Irwin Walot

Harbor-UCLA Medical Center, Torrance, California, United States

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Publications (64)225.33 Total impact

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    ABSTRACT: Cognitive and emotional outcomes after carotid endarterectomy (CEA) and carotid artery stenting with embolic protection device (CAS + EPD) are not clear. Patients were entered prospectively into a United States Food and Drug Administration.approved singlecenter physiciansponsored investigational device exemption between 2004 and 2010 and received either CEA or CAS + EPD. Patients underwent cognitive testing preprocedure and at 6, 12, and 60 months postprocedure. Cognitive domains assessed included attention, memory, executive, motor function, visual spatial functioning, language, and processing speed. Beck Depression and anxiety scales were also compared. There were a total of 38 patients that met conventional indications for carotid surgery (symptomatic with .50% stenosis or asymptomatic with .70% stenosis).12 patients underwent CEA, whereas 26 patients underwent CAS + EPD. Both CEA and CAS + EPD patients showed postprocedure improvement in memory and executive function. No differences were seen at followup in regards to emotional dysfunction (depression and anxiety), attention, visual spatial functioning, language, motor function, and processing speed. Only two patients underwent neuropsychiatric testing at 60 months.these CAS + EPD patients showed sustained improvement in memory, visual spatial, and executive functions. In conclusion, cognitive and emotional outcomes were similar between CEA and CAS + EPD patients.
    No preview · Article · Oct 2015 · The American surgeon

  • No preview · Article · Jun 2015 · Journal of Vascular Surgery

  • No preview · Article · Dec 2013 · Texas Heart Institute journal / from the Texas Heart Institute of St. Luke's Episcopal Hospital, Texas Children's Hospital
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    ABSTRACT: The current paradigm for the treatment of chronic type B aortic dissection involves primarily medical treatment. The patients are then followed for sequelae like progressive dissection or aneurysmal degeneration, selecting this subgroup for further intervention. The European Collaborator Registry, the Talent Thoracic Retrospective Registry, and several meta-analysis showed that the uncomplicated type B dissection patients who underwent thoracic endovascular aortic repair (TEVAR) outperformed their counterpart in the complicated group. The INSTEAD trial, the first randomized trial to examine whether TEVAR is better than medical management in the chronic stable dissection patients, showed no benefit early on although mid-term data might show some benefit. Clearly more randomized controlled trials are necessary to create a paradigm shift. In the United States, the FDA approved TEVAR devices are for the descending thoracic aortic aneurysm and transection only. The use of these devices for dissection is off-label or for investigation only. As future study might broaden the use of TEVAR for the chronic dissection patients, the use of TEVAR in hybrid surgery and in the ascending aorta is also broadening the indication for this technology. With two decades of innovation behind, TEVAR will continue to evolve and innovate in the years ahead.
    No preview · Article · Apr 2013 · The Journal of cardiovascular surgery
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    ABSTRACT: Intravascular ultrasound (IVUS) has an interesting history that parallels that of many of the advancements that have led to the endovascular era. The use of IVUS in conjunction with standard cross-sectional imaging and three-dimensional reconstructions offers a powerful tool in both the diagnosis and treatment of complex vascular pathology. The use of IVUS has increased over the years and is currently in the process of being incorporated into several modalities that will offer more in the way of real-time information in both the aortic arena and the treatment of increasingly complex peripheral vascular disease. Currently, we use IVUS as a powerful adjunct in combination with other modalities to increase our understanding of vessel architecture and assist in the management of complex vascular pathology.
    No preview · Article · Sep 2012 · Seminars in Vascular Surgery
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    ABSTRACT: True and false lumen changes and patient outcomes following thoracic endovascular aortic repair (TEVAR) for patients with stable type B dissection have been described by the The Investigation of Stent Grafts in Aortic Dissection (INSTEAD) trial. However, these changes have not been described in TEVAR patients treated for complications of chronic dissection. A single-institution study was conducted of 73 prospectively evaluated patients treated for complications of chronic type B dissection from 2002 to 2010. Spiral computed tomography reconstructions using M2S (Medical Media Systems, West Lebanon, NH) were analyzed for sequential changes in aortic volume and diameter during patient follow-up. Changes in aortic volume and diameter were tabulated as a percent change from preoperative values. Patient outcomes were determined by sequential evaluations postprocedure. TEVAR was successfully performed in 72 out of the 73 patients (99%). Indications for intervention were aortic enlargement (n = 62), failure of medical management (n = 7), and perforation (n = 4). The 30-day all-cause mortality rate was 14%; events were due to retrograde dissection (n = 4), cardiac-related (n = 4), and rupture (n = 2). Eleven out of the 72 patients (15%) required a secondary procedure for endoleak (n = 7) and persistent distal perfusion of the false lumen (n = 4). Mean percentage expansion of the thoracic true lumen was noted during the follow-up period: 38%, 46%, 71%, and 114% at 1-, 3-, 6-, and 12-month follow-up, respectively. Concomitant regression of the thoracic false lumen of -65%, -68%, -84%, and -84% was observed at the same intervals, respectively. Patients with an initial extension of the thoracic dissection into the infrarenal aorta (n = 46) had an increase in mean percentage change of aortic diameter and volume to 21% and 17% at 1 year, respectively. By contrast, in the patient group without infrarenal dissection (n = 14), the infrarenal aortic diameter and volume remained relatively unchanged at 3% and -0.9%, respectively, at 1-year postintervention. TEVAR is a potential treatment option for patients experiencing complications of chronic type B dissection. During follow-up, there is a predictable expansion of the thoracic true lumen and regression of the thoracic false lumen. These findings correlate with those of the INSTEAD trial, which demonstrated false lumen regression and true lumen expansion in a cohort of patients with stable type B dissection. However, many patients with extension of thoracic dissection into the infrarenal aorta demonstrate continued aortic dilation and, on occasion, the need for secondary intervention for persistent distal perfusion. Further analysis is needed in this subgroup of patients so as to better determine potential predictors and the clinical significance of post-TEVAR infrarenal expansion. Moreover, further investigations may support a role for secondary endovascular intervention in remedying persistent infrarenal aortic expansion after TEVAR for chronic dissection.
    Full-text · Article · May 2012 · Journal of vascular surgery: official publication, the Society for Vascular Surgery [and] International Society for Cardiovascular Surgery, North American Chapter
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    ABSTRACT: Thoracic endovascular aortic repair is a promising means of treating patients with complicated type B aortic dissection by excluding the intimomedial tears. This study aims to characterize the location of tears and to propose a classification of type B aortic dissections based on these findings. Advanced protocols in computed tomography scans of patients with type B aortic dissection were used to identify the size and location of intimomedial tears in relation to the origin of the left subclavian artery. Aortic imaging details in 72 un-operated patients were used as a reference standard. From 1999 to 2005, 44 patients underwent primary endovascular treatment for complications of type B aortic dissection. Each patient had an average of 2.8 +/- 2.11 intimomedial tears. The median intimomedial tear surface area was 0.63 cm(2). The presence of >or=3 or >or=5 intimomedial tears in the descending thoracic aorta did not correlate with aortic branch malperfusion (P > .05). Thirteen of 26 (50%) patients with a tear >1.9 cm(2) had aortic branch malperfusion (P = .032). Ten of 14 (71%) patients with a tear >4.86 cm(2) (mean plus one standard deviation) had aortic branch malperfusion (P = .002). The location of tears ranged from -6 mm to +459.2 mm from the left subclavian artery orifice: 80.5% (n = 99) of these tears were above the reference origin of the celiac artery. Eight of 13 patients (62%) with a tear distal to 282 mm (the orifice of the celiac artery) had aortic branch malperfusion in (P = .04). A classification for the location of intimomedial tears is proposed with potential clinical relevance to endovascular repair: type 1 has no identifiable tears; type 2 has one or more tears with no tears distal to the orifice of the celiac artery; type 3 has tears involving the branch vessels of the abdominal aorta; and type 4 has intimomedial tears distal to the aortic bifurcation. Characterization and location of intimomedial tears using computed tomography (CT) imaging is feasible and represents an important step in the management of type B aortic dissection. The location and surface area of tears is associated with malperfusion. Based on the proposed classification and anatomic reference data, three out of every four patients may have a favorable constellation of intimomedial tears (type 1 or 2) that would be amenable to endovascular repair and reverse aortic remodeling. The clinical correlation will be established in upcoming studies.
    Full-text · Article · Sep 2010 · Journal of vascular surgery: official publication, the Society for Vascular Surgery [and] International Society for Cardiovascular Surgery, North American Chapter
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    Full-text · Article · Aug 2010 · Journal of Vascular Surgery
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    Full-text · Article · Jun 2010 · Journal of Vascular Surgery
  • Irwin Walot · Joe P. Chauvapun
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    ABSTRACT: The need for a sound structural design, in this modern age of endovascular intervention, is paramount. With the forever evolving technology, it is often difficult to keep up with the latest trends in room design. There are, however, several key basic factors that remain unchanged in the design venue. Availability for your core operating room equipment which includes a scrub sink, anesthesia equipment, substerile area for the autoclave, and ample equipment storage area is required. In order to fulfill the dual role of an operating arena and an imaging suite, the modern endovascular suite must be outfitted with a state-of-the-art imaging system. Keywordsendovascular suite design-endovascular imaging systems
    No preview · Chapter · Dec 2009
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    ABSTRACT: The operative mortality and morbidity of patients with complicated acute type B aortic dissection remain high. The endovascular approach has been proposed as a potential alternative. The purpose of this study is to review the contemporary outcome of patients undergoing endovascular treatment for complicated acute type B aortic dissection. A retrospective analysis of 28 patients undergoing endovascular interventions for acute type B aortic dissection was performed. Kaplan-Meier survival analysis was used for statistical computation. Indications for emergency endografting were rupture in 4 (14%) patients, severe lower body malperfusion in 8 (29%) patients, visceral/renal malperfusion in 7 (25%) patients, persistent chest pain despite proper anti-impulsive therapy in 5 (18%) patients, uncontrollable hypertension in 1 (4%) patient, and acute dilatation of false lumen with impending rupture in 3 (11%) patients. Three (11%) patients died early. Three patients died during follow-up of non-aorta-related causes. Overall survival was 82% and 78% at 1 and 5 years' follow-up, respectively. The aorta-related mortality was 10% for the entire follow-up period. Complete thrombosis of the false lumen in the thoracic aorta was achieved in 22 (85%) members of the surviving cohort, and partial thrombosis was achieved in the remainder. The rate of treatment failure according to Stanford criteria was 18% at 5 years. Mean follow-up was 36 months, and follow-up was complete in 28 (100%) patients. Thoracic aortic endografting for complicated acute type B aortic dissection can be performed with a relatively low postoperative morbidity and mortality in experienced hands. The endovascular approach to life-threatening complications of acute type B aortic dissection appears to have a favorable outcome in midterm follow-up.
    Full-text · Article · Oct 2009 · The Journal of thoracic and cardiovascular surgery
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    Full-text · Article · May 2009 · Journal of Vascular Surgery
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    ABSTRACT: The risk factors associated with death after thoracic endovascular aortic repair are poorly understood. The aim of this study is to analyze the risk factors associated with early and late mortality after thoracic endovascular aortic repair. A total of 153 patients underwent 184 thoracic endovascular aortic repairs between 1998 and 2005. Prospectively collected data were entered into statistical software. Univariate and multivariate analyses were performed. The underlying pathologies included descending thoracic aortic aneurysm (n = 91), acute type B aortic dissection (n = 25), chronic type B aortic dissection (n = 42), aortic transection (n = 12), and penetrating aortic ulcer (n = 14). Thoracic endovascular aortic repair was technically successful in all but 3 patients. Another 3 patients required an open repair within the first month. Early and late mortality rates were 9.8% (n = 18) and 19% (n = 35) in a 16-month average period of follow-up, respectively. Type I procedural endoleak was the only significant predictor of early death in the multivariate model (P = .0036; odds ratio: 8.4; 95% confidence interval: 1.6-43.9). Multivariate Cox regression revealed chronic obstructive pulmonary disease (P = .024; odds ratio: 3.8; 95% confidence interval: 1.2-12.1), postoperative myocardial infarction (P = .0053; odds ratio: 9.7; 95% confidence interval: 2.0-48.4), and acute renal failure (P = .0006; odds ratio: 22.8; 95% confidence interval: 3.8-137.6) to be independent risk factors for late mortality. Procedural type I endoleak is an independent risk factor of early mortality after thoracic endovascular aortic repair. Chronic obstructive pulmonary disease, postoperative myocardial infarction, and acute renal failure are predictors of late death in the multivariate analysis.
    No preview · Article · Jun 2008 · The Journal of thoracic and cardiovascular surgery
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    ABSTRACT: Proton magnetic resonance spectroscopy ((1)HMRS) is an in vivo brain imaging method that can be used to investigate psychotropic drug mechanism of action. This study evaluated baseline (1)HMRS spectra of bipolar depressed patients and whether the level of cerebral metabolites changed after an open trial of lamotrigine, an anti-glutamatergic mood stabilizer. Twenty-three bipolar depressed and 12 control subjects underwent a MRS scan of the anterior cingulate/medial prefrontal cortex. The scan was performed on a GE whole-body 1.5 T MRI scanner using single-voxel PRESS (TE/TR=30/3000 ms, 3 x 3 x 3 cm(3) and post-processed offline with LCModel. Baseline CSF-corrected absolute concentrations of glutamate+glutamine ([Glx]), glutamate ([Glu]), and creatine+phosphocreatine ([Cr]) were significantly higher in bipolar depressed subjects vs healthy controls. The non-melancholic subtype had significantly higher baseline [Glx] and [Glu] levels than the melancholic subtype. Remission with lamotrigine was associated with significantly lower post-treatment glutamine ([Gln]) in comparison to non-remission. These data suggest that non-melancholic bipolar depression is characterized by increased glutamate coupled with increased energy expenditure. Lamotrigine appears to reduce glutamine levels associated with treatment remission. Further study is encouraged to determine if these MR spectroscopic markers can delineate drug mechanism of action and subsequent treatment response.
    Full-text · Article · Jan 2008 · Neuropsychopharmacology
  • Anton Mlikotic · Irwin Walot

    No preview · Chapter · Oct 2007
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    ABSTRACT: Recombinant human alpha-L-iduronidase (Aldurazyme, laronidase) was approved as an enzyme replacement therapy for patients with the lysosomal storage disorder, mucopolysaccharidosis I (MPS I). In order to assess the long-term safety and efficacy of laronidase therapy, 5 of 10 patients in the original laronidase Phase 1/2 clinical trial were re-evaluated after 6 years of treatment. Lysosomal storage was further improved at 6 years (urinary glycosaminoglycans (GAG) excretion decreased 76%; mean liver size at 1.84% of body weight). Shoulder maximum range of motion was maintained or further increased and reached a mean 33.2 (R) and 25.0 (L) degrees gained in flexion and 34.0 (R) and 27.3 (L) degrees gained in extension. Sleep apnea was decreased in four of five patients and the airway size index improved. Cardiac disease evaluations showed no progression to heart failure or cor pulmonale but pre-existing significant valve disease did progress in some patients. Substantial growth was observed for the pre-pubertal patients, with a gain of 33 cm (27%) in height and a gain of 31 kg in weight (105%). In general, the evaluated patients reported an improved ability to perform normal activities of daily living. Overall these data represent the first evidence that laronidase can stabilize or reverse many aspects of MPS I disease during long-term therapy and that early treatment prior to the development of substantial cardiac and skeletal disease may lead to better outcomes.
    No preview · Article · Mar 2007 · Molecular Genetics and Metabolism
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    ABSTRACT: Stroke and spinal cord injury (SCI) remain the most devastating complications of thoracic endovascular aortic repair (TEVAR). The risk factors associated with these complications are poorly understood. The aim of this study was to analyze the risk factors associated with neurologic deficits after TEVAR. From 1998 to 2005, 153 patients underwent 184 TEVARs. Computed tomography scans, angiograms, and medical records were reviewed. TEVAR was completed in all but 3 patients. The underlying pathologies included descending thoracic aortic aneurysm in 91, acute type B aortic dissection in 25, chronic type B aortic dissection in 42, aortic transection in 12, and penetrating aortic ulcer in 14. Stroke developed in 8 patients, and SCI developed in another 8 patients (4 immediate, 4 delayed paraplegia/paraparesis). The procedure-associated stroke and SCI rate was 4.3% (8/184). Univariate statistical analysis revealed increased postoperative stroke with obesity, significant intraoperative blood loss, and evidence of peripheral vascular embolization/thrombosis. Aneurysmal pathology, iliac conduit, and hypogastric artery coverage were highly associated with postoperative SCI after TEVAR. Early and late mortality were 9.8% (n = 18) and 19% (n = 35) in a 16-month average period of follow-up. The incidence of stroke and SCI after TEVAR was 4.3% (8/184). The risk factors associated with postoperative stroke were obesity, intraoperative blood loss, and vascular embolization. Aneurysm as an underlying pathology, the use of an iliac conduit, and coverage of the hypogastric artery were all associated with SCI. These risk factors for SCI may be markers of tenuous collateral blood supply to the spinal cord.
    No preview · Article · Mar 2007 · The Annals of thoracic surgery
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    ABSTRACT: A total of 308 patients undergoing endovascular AAA repair by using the AneuRx device at our institution between June 1996 and October 2004 had fine-cut CT imaging data reconstructed as a 3-dimensional model by Medical Metrx Solutions (West Lebanon, NH). The patient population involved had AneuRx stent grafts implanted during phase I, II, and III clinical trials, as well as after FDA approval of the device. We identified 48 (15.6%) of 308 patients who had evidence of stent graft migration of 5 mm or more; 25 (8.1%) of the 308 patients experienced migration of 10 mm or more. Patient imaging data sets were analyzed by comparing their most recent CT scans with their immediate postoperative CT scans. The 8 of 48 migration patients who required proximal aortic cuff placement were analyzed according to the last CT scan before reintervention. The time to initial discovery of migration was noted for life-table analysis, and the total duration of postoperative follow-up was measured. The device oversizing percentage was calculated by using the neck diameter from the preoperative CT scan (30/48 patients) or intraoperative intravascular ultrasonography measurement (18/48 patients).
    Full-text · Article · Jan 2007 · Journal of Vascular Surgery
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    ABSTRACT: Previous studies have shown that HIV-infected children have abnormal cerebral metabolites, measured by proton MR spectroscopy (1H MRS), but the stability of these measurements over time has not been described in HIV-infected children. The authors recently reported a study of cerebral metabolites in 20 HIV-infected children (6 to 16 years of age); the current study followed 12 of these children (10.0 years +/- 3.7 years) and repeated the MR spectroscopy at 24.1 +/- 3.7 weeks and 42.2 +/- 3.5 weeks following the entry time with repeated neuropsychological testing. 1H MR spectra were acquired at 1.5 T (GE Signa, PRESS localization, repetition time = 3,000 msec, echo time = 30 msec). Five brain regions were studied: right frontal white matter, left frontal white matter, right basal ganglia, right hippocampus, and midfrontal gray matter. The concentrations of N-acetylaspartate (NAA), choline (CHO), creatine (CR), and myo-inositol (mI) and the ratio of each metabolite to CR were determined. There were no changes in the metabolite concentrations or metabolite/CR ratios at the three time periods. Similarly, during this follow-up period, HIV-positive children showed no changes in clinical signs, HIV viral loads, CD4%, or CD4 counts, except for improved spatial memory with repeat testing. In a clinically and neurologically stable group of HIV-infected children, cerebral metabolites were stable over a 10-month time period, suggesting that it is possible to assess changes in cerebral metabolites as a measure of cerebral health, but longer follow-up in a larger sample is needed.
    No preview · Article · Apr 2006 · Neurology
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    Full-text · Article · Mar 2006 · Journal of Vascular Surgery

Publication Stats

2k Citations
225.33 Total Impact Points


  • 1996-2015
    • Harbor-UCLA Medical Center
      • • Department of Emergency Medicine
      • • Department of Pediatrics
      Torrance, California, United States
  • 2006
    • Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center
      Torrance, California, United States
  • 1998-2005
    • University of California, Los Angeles
      Los Angeles, California, United States
  • 2004
    • Vascular and Interventional Radiology
      Chicago, Illinois, United States
  • 1997
    • Stanford University
      • Department of Surgery
      Palo Alto, California, United States