Physician-statistician interested in cardiology, data visualization, machine learning, and the statistical analysis of large datasets.

Clinical Focus

  • Cardiology
  • Data Science
  • Fellow

Honors & Awards

  • T1 Catalyst Mobile Health Translational Project Award (30,000), UCSF Clinical and Translational Science Institute (2012)
  • UCSF Mobile Health Consultation Award, UCSF Clinical and Translational Science Institute (2011)
  • The Permanente Medical Group Medical Student Scholarship, Permanente Medical Group (2014)
  • Dean’ s Prize in Research Finalist, UCSF SOM (2012)

Boards, Advisory Committees, Professional Organizations

  • Editor, Two Minute Medicine (2013 - 2017)

Professional Education

  • Doctor of Medicine, University of California San Francisco, Clinical and Translational Research Pathway (2014)
  • Bachelor of Science, Rice University, Statistics (2010)


All Publications

  • What's in a Name? Factors That Influence the Usage of Generic Versus Trade Names for Cardiac Medications Among Healthcare Providers CIRCULATION-CARDIOVASCULAR QUALITY AND OUTCOMES Ouyang, D., Tisdale, R., Cheng, P., Chi, J., Chen, J. H., Ashley, E. 2018; 11 (8)
  • Acetaminophen or Tylenol? A Retrospective Analysis of Medication Digital Communication Practices. Journal of general internal medicine Ouyang, D., Tisdale, R., Ashley, E., Chi, J., Chen, J. H. 2018

    View details for DOI 10.1007/s11606-018-4455-1

    View details for PubMedID 29717410

  • Incidence of temporary mechanical circulatory support before heart transplantation and impact on post-transplant outcomes. The Journal of heart and lung transplantation : the official publication of the International Society for Heart Transplantation Ouyang, D., Gulati, G., Ha, R., Banerjee, D. 2018


    Proposed changes to the United Network for Organ Sharing heart transplant allocation protocol will prioritize patients receiving temporary mechanical circulatory support (tMCS), including extracorporeal membrane oxygenation (ECMO), percutaneous ventricular assist devices (PVADs), and intra-aortic balloon pumps (IABPs). We sought to evaluate contemporary trends in the incidence and outcomes of patients who required tMCS during the hospitalization before heart transplantation.Using the National Inpatient Sample from 1998 to 2014, we identified 6,892 patients who received an orthotopic heart transplant and classified them by pre-transplant ECMO, PVAD, or IABP placement or no pre-transplant tMCS. We compared baseline characteristics and in-hospital outcomes between patients who underwent pre-transplant ECMO, PVAD, or IABP and patients who did not receive tMCS before heart transplantation.Of patients who underwent heart transplantation, 456 (6.6%) received tMCS before transplant. During the study period, the use of tMCS more than doubled, from 17 cases per year from 1998 to 2002 to 40 cases per year from 2012 to 2014 (p < 0.001 for trend). Of patients with tMCS, 341 (74.8%) were supported by IABP, 130 (28.5%) were supported by ECMO, and 21 (4.6%) were supported by PVAD. Before 2007, patients who required tMCS had higher in-hospital mortality than patients who did not require tMCS before transplant (14.3% vs 7.5%, p = 0.05). In the subsequent era (2007 to 2014), mortality was not significantly different (4.7% vs 5.1%, p = 0.9). Hospital mortality improved over time for all patients but most significantly in patients who required tMCS (9.6% absolute risk reduction). However, patients who received tMCS had increased lengths of stays and rates of acute renal, hepatic, and respiratory failure, sepsis, bleeding complications, and surgical reoperations.The use of tMCS before cardiac transplantation is increasing, with no difference in in-patient post-transplant mortality in the recent era between patients who did and did not receive tMCS but with increased complication rates among those who received tMCS. These data support the use of tMCS before cardiac transplantation in appropriately selected patients. Clinicians should balance the above outcomes when making decisions to implant tMCS, given the impending changes to the United Network for Organ Sharing heart allocation protocol.

    View details for DOI 10.1016/j.healun.2018.04.008

    View details for PubMedID 29907499

  • Optimal timing of same-admission orthotopic heart transplantation after left ventricular assist device implantation. World journal of cardiology Gulati, G., Ouyang, D., Ha, R., Banerjee, D. 2017; 9 (2): 154-161


    To investigate the impact of timing of same-admission orthotopic heart transplant (OHT) after left ventricular assist device (LVAD) implantation on in-hospital mortality and post-transplant length of stay.Using data from the Nationwide Inpatient Sample from 1998 to 2011, we identified patients 18 years of age or older who underwent implantation of a LVAD and for whom the procedure date was available. We calculated in-hospital mortality for those patients who underwent OHT during the same admission as a function of time from LVAD to OHT, adjusting for age, sex, race, household income, and number of comorbid diagnoses. Finally, we analyzed the effect of time to OHT after LVAD implantation on the length of hospital stay post-transplant.Two thousand and two hundred patients underwent implantation of a LVAD in this cohort. One hundred and sixty-four (7.5%) patients also underwent OHT during the same admission, which occurred on average 32 d (IQR 7.75-66 d) after LVAD implantation. Of patients who underwent OHT, patients who underwent transplantation within 7 d of LVAD implantation ("early") experienced increased in-hospital mortality (26.8% vs 12.2%, P = 0.0483) compared to patients who underwent transplant after 8 d ("late"). There was no statistically significant difference in age, sex, race, household income, or number of comorbid diagnoses between the early and late groups. Post-transplant length of stay after LVAD implantation was also not significantly different between patients who underwent early vs late OHT.In this cohort of patients who received LVADs, the rate of in-hospital mortality after OHT was lower for patients who underwent late OHT (at least 8 d after LVAD implantation) compared to patients who underwent early OHT. Delayed timing of OHT after LVAD implantation did not correlate with longer hospital stays post-transplant.

    View details for DOI 10.4330/wjc.v9.i2.154

    View details for PubMedID 28289529

    View details for PubMedCentralID PMC5329742

  • Gender trends in authorship of spine-related academic literature - a 39-year perspective. The spine journal : official journal of the North American Spine Society Sing, D. C., Jain, D., Ouyang, D. 2017


    Despite recent advances in gender equity in medicine, the representation of women in orthopaedic and neurosurgery remains particularly low. Furthermore compared to their male colleagues female faculty members are less likely to publish research, limiting opportunities in the academic promotion process. Understanding disparities in research productivity provides insight into the "gender gap" in the spine surgeon workforce.To determine the representation and longevity of female physician-investigators among the authors of five spine-related research journals from 1978 to 2016.Retrospective bibliometric review METHODS: Authors of original research articles from five prominent spine-related journals (European Spine Journal, the Spine Journal, Spine, Journal of Spinal Disorders and Techniques and Journal of Neurosurgery: Spine) were extracted from PubMed. For authors with a complete first name listed, gender was determined by matching first name using an online database containing 216,286 distinct names across 79 countries and 89 languages. The proportion of female first and senior authors was determined during the time periods 1978-1994, 1995-1999, 2000-2004, 2005-2009, and 2010-2016. Authors who had their first paper published between 2000-2009 were included in additional analyses for publication count and longevity (whether additional articles were published 5 years after first publication). Student's t-test, chi-squared analysis, and Cochran-Armitage trend test were used to determine significance between groups.From 1978-2016, 28,882 original research articles were published in the five spine-related journals. 24,334 abstracts (90.9%) had first names listed, identifying 120,723 authors in total of which 100,286 were successfully matched to a gender. 33,480 unique authors were identified (female: 31.8%). Female representation increased for first and senior authors from 6.5% and 4.7% (1978-1994) to 18.5% and 13.6% (2010-2016, p<0.001). Growth in female senior author representation declined after 2000 (12.3% vs. 12.9% vs. 13.5% between 2000-2004, 2005 - 2009, and 2010-2016). Compared to men authors, on average women authors published fewer articles (mean: 2.1 vs 3.3, p<0.001). Of 15,304 authors who first published during 2000-2009, 3,478 authors (22.7%) continued to publish 5 years after their first publication. Women were less likely to continue publishing after their first article (15.3% of female authors vs. 24.8%, p <0.001).Female representation in academic spine research has doubled over the past 4 decades, although the growth of female representation as senior author has plateaued. Female physician-investigators are half as likely to continue participating in spine-related research longer than 5 years and on average publish half as many articles as senior author. In addition to recruiting more women into research, efforts should be made to identify and address barriers in research advancement and promotion for female physician-investigators.

    View details for DOI 10.1016/j.spinee.2017.06.041

    View details for PubMedID 28673828

  • Patient Outcomes when Housestaff Exceed 80 Hours per Week. American journal of medicine Ouyang, D., Chen, J. H., Krishnan, G., Hom, J., Witteles, R., Chi, J. 2016; 129 (9): 993-999 e1


    It has been posited that high workload and long work hours for trainees could affect the quality and efficiency of patient care. Duty hour restrictions seek to balance patient care and resident education by limiting resident work hours. Through a retrospective cohort study, we investigate whether patient care on an inpatient general medicine service at a large academic medical center is impacted when housestaff work greater than eighty hours per week METHODS: We identified all admissions to a housestaff-run general medicine service between June 25, 2013 and June 29, 2014. Each hospitalization was classified by whether or not the patient was admitted by housestaff who have worked more than eighty hours a week during their hospitalization. Housestaff computer activity and duty hours were calculated by institutional electronic heath record audit, as well as length of stay and a composite of in-hospital mortality, ICU transfer rate, and 30-day readmission rate.We identified 4,767 hospitalizations by 3,450 unique patients; of which 40.9% of hospitalizations were managed by housestaff who worked more than eighty hours that week during their hospitalization. There was a significantly higher rate of the composite outcome (19.2% vs. 16.7%, p = 0.031) for patients admitted by housestaff working more than eighty hours a week during their hospitalization. We found a statistically significant higher length of stay (5.12 vs. 4.66 days, p = 0.048) and rate of ICU transfer (3.18% vs. 2.38%, p = 0.029). There was no statistically significant difference in 30-day readmission rate (13.7% vs. 12.8%, p = 0.395), or in-hospital mortality rate (3.18% vs. 2.42%, p = 0.115).There was no correlation with team census on admission and patient outcomes.Patients taken care of by housestaff working more than eighty hours a week had increased length of stay and number of ICU transfers. There was no association between resident work-hours and patient in-hospital mortality or 30-day readmission rate.

    View details for DOI 10.1016/j.amjmed.2016.03.023

    View details for PubMedID 27103047

  • Acute, Unilateral Breast Toxicity From Gemcitabine in the Setting of Thoracic Inlet Obstruction. Journal of oncology practice / American Society of Clinical Oncology Weiskopf, K., Creighton, D., Lew, T., Caswell, J. L., Ouyang, D., Shah, A. T., Hofmann, L. V., Neal, J. W., Telli, M. L. 2016; 12 (8): 763-764

    View details for DOI 10.1200/JOP.2016.014241

    View details for PubMedID 27511721

    View details for PubMedCentralID PMC5012631

  • Internal Medicine Resident Computer Usage: An Electronic Audit of an Inpatient Service. JAMA internal medicine Ouyang, D., Chen, J. H., Hom, J., Chi, J. 2016; 176 (2): 252-254

    View details for DOI 10.1001/jamainternmed.2015.6831

    View details for PubMedID 26642261

  • National trends and complication rates for invasive extraoperative electrocorticography in the USA JOURNAL OF CLINICAL NEUROSCIENCE Rolston, J. D., Ouyang, D., Englot, D. J., Wang, D. D., Chang, E. F. 2015; 22 (5): 823-827


    Invasive electrocorticography (ECoG) is used in patients when it is difficult to localize epileptogenic foci for potential surgical resection. As MR neuroimaging has improved over the past decade, we hypothesized the utilization of ECoG diminishing over time. Using the USA Nationwide Inpatient Sample, we collected demographic and complication data on patients receiving ECoG over the years 1988-2008 and compared this to patients with medically refractory epilepsy during the same time period. A total of 695 cases using extraoperative ECoG were identified, corresponding to 3528 cases nationwide and accounting for 1.1% of patients with refractory epilepsy from 1988-2008. African Americans were less likely to receive ECoG than whites, as were patients with government insurance in comparison to those with private insurance. Large, urban, and academic hospitals were significantly more likely to perform ECoG than smaller, rural, and private practice institutions. The most frequent complication was cerebrospinal fluid leak (11.7%) and only one death was reported from the entire cohort, corresponding to an estimated six patients nationally. Invasive ECoG is a relatively safe procedure offered to a growing number of patients with refractory epilepsy each year. However, these data suggest the presence of demographic disparities in those patients receiving ECoG, possibly reflecting barriers due to race and socioeconomic status. Among patients with nonlocalized seizures, ECoG often represents their only hope for surgical treatment. We therefore must further examine the indications and efficacy of ECoG, and more work must be done to understand if and why ECoG is preferentially performed in select socioeconomic groups.

    View details for DOI 10.1016/j.jocn.2014.12.002

    View details for Web of Science ID 000353929500008

    View details for PubMedID 25669117

  • National Trends in Surgery for Sinonasal Malignancy and the Effect of Hospital Volume on Short-Term Outcomes LARYNGOSCOPE Ouyang, D., El-Sayed, I. H., Yom, S. S. 2014; 124 (7): 1609-1614


    To characterize trends in the management of sinonasal malignancy with a focus on the impact of hospital volume on surgical outcomes.Retrospective cohort study.Time trends were analyzed among patients admitted for surgical resection of sinonasal malignancy in the Nationwide Inpatient Sample (NIS) between 1988 and 2009. Subset analysis was performed on cohorts with skull base or orbital involvement or on cohorts who underwent neck dissection. Patient characteristics and hospital attributes were correlated with morbidity and mortality.Over 22 years, we identified 3,850 cases from 879 hospitals. A total of 24.3% of patients had complications and 0.8% of hospitalizations resulted in mortality. Cases with skull base or orbital involvement, or cases including neck dissection, had more complications and a longer length of stay. Prevalence of neck dissection increased over time. Thirty-two hospitals averaged more than five cases per year, accounting for 28% of all surgeries. These centers were large (73.3%), urban (96.7%), teaching (90%) institutions and performed more high-risk cases: 32.4% of neck dissections, 44.6% of orbital cases, and 43.1% of skull base cases. Compared to lower-volume centers, these centers had more cardiopulmonary and electrolyte complications, but no difference was observed in the lengths of stay. A greater proportion of cases were recently performed at high-volume centers.Over time, complicated surgeries were more likely to occur at higher-volume hospitals without significant changes in surgical complication rates. High-volume centers had increased rates of cardiopulmonary and electrolyte complications, likely representing complex postoperative management, but these were not associated with higher mortality.2c.

    View details for DOI 10.1002/lary.24578

    View details for Web of Science ID 000339481100030

    View details for PubMedID 24390781

  • Trends in surgical treatment for trigeminal neuralgia in the United States of America from 1988 to 2008 JOURNAL OF CLINICAL NEUROSCIENCE Wang, D. D., Ouyang, D., Englot, D. J., Rolston, J. D., Molinaro, A. M., Ward, M., Chang, E. F. 2013; 20 (11): 1538-1545


    Current surgical treatments for refractory trigeminal neuralgia (TN) include microvascular decompression (MVD), percutaneous rhizotomy, and stereotactic radiosurgery (SRS). We aimed to map the trends of utilization of these procedures in the USA and examine factors associated with morbidities and discharge outcome. We performed a retrospective cohort study with time trends of patients admitted to US hospitals for TN between 1988 and 2008 who received MVD, percutaneous rhizotomy, or SRS as reported in the Nationwide Inpatient Sample. Univariate and multivariate analyses were conducted to examine patient demographics, hospital characteristics, and other hospitalization factors affecting complications and discharges. The use of MVD increased significantly by 194% from 1988 to 2008 while rhizotomy decreased by 92%. The use of radiosurgery, introduced in the early 1990s, peaked in 2004 and has declined since. Univariate analysis revealed patient age, length of hospitalization, hospital teaching status, and hospital patient volume to be associated with discharge and complications. Multivariate analysis showed that for MVD, younger age and high hospital volume were predictive of a good discharge outcome. For rhizotomy, age, median income, urban location, and hospital volumes were associated with discharge outcome, but only teaching status, urban location, and hospital volume were associated with complications. For SRS, patient age and length of stay were found to be important by multivariate analysis on discharge. Mortality rates for MVD (0.22%), rhizotomy (0.42%), and SRS (0.12%) were low. The clinical practices for surgical treatment of TN have evolved over time with the rise of MVD and dwindling of rhizotomy procedures.

    View details for DOI 10.1016/j.jocn.2012.12.026

    View details for Web of Science ID 000326906400013

    View details for PubMedID 23932422

  • Community Health Education at Student-Run Clinics Leads to Sustained Improvement in Patients' Hepatitis B Knowledge JOURNAL OF COMMUNITY HEALTH Ouyang, D., Yuan, N., Sheu, L., Lau, G., Chen, C., Lai, C. J. 2013; 38 (3): 471-479


    While student-run clinics are often important healthcare safety nets for underserved populations, their efficacy for improving patient health knowledge has not been thoroughly explored. From September 2011 to April 2012, we assessed patients' retention of hepatitis B virus (HBV) knowledge after receiving student-led education at two student-run HBV screening and vaccination clinics. Patient education was provided by trained first and second-year medical, nursing, and pharmacy students, aided by a script and interpreters. Patient knowledge of HBV was evaluated at three points: before education, after the initial visit, and at one-month follow-up. Student-led education produced improved knowledge of HBV transmission, prevention, and management, which was retained 1 month after education for 52 patients tracked through time. Mean scores on an HBV knowledge survey improved from 56.4 % (SD = 15.2 %) at baseline to 66.6 % (SD = 15.1 %) after education, and 68.3 % (SD = 15.2 %) after one month. There was a statistically significant difference between the first and second (paired T test, p < 0.001) and the first and third tests (paired T test, p < 0.001), but no difference between the second and third tests (paired T test, p = 0.45). Multivariate analysis demonstrated that retention was correlated with patient educational background but independent of patient age, gender, income, primary language and number of years lived in the United States. Our study suggests that trained health professional students can effectively impart health knowledge that is retained by patients for at least 1 month. These results warrant consideration of student-led educational sessions at SRCs as a promising community health education model.

    View details for DOI 10.1007/s10900-012-9631-3

    View details for Web of Science ID 000318373500009

    View details for PubMedID 23161212

  • Relationship between hospital surgical volume, lobectomy rates, and adverse perioperative events at US epilepsy centers. Journal of neurosurgery Englot, D. J., Ouyang, D., Wang, D. D., Rolston, J. D., Garcia, P. A., Chang, E. F. 2013; 118 (1): 169-174


    Epilepsy surgery remains significantly underutilized. The authors recently reported that the number of lobectomies for localized intractable epilepsy in the US has not changed despite the implementation of clear evidence-based guidelines 10 years ago supporting early referral for surgery. To better understand why epilepsy surgery continues to be underused, the authors' objective was to carefully examine hospital-related factors related to the following: 1) where patients are being admitted for the evaluation of epilepsy, 2) rates of utilization for surgery across hospitals, and 3) perioperative morbidity between hospitals with low versus high volumes of epilepsy surgery.The authors performed a population-based cohort study of US hospitals between 1990 and 2008 using the Nationwide Inpatient Sample (NIS), stratifying epilepsy surgery rates and trends as well as perioperative morbidity rates by hospital surgical volume.The number of lobectomies for epilepsy performed at high-volume centers (> 15 lobectomies/year) significantly decreased between 1990 and 2008 (F = 20.4, p < 0.001), while significantly more procedures were performed at middle-volume hospitals (5-15 lobectomies/year) over time (F = 16.1, p < 0.001). No time trend was observed for hospitals performing fewer than 5 procedures per year. However, patients admitted to high-volume centers were significantly more likely to receive lobectomy than those at low-volume hospitals (relative risk 1.05, 95% CI 1.03-1.08, p < 0.001). Also, the incidence of perioperative adverse events was significantly higher at low-volume hospitals (12.9%) than at high-volume centers (6.1%) (relative risk 1.08, 95% CI 1.03-1.07, p < 0.001).Hospital volume is an important predictor of epilepsy surgery utilization and perioperative morbidity. Patients with medically refractory epilepsy should be referred to a comprehensive epilepsy treatment center for surgical evaluation by an experienced clinical team.

    View details for DOI 10.3171/2012.9.JNS12776

    View details for PubMedID 23101453

  • Epilepsy surgery trends in the United States, 1990-2008 NEUROLOGY Englot, D. J., Ouyang, D., Garcia, P. A., Barbaro, N. M., Chang, E. F. 2012; 78 (16): 1200-1206


    To examine national time trends of resective surgery for the treatment of medically refractory epilepsy before and after Class I evidence demonstrating its efficacy and subsequent practice guidelines recommending early surgical evaluation.We performed a population-based cohort study with time trends of patients admitted to US hospitals for medically refractory focal epilepsy between 1990 and 2008 who did or did not undergo lobectomy, as reported in the Nationwide Inpatient Sample.Weighted data revealed 112,026 hospitalizations for medically refractory focal epilepsy and 6,653 resective surgeries (lobectomies and partial lobectomies) from 1990 to 2008. A trend of increasing hospitalizations over time was not accompanied by an increase in surgeries, producing an overall trend of decreasing surgery rates (F = 13.6, p < 0.01). Factors associated with this trend included a decrease in epilepsy hospitalizations at the highest-volume epilepsy centers, and increased hospitalizations to lower-volume hospitals that were found to be less likely to perform surgery. White patients were more likely to have surgery than racial minorities (relative risk [RR], 1.13; 95% confidence interval [CI], 1.10-1.17), and privately insured individuals were more likely to receive lobectomy than those with Medicaid or Medicare (RR, 1.28; 95% CI, 1.25-1.30).Despite Class I evidence and subsequent practice guidelines, the utilization of lobectomy has not increased from 1990 to 2008. Surgery continues to be heavily underutilized as a treatment for epilepsy, with significant disparities by race and insurance coverage. Patients who are medically refractory after failing 2 antiepileptic medications should be referred to a comprehensive epilepsy center for surgical evaluation.

    View details for DOI 10.1212/WNL.0b013e318250d7ea

    View details for Web of Science ID 000302933200005

    View details for PubMedID 22442428