Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 2 de 2
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Heart Rhythm ; 19(7): 1165-1173, 2022 07.
Artigo em Inglês | MEDLINE | ID: mdl-35240311

RESUMO

BACKGROUND: External defibrillators are used for arrhythmia cardioversion and for defibrillating during cardiac arrest. During defibrillation, short-duration biphasic pulses cause intense motion due to rapid chest-wall muscle contraction. A reduced motion external defibrillator (RMD) was constructed by integrating a commercial defibrillator with a Tetanizing-waveform generator. A long-duration, low-amplitude, tetanizing waveform slowly stimulated the chest musculature before the biphasic pulse, reducing muscle contraction during the shock. OBJECTIVE: The purpose of this study was to evaluate RMD defibrillation in swine for subject motion during defibrillation pulses and for defibrillation effectiveness. RMD defibrillation can reduce the duration of arrhythmia ablation therapy or simplify cardioversion procedures. METHODS: The tetanizing unit delivered a triangular 1-kHz pulse of 0.25- to 2.0-second duration and 10- to 100-V peak amplitude, subsequently triggering the conventional defibrillator to output standard 1- to 200-J energy biphasic pulses at the next R wave. Forward limb motion was evaluated by measuring peak acceleration and limb work during RMD (tetanizing + biphasic) or biphasic pulse-only waveforms at 10-3-second sampling rate. Seven swine were arrested electrically and subsequently defibrillated. Biphasic pulse-only and RMD defibrillations were repeated 25-35 times per swine, varying tetanizing parameters and biphasic pulse energy. Defibrillation thresholds (DFTs) were established by measuring the minimum energy required to restore sinus rhythm with biphasic pulse-only or RMD defibrillations. RESULTS: Two forward-limb acceleration peaks occurred during both the tetanizing waveform and biphasic pulse, indicating rapid and slower nociceptic (pain sensation) nerve fiber activation. Optimal RMD tetanizing parameters (25-35 V, 0.25- to 0.75-second duration), relative to biphasic pulse-only defibrillations, resulted in 74% ± 10% smaller peak accelerations and 85% ± 10% reduced limb work. DFT energies were identical when comparing RMD to biphasic pulse-only defibrillations. CONCLUSION: Relative to conventional defibrillations, RMD defibrillations maintain rhythm restoration efficiency with drastically reduced subject motion.


Assuntos
Cardioversão Elétrica , Parada Cardíaca , Animais , Arritmias Cardíacas , Desfibriladores , Cardioversão Elétrica/métodos , Suínos , Fibrilação Ventricular/terapia
2.
IEEE Trans Biomed Eng ; 67(6): 1616-1627, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-31535979

RESUMO

OBJECTIVE: Cardiovascular interventional devices typically have long metallic braids or backbones to aid in steerability and pushability. However, electromagnetic coupling of metallic-based cardiovascular interventional devices with the radiofrequency (RF) fields present during Magnetic Resonance Imaging (MRI) can make a device unsafe for use in an MRI scanner. We aimed to develop MRI conditional actively-tracked cardiovascular interventional devices by sufficiently attenuating induced currents on the metallic braid/tube and internal-cabling using miniaturized resonant floating RF traps (MBaluns). METHOD: MBaluns were designed for placement at multiple locations along a conducting cardiovascular device to prevent the establishment of standing waves and to dissipate RF-induced energy. The MBaluns were constructed with loosely-wound solenoids to be sensitive to transverse magnetic fields created by both surface currents on the device's metallic backbone and common-mode currents on internal cables. Electromagnetic simulations were used to optimize MBalun parameters. Following optimization, two different MBalun designs were applied to MR-actively-tracked metallic guidewires and metallic-braided electrophysiology ablation catheters. Control-devices were constructed without MBaluns. MBalun performance was validated using network-analyzer quantification of current attenuation, electromagnetic Specific-Absorption-Rate (SAR) analysis, thermal tests during high SAR pulse sequences, and MRI-guided cardiovascular navigation in swine. RESULTS: Electromagnetic SAR simulations resulted in ≈20 dB attenuation at the tip of the wire using six successive MBaluns. Network-analyzer tests confirmed ∼17 dB/MBalun surface-current attenuation. Thermal tests indicated temperature decreases of 5.9 °C in the MBalun-equipped guidewire tip. Both devices allowed rapid vascular navigation resulting from good torquability and MR-Tracking visibility. CONCLUSION: MBaluns increased device diameter by 20%, relative to conventional devices, providing a spatially-efficient means to prevent heating during MRI. SIGNIFICANCE: MBaluns allow use of long metallic components, which improves mechanical performance in active MR-guided interventional devices.


Assuntos
Imageamento por Ressonância Magnética , Ondas de Rádio , Animais , Catéteres , Eletrofisiologia , Desenho de Equipamento , Imagens de Fantasmas , Suínos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...