1,721,098 research outputs found
Optical vibrocardiography for non contact monitoring of the cardiac activity: Comparison with other physiological signals
No full textNon contact cardiac monitoring from carotid artery using optical vibrocardiography
No full textThe aim of the present work is to establish a protocol for monitoring the cardiac activity measuring the skin surface vibrations of the main neck vessels, caused by vascular wall motion in carotid artery. The method is based on the optical recording of the movements of the neck by means of laser Doppler interferometry.
The ECG signal and the velocity of vibration of the skin in correspondence of the carotid artery (named optical vibrocardiography: VCG) have been simultaneously recorded on five healthy subjects. Standard heart rate variability tests have been carried out. The capability of VCG signals to be used as a surrogate of the ECG in assessing both cardiac rate and heart rate variability (HRV) has been tested using time and spectral descriptors, and specific statistical analysis. Mean differences have been found lower than 3.13%.
Optical vibrocardiography might be a simple approach to the clinical practice of cardiovascular screening, in particular in harsh environment, such as MR clinical practice, where ECG recordings are corrupted by artefacts and ECG cables might represent an hazard for the patients
Optical vibrocardiography: a novel tool for optical monitoring of cardiac activity
No full textWe present an optical non-contact method for heart beat monitoring, based on the measurement of chest wall movements induced by the pumping action of the heart, which is eligible as a surrogate of electrocardiogram (ECG) in assessing both cardiac rate and heart rate variability (HRV). The method is based on the optical recording of the movements of the chest wall by means of laser Doppler interferometry. To this aim, the ECG signal and the velocity of vibration of the chest wall, named optical vibrocardiography (VCG), were simultaneously recorded on 10 subjects. The time series built from the sequences of consecutive R waves (on ECG) and vibrocardiographic (VV) intervals were compared in terms of heart rate (HR). To evaluate the ability of VCG signals as quantitative marker of the autonomic activity, HRV descriptors were also calculated on both ECG and VCG time series. HR and HRV indices obtained from the proposed method agreed with the rate derived from ECG recordings (mean percent difference <3.1%). Our comparison concludes that optical VCG provides a reliable assessment of HR and HRV analysis, with no statistical differences in term of gender are present. Optical VCG appears promising as non-contact method to monitor the cardiac activity under specific conditions, e.g., in magnetic resonance environment, or to reduce exposure risks to workers subjected to hazardous conditions. The technique may be used also to monitor subjects, e.g., severely burned, for which contact with the skin needs to be minimized
Searching into the invisible: Hunting for present and future ischaemia with fractional flow reserve pullback and wall shear stress
Full text linkTranscatheter Aortic Valve with Embolic Filter: Experiments and Simulations
No full textCerebrovascular events are one of the most critical complications following transcatheter aortic valve replacement. The majority of these events are associated to calcium debris generated by the stenotic valve manipulation. Embolic protection devices were accordingly designed to reduce the risk of these adverse events. Within this context, an innovative transcatheter aortic valve with embolic filter is proposed, which is temporarily released in the ascending aorta, and avoids severe regurgitation while treating the native valve before the replacement. Experimental tests and computational analyses were conducted on a prototype of the Nitinol frame of the device. The frame integrity throughout the clinical procedure was assessed, radial force curves were experimentally measured and used to calibrate a finite element model
Radial basis functions for the interpolation of hemodynamics flow pattern: A quantitative analysis
No full textLaser Doppler vibrometry in non contact monitoring of the heart beat
No full textOptical techniques for vibration measurements, due their non-contact nature, could be an alternative diagnostic tool to be tested in clinic fields. The purpose of this study is to present a non-contact measurement techinique to monitor the heart rate (HR) and follow vital signs
On the unexplored relationship between kinetic energy and helicity in prosthetic heart valves hemodynamics
No full textSurgical replacement of the diseased aortic valve consists in the implantation of a prosthetic heart valve (PHV), either biological or mechanical (BHV and MHV, respectively). Risks of complication have been linked to high levels of turbulence and consequent energy dissipation induced by the PHV. As helicity is an emergent feature in cardiovascular flows, deemed to impact blood flow organization, stability and the turbulent energy cascade, in this study the interplay between the production/decay of phase-averaged and turbulent kinetic energy and helicity in the presence of a BHV or MHV was investigated. Technically, direct numerical simulations of the coupled fluid–structure interaction problem were conducted using the immersed boundary method. A quantitative description of phase-averaged and fluctuating helicity, mean and turbulent kinetic energy was adopted to explore the nature of the kinetic energy vs. helicity relationship. A clear PHV-type dependence of the helicity production/decay in the downstream hemodynamics emerged, with MHVs hemodynamics presenting larger phase-averaged and fluctuating helicity than BHVs. For both heart valve types strong linear correlations were found between volume-average kinetic energy and helicity when based on phase-averaged or fluctuating quantities (Pearson's correlation coefficient r up to 0.98, p<0.001). The generation of turbulent kinetic energy or fluctuating helicity for both heart valve types was delayed with respect to the inflow waveform or the generation of both mean kinetic energy and phase-averaged helicity (up to 5.4% of the cardiac cycle). The exploration of the link between helical and turbulent hemodynamic flow features expands the current understanding of the PHV hemodynamic features associated with clinical complications, potentially translating into improvements of the design of PHVs
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