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Biomedical subjects

F Viñuela

Publications and source records attributed to F Viñuela.

At least 19 recordsLinked to original sources
PubMed1999

Embolization of incidental cerebral aneurysms by using the Guglielmi detachable coil system.

OBJECT: Guglielmi detachable coil (GDC) technology is a valuable therapeutic alternative to the surgical treatment of ruptured or incidental intracranial aneurysms. The authors describe their technical and clinical experience in the use of the GDC technique in patients who underwent endovascular occlusion for the treatment of incidentally found intracranial aneurysms. METHODS: One hundred fifteen patients with 120 incidentally found intracranial aneurysms underwent embolization by means of the GDC endovascular technique. Ninety-one patients were females and 24 were males. Patient age ranged from 13 to 80 years. In 64 patients the incidental aneurysms were discovered when unrelated nonneurological conditions signaled the need for angiography or magnetic resonance angiography (Group 1). Twenty patients who presented with incidental aneurysms that were discovered during treatment for an acutely ruptured aneurysm underwent treatment of both types of aneurysm during the acute phase of subarachnoid hemorrhage (SAH) (Group 2). Sixteen patients with incidental aneurysms were treated during the chronic phase of SAH (Group 3). Group 4 included 15 patients who had incidental aneurysms associated with brain tumors or arteriovenous malformations. Angiographic results revealed complete or near-complete occlusion in 109 aneurysms (91%) and incomplete occlusion in five aneurysms (4%). Guglielmi detachable coil embolization was attempted unsuccessfully in six aneurysms (5%). One hundred nine patients (94.8%) remained neurologically intact or unchanged from their initial clinical status. Five patients (4.3%) deteriorated as a result of immediate procedural complications. All these complications occurred in the first 50 patients treated in the series. No clinical complications were observed in the last 65 patients. In one patient, a partially embolized aneurysm ruptured 3 years postprocedure. In Groups 1 and 3, the average length of hospitalization was 3.3 days. CONCLUSIONS: The evolution of GDC technology has proved to provide safe treatment of incidental aneurysms (a morbidity rate of 0% was achieved in the last 65 patients). The topography of the aneurysm and the clinical condition of the patient did not influence final anatomical or clinical outcomes. The GDC technology also confers a positive economic impact by decreasing hospital length of stay and by eliminating the need for postembolization intensive care.

Adolescent↗
PubMed1999

Endovascular treatment of multiple intracranial aneurysms by using Guglielmi detachable coils.

OBJECT: The purpose of this paper is to present the authors' experience with Guglielmi detachable coil (GDC) embolization of multiple intracranial aneurysms and to evaluate the results of this therapy in single-stage procedures. METHODS: Clinical and angiographic evaluations were performed in 38 consecutive patients with multiple intracranial aneurysms treated by GDC embolization between March 1990 and October 1997. Twenty-nine patients presented with subarachnoid hemorrhage (SAH), four with mass effect, and five were asymptomatic. These 38 patients harbored 101 aneurysms, 79 of which were treated with GDCs, 14 by surgical clipping, and eight were left untreated. Of the GDC-treated lesions, a complete endovascular occlusion was achieved in 55 aneurysms (70%), and 24 (30%) presented neck remnants. Twenty-five patients (66%) underwent GDC embolization of more than one aneurysm in the first session. Eighteen (86%) of 21 patients with acute SAH underwent treatment for all aneurysms within 3 days after admission (15 of 21 in one session). Follow-up angiographic studies in 30 patients demonstrated an unchanged or improved result in 94% of the aneurysms (59 lesions) and coil compaction in 6% (four lesions). The overall clinical outcome was excellent in 34 patients (89%), good in one (3%), fair in one (3%), and death in two (5%). CONCLUSIONS: Endovascular treatment of multiple intracranial aneurysms, regardless of their location, with GDCs was performed safely in one session, even during the acute phase of SAH. Treatment of all aneurysms in one session protected the patient from rebleeding and eliminated the risk of mistakenly treating only the unruptured aneurysms.

Adolescent↗
PubMed1998

Principles and philosophy of modeling in biomedical research.

Despite widespread applications in biomedical research, the role of models and modeling is often controversial and ill understood. It is usual to find that fundamental definitions, axioms, and postulates used in the modeling process have become tacit assumptions. What is essential, however, is a clear vision of the fundamental principles of modeling. This is even more compelling for new and emerging interdisciplinary fields that use techniques from previously separate scientific disciplines. This article outlines and reviews the central nature and philosophy of modeling, the rules that govern it, and its underlying key integral relationship to the 'scientific method'. A comprehensive understanding of these issues is indispensable to successful research and meaningful progress in all facets of biomedicine.

Communication↗
PubMed1998

Hemodynamic changes in arterial feeders and draining veins during embolotherapy of arteriovenous malformations: an experimental study in a swine model.

OBJECTIVE: Transcatheter assessment of changes in draining vein (DV) flow velocity has been proposed recently as a potentially useful procedure for hemodynamic monitoring of the progression of embolotherapy in cerebral arteriovenous malformations (AVMs). We compared and contrasted changes in hemodynamic parameters of arterial feeders (AFs) and DVs during experimental AVM embolotherapy. METHODS: Carotid-jugular fistula-type AVM models were surgically created in eight swine. Pre- and postembolization transcatheter mean AF and DV pressures, DV-time average spectral peak velocity, and AF and DV pulsatility indices were assessed. An expression, the peak systolic velocity minus end-diastolic velocity (Vs - Ved), was also used in evaluating the transvenous Doppler spectra. Pre- and postembolization hemodynamic parameters were compared statistically. RESULTS: Pre-embolization DV flow was pulsatile (Vs - Ved, 12 +/- 4.8 cm/s), with a mean DV velocity of 39.3 +/- 11.4 cm per second. Postembolization, this changed to a less/nonpulsatile pattern (Vs - Ved, 5.4 +/- 2.7 cm/s; P = 0.0035) with a lower mean DV-average spectral peak velocity of 7.0 +/- 3.1 cm per second (P = 0.0001). The mean DV pressure was also reduced from 52.0 +/- 8.2 to 45.5 +/- 8.7 mm Hg (P = 0.0023). The mean AF pressure increased from a mean of 79.5 +/- 15.5 to 96.8 +/- 16.2 mm Hg (P = 0.0004). The DV pulsatility index values also increased from a mean of 0.3 +/- 0.2 to 1.1 +/- 0.5 (P = 0.0003). Periembolization objective hemodynamic changes were detected in the DVs earlier than were the visually subjective angiographic changes observed within the nidus. CONCLUSION: This preliminary study indicates that transvenous assessment of average spectral peak velocity and wave pattern (Vs - Ved) may be useful in the hemodynamic evaluation of AVM shunting. The convergence of these two parameters to a range less than 10 cm per second after nidus embolization may afford a theoretical advantage over AF pressure measurements when used for objective and quantitative monitoring of endovascular embolotherapy.

Angiography↗
PubMed1998

Nonadhesive liquid embolic agent for cerebral arteriovenous malformations: preliminary histopathological studies in swine rete mirabile.

OBJECTIVE: To assess acute and chronic histopathological changes observed in a swine arteriovenous malformation model after endovascular delivery of Embolyx E (Micro Therapeutics Inc., San Clemente, CA) and its organic solvent dimethyl sulfoxide (DMSO). To develop standard endovascular delivery techniques of Embolyx through microcatheters into swine rete mirabile (RMB). METHODS: Forty RMBs in 22 swine were used to analyze acute and chronic angiographic and histological changes after superselective delivery of Embolyx E and/or its organic solvent (DMSO). Four RMBs (two for DMSO and two for Embolyx E study) were used as control specimens. Angiographic and histological evaluations were obtained 18 days, 1 month, 3 months, and 6 months after the procedure. Particular attention was paid to the presence of focal or diffuse angionecrosis, arterial revascularization, and perivascular inflammatory response. RESULTS: Staged and/or continuous delivery of Embolyx E were performed through the DMSO-compatible microcatheters without untoward catheter "gluing." All subacute/chronic specimens embolized with Embolyx E showed no evidence of angiographic recanalization. Twelve RMBs were used in acute studies, and all specimens showed no evidence of angionecrosis or aggressive inflammatory reaction. Subacute and chronic (total, n = 14) histological examinations of the RMBs showed mild inflammatory response manifested by monocellular infiltration and scattered foreign body giant cell reaction. In the 9 of 14 subacute and chronic specimens, focal disruption of elastica was observed along with embolic materials. Fourteen RMBs in eight swine were used to determine the safety range for DMSO injection. Two RMBs were used as control specimens. Rapid intra-arterial delivery (0.5 ml/5-15 s, n = 6) of DMSO caused angiographic vasospasm and histological endothelial necrosis. Slow injection (0.5 ml/30-120 s, n = 8) of DMSO showed minimum or no angiographic vasospasm, minimal adventitial inflammatory response, and no clinical complications. CONCLUSION: Embolyx E, an occlusive and nonadhesive embolic agent, is capable of producing permanent occlusion of swine RMB with the development of mild intra- and perivascular inflammatory changes and no clinical complications. The slow endovascular delivery of DMSO produces no untoward angiographic, pathological, or clinical changes. A fast injection of DMSO causes endothelial necrosis and severe inflammatory response in the arterial wall. This embolic material seems to have appropriate biochemical, anatomic, and histopathological characteristics to be used in the treatment of cerebral arteriovenous malformations or vascular cranial base tumors.

Animals↗
PubMed1998

Unruptured aneurysms presenting with mass effect symptoms: response to endosaccular treatment with Guglielmi detachable coils. Part I. Symptoms of cranial nerve dysfunction.

OBJECT: Embolization of intracranial aneurysms by using Guglielmi detachable coils (GDCs) is proving to be a safe method of protecting aneurysms from rupture. Occasionally, patients with unruptured intracranial aneurysms present with symptoms related to the aneurysm's mass effect on either the brain parenchyma or cranial nerves. In the present study, the authors conducted a retrospective review to evaluate the response to GDC embolization in a series of 19 patients presenting with cranial nerve dysfunction due to mass effect. METHODS: Aneurysms were classified by size, shape, wall calcification, and amount of intraluminal thrombus. Patients were classified by duration of symptoms prior to GDC treatment (range < 1 month to > 10 years). Clinical assessment was performed within days of the GDC procedure and at later follow-up appointments (range 1-70 months, mean 24 months). In the immediate post-GDC period, four patients experienced worsening of cranial nerve deficits. Two of the four patients had transient worsening of visual acuity, which later improved to better than baseline status. Another patient who had presented with headache and seventh and eighth cranial nerve deficits from a vertebrobasilar junction aneurysm had improvement in these symptoms, but developed a new diplopia. The fourth patient had worsening of her visual acuity, which had not resolved at the 1-month follow-up examination; this patient later underwent surgical decompression. CONCLUSIONS: On late follow-up review, the response was classified as complete resolution of symptoms in six patients (32%), improvement in eight patients (42%), no significant change in four patients (21%), and symptom worsening in one patient (5%). Patients with smaller aneurysms and those with shorter pretreatment duration of symptoms were more likely to experience an improvement in their symptoms following GDC treatment, although statistical significance was not reached in this series (p=0.603 and p=0.111, respectively). The presence of aneurysmal wall calcification (six patients) or intraluminal thrombus (12 patients) showed no correlation with the response of mass effect symptoms in these patients.

Adult↗
PubMed1998

The suboccipital carrefour: cervical and vertebral arterial anastomosis.

PURPOSE: Our objective was to anatomically define the anastomoses between cervical and carotid arterial distributions (the carrefour) in the rabbit and to assess the contribution of these collaterals to cortical blood flow (CBF) during cerebral ischemia. METHODS: Angiography was carried out in six rabbits with basilar artery occlusion using selective contrast injection into the right subclavian, external carotid, and internal carotid arteries. Anastomoses were corroborated with methacrylate vascular casts prepared in five additional rabbits. CBF was measured in eight rabbits by H2 clearance after basilar artery occlusion and again after bilateral common carotid artery occlusion. Cortical DC potential was measured during ischemia in these rabbits and in another 19 rabbits after additional occlusion of the cervical collateral arteries. RESULTS: A network of anastomoses between superficial and ascending cervical, superior intercostal, vertebral, and occipital arteries was found by angiography and corrosion casts. Additional communications in the ophthalmic, ethmoidal, and cerebellar arterial distributions are described. These pathways were found to supply a mean of 15 +/- 7 mL/100 g per minute residual CBF during three-vessel ischemia, or 24% of the preischemic CBF. Ischemic depolarization of DC potential occurred in seven of the eight rabbits with collateral CBF at a mean latency of 2.64 +/- 0.59 minutes and at 1.71 +/- 0.09 minutes in those without. CONCLUSION: The suboccipital collateral network of the rabbit resembles that of humans and can contribute significantly to CBF during ischemia. The results suggest that this model may be useful for evaluating methods of optimizing hemodynamic control of the anastomoses in situations such as those encountered during endovascular therapy.

Animals↗
PubMed1998

Direct arteriovenous fistulas (carotid-cavernous and vertebral-venous). Diagnosis and intervention.

Carotid-cavernous and vertebral-venous fistulas are direct arteriovenous fistulas. Their symptoms range from benign to extremely severe ophthalmologic or neurologic complications. Mechanism of symptoms is mostly related to venous drainage. Therapy is widely indicated, as today's endovascular techniques--using mostly detachable balloons and coils--have a high success rate and very few complications.

Arteriovenous Fistula↗
PubMed1998

Predictors of aneurysmal occlusion in the period immediately after endovascular treatment with detachable coils: a multivariate analysis.

BACKGROUND AND PURPOSE: Complete intracranial aneurysmal occlusion by endovascular techniques is required for successful treatment and is presumably influenced by several parameters. The purpose of this study was to investigate whether operator experience and angiographic characteristics of intracranial aneurysms correspond to the degree of endovascular occlusion in the period immediately after treatment with Guglielmi detachable coils (GDCs). METHODS: Pre- and posttreatment angiograms of 72 patients undergoing GDC treatment were reviewed retrospectively. The following angiographic characteristics of the aneurysms were evaluated: largest diameter of the sac, volume, neck size, shape, type, cerebrovascular site, surroundings, and likely direction of aneurysmal inflow as judged by a score developed by measuring aneurysm/parent artery angulation. The chronological sequence in which the aneurysms were treated was used as a measure of operator experience. A chi2-test was used to identify parameters that correlated with outcomes of total (100%) or partial (<100%) occlusion. A multivariate analysis was used to determine the factors most predictive of aneurysmal occlusion at therapy. RESULTS: Parameters that correlated with the unsatisfactory result of partial occlusion were large aneurysmal diameter, volume, and neck size, more direct inflow (ie, increasingly obtuse aneurysm/parent artery angulation), and early chronological presentation in the series. The three factors most predictive of partial occlusion were large aneurysmal diameter, more direct inflow, and early chronological order of treatment. CONCLUSION: Several morphologic features of aneurysms were identified to help predict the immediate outcome of occlusion with GDCs. This study underscores the existence of a steep learning curve associated with GDC use in treating aneurysms and the importance of operator experience in achieving optimal therapeutic results.

Cerebral Angiography↗
PubMed1997

Intra-arterial carboplatin chemotherapy for brain tumors: a dose escalation study based on cerebral blood flow.

PURPOSE: To perform in intra-arterial dose escalation study of carboplatin based on hemispheric blood-flow estimation in patients with recurrent malignant glioma. The primary purpose was to determine the maximally tolerated intra-arterial dose. METHODS AND PATIENTS: Methods included: 1) selective intra-arterial delivery performed with modern microcatheters, 2) pulsatile infusion, and 3) dosage based on local cerebral blood-flow estimation (middle cerebral artery 60%, anterior cerebral artery 20%, posterior cerebral artery 15%, and anterior choroidal artery 5% of the hemispheric blood-flow). The deliveries were performed above the ophthalmic artery in the anterior circulation, or above the anterior inferior cerebellar arteries in the posterior circulation. The doses were escalated from 200 mg/hemisphere at 50 mg increments. Twenty-one patients were studied (14 with glioblastoma multiforme, five anaplastic astrocytoma, one aggressive low-grade glioma, one metastasis). Patients had recurrent glioma limited to one hemisphere and Karnofsky score of 50 or greater. Concomitant therapies were allowed. RESULTS: Carboplatin was escalated to a dose of 1400 mg/hemisphere. One patient had a permanent neuromotor decline. The predominant toxicity was hematopoietic. The median time to tumor progression was 22 weeks, median survival 39 weeks, and the response rate 70% (50% SD and 20% PR) of 19 patients. CONCLUSIONS: Hemispheric blood-flow estimation allowed us to escalate the dose of intra-arterial carboplatin to twice what was previously considered safe. Responses compared favorably to previous studies. Further studies are needed to determine if this method will provide improved and durable responses.

Adult↗
PubMed1997

Ion implantation and protein coating of detachable coils for endovascular treatment of cerebral aneurysms: concepts and preliminary results in swine models.

OBJECTIVE: Complete anatomic obliteration remains difficult to achieve with endovascular treatment of wide-necked aneurysms using Guglielmi detachable platinum coils (GDCs). Ion implantation is a physicochemical surface modification process resulting from the impingement of a high-energy ion beam. Ion implantation and protein coating were used to alter the surface properties (thrombogenicity, endothelial cellular migration, and adhesion) of GDCs. These modified coils were compared with standard GDCs in the treatment of experimental swine aneurysms. METHODS: In an initial study, straight platinum coils were used to compare the acute thrombogenicity of standard and modified coils. Modified coils were coated with albumin, fibronectin, or collagen and underwent Ne+ ion implantation at a dose of 1 x 10(15) ions/cm2 and an energy of 150 keV. Coils were placed in common iliac arteries of 17 swine for 1 hour, to evaluate their acute interactions with circulating blood. In a second study, GDCs were used to treat 34 aneurysms in an additional 17 swine. GDCs were coated with fibronectin, albumin, collagen, laminin, fibrinogen, or vitronectin and then implanted with ions as described above. Bilateral experimental swine aneurysms were embolized with standard GDCs on one side and with ion-implanted, protein-coated GDCs on the other side. The necks of aneurysms were evaluated macroscopically at autopsy, by using post-treatment Day 14 specimens. The dimensions of the orifice and the white fibrous membrane that covered the orifice were measured as the fibrous membrane to orifice proportion. Histopathological evaluation of the neck region was performed by light microscopy and scanning electron microscopy. RESULTS: Fibronectin-coated, ion-implanted coils showed the greatest acute thrombogenicity (average thrombus weight for standard coils, 1.9 +/- 1.5 mg; weight for fibronectin-coated coils, 8.6 +/- 6.2 mg; P < 0.0001). By using scanning electron microscopy, an intensive blood cellular response was observed on ion-implanted coil surfaces, whereas this was rare with standard coils. At Day 14, greater fibrous coverage of the necks of aneurysms was observed in the ion-implanted coil group (mean fibrous membrane to orifice proportion of 69.8 +/- 6.2% for the ion-implanted coil group, compared with 46.8 +/- 15.9% for the standard coil group; P = 0.0143). CONCLUSION: The results of this preliminary experimental study indicate that ion implantation combined with protein coating of GDCs improved cellular adhesion and proliferation. Future application of this technology may provide early wound healing at the necks of embolized, wide-necked, cerebral aneurysms.

Animals↗
PubMed1997

Carotid artery volume flow: in vivo measurement with time-domain-processing US.

PURPOSE: To evaluate carotid artery volume-flow measurements with time-domain-processing ultrasonography (US). MATERIALS AND METHODS: Volume-flow measurements were obtained in the carotid arteries of nine swine with time-domain-processing US. Four swine were prepared with a model of an arteriovenous shunt. Flow through the carotid artery was varied by means of a number of physiologic and pharmacologic interventions. The reference standard for volume flow consisted of measurements with transit-time US flowmetry. At a limited number of measurement points, this reference standard was validated against true volume flow measured with timed collection. RESULTS: For flow rates less than 500 mL/min, a linear correlation existed between measurements with time-domain processing and the US flow meter (r2 = .96, P < .001, slope = 1.117). Values above 500 mL/min were less well correlated with the reference standard. True flow was underestimated with both methods, less so with time-domain processing than with US flowmetry (underestimation, 10% versus 21%). Measurements were significantly less reproducible with time-domain processing than with US flowmetry (P < .001). Interobserver variability was negligible. CONCLUSION: Because of operator errors, measurements with time-domain processing should be repeated at least three times to ensure accuracy and may be inaccurate in flow rates over 500 mL/min.

Animals↗
PubMed1997

Guglielmi detachable coil embolization of acute intracranial aneurysm: perioperative anatomical and clinical outcome in 403 patients.

From December 1990 to July 1995, the investigators participated in a prospective clinical study to evaluate the safety of the Guglielmi detachable coil (GDC) system for the treatment of aneurysms. This report summarizes the perioperative results from eight initial interventional neuroradiology centers in the United States. The report focuses on 403 patients who presented with acute subarachnoid hemorrhage from a ruptured intracranial aneurysm. These patients were treated within 15 days of the primary intracranial hemorrhage and were followed until they were discharged from the hospital or died. Seventy percent of the patients were female and 30% were male. The patients' mean age was 58 years old. Aneurysm size was categorized as small (60.8%), large (34.7%), and giant (4.5%); and neck size was categorized as small (53.6%), wide (36.2%), fusiform (6%), and undetermined (4.2%). Fifty-seven percent of the aneurysms were located in the posterior circulation and 43% in the anterior circulation. Eighty-two patients were classified as Hunt and Hess Grade I (20.3%), 105 Grade II (26.1%), 121 Grade III (30%), 69 Grade IV (17.1%), and 26 Grade V (6.5%). All patients in this study were excluded from surgical treatment either because of anticipated surgical difficulty (69.2%), attempted and failed surgery (12.7%), the patient's poor neurological (12.2%) or medical (4.7%) status, and/or refusal of surgery (1.2%). The GDC embolization was performed within 48 hours of primary hemorrhage in 147 patients (36.5%), within 3 to 6 days in 156 patients (38.7%), 7 to 10 days in 71 patients (17.6%), and 11 to 15 days in 29 patients (7.2%). Complete aneurysm occlusion was observed in 70.8% of small aneurysms with a small neck, 35% of large aneurysms, and 50% of giant aneurysms. A small neck remnant was observed in 21.4% of small aneurysms with a small neck, 57.1% of large aneurysms, and 50% of giant aneurysms. Technical complications included aneurysm perforation (2.7%), unintentional parent artery occlusion (3%), and untoward cerebral embolization (2.48%). There was a 8.9% immediate morbidity rate related to the GDC technique. Seven deaths were related to technical complications (1.74%) and 18 (4.47%) to the severity of the primary hemorrhage. The findings of this study demonstrate the safety of the GDC system for the treatment of ruptured intracranial aneurysms in anterior and posterior circulations. The authors believe additional randomized studies will further identify the role of this technique in the management of acutely ruptured incranial aneurysms.

Acute Disease↗