William E Cohn

Baylor College of Medicine, Houston, Texas, United States

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Publications (124)254.71 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective Although the development of continuous flow ventricular assist devices (CF-VAD) has improved VAD reliability, VAD exchange is still occasionally necessary. The focus of this study was to analyze our institution’s entire experience with primary CF-VAD implants, evaluate baseline variables, determine which factors predict the need for exchange, and evaluate the impact of exchange on survival and event-free survival. Methods We retrospectively reviewed the data of all patients in a single center who received a primary CF-VAD implant between December 1999 and December 2013. All CF-VAD exchanges were reviewed; demographics, indications, pre-operative and operative data, and clinical outcomes were summarized. Univariate and multivariable regression analyses were performed to ascertain predictors for exchange. Time-to-event and survival analyses were also performed. Results We identified 469 patients who underwent 546 CF-VAD implantations. Of these patients, 66 (14%) underwent 77 exchanges from one CF-VAD to another. The primary indications included hemolysis or thrombosis (n=49; 63,6%), infection (n=9; 11.7%), or other causes (n=19; 24.7%). Survival was not significantly different between exchange and non-exchange groups. Multivariable regression analysis identified a history of cerebrovascular events as a significant predictor for exchange. Among exchange patients, 11 underwent heart transplantation, 3 had their CF-VADs explanted, 26 had ongoing support, and 26 died during device support. Conclusions In our series of contemporary CF-VAD exchanges, history of prior cerebrovascular events was a significant predictor for exchange. Exchange did not impact early or late survival. Our data suggest aggressive surgical treatment of pump-related complications with exchange is safe and justified.
    The Journal of Thoracic and Cardiovascular Surgery. 09/2014;
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    ABSTRACT: Rotary blood pumps are emerging as a viable technology for total artificial hearts, and the development of physiological control algorithms is accelerated with new evaluation environments. In this article, we present a novel hybrid mock circulation loop (HMCL) designed specifically for evaluation of rotary total artificial hearts (rTAH). The rTAH is operated in the physical domain while all vasculature elements are embedded in the numerical domain, thus combining the strengths of both approaches: fast and easy exchange of the vasculature model together with improved controllability of the pump. Parameters, such as vascular resistance, compliance, and blood volume, can be varied dynamically in silico during operation. A hydraulic–numeric interface creates a real-time feedback loop between the physical and numerical domains. The HMCL uses computer-controlled resistance valves as actuators, thereby reducing the size and number of hydraulic elements. Experimental results demonstrate a stable interaction over a wide operational range and a high degree of flexibility. Therefore, we demonstrate that the newly created design environment can play an integral part in the hydraulic design, control development, and durability testing of rTAHs.
    Artificial Organs 09/2014; 38(9). · 1.96 Impact Factor
  • Hari R Mallidi, Jatin Anand, William E Cohn
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    ABSTRACT: Mechanical circulatory support of the failing heart has become an important means of treating end-stage heart disease. This rapidly growing therapeutic field has produced impressive clinical outcomes and has great potential to help thousands of otherwise terminal patients worldwide. In this review, we examine the state of the art of mechanical circulatory support: current practice, totally implantable systems of the future, evolving biventricular support mechanisms, the potential for myocardial recovery and adjunctive treatment methods, and miniaturized devices with expanded indications for therapy.
    Texas Heart Institute journal / from the Texas Heart Institute of St. Luke's Episcopal Hospital, Texas Children's Hospital 04/2014; 41(2):115-20. · 0.67 Impact Factor
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    ABSTRACT: We sought to determine the outcomes for patients with advanced hepatic dysfunction undergoing HeartMate II left ventricular assist device (LVAD) implantation. Between November 1, 2003 and December 1, 2012, we implanted the HeartMate II continuous-flow LVAD in 338 patients, either for bridging to heart transplantation or for destination therapy. Twenty-three of these patients (19 men and 4 women; mean age, 47 ± 16 years) had advanced hepatic dysfunction, as characterized by alanine aminotransferase (ALT) or aspartate transaminase (AST) levels five times normal; serum total bilirubin levels three times normal; and/or necessity for a liver biopsy before or during device implantation. Of this group, 17 patients received the LVAD as a bridge to transplantation, and six patients received it for destination therapy. Nine of the 23 patients required either a transjugular or a core liver biopsy during LVAD implantation. Three patients died within the first postoperative month; the 20 surviving patients had significant improvements in their hepatic parameters. The ALT decreased from 238 ± 296 to 27 ± 13 U/L (p = 0.022), AST decreased from 209 ± 199 to 29 ± 8 U/L (p = 0.009), and total bilirubin level decreased from 6.9 ± 6.0 to 0.6 ± 0.1 mg/dL (p = 0.044). The serum albumin level increased from 3.2 ± 0.6 to 4.3 ± 0.3 g/dL (p = 0.003), and creatinine clearance increased from 77.6 ± 35.2 to 110.2 ± 35.7 mL/min/1.73 m(2) (p = 0.101). Continuous-flow LVAD support may significantly improve hepatic function, allowing patients with poor preimplant liver function to become better candidates for heart transplantation.
    Journal of Cardiac Surgery 03/2014; · 1.35 Impact Factor
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    ABSTRACT: Gelatin impregnated non-porous sealed grafts were introduced in the inflow and outflow conduits for use with the HeartMate II (HMII) to eliminate pre-clotting procedures and to reduce operative bleeding.We compared results of 67 patients who received first time LVADs with sealed inflow and outflow grafts (S-graft group) to a preceding 65 patients who received an LVAD with non-sealed grafts (NS-graft group).Overall, the amount of blood product transfusions was less in the S-graft group than in the NS-graft group (red blood cells, 4.9 ± 4.5 vs. 8.0 ± 9.4 units, P=0.022; fresh frozen plasma, 5.0 ± 3.0 vs. 8.7 ± 9.3 units, P=0.004; platelets, 2.9 ± 1.1 vs. 4.5 ± 3.5 units, P=0.001; and cryoprecipitate, 1.2 ± 0.9 vs. 2.01 ± 1.9 units, P=0.002). Within a follow-up period of 6 months, no device-related infections or strokes occurred in the S-group, but the NS-group had 1 (1.5%) driveline infections and 4 (6%) strokes. The 30-day survival rate was not significantly different between groups (P=0.053), but favored the S-group (97%) over the NS-group (88%). Use of a HMII with a sealed graft on the inflow and outflow conduits is associated with less postoperative bleeding, and may have helped to decrease the frequency of postoperative adverse events.
    ASAIO journal (American Society for Artificial Internal Organs: 1992) 03/2014; · 1.39 Impact Factor
  • Journal of Surgical Research 02/2014; 186(2):493. · 2.02 Impact Factor
  • Journal of Surgical Research 02/2014; 186(2):493. · 2.02 Impact Factor
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    ABSTRACT: Background The potential for myocardial reconditioning and device explantation after long-term continuous-flow LVAD support presents an opportunity to delay or avoid transplantation in select patients. Methods Thirty patients (of 811) with end-stage heart failure supported with continuous-flow LVADs were assessed for device explantation. Each patient underwent an individualized process of weaning focused on principles of ventricular unloading, gradual reconditioning, and transition to medical therapy. Results After varying reconditioning periods, 27 patients underwent LVAD explant (16 men, 11 women; age, 39±12 years). Three patients were evaluated for explantation but could not be weaned (2 men, 1 woman; age 22±6 years). The duration of LVAD support was 533±424 days (42–1937) for the explant cohort and 1097±424 days (643–1483) for the non-explant cohort. Left ventricular end diastolic dimension, LV ejection fraction, systolic pulmonary artery pressure, cardiac output, and cardiac index in the explant cohort were significantly improved at explantation (all, p<0.05). Two late deaths occurred after LVAD explantation despite satisfactory native cardiac function, and 1 patient required resumption of LVAD support 2.7 years after device removal. The remaining explant patients remain in NYHA classes I-II with medical management alone (mean survival post-explant, 1172±948 days). All 3 candidates who could not be weaned were ultimately transplanted. Conclusions The potential for recovery of native left ventricular function after long-term continouous-flow LVAD support should encourage a more aggressive approach to ventricular reconditioning with the goal of device explantation and a return to medical management, particularly in young patients with dilated cardiomyopathy.
    The Journal of Heart and Lung Transplantation. 01/2014;
  • William E Cohn, Hari R Mallidi, O H Frazier
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    ABSTRACT: As left ventricular assist devices (LVADs) have become more widely used for treating patients with advanced heart failure, the incidence of pump dysfunction requiring pump replacement has increased. When dysfunction is due to pump failure or driveline injury, isolated pump replacement can be curative. We have developed a quick, safe pump-exchange technique that avoids a redo sternotomy and cardiopulmonary bypass. We have used this technique to exchange malfunctioning HeartMate II LVADs in 14 consecutive patients. The patients were extubated within 3 to 6 hours, and blood loss and transfusion requirements were nominal. There were no periprocedural deaths or strokes.
    The Annals of thoracic surgery 12/2013; 96(6):2259-61. · 3.45 Impact Factor
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    ABSTRACT: Over the last 8 years, we have developed and evaluated a continuous-flow total artificial heart (CFTAH) comprising two rotary blood pumps. To understand the physiologic effects of nonpulsatile circulation, we evaluated the CFTAH in 65 calves for 90 days or less. We describe our experience with 29 calves that survived for 7 days or more. The calves received dual axial-flow (n = 24) or centrifugal-flow (n = 5) pumps. Several iterations of customized atrial cuffs were developed to facilitate an adequate anatomical fit. Pressures (arterial pressure [AoP], pulmonary artery pressure [PAP], left atrial pressure [LAP], and right atrial pressure [RAP]) and pump parameters were continuously monitored. Hematologic and biochemistry values were analyzed. After each case, a necropsy was performed. The calves survived for 7-92 days (mean, 24 days). Pressures were 94 ± 14 (AoP), 25 ± 8 (PAP), 14 ± 6 (RAP), and 16 ± 6 (LAP) mm Hg. Pump flow was maintained at 9.1 ± 1.7 L/minute (right) and 9.4 ± 1.9 L/minute (left). Hematologic and biochemistry values remained acceptable. Eight animals underwent treadmill evaluations, in which oxygen consumption (VO2) was comparable with physiologic total-body VO2. In the two animals that survived to 90 days, the end-organs appeared unremarkable at autopsy, and the CFTAH circuits were free of thrombus. Our results show that a CFTAH can maintain a large animal physiologically and hemodynamically for up to 90 days with continuous flow.
    ASAIO journal (American Society for Artificial Internal Organs: 1992) 11/2013; · 1.39 Impact Factor
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    ABSTRACT: We evaluated the effects of steady state flow and perfusion on end-organ function in a long-term calf model. The animal received a continuous-flow total artificial heart (CFTAH) that we created from two axial-flow ventricular assist devices. Pump flow, blood pressure, and other pump parameters were monitored throughout the study, as were arterial blood gas and hematologic values, including neurohormone levels. Some hematologic values were mildly abnormal transiently after surgery but returned to acceptable levels within the first week. During the 90-day study, the calf showed no signs of hemolysis or thrombosis. Its mental function remained normal, as evidenced by the animal's interest in its surroundings and response to stimuli. End-organ and vasomotor function was not adversely affected by 90 days of steady state flow. This was the first study in which CFTAH support of an animal model was maintained for this duration.
    ASAIO journal (American Society for Artificial Internal Organs: 1992) 11/2013; · 1.39 Impact Factor
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    ABSTRACT: Amiodarone is widely used worldwide as an important drug for managing supraventricular arrhythmias, regardless of its association with potentially severe side effects due to systemic toxicity. Amiodarone reduces the incidence of atrial fibrillation after cardiac surgery, but oral therapy requires a presurgery loading period, lasting from 1 to 4 weeks. In this study, we showed that it is possible to rapidly obtain therapeutic cardiac tissue levels of the drug by infusing aqueous amiodarone intrapericardially, without appreciable systemic exposure. We also examined the long-term histologic safety of intrapericardial infusion. In this observational study, 9 adult sheep, randomized into 3 groups of 3 animals each, were given low (2.5 -mg/h), medium (10-mg/h), or high (50-mg/h) dosages of amiodarone by continuous infusion intrapericardially for 72 hours. An intrapericardial drain prevented tamponade from fluid build-up. Levels of amiodarone and its active metabolite, desethylamiodarone (DEA), were assessed both in plasma and in transmural biopsy specimens taken from the left atrial appendage and left and right ventricular myocardium. Cardiac, hepatic, and renal functions were also assessed. Humane euthanization was performed after 3 months, and cardiac and thoracic tissues were assessed for evidence of epicarditis, severe fibrotic changes, or other adverse effects potentially caused by the local amiodarone administration. Pericardial infusion resulted in rapid uptake and high concentrations of amiodarone and DEA in the myocardial tissues, without an appreciable systemic presence of either drug. The highest and lowest levels of these agents were observed in the left atrium and left ventricle, respectively. Drug concentrations in all cardiac biopsy specimens were similar to, or higher than, those reportedly observed in patients taking long-term oral amiodarone. At 90 days, postmortem microscopic, biochemical, and hematologic evaluation of end-organ tissues from the 8 surviving sheep showed no adverse effects. Excessive inflammation or fibrotic changes were not observed in these 8 sheep. The ninth sheep died prematurely, and its death was deemed not to be related to this study. Short-term intrapericardial delivery of amiodarone is a safe method for rapidly obtaining therapeutic atrial-tissue drug levels. When begun perioperatively, this method may prevent postoperative atrial fibrillation similarly to oral or intravenous amiodarone therapy. However, we have shown that pericardial administration avoids systemic drug distribution and thus may greatly decrease the systemic complicationsresulting from this drug.
    Heart Surgery Forum 10/2013; 16(5):E279-86. · 0.63 Impact Factor
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    ABSTRACT: Trauma-related failure of a continuous-flow left ventricular assist device (LVAD) has not previously been reported. We present 4 cases in which LVAD complications were likely caused by external trauma and led to failure of a HeartMate II device. In 1 case, the onset of symptoms was delayed and the patient did not seek medical attention until months after the traumatic event. All 4 patients required surgical intervention, and 1 patient died of respiratory complications several months postoperatively. In conclusion, a history of external trauma should be considered as a possible etiologic factor when LVAD-supported patients in previously stable condition present with device malfunction.
    The American journal of cardiology 08/2013; · 3.58 Impact Factor
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    ABSTRACT: Successful anatomic fitting of a total artificial heart (TAH) is vital to achieve optimal pump hemodynamics after device implantation. Although many anatomic fitting studies have been completed in humans prior to clinical trials, few reports exist that detail the experience in animals for in vivo device evaluation. Optimal hemodynamics are crucial throughout the in vivo phase to direct design iterations and ultimately validate device performance prior to pivotal human trials. In vivo evaluation in a sheep model allows a realistically sized representation of a smaller patient, for which smaller third-generation TAHs have the potential to treat. Our study aimed to assess the anatomic fit of a single device rotary TAH in sheep prior to animal trials and to use the data to develop a three-dimensional, computer-aided design (CAD)-operated anatomic fitting tool for future TAH development. Following excision of the native ventricles above the atrio-ventricular groove, a prototype TAH was inserted within the chest cavity of six sheep (28-40 kg). Adjustable rods representing inlet and outlet conduits were oriented toward the center of each atrial chamber and the great vessels, with conduit lengths and angles recorded for future analysis. A three-dimensional, CAD-operated anatomic fitting tool was then developed, based on the results of this study, and used to determine the inflow and outflow conduit orientation of the TAH. The mean diameters of the sheep left atrium, right atrium, aorta, and pulmonary artery were 39, 33, 12, and 11 mm, respectively. The center-to-center distance and outer-edge-to-outer-edge distance between the atria, found to be 39 ± 9 mm and 72 ± 17 mm in this study, were identified as the most critical geometries for successful TAH connection. This geometric constraint restricts the maximum separation allowable between left and right inlet ports of a TAH to ensure successful alignment within the available atrial circumference.
    Artificial Organs 03/2013; · 1.96 Impact Factor
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    ABSTRACT: We assessed and compared the performance levels of a fiber-coupled fluorescence affinity sensor (FAS) for glucose detection in the intradermal tissue and intravascular bed during glucose clamping and insulin administration in a large animal model. Research Design and The FAS (BioTex Inc., Houston, TX) was implanted in interstitial tissue and in the intravenous space in nondiabetic, anesthetized pigs over 6-7 h. For intradermal assessment, a needle-type FAS was implanted in the upper back using a hypodermic needle. For intravenous assessment, the FAS was inserted through a catheter into the femoral artery and vein. Blood glucose changes were induced by infusion of dextrose and insulin through a catheterized ear or jugular vein. Based on retrospective analysis, the mean absolute relative error (MARE) of the sensor in blood and interstitial tissue was 11.9% [standard deviation (SD) = ±9.6%] and 23.8% (SD = ±19.4%), respectively. When excluding data sets from sensors that were affected by exogenous insulin, the MARE for those sensors tested in interstitial tissue was reduced to 16.3% (SD = ±12.5%). The study demonstrated that the performance level of the FAS device implanted in interstitial tissue and blood can be very high. However, under certain circumstances, exogenous insulin caused the glucose concentration in interstitial tissue to be lower than in blood, which resulted in an overall lower level of accuracy of the FAS device. How significant this physiological effect is in insulin-treated persons with diabetes remains to be seen. In contrast, the level of accuracy of the FAS device in blood was very high because of high mass transfer conditions in blood. While the use of the FAS in both body sites will need further validation, its application in critically ill patients looks particularly promising.
    Journal of diabetes science and technology 01/2013; 7(1):35-44.
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    ABSTRACT: BACKGROUND: Aortic valve repair is associated with fewer long-term valve-related complications as compared with valve replacement, and repair is being performed increasingly. A current problem is the lack of a geometric annuloplasty ring to facilitate reconstruction. This paper describes the first clinical application of such a device designed to permanently restore physiologic annular size and geometry during aortic valve repair. METHODS: Based on mathematical studies of human cadaver valves, as well as computed tomography angiographic analyses of awake patients with normal valves, a three-dimensional annuloplasty ring has been developed, consisting of low-profile, one-piece titanium construction and Dacron cloth covering. The ring design incorporates 2:3 elliptical base geometry and 10-degree outwardly flaring subcommissural posts. RESULTS: Appropriately sized rings were implanted in 5 patients with severe aortic insufficiency due to annular dilation and anatomic leaflet defects. The rings restored annular geometry and facilitated leaflet repairs in all patients. Each recovered excellent valve function with minimal residual leak. All patients convalesced uneventfully, were discharged within 7 days after surgery, and continue with stable valve function as long as 6 months after implantation. CONCLUSIONS: Initial clinical application of a geometric aortic annuloplasty ring was associated with excellent device performance and perhaps better repairs. Further clinical series and patient follow-up should identify potential benefits of the device, including improved applicability and stability of aortic valve repair.
    The Annals of thoracic surgery 10/2012; · 3.45 Impact Factor
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    ABSTRACT: Abstract  Background: In patients with a left ventricular assist device (LVAD), pump-related infection can cause adverse effects that may result in death. Methods: We describe three patients who had infections related to a fistula between the gastrointestinal (GI) tract and the LVAD pocket and who subsequently underwent successful heart transplantation without developing sepsis. In no case did the LVAD-related infection adversely affect the outcome of transplantation. Conclusions: For detecting the fistulas, full upper-GI endoscopy and colonoscopy were superior to other types of diagnostic imaging studies. (J Card Surg 2012;27:643-645).
    Journal of Cardiac Surgery 09/2012; 27(5):643-5. · 1.35 Impact Factor
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    ABSTRACT: In this report we provide another method of ventricular assist device separation by simply transecting the inflow graft of a Heart Mate II LVAD without the need of dissecting the left ventricular apex for cases of myocardial recovery.
    Journal of Cardiac Surgery 04/2012; 27(3):397-9. · 1.35 Impact Factor
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    ABSTRACT: We evaluated the short- and mid-term in vivo performance of the Innovamedica ventricular assist device (VAD), a new, low-cost, paracorporeal, pneumatically actuated, pulsatile blood pump. We implanted the VAD in six healthy sheep by inserting the stainless-steel inflow cannula into the left ventricular apex and suturing the outflow graft to the descending thoracic aorta. The anesthetized animals were supported for 6 hours, and pump performance, hemodynamic parameters, and hemolysis were monitored. The pump maintained a blood flow of 4.4 ± 0.8 L/min and an arterial blood pressure of 76 ± 15 mm Hg. At 6 hours, the plasma free hemoglobin concentration was 5.11 ± 0.6 mg/dl (baseline value, 4.52 ± 0.7 mg/dl). The VAD was easy to implant and deair and performed well during the 6 hour period. After successful short-term results, we similarly implanted the VAD in two healthy sheep for 30 days. The animals reached the scheduled end point without device-related problems. Postmortem examination of the explanted organs revealed small infarcted areas in the kidneys of one animal, but renal function was unaffected; the animal also had two thrombi (3 and 7 mm) on the outlet valve. This device may offer a simple, economical alternative to currently available VADs.
    ASAIO journal (American Society for Artificial Internal Organs: 1992) 03/2012; 58(2):98-102. · 1.39 Impact Factor
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    ABSTRACT: To increase applicability and stability of aortic valve repair, a three-dimensional aortic annuloplasty ring has been developed for intra-annular placement. The goal of this study was to test the safety of this device with in vivo implantation in the calf model. In 10 chronic calves, the HAART annuloplasty ring was sutured to the aortic valve annulus using cardiopulmonary bypass. The animals were recovered and followed for 1-2 months. Serial echocardiography was used to evaluate valve competence, and contrast aortograms and CT angiograms were obtained in selected animals. After completion of follow-up, each animal was euthanized, and aortic endoscopy was performed under water distension in five. Full autopsies with histologic examinations were performed. All animals survived surgery. Two were euthanized in the first week for complications, and the remaining eight calves were followed uneventfully for the 1-2 months. Serial echocardiography showed completely competent valves in all but one animal, in which the ring was intentionally up-sized to test the sizing strategy. Contrast aortographic and CT angiographic findings were similar to the echocardiograms. Postmortem examination showed proper seating of all rings with endothelialization at 1-2 months. All valves demonstrated good leaflet coaptation and no abnormalities. In vivo testing of a three-dimensional aortic annuloplasty ring in a chronic calf model proved to be very successful and safe. Using the sizing and implant strategies developed, human trials seem indicated.
    European journal of cardio-thoracic surgery: official journal of the European Association for Cardio-thoracic Surgery 02/2012; 42(1):149-54. · 2.40 Impact Factor

Publication Stats

847 Citations
254.71 Total Impact Points

Institutions

  • 2007–2014
    • Baylor College of Medicine
      Houston, Texas, United States
    • Montreal Heart Institute
      • Research Centre
      Montréal, Quebec, Canada
  • 2004–2014
    • Texas Heart Institute
      • Division of Cardiovascular Surgery
      Houston, Texas, United States
  • 2011–2012
    • Vanderbilt University
      • Center for Cognitive Medicine
      Nashville, MI, United States
    • Texas A&M University
      College Station, Texas, United States
  • 2010
    • Alpert Medical School - Brown University
      • Department of Surgery
      Providence, RI, United States
  • 2009
    • St. Luke School of Medicine
      Houston, Texas, United States
  • 2008
    • University of Cincinnati
      Cincinnati, Ohio, United States
    • Houston Methodist Hospital
      Houston, Texas, United States
  • 2006
    • Université de Montréal
      • Department of Pharmacology
      Montréal, Quebec, Canada
  • 1997–2003
    • Harvard Medical School
      Boston, Massachusetts, United States
  • 1995–2002
    • Beth Israel Deaconess Medical Center
      • Department of Surgery
      Boston, MA, United States
  • 2000
    • Rhode Island Hospital
      Providence, Rhode Island, United States