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Pla L, Berdún S, Mir M, Rivas L, Miserere S, Dulay S, Samitier J, Eixarch E, Illa M, Gratacós E. Non-invasive monitoring of pH and oxygen using miniaturized electrochemical sensors in an animal model of acute hypoxia. J Transl Med 2021; 19:53. [PMID: 33541374 PMCID: PMC7863274 DOI: 10.1186/s12967-021-02715-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 01/23/2021] [Indexed: 12/02/2022] Open
Abstract
Background One of the most prevalent causes of fetal hypoxia leading to stillbirth is placental insufficiency. Hemodynamic changes evaluated with Doppler ultrasound have been used as a surrogate marker of fetal hypoxia. However, Doppler evaluation cannot be performed continuously. As a first step, the present work aimed to evaluate the performance of miniaturized electrochemical sensors in the continuous monitoring of oxygen and pH changes in a model of acute hypoxia-acidosis. Methods pH and oxygen electrochemical sensors were evaluated in a ventilatory hypoxia rabbit model. The ventilator hypoxia protocol included 3 differential phases: basal (100% FiO2), the hypoxia-acidosis period (10% FiO2) and recovery (100% FiO2). Sensors were tested in blood tissue (ex vivo sensing) and in muscular tissue (in vivo sensing). pH electrochemical and oxygen sensors were evaluated on the day of insertion (short-term evaluation) and pH electrochemical sensors were also tested after 5 days of insertion (long-term evaluation). pH and oxygen sensing were registered throughout the ventilatory hypoxia protocol (basal, hypoxia-acidosis, and recovery) and were compared with blood gas metabolites results from carotid artery catheterization (obtained with the EPOC blood analyzer). Finally, histological assessment was performed on the sensor insertion site. One-way ANOVA was used for the analysis of the evolution of acid-based metabolites and electrochemical sensor signaling results; a t-test was used for pre- and post-calibration analyses; and chi-square analyses for categorical variables. Results At the short-term evaluation, both the pH and oxygen electrochemical sensors distinguished the basal and hypoxia-acidosis periods in both the in vivo and ex vivo sensing. However, only the ex vivo sensing detected the recovery period. In the long-term evaluation, the pH electrochemical sensor signal seemed to lose sensibility. Finally, histological assessment revealed no signs of alteration on the day of evaluation (short-term), whereas in the long-term evaluation a sub-acute inflammatory reaction adjacent to the implantation site was detected. Conclusions Miniaturized electrochemical sensors represent a new generation of tools for the continuous monitoring of hypoxia-acidosis, which is especially indicated in high-risk pregnancies. Further studies including more tissue-compatible material would be required in order to improve long-term electrochemical sensing.
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Affiliation(s)
- Laura Pla
- BCNatal
- Fetal Medicine Research Center (Hospital Clínic and Hospital Sant Joan de Déu), Universitat de Barcelona, Barcelona, Spain
| | - Sergio Berdún
- BCNatal
- Fetal Medicine Research Center (Hospital Clínic and Hospital Sant Joan de Déu), Universitat de Barcelona, Barcelona, Spain
| | - Mònica Mir
- Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales Y Nanomedicina (CIBER-BBN), Monforte de Lemos 3-5, Pabellón 11, 28029, Madrid, Spain.,Nanobioengineering Group, Institute for Bioengineering of Catalonia (IBEC) Barcelona Institute of Science and Technology (BIST), 12 Baldiri Reixac 15-21, 08028, Barcelona, Spain.,Department of Electronics and Biomedical Engineering, University of Barcelona, Martí I Franquès 1, 08028, Barcelona, Spain
| | - Lourders Rivas
- Nanobioengineering Group, Institute for Bioengineering of Catalonia (IBEC) Barcelona Institute of Science and Technology (BIST), 12 Baldiri Reixac 15-21, 08028, Barcelona, Spain
| | - Sandrine Miserere
- Nanobioengineering Group, Institute for Bioengineering of Catalonia (IBEC) Barcelona Institute of Science and Technology (BIST), 12 Baldiri Reixac 15-21, 08028, Barcelona, Spain
| | - Samuel Dulay
- Nanobioengineering Group, Institute for Bioengineering of Catalonia (IBEC) Barcelona Institute of Science and Technology (BIST), 12 Baldiri Reixac 15-21, 08028, Barcelona, Spain
| | - Josep Samitier
- Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales Y Nanomedicina (CIBER-BBN), Monforte de Lemos 3-5, Pabellón 11, 28029, Madrid, Spain.,Nanobioengineering Group, Institute for Bioengineering of Catalonia (IBEC) Barcelona Institute of Science and Technology (BIST), 12 Baldiri Reixac 15-21, 08028, Barcelona, Spain.,Department of Electronics and Biomedical Engineering, University of Barcelona, Martí I Franquès 1, 08028, Barcelona, Spain
| | - Elisenda Eixarch
- BCNatal
- Fetal Medicine Research Center (Hospital Clínic and Hospital Sant Joan de Déu), Universitat de Barcelona, Barcelona, Spain.,Institut D'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain.,Centre for Biomedical Research On Rare Diseases (CIBER-ER), Barcelona, Spain
| | - Miriam Illa
- BCNatal
- Fetal Medicine Research Center (Hospital Clínic and Hospital Sant Joan de Déu), Universitat de Barcelona, Barcelona, Spain. .,Institut de Recerca Sant Joan de Déu, Esplugues de Llobregat, Spain.
| | - Eduard Gratacós
- BCNatal
- Fetal Medicine Research Center (Hospital Clínic and Hospital Sant Joan de Déu), Universitat de Barcelona, Barcelona, Spain.,Institut D'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain.,Centre for Biomedical Research On Rare Diseases (CIBER-ER), Barcelona, Spain.,Institut de Recerca Sant Joan de Déu, Esplugues de Llobregat, Spain
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Monitoring with In Vivo Electrochemical Sensors: Navigating the Complexities of Blood and Tissue Reactivity. SENSORS 2020; 20:s20113149. [PMID: 32498360 PMCID: PMC7308849 DOI: 10.3390/s20113149] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 05/29/2020] [Accepted: 05/31/2020] [Indexed: 12/18/2022]
Abstract
The disruptive action of an acute or critical illness is frequently manifest through rapid biochemical changes that may require continuous monitoring. Within these changes, resides trend information of predictive value, including responsiveness to therapy. In contrast to physical variables, biochemical parameters monitored on a continuous basis are a largely untapped resource because of the lack of clinically usable monitoring systems. This is despite the huge testing repertoire opening up in recent years in relation to discrete biochemical measurements. Electrochemical sensors offer one of the few routes to obtaining continuous readout and, moreover, as implantable devices information referable to specific tissue locations. This review focuses on new biological insights that have been secured through in vivo electrochemical sensors. In addition, the challenges of operating in a reactive, biological, sample matrix are highlighted. Specific attention is given to the choreographed host rejection response, as evidenced in blood and tissue, and how this limits both sensor life time and reliability of operation. Examples will be based around ion, O2, glucose, and lactate sensors, because of the fundamental importance of this group to acute health care.
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Song K, Kim J, Cho S, Kim N, Jung D, Choo H, Lee J. Flexible-Device Injector with a Microflap Array for Subcutaneously Implanting Flexible Medical Electronics. Adv Healthc Mater 2018; 7:e1800419. [PMID: 29938924 DOI: 10.1002/adhm.201800419] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 05/30/2018] [Indexed: 11/09/2022]
Abstract
Implantable electronics in soft and flexible forms can reduce undesired outcomes such as irritations and chronic damages to surrounding biological tissues due to the improved mechanical compatibility with soft tissues. However, the same mechanical flexibility also makes it difficult to insert such implants through the skin because of reduced stiffness. In this paper, a flexible-device injector that enables the subcutaneous implantation of flexible medical electronics is reported. The injector consists of a customized blade at the tip and a microflap array which holds the flexible implant while the injector penetrates through soft tissues. The microflap array eliminates the need of additional materials such as adhesives that require an extended period to release a flexible medical electronic implant from an injector inside the skin. The mechanical properties of the injection system during the insertion process are experimentally characterized, and the injection of a flexible optical pulse sensor and electrocardiogram sensor is successfully demonstrated in vivo in live pig animal models to establish the practical feasibility of the concept.
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Affiliation(s)
- Kwangsun Song
- School of Mechanical Engineering; Gwangju Institute of Science and Technology (GIST); 123 Cheomdangwagi-ro, Buk-gu Gwangju 61005 Republic of Korea
- Research Institute for Solar and Sustainable Energies; Gwangju Institute of Science and Technology (GIST); 123 Cheomdangwagi-ro, Buk-gu Gwangju 61005 Republic of Korea
| | - Juho Kim
- School of Mechanical Engineering; Gwangju Institute of Science and Technology (GIST); 123 Cheomdangwagi-ro, Buk-gu Gwangju 61005 Republic of Korea
- Research Institute for Solar and Sustainable Energies; Gwangju Institute of Science and Technology (GIST); 123 Cheomdangwagi-ro, Buk-gu Gwangju 61005 Republic of Korea
| | - Sungbum Cho
- School of Mechanical Engineering; Gwangju Institute of Science and Technology (GIST); 123 Cheomdangwagi-ro, Buk-gu Gwangju 61005 Republic of Korea
| | - Namyun Kim
- School of Mechanical Engineering; Gwangju Institute of Science and Technology (GIST); 123 Cheomdangwagi-ro, Buk-gu Gwangju 61005 Republic of Korea
| | - Dongwuk Jung
- School of Mechanical Engineering; Gwangju Institute of Science and Technology (GIST); 123 Cheomdangwagi-ro, Buk-gu Gwangju 61005 Republic of Korea
- Research Institute for Solar and Sustainable Energies; Gwangju Institute of Science and Technology (GIST); 123 Cheomdangwagi-ro, Buk-gu Gwangju 61005 Republic of Korea
| | - Hyuck Choo
- Department of Medical Engineering; California Institute of Technology; Pasadena CA 91125 USA
- Department of Electrical Engineering; California Institute of Technology; Pasadena CA 91125 USA
| | - Jongho Lee
- School of Mechanical Engineering; Gwangju Institute of Science and Technology (GIST); 123 Cheomdangwagi-ro, Buk-gu Gwangju 61005 Republic of Korea
- Research Institute for Solar and Sustainable Energies; Gwangju Institute of Science and Technology (GIST); 123 Cheomdangwagi-ro, Buk-gu Gwangju 61005 Republic of Korea
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Ledo A, Lourenço CF, Laranjinha J, Brett CMA, Gerhardt GA, Barbosa RM. Ceramic-Based Multisite Platinum Microelectrode Arrays: Morphological Characteristics and Electrochemical Performance for Extracellular Oxygen Measurements in Brain Tissue. Anal Chem 2017; 89:1674-1683. [DOI: 10.1021/acs.analchem.6b03772] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Ana Ledo
- Center
for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal
| | - Cátia F. Lourenço
- Center
for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal
| | - João Laranjinha
- Center
for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal
- Faculty
of Pharmacy, University of Coimbra, Health Sciences Campus, Azinhaga de Santa Comba, 3000-548, Coimbra, Portugal
| | - Christopher M. A. Brett
- Department
of Chemistry, Faculty of Sciences and Technology, University of Coimbra, 3004-535, Coimbra, Portugal
| | - Greg A. Gerhardt
- Center
for Microelectrode Technology (CenMeT), Department of Neuroscience, University of Kentucky Medical Center, Lexington, Kentucky 40536, United States
| | - Rui M. Barbosa
- Center
for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal
- Faculty
of Pharmacy, University of Coimbra, Health Sciences Campus, Azinhaga de Santa Comba, 3000-548, Coimbra, Portugal
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Bolger FB, Bennett R, Lowry JP. An in vitro characterisation comparing carbon paste and Pt microelectrodes for real-time detection of brain tissue oxygen. Analyst 2011; 136:4028-35. [DOI: 10.1039/c1an15324b] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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6
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Ortiz-Prado E, Natah S, Srinivasan S, Dunn JF. A method for measuring brain partial pressure of oxygen in unanesthetized unrestrained subjects: the effect of acute and chronic hypoxia on brain tissue PO(2). J Neurosci Methods 2010; 193:217-25. [PMID: 20817029 DOI: 10.1016/j.jneumeth.2010.08.019] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Revised: 08/19/2010] [Accepted: 08/23/2010] [Indexed: 10/19/2022]
Abstract
The level of tissue oxygenation provides information related to the balance between oxygen delivery, oxygen utilization, tissue reactivity and morphology during physiological conditions. Tissue partial pressure of oxygen (PtO(2)) is influenced by the use of anesthesia or restraint. These factors may impact the absolute level of PtO(2). In this study we present a novel fiber optic method to measure brain PtO(2). This method can be used in unanesthetized, unrestrained animals, provides absolute values for PO(2), has a stable calibration, does not consume oxygen and is MRI compatible. Brain PtO(2) was studied during acute hypoxia, as well as before and after 28 days of high altitude acclimatization. A sensor was chronically implanted in the frontal cortex of eight Wistar rats. It is comprised of a fiber optic probe with a tip containing material that fluoresces with an oxygen dependent lifetime. Brain PtO(2) declines by 80% and 76% pre- and post-acclimatization, respectively, when the fraction of inspired oxygen declines from 0.21 to 0.08. In addition, a linear relationship between brain PtO(2) and inspired O(2) levels was demonstrated r(2)=0.98 and r(2)=0.99 (pre- and post-acclimatization). Hypoxia acclimatization resulted in an increase in the overall brain PtO(2) by approximately 35%. This paper demonstrates the use of a novel chronically implanted fiber optic based sensor for measuring absolute PtO(2). It shows a very strong linear relationship in awake animals between inspired O(2) and tissue O(2), and shows that there is a proportional increase in PtO(2) over a range of inspired values after exposure to chronic hypoxia.
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Affiliation(s)
- E Ortiz-Prado
- Department of Radiology, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
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Bazzu G, Puggioni GGM, Dedola S, Calia G, Rocchitta G, Migheli R, Desole MS, Lowry JP, O'Neill RD, Serra PA. Real-time monitoring of brain tissue oxygen using a miniaturized biotelemetric device implanted in freely moving rats. Anal Chem 2010; 81:2235-41. [PMID: 19222224 DOI: 10.1021/ac802390f] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A miniaturized biotelemetric device for the amperometric detection of brain tissue oxygen is presented. The new system, derived from a previous design, has been coupled with a carbon microsensor for the real-time detection of dissolved O(2) in the striatum of freely moving rats. The implantable device consists of a single-supply sensor driver, a current-to-voltage converter, a microcontroller, and a miniaturized data transmitter. The oxygen current is converted to a digital value by means of an analog-to-digital converter integrated in a peripheral interface controller (PIC). The digital data is sent to a personal computer using a six-byte packet protocol by means of a miniaturized 434 MHz amplitude modulation (AM) transmitter. The receiver unit is connected to a personal computer (PC) via a universal serial bus. Custom developed software allows the PC to store and plot received data. The electronics were calibrated and tested in vitro under different experimental conditions and exhibited high stability, low power consumption, and good linear response in the nanoampere current range. The in vivo results confirmed previously published observations on oxygen dynamics in the striatum of freely moving rats. The system serves as a rapid and reliable model for studying the effects of different drugs on brain oxygen and brain blood flow and it is suited to work with direct-reduction sensors or O(2)-consuming biosensors.
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Affiliation(s)
- Gianfranco Bazzu
- Department of Neuroscience, Medical School, University of Sassari, Viale S. Pietro 43/b, 07100 Sassari, Italy
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A new bioartificial pancreas utilizing amphiphilic membranes for the immunoisolation of porcine islets: a pilot study in the canine. ASAIO J 2009; 55:400-5. [PMID: 19506465 DOI: 10.1097/mat.0b013e3181a8deba] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
We have developed a replaceable bioartificial pancreas to treat diabetes utilizing a unique cocontinous amphiphilic conetwork membrane created for macroencapsulation and immunoisolation of porcine islet cells (PICs). The membrane is assembled from hydrophilic poly(N,N-dimethyl acrylamide) and hydrophobic/oxyphilic polydimethylsiloxane chains cross-linked with hydrophobic/oxyphilic polymethylhydrosiloxane chains. Our hypothesis is that this membrane allows the survival of xenotransplanted PICs in the absence of prevascularization or immunosuppression because of its extraordinarily high-oxygen permeability and small hydrophilic channel dimensions (3-4 nm). The key components are a 5-10 microm thick semipermeable amphiphilic conetwork membrane reinforced with an electrospun nanomat of polydimethylsiloxane-containing polyurethane, and a laser-perforated nitinol scaffold to provide geometric stability. Devices were loaded with PICs and tested for their ability to maintain islet viability without prevascularization, prevent rejection, and reverse hyperglycemia in three pancreatectomized dogs without immunosuppression. Tissue tolerance was good and there was no systemic toxicity. The bioartificial pancreas protected PICs from toxic environments in vitro and in vivo. Islets remained viable for up to 3 weeks without signs of rejection. Neovascularization was observed. Hyperglycemia was not reversed, most likely because of insufficient islet mass. Further studies to determine long-term islet viability and correction of hyperglycemia are warranted.
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A novel macroencapsulating immunoisolatory device: the preparation and properties of nanomat-reinforced amphiphilic co-networks deposited on perforated metal scaffold. Biomed Microdevices 2009; 11:297-312. [PMID: 18987977 DOI: 10.1007/s10544-008-9236-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
This paper describes the design and preparation of the non-biological components (the "hardware") of a conceptually novel bioartificial pancreas (BAP) to correct diabetes. The key components of the hardware are (1) a thin (5-10 microm) semipermeable amphiphilic co-network (APCN) membrane [i.e., a membrane of cocontinuous poly(dimethyl acryl amide) (PDMAAm)/polydimethylsiloxane (PDMS) domains cross-linked by polymethylhydrosiloxane (PMHS)] expressly created for macroencapsulation and immunoisolation of a tissue graft; (2) an electrospun nanomat of PDMS-containing polyurethane to reinforce the water-swollen APCN membrane; and (3) a perforated hollow-ribbon nitinol scaffold to stiffen and provide geometric stability to the construct. The reinforcement of water-swollen hydrogels with an electrospun nanomat is a generally applicable new method for hydrogel reinforcement. Details of device design and preparation are discussed. The advantages and disadvantages of micro- and macro-immunoisolation are analyzed, and the requirements for the ideal immunoisolatory membrane are presented. Burst pressure, and glucose and insulin permeabilities of representative devices have been determined and the effect of device composition and wall thickness on these properties is discussed.
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Abstract
Amperometric sensors for continuous glucose monitoring could prevent acute and chronic complications of diabetes, but research is needed to improve accuracy and stability. In designing sensors, interference from non-glucose analytes can be minimized by use of filtration membranes or electron transfer mediators that allow polarization at low potentials. If oxygen is required for the enzymatic reaction with glucose, then the outer permselective membrane must have substantial oxygen permeability. For this reason, during development of permselective membranes, permeability studies (such as performed by Tipnis and colleagues in this issue) can be used to measure transport of glucose and oxygen and optimize membrane structure. Tipnis and colleagues present a novel biosensor based with separate layers for glucose-oxygen permselectivity, enzymatic conversion, and avoidance of interference. They also address sensor stability, in part by comparing sensor function during ascending vs descending glucose levels. By measuring the difference, they were able to minimize this aspect of instability (hysterisis), which assisted them in selecting a promising permselective membrane based on iron and humic acid.
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Kusumoto F, Goldschlager N. Beyond heart rhythms: new directions for implantable devices. J Interv Card Electrophysiol 2005; 14:5-7. [PMID: 16311933 DOI: 10.1007/s10840-005-4347-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Implantable cardiac devices have become firmly entrenched as important therapeutic tools for a variety of conditions. Pacemakers are the only available treatment for symptomatic bradycardia not due to reversible causes. Large randomized studies have demonstrated a small but statistically significant reduction in atrial fibrillation associated with pacing modes that maintain atrioventricular synchrony. In contrast, pacing mode appears to have a less dramatic effect in patients with atrioventricular block. Cardiac resynchronization with specialized left ventricular leads has been shown to reduce symptoms and improve survival in patients with symptomatic heart failure, systolic dysfunction, and widened QRS complexes. The implantable cardioverter defibrillator has become the standard therapy for protecting patients against sudden cardiac death. Two recent trials, Multicenter Automatic Defibrillator Trial II (MADIT II) and the Sudden Cardiac Death Heart Failure Trial (SCD-HEFT), demonstrated that the ICD is associated with a significant survival benefit for patients with reduced ejection fraction (< 0.30-0.35) particularly if heart failure symptoms are present. Finally the implantable loop recorder has become an important diagnostic tool for the patient with unexplained syncope. This brief overview summarizes the indications and follow-up of the wide array of implantable cardiac devices available to the clinical cardiologist.
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Ward WK, Quinn MJ, Wood MD, Tiekotter KL, Pidikiti S, Gallagher JA. Vascularizing the tissue surrounding a model biosensor: how localized is the effect of a subcutaneous infusion of vascular endothelial growth factor (VEGF)? Biosens Bioelectron 2004; 19:155-63. [PMID: 14611750 DOI: 10.1016/s0956-5663(03)00180-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Implantable continuous biosensors would improve disease management but long term function of such devices have been limited by a hypovascular foreign body capsule that inhibits influx of analytes. To assess whether capsule vascularity could be increased, we studied the histologic effects of a 28-day continuous infusion of vascular endothelial growth factor (VEGF) (0.45 microg/day) vs. saline from the surface of a model disk biosensor that was implanted subcutaneously in rats. At day 40, tissue was obtained at varying distances from the infusion port and capsular microvessels were counted using two histologic techniques. VEGF treatment led to a marked increase in capillary density. In tissue located 1 mm away from the infusion site, capillary density in VEGF-treated animals was 200-300% higher than in saline controls. Tissue located 13 mm away, but not 25 mm away, also demonstrated neovascularization. Serum obtained from a distant vein during the infusion did not show an elevated concentration of VEGF. These data demonstrate that a subcutaneous infusion of VEGF creates localized neovascularization of the foreign body capsule and suggest that systemic effects of VEGF are avoidable. Vascularization of a foreign body capsule surrounding a subcutaneous biosensor might well extend its useful life.
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Affiliation(s)
- W Kenneth Ward
- Legacy Health System, Legacy Clinical Research and Technology Center, 1225 NE 2nd Avenue, Portland, OR 97232, USA.
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