Spatiotemporally Controlled Cardiac Conduction Block Using High-Frequency Electrical Stimulation

Background: Methods for the electrical inhibition of cardiac excitation have long been sought to control excitability and conduction, but to date remain largely impractical. High-amplitude alternating current (AC) stimulation has been known to extend cardiac action potentials (APs), and has been recently exploited to terminate reentrant arrhythmias by producing reversible conduction blocks. Yet, low-amplitude currents at similar frequencies have been shown to entrain cardiac tissues by generation of repetitive APs, leading in some cases to ventricular fibrillation and hemodynamic collapse in vivo. Therefore, an inhibition method that does not lead to entrainment – irrespective of the stimulation amplitude (bound to fluctuate in an in vivo setting) – is highly desirable. Methodology/Principal Findings: We investigated the effects of broader amplitude and frequency ranges on the inhibitory effects of extracellular AC stimulation on HL-1 cardiomyocytes cultured on microelectrode arrays, using both sinusoidal and square waveforms. Our results indicate that, at sufficiently high frequencies, cardiac tissue exhibits a binary response to stimulus amplitude with either prolonged APs or no effect, thereby effectively avoiding the risks of entrainment by repetitive firing observed at lower frequencies. We further demonstrate the ability to precisely define reversible local conduction blocks in beating cultures without influencing the propagation activity in non-blocked areas. The conduction blocks were spatiotemporally controlled by electrode geometry and stimuli duration, respectively, and sustainable for long durations (300 s). Conclusion/Significance: Inhibition of cardiac excitation induced by high-frequency AC stimulation exhibits a binary response to amplitude above a threshold frequency, enabling the generation of reversible conduction blocks without the risks of entrainment. This inhibition method could yield novel approaches for arrhythmia modeling in vitro, as well as safer and more efficacious tools for in vivo cardiac mapping and radio-frequency ablation guidance applications

Polypharmacy and its related factors among the elderly population in Kashan, Iran during 2011-2012

Background: Elderly individuals use more drug and they are at a higher risk of polypharmacy complications. This study aimed to evaluate the polypharmacy and its related factors among the elderly group in Kashan (Iran) during 2011-2012. Materials and Methods: In a cross-sectional study, 360 elderly people over 60 years old were selected using the cluster-randomized method. Data were gathered based on a questionnaire contained demographic variables (e.g. age, sex, marital status, income status, level of education, hospitalization history) and main variables (e.g. the name and number of medications used, duration of use, the number of physicians prescribed drug, the number of potentially inappropriate medication use in elderly due to their background diseases and the number of potentially inappropriate medication used in an elderly group using the 2000 Beers criteria.Results: A total of 308 (88) elderly (170 women and 138 men) had taken at least one medication during the interview. Mean and range of age of the elderly were 70.8± 7.9 and 60-100 years, respectively. Mean and range of medications were 6.2±3.53 and 1-23 respectively had taken by among individuals older than age 60 in kashan. Prevalence of polypharmacy in related population was 54.5 (167 cases) and 66 elderly people (21.4) at least took one inappropriate drug among their medications. Conclusion: Polypharmacy among the Kashan elderly population is relatively high. Therefore, to decrease the number of prescribed medications and their related side effects in elderly individuals, applying up to date criteria in prescribing the medication for aged population is recommended

Blood pressure variability and plasma Alzheimer’s disease biomarkers in older adults

Blood pressure variability is an emerging risk factor for Alzheimer’s disease in older adults, independent of average blood pressure levels. Growing evidence suggests increased blood pressure variability is linked to Alzheimer’s disease pathophysiology indexed by cerebrospinal fluid and positron emission tomography markers, but relationships with plasma Alzheimer’s disease markers have not been investigated. In this cross-sectional study of 54 community-dwelling older adults (aged 55–88, mean age 69.9 [8.2 SD]), elevated blood pressure variability over 5 min was associated with lower levels of plasma Aβ1–42 (standardized ß = − 0.36 [95% CI − 0.61, − 0.12]; p = 0.005; adjusted R2 = 0.28) and Aβ1–42: Aβ1–40 ratio (ß = − 0.49 [95% CI − 0.71, − 0.22]; p < 0.001; adjusted R2 = 0.28), and higher levels of total tau (ß = 0.27 [95% CI 0.01, 0.54]; p = 0.04; adjusted R2 = 0.19) and Ptau181:Aβ1–42 ratio (ß = 0.26 [95% CI 0.02, 0.51]; p = 0.04; adjusted R2 = 0.22). Findings suggest higher blood pressure variability is linked to plasma biomarkers of increased Alzheimer’s disease pathophysiology. © 2022, The Author(s).Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]