AN IMPACT-BASED PIEZOELECTRIC ENERGY HARVESTER UTILIZING SPHERICAL MASS COLLISION PHENOMENON

The base-excitation piezoelectric energy harvesters have been vastly investigated under periodic base excitation as a conventional method. However, the waveforms of environment’s vibrations are mostly non-harmonic low-frequency periodic signals that reduce the efficiency of the harmonic-based resonance harvester. This study presents an alternative piezoelectric energy generation, the impact-based piezoelectric energy harvester concept rather than the typical harmonic-based one. The harvester benefits from impact excitation, leading to higher frequencies around the harvester’s natural frequencies. The impact concept is utilized for energy harvesting based on contact between a piezoelectric patch and a miniatured spherical mass. An experimental study was carried out to evaluate the effects of impact velocity and boundary condition on the dynamic behavior and power generation of the piezoelectric energy harvester. Moreover, a finite element model implemented a feasible framework to investigate the output power of the energy harvester under various impact forces. The results demonstrated μJ-scale energy generation by a single impact, indicating great energy generation possibilities for ultra-low-frequencies. The results also indicated that the boundary condition plays a critical role in energy harvesting, affecting the probability of voltage cancelation phenomenon occurrence. It was shown that the optimal boundary condition decreases the negative effects of voltage cancelation to improve the performance of the impact-based energy harvester

Marine <i>n</i>-3 PUFA, heart rate variability and ventricular arrhythmias in patients on chronic dialysis:a cross-sectional study

AbstractMarine n-3 PUFA may improve autonomic dysfunction by an increase in heart rate variability (HRV) and may reduce the risk of malignant ventricular arrhythmias. Only a few smaller studies have examined such effects in patients on chronic dialysis, who often have autonomic dysfunction and a high risk of sudden cardiac death, which accounts for almost 30 % of all deaths. This cross-sectional study investigated the association between the plasma phospholipid content of n-3 PUFA and 24-h HRV or ventricular arrhythmias in patients on chronic dialysis. A 48-h Holter monitoring was performed on 169 patients on in-centre dialysis (83 %), home haemodialysis (10 %) or peritoneal dialysis (7 %) obtaining data on arrhythmias (n 152) and 24-h HRV (n 135). The mean overall HRV (standard deviation of normal intervals (SDNN)) was low and 71 % had a reduced overall HRV (SDNN&lt;100 ms) indicating autonomic dysfunction. No significant associations between plasma phospholipid content of total marine n-3 PUFA, EPA (22 : 5n-3) or DHA (22 : 6n-3) and time-domain or frequency-domain HRV were detected in crude or adjusted linear regression analysis. However, a higher plasma phospholipid content of DHA was associated with a significantly lower proportion of patients with ventricular tachycardia (higher DHA-tertile: 9 % v. lower DHA-tertile: 28 %, P=0·02). In conclusion, the content of marine n-3 PUFA in plasma phospholipids was not associated with 24-h HRV, but a higher plasma phospholipid content of DHA was associated with a lower occurrence of ventricular tachycardia suggesting an antiarrhythmic effect of marine n-3 PUFA in patients on chronic dialysis.</jats:p

Using the C₂HEST score for predicting postoperative atrial fibrillation after cardiac surgery: A report from the Western Denmark Heart Registry, the Danish National Patient Registry, and the Danish National Prescription Registry

ObjectivesNew-onset postoperative atrial fibrillation (POAF) is a common complication after cardiac surgery. A targeted approach is necessary for prophylactic handling of the complication. The authors tested the performance of the C2HEST score to predict POAF in patients undergoing cardiac surgery.DesignRegister-based cohort study.SettingThree cardiothoracic centers.ParticipantsAll adult patients undergoing cardiac surgery in Western Denmark between January 1, 2010, and December 31, 2018, were included. Data on patient comorbidities before surgery were obtained from the Western Denmark Heart Registry, the Danish National Patient Registry, and the Danish National Prescription Registry.InterventionsThe C2HEST score (C2: Coronary Artery Disease/Chronic Obstructive Pulmonary Disease [1 point each]; H: Hypertension; E: Elderly [Age ≥75, 2 points]; S: Systolic Heart Failure [2 points]; T: Thyroid disease [hyperthyroidism]) was calculated for each patient. The primary outcome was POAF within the primary hospital stay. The C2HEST score's discriminative ability was evaluated and compared with an age-stratified version (mC2HEST) as well as 2 validated clinical risk models (CHADS2 and CHA2DS2-VASc).Measurements and main resultsAmong the 14,279 patients included, 4,298 (30.1%) developed POAF. The C2HEST score's performance was not significantly better than the CHADS2 and CHA2DS2-VASc scores (area under the curve [AUC] 0.553 [95% confidence interval {CI} 0.543; 0.563] v 0.543 [95% CI 0.535; 0.552] and 0.565 [95% CI 0.555; 0.574], respectively). The age-modified (mC2HEST) score showed only modest improvement in the risk model, with an AUC of 0.580 (95% CI 0.570; 0.590).ConclusionThe discriminative ability of the C2HEST score, measured by the AUC, was limited in this population, and was not proven to be superior to the CHADS2, CHA2DS2-VASc, and mC2HEST scores in predicting POAF after cardiac surgery

Non-invasive estimation of QLV from the standard 12-lead ECG in patients with left bundle branch block

Background: Cardiac resynchronization therapy (CRT) is a treatment for patients with heart failure and electrical dyssynchrony, i.e., left bundle branch block (LBBB) ECG pattern. CRT resynchronizes ventricular contraction with a right ventricle (RV) and a left ventricle (LV) pacemaker lead. Positioning the LV lead in the latest electrically activated region (measured from Q wave onset in the ECG to LV sensing by the left pacemaker electrode [QLV]) is associated with favorable outcome. However, optimal LV lead placement is limited by coronary venous anatomy and the inability to measure QLV non-invasively before implantation. We propose a novel non-invasive method for estimating QLV in sinus-rhythm from the standard 12-lead ECG. Methods: We obtained 12-lead ECG, LV electrograms and LV lead position in a standard LV 17-segment model from procedural recordings from 135 standard CRT recipients. QLV duration was measured post-operatively. Using a generic heart geometry and corresponding forward model for ECG computation, the electrical activation pattern of the heart was fitted to best match the 12-lead ECG in an iterative optimization procedure. This procedure initialized six activation sites associated with the His-Purkinje system. The initial timing of each site was based on the directions of the vectorcardiogram (VCG). Timing and position of the sites were then changed iteratively to improve the match between simulated and measured ECG. Noninvasive estimation of QLV was done by calculating the time difference between Q-onset on the computed ECG and the activation time corresponding to centroidal epicardial activation time of the segment where the LV electrode is positioned. The estimated QLV was compared to the measured QLV. Further, the distance between the actual LV position and the estimated LV position was computed from the generic ventricular model. Results: On average there was no difference between QLV measured from procedural recordings and non-invasive estimation of QLV ( [Formula: see text] ). Median distance between actual LV pacing site and the estimated pacing site was 18.6 mm (IQR 17.3 mm). Conclusion: Using the standard 12-lead ECG and a generic heart model it is possible to accurately estimate QLV. This method may potentially be used to support patient selection, optimize implant procedures, and to simulate optimal stimulation parameters prior to pacemaker implantation