William E Cohn

Baylor College of Medicine, Houston, Texas, United States

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Publications (144)415.83 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We tested the short-term effects of completely nonpulsatile versus pulsatile circulation after ventricular excision and replacement with total implantable pumps in an animal model on peripheral vascular permeability. Ten calves underwent cardiac replacement with two HeartMate III continuous-flow rotary pumps. In five calves, the pump speed was rapidly modulated to impart a low-frequency pulse pressure in the physiologic range (10-25 mm Hg) at a rate of 40 pulses per minute (PP). The remaining five calves were supported with a pulseless systemic circulation and no modulation of pump speed (NP). Skeletal muscle biopsies were obtained before cardiac replacement (baseline) and on postoperative days (PODs) 1, 7, and 14. Skeletal muscle-tissue water content was measured, and morphologic alterations of skeletal muscle were assessed. VE-cadherin, phospho-VE-cadherin, and CD31 were analyzed by immunohistochemistry. There were no significant changes in tissue water content and skeletal muscle morphology within group or between groups at baseline, PODs 1, 7, and 14, respectively. There were no significant alterations in the expression and/or distribution of VE-cadherin, phospho-VE-cadherin, and CD31 in skeletal muscle vasculature at baseline, PODs 1, 7, and 14 within each group or between the two groups, respectively. Although continuous-flow total artificial heart (CFTAH) with or without a pulse pressure caused slight increase in tissue water content and histologic damage scores at PODs 7 and 14, it failed to reach statistical significance. There was no significant adherens-junction protein degradation and phosphorylation in calf skeletal muscle microvasculature after CFTAH implantation, suggesting that short term of CFTAH with or without pulse pressure did not cause peripheral endothelial injury and did not increase the peripheral microvascular permeability. Copyright © 2015 Elsevier Inc. All rights reserved.
    Journal of Surgical Research 06/2015; DOI:10.1016/j.jss.2015.06.035 · 2.12 Impact Factor
  • William E Cohn · Daniel L Timms · O H Frazier
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    ABSTRACT: A practical artificial heart has been sought for >50 years. An increasing number of people succumb to heart disease each year, but the number of hearts available for transplantation remains small. Early total artificial hearts mimicked the pumping action of the native heart. These positive-displacement pumps could provide adequate haemodynamic support and maintain the human circulation for short periods, but large size and limited durability adversely affected recipients' quality of life. Subsequent research into left ventricular assist devices led to the use of continuous-flow blood pumps with rotating impellers. Researchers have attempted to integrate this technology into modern total artificial hearts with moderate clinical success. The importance of pulsatile circulation remains unclear. Future research is, therefore, needed into positive-displacement and rotary total artificial hearts.
    Nature Reviews Cardiology 06/2015; DOI:10.1038/nrcardio.2015.79 · 10.15 Impact Factor
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    ABSTRACT: Arteriovenous fistulae (AVFs) created by conventional surgical techniques are associated with suboptimal short- and long-term patency. This study investigated the feasibility of creating fistulae with a percutaneous system and evaluated the utility of percutaneous AVFs (pAVFs) in providing hemodialysis access. From August 2012 to September 2013, a percutaneous system was used to attempt pAVF creation between the proximal ulnar artery and a closely associated ulnar vein in 33 patients. Technical success, adverse events, and time to pAVF maturity were recorded, as was clinical effectiveness at 6 months. A pAVF was successfully created in 32 of 33 patients (97%). Four patients died during the follow-up period from causes unrelated to the procedure; one patient was lost to follow-up. Of the remaining 27 patients, 24 were undergoing successful dialysis via their pAVF at 6 months. Two additional patients had usable access but did not initiate dialysis during the study. One spontaneous pAVF thrombosis occurred in a patient with preexisting central vein stenosis. Cumulative pAVF patency at 6 months was 96.2% (26 of 27; standard error, 3.8%). Mean time to pAVF maturation was 58 days (range, 37-168 d). There was one serious procedure-related adverse event and five minor procedure-related adverse events. Although larger studies are required to validate efficacy in a wide range of patients, this study demonstrates hemodialysis access successfully created with an endovascular catheter-based system. Patency of pAVFs and time to maturation were superior to published results of surgical techniques. Copyright © 2015 SIR. Published by Elsevier Inc. All rights reserved.
    Journal of vascular and interventional radiology: JVIR 04/2015; 26(4). DOI:10.1016/j.jvir.2014.12.018 · 2.15 Impact Factor
  • The Journal of Heart and Lung Transplantation 04/2015; 34(4):S41-S42. DOI:10.1016/j.healun.2015.01.099 · 5.61 Impact Factor
  • The Journal of Heart and Lung Transplantation 04/2015; 34(4):S24-S25. DOI:10.1016/j.healun.2015.01.055 · 5.61 Impact Factor
  • The Journal of Heart and Lung Transplantation 04/2015; 34(4):S248. DOI:10.1016/j.healun.2015.01.688 · 5.61 Impact Factor
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    ABSTRACT: Cardiac surgical procedures carry a high risk of perioperative bleeding. Surgical sealants are often used to prevent suture line bleeding. PreveLeak™ is a surgical sealant composed of bovine serum albumin, a polyaldehyde cross-linker, and other components that forms a soft, flexible, water-tight, mechanical seal that is biocompatible and bioresorbable. A prospective, multicentre study evaluated PreveLeak use in 44 subjects undergoing 63 cardiac procedures, primarily coronary artery bypass grafting (n = 23/63, 36.5%) and aortic valve replacement (n = 19/63, 30.2%). PreveLeak was applied to 127 suture lines and the time to sealing evaluated upon clamp release. The primary safety endpoint was the incidence of significant bleeding, infections, neurological deficits and immune/inflammatory allergic responses within 6 weeks post-treatment; subjects were followed for 3 months. Immediate sealing was achieved at all sites in 42 of 44 subjects (95.5%) and 125 of 127 treatment sites (98.4%). There were nine primary safety events: eight infections and one transient neurological deficit. Most adverse events were mild (n = 46/71, 64.8%) or moderate (n = 18/71, 25.4%) in severity. One adverse event (transient vasospasm) was considered possibly sealant-related. One death occurred due to a cardiac arrest. PreveLeak prevented bleeding at 98.4% of treated sites and was well tolerated; adverse events were consistent with those commonly observed in subjects undergoing surgical procedures. These results compared favourably with published studies of other sealants. The observed prevention of bleeding is clinically important in cardiac surgical patients. A randomized, comparative study is justified to further evaluate PreveLeak and confirm the findings from this study. © The Author 2015. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
    Interactive Cardiovascular and Thoracic Surgery 03/2015; 20(6). DOI:10.1093/icvts/ivv061 · 1.11 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 09/2014; 34(6). DOI:10.1016/j.healun.2014.09.015 · 5.61 Impact Factor
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    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.
    Journal of Thoracic and Cardiovascular Surgery 09/2014; 149(1). DOI:10.1016/j.jtcvs.2014.08.054 · 3.99 Impact Factor
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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). DOI:10.1111/aor.12380 · 1.87 Impact Factor
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    ABSTRACT: Although there is limited consensus about the strict requirement to deliver pulsatile perfusion to the human circulatory system, speed modulation of rotary blood pumps is an approach that may capture the benefits of both positive displacement and continuous flow blood pumps. In the current stage of development of the BiVACOR Total Artificial Heart emphasis is placed on providing pulsatile outflow from the pump. Multiple pulsatile speed profiles have been applied in preliminary in-vivo operation in order to assess the capability of the TAH to recreate a physiologic pulse. This paper provides an overview about recent research towards pulsatile BiVACOR operation with special emphasis on motor and control requirements and developments.
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    ABSTRACT: A mock circulatory loop was constructed to facilitate total artificial heart development. The loop includes many novel features such as a pressure-regulated tank to simulate exercise conditions, controllable systemic and pulmonary vascular resistance to create left-right flow imbalances as seen in postural change and breathing, and a left atrial suction valve. Dual HeartMate II pumps and the BiVACOR® rotary total artificial heart were used to generate pressure and flow data characterizing the flow loop.
  • The Journal of Heart and Lung Transplantation 04/2014; 33(4):S204. DOI:10.1016/j.healun.2014.01.891 · 5.61 Impact Factor
  • The Journal of Heart and Lung Transplantation 04/2014; 33(4):S237-S238. DOI:10.1016/j.healun.2014.01.913 · 5.61 Impact Factor
  • The Journal of Heart and Lung Transplantation 04/2014; 33(4):S210. DOI:10.1016/j.healun.2014.01.907 · 5.61 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. DOI:10.14503/THIJ-14-4143 · 0.63 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; 29(3). DOI:10.1111/jocs.12318 · 0.89 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; 60(3). DOI:10.1097/MAT.0000000000000071 · 1.39 Impact Factor
  • D.K. Rajan · A.A. Ebner · J.M. Rios · S. Desai · W.E. Cohn
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    ABSTRACT: Purpose To evaluate the feasibility, safety and efficacy of the FLEX system to create a non-surgical percutaneous autogenous AV fistula that supports hemodialysis. Materials and Methods Thirty three patients with end-stage renal disease were enrolled in four cohorts (A=7, B=9, C=8, D=9) and underwent percutaneous AVF creation with the FLEX system. The procedure evolved between cohorts. Cohorts A/ B underwent a secondary procedure one month later with selective coiling. In cohorts C/ D, coil embolization of the brachial vein was performed during the initial procedure. Patients were followed 24 hours to 6 months with ultrasound and/or fistulography to assess fistula maturation. Primary endpoints included technical success, safety, and time to fistula maturation. Suitability for cannulation was determined by the patient's nephrologist. Fistula efficacy was assessed by successful hemodialysis delivery of >75% of dialysis sessions for at least one month. Results Technical success was 97% (32/33). Mean procedure time was 49 minutes. In cohorts A-C, 20/24 patients had mature fistulas and were suitable for dialysis (1 patient with central venous stenosis developed venous hypertension and subsequent closure of the fistula 3 months after creation. One patient died from hyperkalemia and one died from foot gangrene. In one patient the procedure was unsuccessful at creating a fistula. Average maturation time was 74 days post procedure through all cohorts. 17/20 patients received dialysis via their percutaneous AVF for >1 month (Two patients were dialysis-ready but do not initiate dialysis and one patient developed a pseudoaneurysm in dialysis clinic during cannulation). Follow-up for cohort D patients is ongoing. Device and procedure-related complications included two pseudoaneurysms (Cohort A), 1 device fracture, 1 venous hypertension (Cohort C), and 1 hospital-acquired infection (Cohort D). Patients in cohorts A-C have been followed for 6 months with no interventions required. Conclusion We observed high technical success and fistula patency with most fistulas now supporting hemodialysis beyond one month without additional intervention. The results surpass historical outcomes for surgically created AV fistulas.
    Journal of Vascular and Interventional Radiology 03/2014; 25(3):S19. DOI:10.1016/j.jvir.2013.12.045 · 2.15 Impact Factor
  • J. Anand · A. Baldwin · S. Parnis · W.E. Cohn · O. Frazier
    Journal of Surgical Research 02/2014; 186(2):493. DOI:10.1016/j.jss.2013.11.014 · 2.12 Impact Factor

Publication Stats

1k Citations
415.83 Total Impact Points

Institutions

  • 2007–2015
    • Baylor College of Medicine
      • • Department of Surgery
      • • Division of Cardiothoracic Surgery
      Houston, Texas, United States
    • Université de Montréal
      • Department of Pharmacology
      Montréal, Quebec, Canada
  • 2004–2015
    • Texas Heart Institute
      • Division of Cardiovascular Surgery
      Houston, Texas, United States
  • 2006–2014
    • St. John's Episcopal Hospital
      Rockaway, New Jersey, United States
  • 2008–2011
    • Houston Methodist Hospital
      Houston, Texas, United States
    • University of Cincinnati
      Cincinnati, Ohio, United States
  • 2009
    • St. Luke School of Medicine
      Houston, Texas, United States
  • 2008–2009
    • University of Houston
      • Department of Mechanical Engineering
      Houston, Texas, United States
  • 1997–2003
    • Harvard Medical School
      • Department of Surgery
      Boston, Massachusetts, United States
  • 1995–2003
    • Harvard University
      Cambridge, Massachusetts, United States
  • 1997–2002
    • Beth Israel Deaconess Medical Center
      • Department of Surgery
      Boston, Massachusetts, United States
  • 2000
    • Rhode Island Hospital
      Providence, Rhode Island, United States