46 research outputs found
Circadian modulation on T-wave alternans activity in chronic heart failure patients
No full textConference paper: Computing in Cardiology 2015; 42:845-848. Alba Martín-Yebra, Enrico G Caiani, Pablo Laguna, Violeta Monasterio, Juan Pablo Martíne
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
No full textIt 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
Ultra-short-term heart rate variability analysis on accelerometric signals from mobile phone
No full textThe 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
No full textWeightlessness and Cardiac Rhythm Disorders: Current Knowledge from Space Flight and Bed-Rest Studies
No full textIsolatedepisodesofheartrhythmdisordershavebeenreportedduring40yearsofspaceflight,triggeringresearchtoevaluatetheriskofdevelopinglife-threateningarrhythmiasinducedbyprolongedexposuretoweightlessness.Infact,theseeventscouldcompromiseastronautperformanceduringexploratorymissions,aswellasposeatrisktheastronauthealth,duetolimitedoptionsofcareonboardtheInternationalSpaceStation.Startingfromoriginalobservations,thisminireviewwillexplorethelatestresearchinthisfield,consideringresultsobtainedbothduringspaceflightandonEarth,thelatterbysimulatinglong-termexposuretomicrogravitybyhead-downbedrestmaneuverinordertoelicitcardiovasculardeconditioningonnormalvolunteers
Ventricular repolarization changes driven by deconditioning after 21-days of head-down bed-rest
No full text
Beat-to-beat heart rate detection by smartphone's accelerometers: Validation with ECG
No full textMobile phones offer the possibility to monitor and track health parameters. Our aim was to test the feasibility and accuracy of measuring beat-to-beat heart rate using smartphone accelerometers by recording the vibrations generated by the heart during its function and transmitted to the chest wall, i.e. the so-called seismocardiographic signal (SCG). Methods: 9 healthy male volunteers were studied in supine (SUP) and in standing (ST) posture. A smartphone (iPhone6, Apple) was positioned on the thorax (POS1) to acquire SCG signal. While supine, a second smartphone was positioned on the navel (POS2). The SCG signal was recorded for 3 minutes during spontaneous respiration, synchronous with 3-leads ECG. Using a fully automated algorithm based on amplitude thresholding after rectification, the characteristic peak of the SCG signal (IVC) was detected and used to compute beat-to-beat heart duration, to be compared with the corresponding RR intervals extracted from the ECG. Results: A 100% feasibility of the approach resulted for POS1 in SUP, while 89% in POS2, and 78% for POS1 in ST. In supine, for each smartphones' position, the automated algorithm correctly identified the cardiac beats with >98% accuracy. Linear correlation (r2) with RR was very high (>0.98) in each posture and position, with no bias and narrow limits of agreement. Conclusions: The obtained results proved the feasibility of the proposed approach and the robustness of the applied algorithm in measuring the beat-to-beat heart rate from smartphone-derived SCG, with high accuracy compared to conventional ECG-derived measure
