Circulation
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Comparative Study
99mTc-HL91. Effects of low flow and hypoxia on a new ischemia-avid myocardial imaging agent.
99mTc-HL91 is a potential imaging agent that has demonstrated increased uptake in hypoxic tumor cells. The purpose of this study was to determine if 99mTc-HL91 demonstrates increased uptake and retention in ischemic and hypoxic myocardium. ⋯ This study introduces a new myocardial "hot spot" imaging agent, 99mTc-HL91. This agent demonstrates increased myocardial uptake and retention in hypoxic and low-flow ischemic models. Further in vivo imaging studies are warranted to determine the clinical potential of this agent.
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Comparative Study Clinical Trial Controlled Clinical Trial
Defibrillation efficacy of commercially available biphasic impulses in humans. Importance of negative-phase peak voltage.
Recent studies have shown that specifically shaped biphasic waveforms can lower energy requirements for ventricular defibrillation. We prospectively compared the defibrillation efficacy of three different biphasic wave shapes incorporated in three commercially available implantable defibrillators. The results led to the development of a second protocol in which the importance of negative-phase peak voltage and duration was investigated. ⋯ Our results suggest that specifically shaped biphasic waveforms delivered from commercially available devices can affect energy requirements for defibrillation. More importantly, the amplitude of the P2 peak voltage may be a more critical determinant than the P2 duration for defibrillation success of biphasic waveforms in humans.
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Central aortic pressures and waveform convey important information about cardiovascular status, but direct measurements are invasive. Peripheral pressures can be measured noninvasively, and although they often differ substantially from central pressures, they may be mathematically transformed to approximate the latter. We tested this approach, examining intersubject and intrasubject variability and the validity of using a single averaged transformation, which would enhance its applicability. ⋯ Central aortic pressures can be accurately estimated from radial tonometry with the use of a generalized TF. The reconstructed waveform can provide arterial compliance estimates but may underestimate the augmentation index because the latter requires greater fidelity reproduction of the wave contour.