Bio

Clinical Focus


  • Gastroenterology

Academic Appointments


Professional Education


  • Board Certification: Internal Medicine, American Board of Internal Medicine (2015)
  • Residency:Stanford University Internal Medicine Residency (2015) CA
  • Medical Education:University of Pittsburgh School of Medicine (2012) PA
  • Fellowship:Stanford University Gastroenterology FellowshipCA

Publications

All Publications


  • ARTERIOVENOUS MALFORMATIONS RESPOND POORLY TO ARGON PLASMA COAGULATION IN PATIENTS WITH CONTINUOUS FLOW LEFT VENTRICULAR ASSIST DEVICES Zikos, T., Namdaran, P., Banerjee, D., Friedland, S., Pan, J. Y. MOSBY-ELSEVIER. 2019: AB563–AB564
  • PER-ORAL ENDOSCOPIC MYOTOMY HAS SIMILAR EFFICACY COMPARED TO LAPAROSCOPIC HELLER MYOTOMY AFTER 4 YEARS: A SINGLE CENTER EXPERIENCE Podboy, A. J., Hwang, J., Rivas, H., Azagury, D., Hawn, M. T., Kamal, A., Triadafilopoulos, G., Zikos, T., Clarke, J. O. MOSBY-ELSEVIER. 2019: AB201–AB202
  • High Prevalence of Slow Transit Constipation in Patients With Gastroparesis JOURNAL OF NEUROGASTROENTEROLOGY AND MOTILITY Zikos, T. A., Kamal, A. N., Neshatian, L., Triadafilopoulos, G., Clarke, J. O., Nandwani, M., Nguyen, L. A. 2019; 25 (2): 267–75

    View details for DOI 10.5056/jnm18206

    View details for Web of Science ID 000464525700012

  • High Prevalence of Slow Transit Constipation in Patients With Gastroparesis. Journal of neurogastroenterology and motility Zikos, T. A., Kamal, A. N., Neshatian, L., Triadafilopoulos, G., Clarke, J. O., Nandwani, M., Nguyen, L. A. 2019

    Abstract

    Background/Aims: Current evidence suggests the presence of motility or functional abnormalities in one area of the gastrointestinal tract increases the likelihood of abnormalities in others. However, the relationship of gastroparesis to chronic constipation (slow transit constipation and dyssynergic defecation) has been incompletely evaluated.Methods: We retrospectively reviewed the records of all patients with chronic dyspeptic symptoms and constipation who underwent both a solid gastric emptying scintigraphy and a highresolution anorectal manometry at our institution since January 2012. When available, Xray defecography and radiopaque marker colonic transit studies were also reviewed. Based on the gastric emptying results, patients were classified as gastroparesis or dyspepsia with normal gastric emptying (control group). Differences in anorectal and colonic findings were then compared between groups.Results: Two hundred and six patients met the inclusion criteria. Patients with gastroparesis had higher prevalence of slow transit constipation by radiopaque marker study compared to those with normal emptying (64.7% vs 28.1%, P = 0.013). Additionally, patients with gastroparesis had higher rates of rectocele (88.9% vs 60.0%, P = 0.008) and intussusception (44.4% vs 12.0%, P = 0.001) compared to patients with normal emptying. There was no difference in the rate of dyssynergic defecation between those with gastroparesis vs normal emptying (41.1% vs 42.1%, P = 0.880), and no differences in anorectal manometry findings.Conclusions: Patients with gastroparesis had a higher rate of slow transit constipation, but equal rates of dyssynergic defecation compared to patients with normal gastric emptying. These findings argue for investigation of possible delayed colonic transit in patients with gastroparesis and vice versa.

    View details for PubMedID 30870880

  • Thalidomide Use Reduces Risk of Refractory Gastrointestinal Bleeding in Patients with Continuous Flow Left Ventricular Assist Devices. ASAIO journal (American Society for Artificial Internal Organs : 1992) Namdaran, P., Zikos, T. A., Pan, J. Y., Banerjee, D. 2019

    Abstract

    Gastrointestinal (GI) bleeding is a common complication seen in patients with implanted continuous flow left ventricular assist devices (CF-LVAD), often attributed to arteriovenous malformations (AVMs). Whether thalidomide reduces recurrent GI bleeding risk in CF-LVAD patients has been incompletely evaluated. We conducted a retrospective review of all CF-LVAD patients at our institution with GI bleeding from AVMs who had a trial both off and on thalidomide. The primary endpoint was time to rebleed, while secondary endpoints included overall GI bleeding events, packed red blood cell (PRBC) transfusion requirements, and adverse events related to thalidomide. We report on 24 patients with recurrent AVM-associated GI bleeding who met criteria for and received thalidomide therapy, of which 17 had sufficient follow-up to be ultimately included for final analysis. We found the risk of rebleeding was significantly reduced in those on thalidomide therapy versus off (hazard ratio = 0.23, p = 0.022). The median number of GI bleeds per year was reduced from 4.6 to 0.4 (p = 0.0008) and the PRBC requirement was lower (36.1 vs. 0.9 units per year, p = 0.004) in those on thalidomide therapy. The adverse event rate with thalidomide was 59%, with symptoms resolution in most following dose reduction without increased bleeding. Thalidomide reduced the risk of AVM-associated GI rebleeding, number of bleeding events, and PRBC requirements in CF-LVAD patients. When initiating therapy, potential side effects and overall clinical context should be considered.

    View details for DOI 10.1097/MAT.0000000000001054

    View details for PubMedID 31425265

  • Gastric per-oral endoscopic myotomy: Current status and future directions. World journal of gastroenterology Podboy, A., Hwang, J. H., Nguyen, L. A., Garcia, P., Zikos, T. A., Kamal, A., Triadafilopoulos, G., Clarke, J. O. 2019; 25 (21): 2581–90

    Abstract

    Gastroparesis, or symptomatic delayed gastric emptying in the absence of mechanical obstruction, is a challenging and increasingly identified syndrome. Medical options are limited and the only medication approved by the Food and Drug Administration for treatment of gastroparesis is metoclopramide, although other agents are frequently used off label. With this caveat, first-line treatments for gastroparesis include dietary modifications, antiemetics and promotility agents, although these therapies are limited by suboptimal efficacy and significant medication side effects. Treatment of patients that fail first-line treatments represents a significant therapeutic challenge. Recent advances in endoscopic techniques have led to the development of a promising novel endoscopic therapy for gastroparesis via endoscopic pyloromyotomy, also referred to as gastric per-oral endoscopic myotomy or per-oral endoscopic pyloromyotomy. The aim of this article is to review the technical aspects of the per-oral endoscopic myotomy procedure for the treatment of gastroparesis, provide an overview of the currently published literature, and outline potential next directions for the field.

    View details for DOI 10.3748/wjg.v25.i21.2581

    View details for PubMedID 31210711

    View details for PubMedCentralID PMC6558440

  • Arteriovenous malformations respond poorly to argon plasma coagulation in patients with continuous flow left ventricular assist devices. European journal of gastroenterology & hepatology Zikos, T. A., Namdaran, P., Banerjee, D., Friedland, S., Pan, J. Y. 2019; 31 (7): 792–98

    Abstract

    Gastrointestinal bleeding in patients with continuous flow left ventricular assist devices (LVADs) causes significant morbidity. Arteriovenous malformations (AVMs) cause 30-60% of bleeds, yet the efficacy of endoscopic interventions and risk factors for rebleeding have not been studied.The charts of all LVAD patients undergoing endoscopy for gastrointestinal bleeding at Stanford between January 2010 and December 2017 were reviewed. Cox proportional hazard modeling was used to evaluate risk factors for rebleeding, including the type of endoscopic treatment, patient characteristics, and endoscopic findings.Of 54 total LVAD patients presenting with gastrointestinal bleeding, 23 (42.6%) had AVMs documented on endoscopy. Treatment with argon plasma coagulation (APC) alone was associated with a higher risk of rebleeding compared to no treatment [hazard ratio (HR)=4.77, P=0.012], and compared with clip±APC (HR=7.47, P=0.012). The 90-day bleed-free rate was 10.9% with APC, 100% with clipping±APC, and 83.3% with no endoscopic treatment. Additional risk factors for rebleeding included the presence of gastric AVMs (HR=3.64, P=0.024), and presence of hematochezia (HR=5.15, P=0.05). In a multiple Cox regression model, only the presence of gastric AVMs (HR=5.50, P=0.029) and APC use (HR=14.3, P=0.008) remained significant predictors of rebleeding.The use of APC alone for the treatment of AVMs in LVAD patients had a high failure rate. The presence of gastric AVMs was a significant risk factor for rebleeding in LVAD patients. Management decisions should take these factors into account.

    View details for DOI 10.1097/MEG.0000000000001427

    View details for PubMedID 31150365

  • Esophagogastroduodenoscopy and Esophageal Involvement in Patients With Pemphigus Vulgaris Ozeki, K., Zikos, T. A., Clarke, J., Sonu, I. NATURE PUBLISHING GROUP. 2018: S177
  • Blood and Guts: Diarrhea from Colonic Involvement in Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma. Digestive diseases and sciences Zikos, T. A., Triadafilopoulos, G., Berube, C., Regalia, K. A. 2018

    View details for PubMedID 30155841

  • Use of Esophageal pH Monitoring to Minimize Proton-Pump Inhibitor Utilization in Patients with Gastroesophageal Reflux Symptoms. Digestive diseases and sciences Triadafilopoulos, G., Zikos, T., Regalia, K., Sonu, I., Fernandez-Becker, N. Q., Nguyen, L., Nandwani, M. C., Clarke, J. O. 2018

    Abstract

    BACKGROUND: Due to concerns about long-term PPI use in patients with acid reflux, we aimed at minimizing PPI use, either by avoiding initiating therapy, downscaling to other therapies, or introducing endoscopic or surgical options.AIMS: To examine the role of esophageal ambulatory pHmetry in minimizing PPI use in patients with heartburn and acid regurgitation.METHODS: Retrospective cohort analysis of patients with reflux symptoms, who underwent endoscopy, manometry, and ambulatory pHmetry to define the need for PPI. Patients were classified as: (1) never users; (2) partial responders to PPI; (3) users with complete response to PPI. Patients were then managed as: (1) PPI non-users; (2) PPI-initiated, and (3) PPI-continued.RESULTS: Of 286 patients with heartburn and regurgitation, 103 (36%) were found to have normal and 183 (64%) abnormal esophageal acid exposure (AET). In the normal AET group, 44/103 had not been treated and were not initiated on PPI. Of the 59 who had previously received PPI, 52 stopped and 7 continued PPI. Hence, PPI were avoided in 96/103 patients (93%). In the abnormal AET group, 61/183 had not been treated and 38 were initiated on PPI and 23 on other therapies. In the 122 patients previously treated with PPI, 24 were not treated with PPI, but with H2RAs, prokinetics, endoscopic, or surgical therapy. Hence, PPI therapy was avoided in 47/183 patients (26%).CONCLUSIONS: In patients with GER symptoms, esophageal pHmetry may avert PPI use in 50%. In the era of caution regarding PPIs, early testing may provide assurance and justification.

    View details for PubMedID 29959725

  • A Positive Correlation Between Gastric and Esophageal Dysmotility Suggests Common Causality. Digestive diseases and sciences Zikos, T. A., Clarke, J. O., Triadafilopoulos, G., Regalia, K. A., Sonu, I. S., Fernandez-Becker, N. Q., Nandwani, M. C., Nguyen, L. A. 2018

    Abstract

    BACKGROUND: Gastric and esophageal dysmotility syndromes are some of the most common motility diagnoses, but little is known about their interrelationship.AIMS: The aim of our study was to determine if a correlation exists between gastric and esophageal dysmotility syndromes.METHODS: We reviewed the records of all patients who underwent both solid gastric emptying scintigraphy (GES) and high-resolution esophageal manometry (HRM) withina 2 year period, with both done between August 2012 and August 2017. All GESs were classified as either rapid, normal, or delayed. All HRMs were classified according to the Chicago Classification 3.0. Correlations were assessed using Fisher's exact test and multiple logistic regression.RESULTS: In total, 482 patients met inclusion criteria. Of patients with a normal, delayed, and rapid GES, 53.1, 64.5, and 77.3% had an abnormal HRM, respectively (p<0.05 vs. normal GES). Likewise, patients with an abnormal HRM were more likely to have an abnormal GES (54.9 vs. 41.8%, p=0.005). Multiple logistic regression showed abnormal GES [odds ratio (OR) 2.14], age (OR 1.013), scleroderma (OR 6.29), and dysphagia (OR 2.63) were independent predictors of an abnormal HRM. Likewise, an abnormal HRM (OR 2.11), diabetes (OR 1.85), heart or lung transplantation (OR 2.61), and autonomic dysfunction (OR 2.37) were independent predictors of an abnormal GES.CONCLUSIONS: The correlation between an abnormal GES and HRM argues for common pathogenic mechanisms of these motility disorders, and possibly common future treatment options. Clinicians should have a high index of suspicion for another motility disorder if one is present.

    View details for PubMedID 29946871

  • Outcomes of Endoscopic Procedures on Patients With Left-Ventricular Assist Devices: Experiences From a Single-Center Retrospective Case Series Pan, J. Y., Zikos, T., Chang, M. S., Limketkai, B., Banerjee, D., Fernandez-Becker, N. MOSBY-ELSEVIER. 2017: AB207–AB208
  • Efficacy of Video Capsule Endoscopy in the Management of Suspected Small Bowel Bleeding in Patients With Continuous Flow Left Ventricular Assist Devices. Gastroenterology research Zikos, T. A., Pan, J., Limketkai, B., Banerjee, D., Fernandez-Becker, N. 2017; 10 (5): 280–87

    Abstract

    Continuous flow left ventricular assist device (CF-LVAD) patients have a high prevalence of gastrointestinal bleeding from the small bowel. Video capsule endoscopy (VCE) is often used for diagnosis in these patients, but efficacy has yet to be determined. In this study, we evaluated the efficacy of VCE in the management of CF-LVAD patients with suspected small bowel bleeding by comparing to a non-VCE CF-LVAD control group.We retrospectively reviewed the charts of all patients with CF-LVADs implanted at Stanford Hospital from January 2010 to October 2015. Patients were included in the study if there was a clinical suspicion of small bowel bleeding and either a negative upper endoscopy or colonoscopy.A total of 26 patients met inclusion criteria for a total of 15 encounters where VCE was done, and 25 where VCE was not done. There were no statistical differences when comparing these groups in terms of medical therapy use (thalidomide or octreotide), enteroscopy use (double-balloon or push), intervention on lesions, or any 30-day outcomes. There was no advantage to VCE with regard to the composite endpoint time to re-bleed or death related to re-bleeding (median 114 vs. 161 days, P = 0.15) after removing patients who did not get a VCE due to death or critical illness.We did not find VCE changed management or outcomes in CF-LVAD patients with suspected small bowel bleeding at our institution when compared to a non-VCE control group. Our experience is small and single center, and larger, multi-center studies could further elucidate the utility of VCE in this patient population.

    View details for PubMedID 29118868

    View details for PubMedCentralID PMC5667693

  • Eculizumab Induces Sustained Remission in a Patient With Refractory Primary Catastrophic Antiphospholipid Syndrome JCR-JOURNAL OF CLINICAL RHEUMATOLOGY Zikos, T. A., Sokolove, J., Ahuja, N., Berube, C. 2015; 21 (6): 311-313
  • Eculizumab Induces Sustained Remission in a Patient With Refractory Primary Catastrophic Antiphospholipid Syndrome. Journal of clinical rheumatology : practical reports on rheumatic & musculoskeletal diseases Zikos, T. A., Sokolove, J., Ahuja, N., Berube, C. 2015; 21 (6): 311-313

    Abstract

    Catastrophic antiphospholipid syndrome (CAPS) is fatal in approximately 44% of patients in whom the diagnosis is made, thus demonstrating the inadequacy of current medical therapy. In this report, we discuss a 47-year-old man with a known history of primary antiphospholipid syndrome, who presented with CAPS after undergoing cholecystectomy and a treatment-refractory early relapse after development of colitis. Given the potential therapeutic efficacy of complement inhibition in antiphospholipid syndrome, the patient was administered eculizumab, a terminal complement inhibitor. Progressive clinical improvement and laboratory improvement were observed upon initiation of eculizumab. He has remained in remission for over 16 months of follow-up while on eculizumab. In conclusion, this case represents successful use of eculizumab for the treatment of primary CAPS.

    View details for DOI 10.1097/RHU.0000000000000290

    View details for PubMedID 26267719

  • Cyst Fluid Glucose is Rapidly Feasible and Accurate in Diagnosing Mucinous Pancreatic Cysts. American journal of gastroenterology Zikos, T., Pham, K., Bowen, R., Chen, A. M., Banerjee, S., Friedland, S., Dua, M. M., Norton, J. A., Poultsides, G. A., Visser, B. C., Park, W. G. 2015; 110 (6): 909-914

    Abstract

    Better diagnostic tools are needed to differentiate pancreatic cyst subtypes. A previous metabolomic study showed cyst fluid glucose as a potential marker to differentiate mucinous from non-mucinous pancreatic cysts. This study seeks to validate these earlier findings using a standard laboratory glucose assay, a glucometer, and a glucose reagent strip.Using an IRB-approved prospectively collected bio-repository, 65 pancreatic cyst fluid samples (42 mucinous and 23 non-mucinous) with histological correlation were analyzed.Median laboratory glucose, glucometer glucose, and percent reagent strip positive were lower in mucinous vs. non-mucinous cysts (P<0.0001 for all comparisons). Laboratory glucose<50 mg/dl had a sensitivity of 95% and a specificity of 57% (LR+ 2.19, LR- 0.08). Glucometer glucose<50 mg/dl had a sensitivity of 88% and a specificity of 78% (LR+ 4.05, LR- 0.15). Reagent strip glucose had a sensitivity of 81% and a specificity of 74% (LR+ 3.10, LR- 0.26). CEA had a sensitivity of 77% and a specificity of 83% (LR+ 4.67, LR- 0.27). The combination of having either a glucometer glucose<50 mg/dl or a CEA level>192 had a sensitivity of 100% but a low specificity of 33% (LR+ 1.50, LR- 0.00).Glucose, whether measured by a laboratory assay, a glucometer, or a reagent strip, is significantly lower in mucinous cysts compared with non-mucinous pancreatic cysts.

    View details for DOI 10.1038/ajg.2015.148

    View details for PubMedID 25986360

  • Evaluation and Management of Pancreatic Cystic Lesions Journal of Clinical Outcomes Management Zikos, T., Park, W. G. 2015; 22 (12): 566-576
  • Rapid Point-of-Care Measurement of Cyst Fluid Glucose Is Feasible and Accurate in Predicting Mucinous Pancreatic Cysts Zikos, T., Pham, K., Chen, A., Banerjee, S., Friedland, S., Dua, M., Norton, J., Poultsides, G., Visser, B., Park, W. NATURE PUBLISHING GROUP. 2014: S86
  • Lung T-cell subset composition at the time of surgical resection is a prognostic indicator in non-small cell lung cancer CANCER IMMUNOLOGY IMMUNOTHERAPY Zikos, T. A., Donnenberg, A. D., Landreneau, R. J., Luketich, J. D., Donnenberg, V. S. 2011; 60 (6): 819-827

    Abstract

    NSCLC arises in the complex environment of chronic inflammation. Depending on lung immune polarization, infiltrating immune cells may either promote or suppress tumor growth. Despite the importance of the immune microenvironment, current staging techniques for NSCLC do not take into consideration the immune milieu in which the neoplasms arise. T-cell subset content was compared between paired tumor-bearing and contralateral lungs, patient and control peripheral blood. The relationship between T-cell subset distribution and survival were evaluated. CD4 and CD8+ T cells were subsetted by CD45RA/CD27 and analyzed for expression of activation, adhesion, and homing markers. Strikingly, T-cell content was indistinguishable between lungs. Compared with peripheral blood, naïve CD4 and CD8 T cells were rare in BAL. CD4+ BAL T cells showed increased CD95 (higher apoptotic potential) and CD103 expression (epithelial adhesion), but decreased CD38 (activation) and CCR7 expression (lymph node homing). CD8+ BAL T cells showed increased CD103 expression and decreased CD28 expression (co-stimulation). Differences in CD28, CD95, and CCR7 expression were more pronounced within memory cells, while differences in CD4+ CD103 expression were more prominent in effector/memory cells. Of these populations, the absence of lung CD4 T cells with an effector-like phenotype (CD45RA+/CD27-) emerged as a predictor of favorable outcome. Patients with a low proportion (≤0.44%) had 90% 5-year survival (n = 10, median survival 2,343 days), compared with 0% (n = 9, median survival 516 days) of patients with a higher proportion. Further study is required to confirm this association prospectively and define the function of this subpopulation.

    View details for DOI 10.1007/s00262-011-0996-4

    View details for Web of Science ID 000290802200006

    View details for PubMedID 21373990

  • The Impact of Scoliosis Among Patients with Giant Paraesophageal Hernia JOURNAL OF GASTROINTESTINAL SURGERY Schuchert, M. J., Adusumilli, P. S., Cook, C. C., Colovos, C., Kilic, A., Nason, K. S., Landreneau, J. P., Zikos, T., Jack, R., Luketich, J. D., Landreneau, R. J. 2011; 15 (1): 23-28

    Abstract

    Kyphoscoliosis is seen in approximately 1.4-15% of the octogenarian population of the US. We hypothesized that patients with kyphoscoliosis are affected with a reduced intra-abdominal volume and progressive laxity of the diaphragmatic hiatal sling musculature leading to an increased risk of hiatal hernia formation and progression over time.We retrospectively reviewed the clinical history and roentgenographic data of 320 paraesophageal hernia patients from 2003 to 2007. The prevalence of kyphoscoliosis among this patient cohort and the outcomes of surgical management were compared to paraesophageal hernia patients without kyphoscoliosis.Ninety-three of the 320 patients (29.1%) were found to have significant K/S (mean age 74; 83% female). Laparoscopic repair of paraesophageal hernia with fundoplication was performed in 91% of these patients. There was one death (1.1%; aspiration pneumonia) and 17.2% major postoperative morbidity. Mean length of hospital stay was 8 days (median = 4; range 2-71). Prolonged stays were related mainly to marginal pulmonary status. Kyphoscoliosis was associated with increased peri-operative pulmonary morbidity (16.1%) compared to patients without kyphoscoliosis (7.0%, p = 0.02).Kyphoscoliosis may contribute to the development and progression of paraesophageal hernias. Surgeons approaching paraesophageal hernia repair should be aware of the increased pulmonary morbidity and the postoperative care required in managing these patients.

    View details for DOI 10.1007/s11605-010-1307-7

    View details for Web of Science ID 000286396600003

    View details for PubMedID 20824386