Andrew L Rivard

University of Mississippi Medical Center, Jackson, Mississippi, United States

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Publications (35)51.8 Total impact

  • Andrew L Rivard
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    ABSTRACT: The Asporto Heart Preservation Device is a system providing perfusion of cardioplegia to the donor heart using a computer-controlled peristaltic pump in a thermoelectrically cooled and insulated container. In 1998, a user interface was developed at the University of Minnesota consisting of a touch screen and battery-backed microcontroller. Power was supplied by a 120 VAC to 12 VDC converter. An upgrade to the insulated cooler and microcontroller occurred in 2002, which was followed by proof of concept experimental pre-clinical transplants and tests demonstrating the efficacy of the device with isolated donor hearts. During the period between 2002 and 2006, a variety of donor organ containers were developed, modified, and tested to provide an optimal sterile environment and fluid path. Parallel development paths encompass formalized design specifications for final prototypes of the touch screen/microcontroller, organ container, and thermoelectric cooler.
    No preview · Article · Sep 2015 · The Journal of extra-corporeal technology

  • No preview · Article · Feb 2015 · Journal of the Mississippi State Medical Association
  • Richard Edward Hosch · Andrew L Rivard
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    ABSTRACT: Providing patients and clinicians with self-contained PACS viewer on CD format is a common and necessary tool to share vital imaging data. However, to be useful, this tool should be reliable, robust, and convenient. Numerous PACS viewer options are available, often without empirical data to guide in choosing one for routine use. To assist in making a standardized choice for our institution, we chose four common viewers, benchmarked on four different workstations reflecting the variety of environments used by non-radiologist clinicians who would receive a CD. Four CD-based DICOM viewers from eFilm, Philips, Pacsgear Gearview, and iSite were examed on two radiology PACS workstations, a standard desktop computer, and a laptop using a test case consisting of a multi-series CTA with 13 series and 3,035 total images. Multiple objective measures, subjective measures, and presence of key features were evaluated including program time to load, image time to load, cine/movie mode, ability to adequately window and level, pan and zoom functionality, basic measurement tools, and perceived lag when scrolling through a multi-image series. Substantial differences in speed of operation and behavior on multiple systems were documented, which could potentially add several minutes to the time required to open and view a patient's imaging data. The eFilm and iSite viewers operated consistently and reliably across all tested computer environments. The iSite viewer, having among the quickest load times in the group tested and consistently low subjective scroll lag during series viewing, and also beneficially allowing partial viewing while images load in the background, was found to generate the best overall user experience. Because of these significant differences, we have recommended that our institution standardize all patient imaging CD creation using the iSite viewer.
    No preview · Article · Apr 2014 · Journal of Digital Imaging
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    ABSTRACT: Background Aortoenteric fistula is a communication between the aorta and adjacent bowel. It is rare, potentially fatal, and is difficult to diagnose and manage. These patients often present with a “herald bleed,” followed by massive gastrointestinal hemorrhage. Patient and methods A 67 year old man presented with right upper quadrant pain, hematochezia and hypotension. Two months ago, the patient underwent elective open repair of an abdominal aortic aneurysm. On upper endoscopy, fresh blood and adherent clots were seen in the third/fourth portion of the duodenum. After some of the clots were gently washed off with water flushing, a fistula opening was seen on posterior superior wall of the duodenum. The fistula opening was surrounded by edematous duodenal mucosal. An aortoenteric fistula was highly suspected and the patient went to emergent laparotomy. Results During surgery, significant inflammation was noted surrounding the aorta with friable tissues of the aorta itself. A definite aortoenteric fistula was seen arising in the native aorta. Unfortunately, the patient expired due to cardiac vascular collapse. Conclusions Diagnosis of aortoenteric fistula requires a high index of suspicion and careful history-taking. Endoscopic findings include adherent clots or bleeding at the fistula opening and/or eroded vascular graft or stent into the bowel.
    Full-text · Article · Apr 2014 · Video Journal and Encyclopedia of GI Endoscopy

  • No preview · Chapter · Dec 2013
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    ABSTRACT: Left ventricular diverticulum is an extremely rare anomaly, especially in the absence of other findings, and as such it has been rarely imaged, rarely seen intraoperatively, and has no standardized management algorithm. We report our suggested imaging and management in the context of previous management philosophies.
    No preview · Article · Jul 2013 · World Journal for Pediatric and Congenital Hearth Surgery

  • No preview · Article · Feb 2013 · The Journal of pediatrics

  • No preview · Chapter · Jan 2013

  • No preview · Article · May 2011 · The international journal of cardiovascular imaging
  • Andrew L Rivard

    No preview · Article · Apr 2011 · Journal of the American College of Radiology: JACR
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    ABSTRACT: The CryoMaze procedure is usually limited to endocardial ablation under cardio-pulmonary bypass. Epicardial ablation is considered inferior as endocardial islets of atrial tissue could theoretically remain viable, protected from cryoinjury by epicardial fat and endocardial circulating warm blood. Novel argon-powered cryoprobes with lower ablation temperatures have recently become available. It is unclear if these instruments can reliably induce transmural atrial fibrosis by epicardial cryoablation on the beating heart. Ten sheep were divided into two equal groups. CryoMaze ablations were applied using an argon-powered cryoprobe with an ablation temperature of -185°C. In the control group, standardized ablations (n = 50) were applied endocardially under cardiopulmonary bypass. In the experimental group, corresponding ablations (n = 50) were applied epicardially on the beating heart. Postoperatively the animals were monitored for 30 days. At necropsy, the lesions were explanted and analyzed histologically for evidence of transmural fibrosis. Two animals in the control group and one animal in the experimental group died prematurely. Autopsy of the remaining animals showed that all lesions (n = 70) had retained their structural integrity. In the control group, histology demonstrated transmural fibrosis in 94% (28/30) of the endocardially applied lesions. In the experimental group, histology demonstrated transmural fibrosis in 95% (38/40) of the epicardially applied lesions. Statistical analysis revealed no significant difference between the two groups (p = 0.96). Argon-powered epicardial cryoablation on the beating heart is as efficient in inducing transmural fibrosis as the traditional technique of endocardial ablation under cardio-pulmonary bypass.
    No preview · Article · Mar 2011 · Journal of Cardiac Surgery
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    ABSTRACT: The pulmonary atresia and intact ventricular septum (PAIVS) spectrum usually includes very hypoplastic right ventricles (RVs) and tricuspid valves (TVs) and often RV-coronary artery connections (RV-CACs). These abnormalities are often thought irreversible and typically only 30% reach a 2-ventricle repair (2VR). Our hypothesis, however, has been PAIVS is a developmental defect and catch-up growth is possible in all. To answer this question, we attempted to obtain up to 10 year echo data on RV and TV growth and function in the 24 survivors (of 28 patients) from 1989 to 1999. To maximize the validity of the growth results obtained, we used only paired studies and required biplane echos to accurately estimate RV volumes, TV size, and function. Measurements were indexed to determine the z score (standard deviation of the mean from predicted).All patients had an RV outflow patch and ASD reduction. We have found catch-up growth required complete relief of RV obstruction and a mildly restrictive (3–5 mm Hg) ASD to encourage TV flow. A central shunt was placed in 38%. RV-CACs (2.7 ± 1.6/pt) were uneventfully ligated off bypass in 9/28 (32%). For the 24 survivors, 19 adequate paired biplane studies were obtained from here and elsewhere and for 12 allowed a 10 year follow-up.The RV volume z scores grew from − 5.1 ± 2.5 to 0.9 ± 1.9 about 10 years later. The TVs, even with increased flow early, grew more slowly than the RVs. Nevertheless, the very small TVs in 10 pts went from z scores of − 4.6 ± 0.4 to − 0.04 ± − 1.5 within about 5–10 years. Valvotomies were done in 3. RV function was high normal (EF = 74.5 ± 0.1%) presumably because of pulmonary regurgitation in the 8 pts who had adequate studies.We conclude: (1) Catch-up growth appears reliable in PAIVS pts when RV obstruction is relieved and TV flow is increased (2) RV function was good and resembled well-repaired TOF (3) These results encourage pursuing 2VRs in PAIVS patients.
    No preview · Article · May 2010 · Progress in Pediatric Cardiology
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    ABSTRACT: In percutaneous aortic valve replacement (AVR), whilst calcifications are used as landmarks in fluoroscopic placement of the stent, they may also complicate stent placement. In response to this problem, the study aim was to examine severe aortic root calcification by using multi-detector computed tomography (MDCT), to better understand the pathology complicating percutaneous valve placement. In 33 patients with severe aortic stenosis and scheduled for surgery, the 'inner orifice' and 'outer fibrous' annulus diameter and area (with and without calcification) were measured, in addition to the distances of the calcifications and coronary ostia from the annulus, using by ECG-gated 64-slice MDCT. Aortic root calcification was evaluated as minimal (< 25% of total circumference), mild (25-50%), moderate (50-75%), and severe (75-100%). The inner orifice annulus area was 5.9 +/- 1.9 cm2 (range: 1.4-10.1 cm2), while the outer fibrous area was 7.5 +/- 1.8 cm2 (range: 4.7-11.5 cm2). The proximal-to-distal extent of valve calcification from the annulus in the mid-center of leaflets was 0.8 +/- 0.26 cm. In 36% of patients, valvular calcification extended +/- 3 mm within the coronary-ostium level. The distance of the coronary ostia from the annulus was variable, with a mean of 1.3 +/- 0.35 cm (range: 0.6-2.4 cm) for the left coronary artery. In 42% of patients, a 'low coronary ostium' (< or = 1.1 cm), and in 6% a 'critical-low-coronary ostium' (< or = 8 mm) was identified. Annulus calcification was present in 100% of cases, but the severity varied widely (severe 50%, moderate 35%, mild 15%). In 36% of cases, the aortic annulus calcification extended caudally into the membranous part of the interventricular septum (and thus into the left ventricular outflow tract), and in 42% of cases (n = 14) into the anterior mitral valve leaflet. The present results indicated that cardiac MDCT may qualify as a primary pre-procedural imaging modality to select patients for percutaneous AVR, based on the measurement and characterization of the aortic root and valve calcification. In comparison to echocardiography, CT will reduce--if not eliminate--difficulties in visualizing the aortic orifice area in heavily calcified valves. Furthermore, knowledge of the exact location of calcific deposits provides a distinct advantage to the fluroscopist for precise placement of the percutaneous aortic valve. Likewise, knowledge of the coronary arteries orifice in relation to the valve plane is critical to prevent inadvertent coronary artery occlusion, and would clearly be beneficial when planning future valve designs.
    Full-text · Article · Nov 2009 · The Journal of heart valve disease
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    ABSTRACT: As a consequence of technology improvements and refinement, perfusion of the donor heart has moved from the research laboratory to clinical studies. Multiple investigators are currently leading pre-clinical trials of devices using perfusion preservation, and one device is now in European clinical trials. One major problem with the donor heart is the high metabolism relative to other organs, and depletion of ATP leads rapidly to acidosis and necrosis of the myocardium. Two techniques in development to address the issue are normothermic and hypothermic perfusion. This review examines the current issues regarding donor heart preservation and techniques of preclinical evaluation necessary for regulatory approval.
    No preview · Article · Sep 2009 · The Journal of extra-corporeal technology
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    ABSTRACT: Effective outcomes in cardiothoracic surgical research using rodents are dependent upon adequate techniques for intubation and mechanical ventilation. Multiple methods are available for intubation of the rat; however, not all techniques are appropriate for survival studies. This article presents a refinement of intubation techniques and a simplified mechanical ventilation setup necessary for intrathoracic surgical procedures using volatile anesthetics. The procedure is defined and complications of the procedure are elucidated that provide a justification for animal numbers needed for initiating new studies. Lewis rats weighing 178-400 g (287 +/- 44) were anesthetized using Enflurane and intubated with a 16-G angiocatheter using transillumination. Mechanical ventilation (85 bpm, 2.5 mL TV, enflurane 1.5-2%) maintained adequate sedation for completion of an intrathoracic procedure. Complications of the intubation and ventilation included mortality from anesthetic overdose, intubation difficulty, pneumothorax, traumatic extubation, and ventilation disconnection. Anesthetic agents and their related effects on the rat heart and reflexes are compared. This article also underscores the importance of refinement, reduction, and replacement in the context of cardiothoracic surgery using rodent models.
    Full-text · Article · Jul 2009 · Journal of Investigative Surgery
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    ABSTRACT: To determine the pattern of feeding milestones following primary repair of long-gap esophageal atresia (EA). A questionnaire based upon well established feeding milestones was used. Children after long-gap EA repair, n=40, were compared from after primary repair to healthy children from birth, n=102. The age when surveyed of the EA group and controls was different: 6.2+/-4.7 (mean+/-standard deviation) years, range 1.1-20.9, versus 2.5+/-2.4 years, range 0.0-12.1, p=0.00. The esophageal gap length in the EA group was 5.1+/-1.2 cm and age at repair was 5.5+/-5.0 months. There was no statistically significant difference between the atresia group and controls for feeding milestones; Self feeding finger foods approached significance. There was, however, greater variability in the timing of milestones in the atresia group compared to controls. Feeding milestones were negatively correlated with age at primary repair: drinking with a covered sippy cup, rho=-0.51, p=0.01 and self feeding finger foods, rho=-0.36, p=0.04 were statistically significant. Drinking from a cup correlated with gestational age, rho=0.38, p=0.04, and negatively correlated to esophageal gap length, rho=-0.45, p=0.01. Despite delayed onset of feeding, major milestones after EA repair occurred in similar pattern to normal infants. An early referral for primary repair is beneficial for earlier acquisition of milestones for infants with long-gap EA.
    No preview · Article · Feb 2009 · Early human development
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    ABSTRACT: The modern era of cardiac surgery is largely considered to have begun in the animal research laboratories. Today, animal models continue to be used for the study of cardiovascular diseases and are required for the preclinical assessment of pharmaceuticals, mechanical devices, therapeutic procedures, and/or continuation therapies. This chapter was designed to provide readers and potential investigators with important background information necessary for the process of matching an experimental hypothesis to an animal species that will serve as an appropriate model for studying a specific cardiovascular disease or for testing a given medical device. A review of the current animal models used in cardiac research is provided and arranged by disease state. Critical factors to consider when choosing an appropriate animal model including cost, reproducibility, and degree of similarity of the model to human disease are discussed. Thus, this chapter can be utilized as a practical guide for planning of research protocols. KeywordsAnimal model–Isolated cardiomyocytes–Isolated perfused heart–Valve disease–Atrial fibrillation–Myocardial ischemia–Heart failure–Heart transplantation–Mechanical device testing–Cardiomyoplasty–Stem cell research
    No preview · Chapter · Dec 2008
  • Andrew L Rivard · Melissa Themar-Geck · Philip S Cook · Lori Deitte

    No preview · Article · Dec 2008 · Journal of the American College of Radiology: JACR
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    ABSTRACT: A major problem in procurement of donor hearts is the limited time a donor heart remains viable. After cardiectomy, ischemic hypoxia is the main cause of donor heart degradation. The global myocardial ischemia causes a cascade of oxygen radical formation that cumulates in an elevation in hydrogen ions (decrease in pH), irreversible cellular injury, and potential microvascular changes in perfusion. To determine the changes of prolonged storage times on donor heart microvasculature and the effects of intermittent antegrade perfusion. Using porcine hearts flushed with a Ribosol-based cardioplegic solution, we examined how storage time affects microvascular myocardial perfusion by using contrast-enhanced magnetic resonance imaging at a mean (SD) of 6.1 (0.6) hours (n = 13) or 15.6 (0.6) hours (n = 11) after cardiectomy. Finally, to determine if administration of cardioplegic solution affects pH and microvascular perfusion, isolated hearts (group 1, n = 9) given a single antegrade dose, were compared with hearts (group 2, n = 8) given intermittent antegrade cardioplegia (150 mL, every 30 min, 150 mL/min) by a heart preservation device. Khuri pH probes in left and right ventricular tissue continuously measured hydrogen ion levels, and perfusion intensity on magnetic resonance images was plotted against time. Myocardial perfusion measured via magnetic resonance imaging at 6.1 hours was significantly greater than at 15.6 hours (67% vs 30%, P = .00008). In group 1 hearts, the mean (SD) for pH at the end of 6 hours decreased to 6.2 (0.2). In group 2, hearts that received intermittent antegrade cardioplegia, pH at the end of 6 hours was higher at 6.7 (0.3) (P = .0005). Magnetic resonance imaging showed no significant differences between the 2 groups in contrast enhancement (group 1, 62%; group 2, 40%) or in the wet/dry weight ratio. Intermittent perfusion maintains a significantly higher myocardial pH than does a conventional single antegrade dose. This difference may translate into an improved quality of donor hearts procured for transplantation, allowing longer distance procurement, tissue matching, improved outcomes for transplant recipients, and ideally a decrease in transplant-related costs.
    No preview · Article · Jul 2008 · Progress in transplantation (Aliso Viejo, Calif.)

  • No preview · Article · Feb 2008 · Journal of Surgical Research

Publication Stats

234 Citations
51.80 Total Impact Points

Institutions

  • 2013-2014
    • University of Mississippi Medical Center
      • Department of Radiology
      Jackson, Mississippi, United States
  • 2011-2014
    • University of Mississippi
      • Department of Radiology
      Mississippi, United States
  • 2005-2013
    • University of Minnesota Duluth
      • Medical School
      Duluth, Minnesota, United States
  • 2007-2011
    • University of Florida
      Gainesville, Florida, United States
    • Texas Tech University Health Sciences Center
      • Department of Obstetrics and Gynecology
      El Paso, Texas, United States
  • 2004
    • Geisinger Medical Center
      Danville, Pennsylvania, United States