Massive PE (n=28) and submassive PE (n=73) were treated with immediate catheter-directed mechanical or pharmacomechanical thrombectomy and/or catheter-directed thrombolysis via low-dose hourly drug infusion with tPA or urokinase. Clinical success was defined as meeting all criteria: stabilization of hemodynamics, improvement in pulmonary hypertension and/or right heart strain, and survival to hospital discharge. Primary safety outcomes were major procedure-related complications and major bleeding events. There were 53 men and 48 women with average age of 60 years (range, 22-86 years) and mean BMI of 31.03±7.20 kg/m2. The average thrombolytic doses were 28.0±11 mg tPA (n=76) and 2,697,101±936,287 IU for urokinase (n=23). Clinical success was achieved in 24/28 (85.7%)(95% CI, 67.3%-96.0%) patients with massive PE and 71/73 (97.3%)(95% CI, 90.5%-99.7%) with submassive PE. The mean PA pressure improved from 51.17±14.06 mmHg to 37.23±15.81 mmHg (n=92)(P<0.0001). Among patients monitored with follow-up echocardiography, 57/64 (89.1%)(95% CI, 78.8%-95.5%)(p<0.0001) showed improvement in right heart strain. There were no major procedure-related complications, no major hemorrhages, and no hemorrhagic strokes. Catheter-directed therapy improves clinical outcomes in acute PE patients while minimizing the risk of major bleeding. At experienced centers, CDT is a safe and effective treatment for both acute massive and submassive PE. NCT01097928, available at http://clinicaltrials.gov/show/NCT01097928.
    Chest 04/2015; DOI:10.1378/chest.15-0119 · 7.13 Impact Factor
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    ABSTRACT: The purpose of the study is to evaluate the influence of respiratory-induced vena caval hemodynamic changes on filter migration/penetration. After placement of either a Gunther Tulip or Celect IVC filter, 101 consecutive patients scheduled for filter retrieval were prospectively enrolled in this study. Pre-retrieval CT scans were used to assess filter complications and to calculate cross-sectional area in three locations: at level of filter strut fixation, 3 cm above and 3 cm below. A 3D finite element simulation was constructed on these data and direct IVC pressure was recorded during filter retrieval. Cross-sectional areas and pressures of the vena cava were measured during neutral breathing and in Valsalva maneuver and identified filter complications were recorded. A statistical analysis of these variables was then performed. During Valsalva maneuvers, a 60 % decrease of the IVC cross-sectional area and a fivefold increase in the IVC pressure were identified (p < 0.001). There was a statistically significant difference in the reduction of the cross-sectional area at the filter strut level (p < 0.001) in patient with filter penetration. Difficulty in filter retrieval was higher in penetrated or tilted filters (p < 0.001; p = 0.005). 3D computational models showed significant IVC deformation around the filter during Valsalva maneuver. Caval morphology and hemodynamics are clearly affected by Valsalva maneuvers. A physiological reduction of IVC cross-sectional area is associated with higher risk of filter penetration, despite short dwell times. Physiologic data should be used to improve future filter designs to remain safely implanted over longer dwell times.
    CardioVascular and Interventional Radiology 03/2015; DOI:10.1007/s00270-015-1077-4 · 1.97 Impact Factor
  • Journal of Vascular and Interventional Radiology 02/2015; 26(2):S227. DOI:10.1016/j.jvir.2014.12.604 · 2.15 Impact Factor
  • William T Kuo · Scott W Robertson
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    ABSTRACT: A 46-year-old woman underwent inferior vena cava filter placement before bariatric surgery and returned within 6 months for routine removal. She complained of a 1-week history of severe chest pain, and during retrieval, two fractured filter components were identified including one arm in the right ventricle. The filter body and one fragment were successfully retrieved, but the fragment in the right ventricle was refractory to percutaneous retrieval. During open-heart surgery, the fragment was found traversing through the ventricular wall resulting in cardiac tamponade. Electron microscopic fragment analysis revealed high-cycle metal fatigue indicating the filter design failed to withstand this patient's natural inferior vena cava biomechanical motions. Copyright © 2015 SIR. Published by Elsevier Inc. All rights reserved.
    Journal of vascular and interventional radiology: JVIR 01/2015; 26(1):111-115.e1. DOI:10.1016/j.jvir.2014.08.001 · 2.15 Impact Factor
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    ABSTRACT: To optimize surveillance schedules for the detection of recurrent hepatocellular carcinoma (HCC) after liver-directed therapy. New methods have emerged that allow quantitative analysis and optimization of surveillance schedules for diseases with substantial rates of recurrence such as HCC. These methods were applied to 1,766 consecutive chemoembolization, radioembolization, and radiofrequency ablation procedures performed on 910 patients between 2006 and 2011. Computed tomography or magnetic resonance imaging performed just before repeat therapy was set as the time of "recurrence," which included residual and locally recurrent tumor as well as new liver tumors. Time-to-recurrence distribution was estimated by Kaplan-Meier method. Average diagnostic delay (time between recurrence and detection) was calculated for each proposed surveillance schedule using the time-to-recurrence distribution. An optimized surveillance schedule could then be derived to minimize the average diagnostic delay. Recurrence is 6.5 times more likely in the first year after treatment than in the second. Therefore, screening should be much more frequent in the first year. For eight time points in the first 2 years of follow-up, the optimal schedule is 2, 4, 6, 8, 11, 14, 18, and 24 months. This schedule reduces diagnostic delay compared with published schedules and is cost-effective. The calculated optimal surveillance schedules include shorter-interval follow-up when there is a higher probability of recurrence and longer-interval follow-up when there is a lower probability. Cost can be optimized for a specified acceptable diagnostic delay or diagnostic delay can be optimized within a specified acceptable cost. Copyright © 2014 SIR. Published by Elsevier Inc. All rights reserved.
    Journal of vascular and interventional radiology: JVIR 11/2014; 26(1). DOI:10.1016/j.jvir.2014.09.013 · 2.15 Impact Factor
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    ABSTRACT: To study changes produced within the inferior vena cava (IVC) during respiratory movements and identify their possible clinical implications.
  • Journal of Vascular and Interventional Radiology 03/2014; 25(3):S25. DOI:10.1016/j.jvir.2013.12.060 · 2.15 Impact Factor
  • William T Kuo · Steven E Deso · Scott W Robertson
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    ABSTRACT: A 48-year-old man presented with symptomatic inferior vena cava (IVC) occlusion from a chronically thrombosed and embedded Vena Tech LGM filter resulting in exercise intolerance from diminished cardiac preload and postthrombotic syndrome from chronic venous insufficiency. The patient was treated using a new PRIME technique-Piecemeal Removal by Intentional MEchanical fracture-to achieve successful filter retrieval 16 years after implantation. Removal of the obstructing filter permitted endovascular IVC recanalization with restoration of venous outflow and alleviation of venous obstructive symptoms. Cardiac preload was restored, allowing the patient to resume long-distance running, and he successfully completed a half-marathon 3 months after treatment.
    Journal of vascular and interventional radiology: JVIR 11/2013; 24(11):1731-7. DOI:10.1016/j.jvir.2013.07.028 · 2.15 Impact Factor
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    ABSTRACT: BACKGROUND: ALTHOUGH CHRONICALLY IMPLANTED INFERIOR VENA CAVA FILTERS MAY RESULT IN FILTER-RELATED MORBIDITY, THERE IS CURRENTLY NO ROUTINE OPTION FOR REMOVING SUCH FILTERS WHEN THEY BECOME FIRMLY EMBEDDED ALONG THE VENA CAVA ENDOTHELIUM.METHODS AND RESULTS: DURING A 3-YEAR PERIOD, 100 CONSECUTIVE PATIENTS WERE PROSPECTIVELY ENROLLED IN A SINGLE-CENTER STUDY. THERE WERE 42 MEN AND 58 WOMEN (MEAN AGE, 46 YEARS; LIMITS, 1876 YEARS). RETRIEVAL INDICATIONS INCLUDED FILTER-RELATED ACUTE INFERIOR VENA CAVA THROMBOSIS, CHRONIC INFERIOR VENA CAVA OCCLUSION, AND PAIN FROM RETROPERITONEAL OR BOWEL PENETRATION. FILTER RETRIEVAL WAS ALSO PERFORMED TO PREVENT RISKS FROM PROLONGED IMPLANTATION AND TO POTENTIALLY ELIMINATE THE NEED FOR LIFELONG ANTICOAGULATION. AFTER STANDARD METHODS FAILED, PHOTOTHERMAL TISSUE ABLATION WAS ATTEMPTED WITH A LASER SHEATH POWERED BY A 308-NM XENON CHLORIDE EXCIMER LASER. APPLIED FORCES WERE RECORDED WITH A DIGITAL TENSION METER BEFORE AND DURING LASER ACTIVATION. LASER-ASSISTED RETRIEVAL WAS SUCCESSFUL IN 98.0% (95% CONFIDENCE INTERVAL [CI], 93.0%99.8%) WITH MEAN IMPLANTATION OF 855 DAYS (LIMITS, 376663 DAYS; 18 YEARS). GNTHER-TULIP (N=34), CELECT (N=12), OPTION (N=17), OPTEASE (N=20, 1 FAILURE), TRAPEASE (N=6, 1 FAILURE), SIMON-NITINOL (N=1), 12F STAINLESS STEEL GREENFIELD (N=4), AND TITANIUM GREENFIELD (N=6). THE AVERAGE FORCE DURING FAILED STANDARD RETRIEVALS WAS 7.2 VERSUS 4.6 POUNDS DURING LASER-ASSISTED RETRIEVALS (P0.0001). THE MAJOR COMPLICATION RATE WAS 3.0% (95% CI, 0.6%8.5%), THE MINOR COMPLICATION RATE WAS 7.0% (95% CI, 0.3%13.9%), AND THERE WERE 4 ADVERSE EVENTS (2 COAGULOPATHIC HEMORRHAGES, 1 RENAL INFARCTION, AND 1 CHOLECYSTITIS; 4.0%; 95% CI, 1.1%9.9%) AT MEAN FOLLOW-UP OF 500 DAYS (LIMITS, 841079 DAYS). SCAR TISSUE ABLATION WAS HISTOLOGICALLY CONFIRMED IN 96.0% (95% CI, 89.9%98.9%). SUCCESSFUL RETRIEVAL ALLOWED CESSATION OF ANTICOAGULATION IN 30 OF 30 (100%) PATIENTS AND ALLEVIATED MORBIDITY IN 23 OF 24 PATIENTS (96%).CONCLUSIONS: EXCIMER LASERASSISTED REMOVAL IS EFFECTIVE IN REMOVING EMBEDDED INFERIOR VENA CAVA FILTERS REFRACTORY TO STANDARD RETRIEVAL AND HIGH FORCE. THIS METHOD CAN BE SAFELY USED TO PREVENT AND ALLEVIATE FILTER-RELATED MORBIDITY.CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01158482.
    Circulation Cardiovascular Interventions 09/2013; 6(5). DOI:10.1161/CIRCINTERVENTIONS.113.000665 · 6.98 Impact Factor
  • Journal of Vascular and Interventional Radiology 04/2013; 24(4):S84. DOI:10.1016/j.jvir.2013.01.202 · 2.15 Impact Factor
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    ABSTRACT: On finding that the length of undeployed Viabil covered stents is shorter than the nominal length, we sought to determine the actual length of Viabil stents deployed in patients to treat biliary obstruction. This retrospective study evaluates the actual length of deployed Viabil stents when delivered through standard pin-pull techniques.Materials and Methods We retrospectively reviewed our procedure records for Viabil stent placement procedures performed between Feb. 2006 and May 2012. We measured the actual length of deployed Viabil stents using two methods: (1) Postplacement CT data was sent to a 3D viewer, and a multisegment measuring tool was used to measure thin-slice multiplanar reconstructed images along the center line (n=42), or (2). Measurements were performed on digital spot film images using an internal reference of known length (n=21). Six patients were measured using both techniques.ResultsIn the 88 procedures performed in 86 patients, 138 Viabil stents were deployed (range 1-5 per patient). 57 procedures resulted in placement of stents that could be measured with the techniques described. All but one stent was shorter post-deployment than its nominal length (Table). 48 stents were fenestrated; the mean length of the fenestrated segment was 1.8 cm (nominal 2 cm; range 1.3 to 2.0). At least 3 patients required placement of additional stent to cover a distance within the nominal range of the initially placed stent.Conclusion The actual deployed length of Viabil covered stents falls short of nominal length when deployed with standard pin-pull technique. To prevent inadequate coverage that may require additional stent placement, this difference should be accounted for during stent selection or by following the manufacturer's suggested technique of putting traction on the device shaft during deployment to elongate the stent. Table 1
    Journal of Vascular and Interventional Radiology 04/2013; 24(4):S53. DOI:10.1016/j.jvir.2013.01.121 · 2.15 Impact Factor
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    ABSTRACT: Viabil ePTFE/FEP-covered biliary stents have shown excellent patency and reported migration rates of 0.3% based on early clinical studies in patients with malignant biliary strictures. Strictures at surgical hepaticojejunostomy sites present a particular challenge because of the short landing zone within the duct. The purpose of this study is to assess outcomes of Viabil stent placement for hepaticojejunostomy strictures.Materials and Methods We retrospectively reviewed our records for Viabil stent placement procedures performed between Feb. 2006 and Sept. 2012 and included in this study patients who had undergone Viabil placement to treat hepaticojejunostomy strictures. The cause of stricture and follow-up clinical and radiographic data were collected.ResultsOf a total of 90 Viabil placement procedures in 88 patients, 13 patients underwent 14 interventions in which a Viabil stent was deployed across a hepaticojejunostomy for malignant (n=12) and benign (n=1) biliary strictures. The following sizes were used: 8×4 (n=5), 8×6 (n=6), 10×6 (n=4), 10×8 (n=1), and 10×10 (n=1) (mm diameter × cm length). One patient underwent stent placement in a double-barrel configuration, and another underwent stent placement in a Y configuration. During followup (mean 115 d, range 0-404 d), three stents (21% of placements), all 8x4 size, migrated: one on the day of placement and two detected 200 and 340 days later. There were no complications from stent passage. Three patients required reintervention for occluded 10 mm stents (21% of placements): One with benign stricture underwent stent removal (381 d), and two underwent biliary drain placement (137 and 155 d). One of the stent occlusion patients had Viabil stents placed in a Y configuration.Conclusion Viabil placement for hepaticojejunostomy strictures is technically feasible but is associated with higher rates of stent migration (21%) than described in the literature. As the migrated stents were only 4 cm long, use of longer fenestrated stents, with greater apposition to the hepatic ducts, may be helpful to avoid that complication.
    Journal of Vascular and Interventional Radiology 04/2013; 24(4):S54. DOI:10.1016/j.jvir.2013.01.124 · 2.15 Impact Factor
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    ABSTRACT: PURPOSE: To evaluate clinical outcomes, characterize adherent tissue, and analyze inferior vena cava (IVC) filter fractures in patients undergoing complex retrieval for management of filter-related complications. To elucidate mechanisms of filter fracture by radiographic and electron microscopic (EM) evaluation. MATERIALS AND METHODS: Over 2.5 years, 50 consecutive patients with fractured and/or penetrating filter components were prospectively enrolled into a single-center study. There were 19 men and 31 women (mean age, 42 y; range, 15-73 y). All patients underwent complex filter retrieval after failure of standard methods, and retrieval indications along with resultant clinical outcomes were evaluated. Specimens with adherent tissue underwent histologic analysis, and all fractured components were studied with EM. RESULTS: Retrieval was successful in all 50 cases (mean implantation, 815 d; range, 20-2,599 d) among the following filters: G2X (n = 23),G2 (n = 9), Eclipse (n = 3), Recovery (n = 4), ALN (n = 1), Celect (n = 7), OptEase (n = 2), and Simon Nitinol (n = 1). Mean indwell time in fractured filters (n = 31) was 1,082 days, versus 408 days in nonfractured filters (n = 19; P = .00169). Neointimal hyperplasia/fibrosis was seen in 46 of 48 specimens with adherent tissue (96%). Among 61 fractured components from conical filters, 35 had extravascular penetration whereas 26 remained intravascular (11 free-floating in IVC, 15 embolized centrally), and EM revealed fracture modes of high-cycle fatigue (n = 53), overload (n = 6), and indeterminate (n = 2). Following retrieval, previously prescribed lifelong anticoagulation was discontinued in 30 of 31 patients (97%). Filter-related symptoms from IVC occlusion, component embolization, and penetration-induced abdominal pain, duodenal injury, and/or small-bowel volvulus were alleviated in all 26 cases (100%). There were no long-term complications at a mean follow-up of 371 days (range, 67-878 d). CONCLUSIONS: The risk of filter fracture increases after 408 days (ie,>1 y) of implantation and is associated with symptomatic extravascular penetration and/or intravascular embolization. Complex methods can be used to safely remove these devices, alleviate filter-related morbidity, and allow cessation of anticoagulation.
    Journal of vascular and interventional radiology: JVIR 03/2013; 24(5). DOI:10.1016/j.jvir.2013.01.008 · 2.15 Impact Factor
  • William T Kuo
    Journal of vascular and interventional radiology: JVIR 01/2013; 24(1):24-6. DOI:10.1016/j.jvir.2012.10.023 · 2.15 Impact Factor
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    ABSTRACT: Compression of the left common iliac vein (CIV; LCIV) is a known risk factor for lower-extremity deep vein thrombosis (DVT). This study was performed to model the probability of DVT based on LCIV diameter and apply this to a quantitative DVT risk factor scoring system. Medical records were used to identify female patients younger than 45 years of age who were diagnosed with lower-extremity DVT (n = 21) and age-matched control subjects (n = 26) who presented to the emergency department with abdominal pain. Minimum CIV diameters were measured on computed tomography. Based on published reporting standards, 13 risk factors were scored for patients diagnosed with left-sided DVT and for control subjects. The association between vein diameter and DVT was examined by Mann-Whitney test. Odds of DVT based on vein diameter was assessed by logistic regression. Mean minimum LCIV diameters were 4.0 mm for patients with DVT and 6.5 mm for patients without DVT (P = .001). The odds of left DVT increased by a factor of 1.68 for each millimeter decrease in LCIV diameter (odds ratio = 1.68; P = .006; 95% confidence interval, 1.16-2.43). As the risk factor score increased, the relationship between diameter and risk for DVT became stronger; identical LCIV diameters were associated wtih a higher probability of developing DVT if the risk factor score was higher. Stenosis of the LCIV was found to be a strong independent risk factor for development of DVT. Moreover, each millimeter decrease in CIV diameter increased the odds of DVT by a factor of 1.68.
    Journal of vascular and interventional radiology: JVIR 11/2012; 23(11):1467-72. DOI:10.1016/j.jvir.2012.07.030 · 2.15 Impact Factor
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    ABSTRACT: To determine the feasibility and efficacy of applying an established innovation process to an active academic interventional radiology (IR) practice. The Stanford Biodesign Medical Technology Innovation Process was used as the innovation template. Over a 4-month period, seven IR faculty and four IR fellow physicians recorded observations. These observations were converted into need statements. One particular need relating to gastrostomy tubes was diligently screened and was the subject of a single formal brainstorming session. Investigators collected 82 observations, 34 by faculty and 48 by fellows. The categories that generated the most observations were enteral feeding (n = 9, 11%), biopsy (n = 8, 10%), chest tubes (n = 6, 7%), chemoembolization and radioembolization (n = 6, 7%), and biliary interventions (n = 5, 6%). The output from the screening on the gastrostomy tube need was a specification sheet that served as a guidance document for the subsequent brainstorming session. The brainstorming session produced 10 concepts under three separate categories. This formalized innovation process generated numerous observations and ultimately 10 concepts to potentially to solve a significant clinical need, suggesting that a structured process can help guide an IR practice interested in medical innovation.
    Journal of vascular and interventional radiology: JVIR 04/2012; 23(4):488-94. DOI:10.1016/j.jvir.2011.12.029 · 2.15 Impact Factor
  • Journal of Vascular and Interventional Radiology 03/2012; 23(3):S26–S27. DOI:10.1016/j.jvir.2011.12.095 · 2.15 Impact Factor
  • Journal of Vascular and Interventional Radiology 03/2012; 23(3):S16. DOI:10.1016/j.jvir.2011.12.065 · 2.15 Impact Factor
  • Journal of Vascular and Interventional Radiology 03/2012; 23(3):S128. DOI:10.1016/j.jvir.2011.12.371 · 2.15 Impact Factor
  • Journal of Vascular and Interventional Radiology 03/2012; 23(3):S150. DOI:10.1016/j.jvir.2011.12.494 · 2.15 Impact Factor

Publication Stats

526 Citations
222.25 Total Impact Points

Institutions

  • 2008–2015
    • Stanford Medicine
      • • Division of Interventional Radiology
      • • Department of Radiology
      Stanford, California, United States
  • 2014
    • University of Zaragoza
      Caesaraugusta, Aragon, Spain
  • 2010–2013
    • Vascular and Interventional Radiology
      Chicago, Illinois, United States
  • 2008–2013
    • Stanford University
      • • Department of Radiology
      • • Division of Interventional Radiology
      Palo Alto, California, United States