Marcelo Guimaraes

Medical University of South Carolina, Charleston, South Carolina, United States

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Publications (32)66.57 Total impact

  • R Yamada · M Guimaraes · J Adams · C Schonholz
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    ABSTRACT: Microembolization during carotid artery stenting (CAS) is the result of embolic events shown by intra-procedural transcranial Doppler (TCD) or post-procedure diffusion-weighted MRI that do not lead to acute neurological deficit. Although the long term clinical outcome of these silent infarcts is not yet well established, there is increasing evidence that these events could be associated with neurological impairments, such as cognitive decline. In order to prevent microembolization due to excessive catheter manipulation at the time of guiding catheter placement in patients with challenging anatomy,a cervical access system with flow reversal protection was developed. Other embolic events are often seen as the result of plaque protrusion through stent struts. A new type of stent, so-called "hybrid" stent, incorporates the flexibility and conformability of an open-cell stent as well as plaque coverage seen with a close-cell stent, with the goal of achieving better plaque stabilization reducing macro and microembolization, while maintaining original vessel anatomy and flow hemodynamic.At the present time there are 3 different stents under investigation or this application.
    No preview · Article · Jul 2015 · The Journal of cardiovascular surgery
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    R Yamada · J Adams · M Guimaraes · C Schonholz
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    ABSTRACT: Catheter--directed thrombolysis (CDT) has been used as the first therapeutic option for acute limb ischemia (ALI) due to its less invasive nature, however recent systematic review showed higher incidence of major complications related to lytic infusion, including hemorrhagic stroke. In this setting, aspiration thrombectomy with Indigo has the greatest advantage of not increasing systemic risk of bleeding. The Indigo™ system from Penumbra® (Alameda, CA) promotes active thrombectomy using a vacuum pump that generates substantial suction, enabling aspiration of clots of varying sizes and lengths. The device has three components: aspiration catheter, separator and pump. There are 2 aspiration catheter sizes: CAT 3 and CAT 5. The separators are intended to mobilize the clot and clean the catheter lumen, and therefore restoring flow for continuous aspiration. The pump is small--sized equipment capable of applying near pure vacuum aspiration pressure of - 29 mmHg. Aspiration Thrombectomy with Indigo has two key advantages: it does not require the use of lytics, and it provides immediate flow reestablishment. Its use when thrombolysis is contra--indicated or has failed is already well established and, in the future, it may likely become the first line endovascular option in patients with acute limb ischemia.
    Full-text · Article · Feb 2015 · The Journal of cardiovascular surgery

  • No preview · Article · Feb 2015 · Journal of Vascular and Interventional Radiology
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    ABSTRACT: Purpose: To report the initial clinical experience with a new hybrid stent to prevent neurological events during carotid artery stenting. Case report: A 77-year-old asymptomatic man presented with de novo high-grade stenosis (80%) of the right internal carotid artery (ICA) and occlusion of the contralateral ICA. He was referred for right ICA stenting with a 6/8-mm×40-mm Gore Carotid Stent under cerebral protection using the Gore Carotid Filter. The stent delivery system tracked well over the filter wire and deployment was precise. The result was satisfactory, with 10% residual stenosis. No neurological events occurred during 6 months of follow-up. Conclusion: Initial clinical experience with this new carotid hybrid stent showed satisfactory results, including ease of use, precise deployment, conformability to the wall, and protection against embolization.
    Full-text · Article · Aug 2014 · Journal of Endovascular Therapy
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    ABSTRACT: Purpose Describe the technique and present the results of RF wire puncture for the recanalization of chronic arterial occlusions in symptomatic patients. Materials and Methods Between January and June 2012, 6 patients (5 male), age ranging from 58-72 years, presented with signs and symptoms of arterial occlusive disease. The lesions ranged from TASC C to D and were identified within the common iliac and superficial femoral artery. Despite multiple repeat attempts at recanalization using conventional endovascular techniques, the lesions were unable to be crossed. PowerWire RF wire (Baylis Medical, Canada) was advanced (via intra-luminal or subintimal approach) within a 5-Fr KMP catheter using a 10 mm snare (iliac lesions) or arterial wall calcification (femoral lesions) as a target. Pre-stent balloon angioplasty was followed by stent placement. If the RF wire puncture was inadequate, a new location was pursued. Clinical assessment along with targeted diagnostic and imaging follow up was performed at 30 days and then at 3, 6, and 12 months. Results All patients were successfully treated with RF wire after previous failed attempts at recanalization using different combinations of catheter/wire techniques. There were no complications. All patients improved clinically and imaging of the treated segment showed patency at 10 months mean follow-up. Conclusion RF wire is a safe alternative in the recanalization of chronic arterial occlusions when conventional techniques have failed and provides an endovascular solution for patients who would otherwise be forced into undergoing surgical repair.
    No preview · Article · Apr 2013 · Journal of Vascular and Interventional Radiology
  • R Yamada · M B Anderson · M Guimaraes · C Schönholz
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    ABSTRACT: During the last 20 years, asymptomatic patients with high-grade carotid stenosis have been treated with carotid endarterectomy and more recently with carotid artery stenting in order to prevent stroke. New, best medical treatment including statins, beta-blockers, antiplatelet therapies, and better diabetes and blood pressure control might reduce the incidence of stroke in this patient population making invasive treatment unnecessary. However, patients with asymptomatic carotid stenosis cannot be considered a homogenous population, and therefore, the therapeutic approach should take into consideration a subgroup of patients with greater risk of cerebrovascular event. Unfortunately, these risk factors are not well categorized thus far, although multiple publications have addressed each one of these factors individually. Recognizing these risk factors is essential for optimizing surveillance and therapeutic approach based on individual risk. The purpose of this article is to review such factors, including patient history, presence of embolic signals on Transcranial Doppler ultrasound, and plaque morphology. These factors should identify high risk asymptomatic individuals who could benefit from carotid stenting or carotid endarterectomy.
    No preview · Article · Feb 2013 · The Journal of cardiovascular surgery
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    ABSTRACT: In an era of increasing emphasis on minimally invasive surgery, distal embolization remains a concern in the absence of distal flow control. We present a case using an endovascular flow control technique that can be used for reducing distal embolic events during endovascular recanalization of aortoiliac occlusive disease. This technique has been used in four patients so far (two with native anatomy and two with aorto-bi-iliac grafts) with no evidence of angiographic or clinical embolic complications.
    Full-text · Article · Sep 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: To report the technique and acute technical results associated with the PowerWire Radiofrequency (RF) Guidewire used to recanalize central vein occlusions (CVOs) after the failure of conventional endovascular techniques. A retrospective study was conducted from January 2008 to December 2011, which identified all patients with CVOs who underwent treatment with a novel RF guide wire. Forty-two symptomatic patients (with swollen arm or superior vena cava [SVC] syndrome) underwent RF wire recanalization of 43 CVOs, which were then implanted with stents. The distribution of CVOs in central veins was as follows: six subclavian, 29 brachiocephalic, and eight SVC. All patients had a history of central venous catheter placement. Patients were monitored with regular clinical evaluations and central venography after treatment. All 42 patients had successful recanalization of CVOs facilitated by the RF wire technique. There was one complication, which was not directly related to the RF wire: one case of cardiac tamponade attributed to balloon angioplasty after stent placement. Forty of 42 patients (95.2%) had patent stents and were asymptomatic at 6 and 9 months after treatment. The present results suggest that the RF wire technique is a safe and efficient alternative in the recanalization of symptomatic and chronic CVOs when conventional endovascular techniques have failed.
    No preview · Article · Jun 2012 · Journal of vascular and interventional radiology: JVIR
  • M.C. Fortes · A.P. Dias · R. Uflacker · M. Guimaraes

    No preview · Article · Mar 2012 · Journal of Vascular and Interventional Radiology

  • No preview · Article · Mar 2012 · Journal of Vascular and Interventional Radiology
  • M. Guimaraes · C. Schonholz · M.B. Anderson · C. Hannegan · B. Selby

    No preview · Article · Mar 2012 · Journal of Vascular and Interventional Radiology
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    ABSTRACT: To compare an injectable hydrogel embolic device with a pushable AZUR device procedurally, angiographically, and histologically in the embolization of porcine arteries. In 12 pigs, embolization of renal, gluteal, and hepatic or thoracic arteries was performed with either injectable hydrogel embolic devices (two arteries per pig) or an AZUR device (one artery per pig). Follow-up angiography was performed before sacrifice in five pigs at 7 days after embolization and seven pigs at 90 days after embolization. The harvested tissues were evaluated histologically. Continuous and ordinal results were compared using analysis of variance and χ(2) tests. For the sites with embolization performed with injectable hydrogel, complete angiographic occlusion was obtained in 21 of 24 (88%) sites after treatment, 10 of 10 (100%) sites at 7 days, and 10 of 14 (72%) sites at 90 days. For the sites with embolization performed with AZUR devices, complete angiographic occlusion was obtained in 10 of 12 (83%) sites after treatment, 4 of 5 (80%) sites at 7 days, and 5 of 7 (72%) sites at 90 days. Statistically significant differences in angiographic occlusion were not observed at 7 days (P = .13) or 90 days (P = .35). The embolization time of the injectable hydrogel group (14 minutes ± 8) was significantly reduced (P = .02) compared with the AZUR group (22 minutes ± 12). Differences between the groups in arterial wall damage were not evident at either 7 days or 90 days, although greater damage was observed in both groups at 90 days. In both groups, inflammation was nonexistent to minimal at 7 days and minimal to mild at 90 days. Embolization of porcine arteries was as effective with injectable hydrogel embolic devices as pushable AZUR devices, as evidenced by the procedural, angiographic, and histologic results.
    No preview · Article · Sep 2011 · Journal of vascular and interventional radiology: JVIR
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    Marcelo Guimaraes · Mathew Wooster
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    ABSTRACT: Onyx is a nonadhesive liquid embolic agent approved for the treatment of brain arteriovenous malformations. Here, the use of Onyx is discussed in different peripheral procedures. The Onyx's features, its manipulation, technical details, tips, and tricks are presented followed by illustrative cases.
    Full-text · Article · Sep 2011 · Seminars in Interventional Radiology
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    ABSTRACT: To define predictive factors for endoleak type II (EL-II) based on quantifiable factors in the imaging studies of patients undergoing endovascular aneurysm repair (EVAR). The data on 208 consecutive patients (137 men; mean age 75.2 years, range 62-84) who underwent EVAR between the years 2003 and 2008 were retrospectively reviewed. The abdominal aortic aneurysm (AAA) diameter ranged from 4.8 to 12.8 cm. Data were collected on the type of AAA; the type of stent-graft (aortomonoiliac versus bifurcated); the performance of hypogastric artery embolization; the presence, number, diameter, and patency of aortoiliac branches identified on the pre and post-EVAR imaging studies; and the presence and type of EL-II (transient vs. persistent) with the goal of identifying any imaging-based predictive factors for the development of EL-II. Among the 208 cases, 11 patients had endoleaks other than type II and were excluded, leaving 195 patients for analysis. In all, 28 (13.4%) patients were diagnosed with EL-II. All had ≥4 patent lumbar arteries (mean diameter >2.3 mm). Ten patients with a transient EL-II had a mean of 4.3 patent lumbar arteries, which had diameters <2 mm (mean 1.5 mm). In the 18 patients with persistent EL-II, the mean diameter of the 4 lumbar arteries was 2.7 mm; at least 1 of the lumbar arteries was >2 mm. The presence of at least 4 patent lumbar arteries (p<0.001) and at least 1 patent hypogastric artery (p<0.001) were predictive factors for EL-II. At least 1 lumbar artery >2 mm in diameter was a positive predictive factor for the development of persistent EL-II (p<0.001). Patent hypogastric and lumbar arteries are significantly associated with a higher risk of developing EL-II. Larger diameter lumbar arteries tend to be associated with persistent EL-IIs, while lumbar arteries <2 mm would more likely be seen with a transient EL-II. If substantiated in larger studies, these angiographic criteria may guide early treatment of EL-II to avoid aneurysm sac expansion and potential rupture.
    No preview · Article · Jun 2011 · Journal of Endovascular Therapy
  • Marcelo Guimaraes · Renan Uflacker
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    ABSTRACT: Locoregional therapies for hepatocellular carcinoma have progressed greatly in the last 30 years, beginning with the introduction of chemoembolization. Embolization techniques have evolved with the use of drug-eluting beads and radioembolization with yttrium-90. In the last 10 years, several new ablation techniques were developed including radiofrequency ablation, microwave ablation, cryoablation, laser ablation, and irreversible electroporation. Isolated or in combination, these techniques have already shown that they can improve patient survival and/or provide acceptable palliation.
    No preview · Article · May 2011 · Clinics in liver disease
  • C. Schönholz · R. Uflacker · M. Guimaraes · J.C. Parodi

    No preview · Article · Mar 2011
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    ABSTRACT: The secundum type atrial septal defect (ASD) is a relatively common finding in the general population, occurring at a reported rate of 3.78 per 100,000 live births [1], and comprising approximately 6-10% of all congenital cardiac defects [2]. When faced with a symptomatic ASD, there are several methods of treatment available. Open surgery with occlusion of the ASD is the time-honored treatment [3], but percutaneous placement of an occluder device has been the preferred treatment for several years [4]. The choice for the closure method is mainly based on the severity of symptoms, the underlying medical condition, cardiovascular anatomy [5, 6], and the size of the septal defect [7]. Surgical repair has been practiced for more than 50 years and often is preferred when the ASD size is larger and the symptoms are more severe [3]. However, percutaneous occluder device placement has largely replaced surgery when the patient is incapable of withstanding a major procedure, when the septal defect is\24 mm [8], and when the septal defect is not located near other vital cardiovascular structures [6]. The Amplatzer septal occluder (ASO) device has been extensively studied for the percutaneous closure of both ventricular as well as atrial septal defects [9, 10]. Using the approach first described in 1976 by King and Mills [4], the Amplatzer device can be placed via a venous route, and may be secured without placing the patient under general anesthesia or using cardiopulmonary bypass. Although percutaneous device placement has been found to have a lower rate of overall complications than surgical closure [5], there have been several reports of adverse events in the literature [5, 6, 8]. The case presented here describes a complication that has not yet been reported, related to the migration of the device to the aortic arch. © 2011 Springer Science+Business Media, LLC and the Cardiovascular and Interventional Radiological Society of Europe (CIRSE).
    No preview · Article · Mar 2011 · CardioVascular and Interventional Radiology
  • R. Uflacker · M. Guimaraes · C. Schonholz · B. Selby Jr · C. Hannegan

    No preview · Article · Mar 2011 · Journal of Vascular and Interventional Radiology

  • No preview · Article · Mar 2011 · Journal of Vascular and Interventional Radiology
  • M. Guimaraes · R. Uflacker · C. Schonholz · C. Hannegan · B. Selby Jr

    No preview · Article · Mar 2011 · Journal of Vascular and Interventional Radiology

Publication Stats

146 Citations
66.57 Total Impact Points


  • 2006-2015
    • Medical University of South Carolina
      • • Department of Radiology
      • • Division of Vascular-Interventional Radiology
      • • Division of Neuro-Interventional Radiology
      Charleston, South Carolina, United States
  • 2011
    • Vascular and Interventional Radiology
      Chicago, Illinois, United States