1,720,985 research outputs found
OPERATION OF IMPLANTABLE MEDICAL DEVICE SYSTEM TO DETERMINE ATRIAL FIBRILLATION RECURRENCE LIKELIHOOD
No full textIn some examples a medical system comprising an implantable medical device and processing circuitry. The implantable medical device is configured to: sense a cardiac signal of a patient; detect a plurality of episodes of atrial fibrillation (AF) over a time period based on the cardiac signal; and stare AF episode data for the plurality of episodes of AF detected over the time period. The processing circuitry configured to: determine, based on the AF episode data, a first parameter representing a prevalence over the time of AF episodes and a second parameter representing a degree of temporal clustering of the AF episodes; determine a likelihood of recurrence of AF after an AF treatment procedure based on the first parameter and the second parameter; and transmit the likelihood to a computing device for presentation to a clinician
Evaluation of T-wave alternans activity under stress conditions after 5 d and 21 d of sedentary head-down bed rest
Get PDFIt is well known that prolonged microgravity leads to cardiovascular deconditioning, inducing significant changes in autonomic control of the cardiovascular system. This may adversely influence cardiac repolarization, and provoke cardiac rhythm disturbances. T-wave alternans (TWA), reflecting temporal and spatial repolarization heterogeneity, could be affected. The aim of this work was to test the hypothesis that 5 d and 21 d head-down (-6°) bed rest (HDBR) increases TWA, thus suggesting a higher underlying electrical instability and related arrhythmogenic risk.Forty-four healthy male volunteers were enrolled in the experiments as part of the European Space Agency's HDBR studies. High-fidelity ECG was recorded during orthostatic tolerance (OT) and aerobic power (AP) tests, before (PRE) and after HDBR (POST). A multilead scheme for TWA amplitude estimation was used, where non-normalized and T-wave amplitude normalized TWA indices were computed. In addition, spectral analysis of heart rate variability during OT was assessed.Both 5 d and 21 d HDBR induced a reduction in orthostatic tolerance time (OTT), as well as a decrease in maximal oxygen uptake and reserve capacity, thus suggesting cardiovascular deconditioning. However, TWA indices were found not to increase. Interestingly, subjects with lower OTT after 5 d HDBR also showed higher TWA during recovery after OT testing, associated with unbalanced sympathovagal response, even before the HDBR. In contrast with previous observations, augmented ventricular heterogeneity related to 5 d and 21 d HDBR was not sufficient to increase TWA under stress conditions
Ventricular repolarization changes driven by deconditioning after 21-days of head-down bed-rest
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Ultra-short-term heart rate variability analysis on accelerometric signals from mobile phone
Get PDFThe feasibility of measuring stress-related parameters by ultra-short variability (USV) indices calculated from the ballistocardiographic signal acquired by the mobile phone accelerometers (m-BCG) positioned on the navel was tested, and its accuracy compared with gold standard ECG-derived indices. The m-BCG was acquired in six healthy volunteers while in supine position, during spontaneous breathing (CTRL) and during 1 minute of mental stress (MS) induced by arithmetic serial subtraction task. Beat occurrence was independently and automatically extracted from both ECG and m-BCG signals, to compute USV parameters in 30 s intervals, during both the CTRL and MS. Linear regression and Bland-Altman analyses between RR series and m-BCG derived beat-to-beat measurements (JJ series) showed very high correlation (r2>0.97), no bias, and narrow limits of agreement (±2SD < ±34 ms) for both CTRL and MS. A significant decrease (p=0.03 Wilcoxon test) in beat duration, SDNN and RMSSD was found in MS compared to CTRL, in both RR and JJ variability series, underlying the ability of m-BCG in capturing the decrease in parasympathetic tone in agreement with the induced stimulus
T-wave alternans and autonomic nervous system activity during orthostatic stress after 5 days of head-down bed-rest
Get PDFIndex of T-wave variation as a predictor of sudden cardiac death in chronic heart failure patients with atrial fibrillation
Get PDFChronic heart failure (CHF) and atrial fibrillation (AF) are worldwide leading causes of morbidity and mortality in elders, a large part due to sudden cardiac deaths (SCD). The high irregularity of ventricular response in AF patients makes the use of standard SCD-risk markers inappropriate in this target population. The aim of this study was twofold: i) to propose a new index, suitable for AF patients, able to quantify ventricular repolarization changes; and ii) to evaluate its prognostic value in a CHF population with AF. Holter ECG recordings from 176 consecutive CHF patients with AF (22 SCD) were analyzed. The index of T-wave variation (ITV), quantifying the average T-wave changes in pairs of consecutive beats under stable rhythm conditions, was computed using a fully-automatic method. Survival analysis was performed considering SCD as an independent endpoint. ITVwas higher for SCD than non-SCD victims (median (Q1;Q3): 24.9 (14.4;85.4) Î1⁄4V vs 17.1 (11.3;28.2) Î1⁄4V, p=0.06). In a survival analysis where the threshold was set on the third quartile of ITVvalues, ITV(+) outcome was successfully associated to SCD (Hazard Ratio (CI):3.22 (1.36, 7.58)per Î1⁄4V, p=0.008). In conclusion, we show in this work that Ijy stratifies CHF patients with AF according to their risk of SCD, with larger ITVassociated to lower survival probability
Weightlessness and Cardiac Rhythm Disorders: Current Knowledge from Space Flight and Bed-Rest Studies
Get PDFIsolatedepisodesofheartrhythmdisordershavebeenreportedduring40yearsofspaceflight,triggeringresearchtoevaluatetheriskofdevelopinglife-threateningarrhythmiasinducedbyprolongedexposuretoweightlessness.Infact,theseeventscouldcompromiseastronautperformanceduringexploratorymissions,aswellasposeatrisktheastronauthealth,duetolimitedoptionsofcareonboardtheInternationalSpaceStation.Startingfromoriginalobservations,thisminireviewwillexplorethelatestresearchinthisfield,consideringresultsobtainedbothduringspaceflightandonEarth,thelatterbysimulatinglong-termexposuretomicrogravitybyhead-downbedrestmaneuverinordertoelicitcardiovasculardeconditioningonnormalvolunteers
Sviluppo di un algoritmo per l'estrazione dei punti fiduciari da segnale ballistocardiografico acquisito con piattaforma di forza
No full textLAUREA MAGISTRALENegli ultimi anni, inoltre, sono state effettuate acquisizioni del segnale BCG in assenza di gravità in modo da valutare le sole accelerazioni del corpo dovute allo spostamento della massa di sangue sotto condizioni isotrope e per studiare la modifica delle proprietà fisiologiche del cuore sottoposto alla assenza di gravità. Questo lavoro di tesi fa parte di una ricerca ben più vasta che è volta a studiare in modo completamente non invasivo gli effetti della microgravità sulla meccanica cardiaca tramite l'analisi del segnale BCG. Questo lavoro ha l'obiettivo di caratterizzare il segnale BCG registrato a terra, in modo da valutare le informazioni che effettivamente si possono ricavare e di creare una base di dati fruibili per il confronto con i dati acquisiti in microgravità.
A tale fine è stato predisposto un opportuno protocollo sperimentale per poter acquisire contemporaneamente il segnale BCG, tramite pedana di forza, ed il segnale ECG, utilizzato come riferimento.In the last years, BCG was also acquired under zero gravity (0G) in order to evaluate the acceleration of the body under isotropic conditions and to investigate the physiological changes of the heart under sustained 0G. This master’s thesis is part of a research project aimed at the evaluation of microgravity effects on cardiac mechanics through a non-invasive analysis of the BCG signal. We have performed a previous on-ground characterization of the BCG signal, with the aim of better understanding the 3D signal content and having available a new on-ground database, useful for comparing results with those obtained under microgravity conditions.
In order to do that, an appropriate experimental protocol to simultaneously acquire the BCG signal, using a force platform, and the electrocardiogram (ECG) signal (used as a reference) has been proposed
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