Axenic culture of Brachionus plicatilis using antibiotics

The rotifer Brachionus plicatilis culture is composed of complex microcosms including bacteria, protozoans, algae, and fungi. Previous studies reported methods to establish axenic rotifer cultures, but further refinement of these techniques is needed, for molecular biological research which requires pure culture to isolate nucleic acids from rotifers only. In order to render rotifer culture axenic, we tested five antibiotics: ampicillin (Amp), chloramphenicol (Cp), kanamycin (Km), nalidixic acid (Na), and streptomycin (Sm) at 30-100 μg/ml. Except for Cp, which reduces rotifer reproduction, all other antibiotics at the tested concentrations did not affect rotifer reproduction or show any toxic effects. A rotifer disinfection method was finally established by treating the resting eggs with 0.25% (w/v) sodium hypochlorite (NaOCl) for 3 min, washing with sterilized sea water, and then exposing the neonates to an Amp, Km, Na, and Sm mixture. Using four nutrient media, we confirmed that this protocol renders the rotifer culture bacterial and fungus free. The axenic rotifer culture generated here is useful not only for genetic analysis of Brachionus plicatilis, but for studying the rotifer life cycle without bacterial influence

Current status of atrial pacing algorithms for the prevention of atrial fibrillation: Should algorithms be used?

Since the development of an atrial pacing algorithm for preventing atrial fibrillation (AF), approximately 20 years ago, many clinical trials have demonstrated the effectiveness of atrial pacing with respect to AF prevention. Nevertheless, the actual effectiveness of AF suppression via atrial pacing remains under debate, and no definitive conclusion has been reached. The AF suppression algorithms embedded in pacemakers have not demonstrated an unequivocal clinical efficacy that would support changing of the guidelines to recommend such algorithms. In this review of studies conducted since 2006, we discuss the efficacies of these AF suppression algorithms and their usefulness in patients requiring pacemaker implantation

Shortening of intraventricular conduction time with rapid ventricular pacing

Background: Supernormal conduction (SNC) of the human ventricular myocardium has been reported, but its mechanism remains controversial. Methods: We recorded monophasic action potentials during rapid ventricular pacing from the right ventricular endocardium in 24 patients with supraventricular tachyarrhythmias who underwent catheter ablation. Results: In 7 of 24 patients, shortening of the QRS duration was observed at a pacing cycle length ≤400 ms and lengthening of the QRS duration was observed in 3. Conclusions: Shortening of the QRS duration during rapid ventricular pacing was observed in the patients

Spatial and temporal variability of the complex fractionated atrial electrogram activity and dominant frequency in human atrial fibrillation

Background: The presence of complex fractionated atrial electrograms (CFAEs) and high dominant frequencies (DFs) during atrial fibrillation (AF) have been demonstrated to be related to AF maintenance. Therefore, sequential mapping of CFAEs and DFs have been used for target sites of AF ablation. However, such mapping strategies are valid only if the CFAEs and DFs are spatiotemporally stable during the mapping procedure. We obtained spatially stable multi-electrode recordings to assess the spatiotemporal stability of CFAEs and DFs. Methods: We recorded electrical activity during AF for 10 min with a 64-electrode basket catheter (48 bipole electrode pairs) placed in the left atrium in 36 patients with AF (paroxysmal AF [PAF], n=16; persistent AF [PerAF], n=20). The spatial and temporal distribution of the CFAEs (fractionation interval 8 Hz) at 1-min intervals for 10 min were compared for each of the 48 bipoles. Results: The baseline CFAEs were located at 68.5±14.0% (32.9±6.7) of the 48 bipoles; however, the high DF sites were fewer (9.6±8.6% [4.6±4.1 bipoles]). The CFAEs sites did not change significantly during the 10-min recording period (kappa statistic: 0.71±0.24); however, the high DF sites changed significantly (kappa statistic: 0.07±0.19). These spatiotemporal changes in the CFAEs and high DFs did not differ between patients with PAF and PerAF. Conclusions: Regardless of the AF type, CFAEs sites, but not high DF sites, showed a high degree of spatial and temporal stability

Analysis of the spatial and transmural dispersion of repolarization and late potentials derived using signal-averaged vector-projected 187-channel high-resolution electrocardiogram in patients with early repolarization pattern

Background: Electrophysiological characteristics of early repolarization syndrome (ERS), i.e., the spatial and transmural dispersion of ventricular repolarization and ventricular late potentials can be evaluated using a signal-averaged vector-projected 187-channel high-resolution electrocardiogram (187-ch SAVP-ECG). We investigated these characteristics as markers of ventricular fibrillation and sudden cardiac arrest in patients presenting with an ER pattern. Methods: The 187-ch SAVP-ECGs were recorded for 8 patients with idiopathic ventricular fibrillation associated with ERS (ERS patients), and 5 patients with an ER pattern without arrhythmic events (ER pattern patients). Results: The ER pattern was located in the inferior leads (n=7), lateral leads (n=1), or both inferior and lateral leads (n=5). The corrected RT(RTc) (peak point of the R wave − positive maximum peak of the first derivative of the T wave interval corrected using the Bazett formula) interval and T(peak-end)-c interval from the 187 channels were calculated. Late potentials were positive in 7 of 8 ERS patients and in 3 of 5ER pattern patients (P=0.25). The average RTc was shorter in patients with ERS (192.6±29.8 ms vs. 234.0±25.5 ms, P=0.04). However, average T(peak-end)-c interval did not differ between the 2 groups. Conclusion: Late ventricular potentials were common in ERS and ER pattern patients. Lethal arrhythmia in ERS patients appeared to be related to the relatively short average repolarization time rather than the spatial and transmural dispersion of repolarization

A case of cardiac sarcoidosis presenting with double tachycardia

Although the most feared cardiac manifestation in cardiac sarcoidosis is the onset of ventricular arrhythmia, some patients may present with supraventricular arrhythmias. We present a rare case of cardiac sarcoidosis associated with double tachycardia manifesting as atrial flutter and ventricular tachycardia

Wavefront direction and cycle length affect left atrial electrogram amplitude

Background: The relationship between atrial electrogram (EGM) characteristics in atrial fibrillation (AF) and those in sinus rhythm (SR) are generally unknown. The activation rate and direction may affect EGM characteristics. We examined characteristics of left atrial (LA) EGMs obtained during pacing from different sites. Methods: The study included 10 patients undergoing pulmonary vein isolation for AF. Atrial EGMs were recorded from a 64-pole basket catheter placed in the LA, and bipolar EGM amplitudes from the distal electrode pair (1–2) and proximal electrode pair (6–7) from 8 splines were averaged. The high right atrium (HRA), proximal coronary sinus (CSp), and distal coronary sinus (CSd) were paced at 600 ms and 300 ms. Results: When the LA voltage at SR was ≥1.5 mV, bipolar voltages of the HRA were greater than those of the CSp, which were greater than those of the CSd, regardless of the pacing cycle length. The shorter pacing cycle length resulted in a reduction of the LA EGM voltage at sites of SR voltage ≥1.5 mV, but no significant difference was seen at sites where the SR EGM amplitude was between >0.5 and <1.5 mV. No significant differences were seen in intra-basket conduction times between pacing cycle lengths of 600 ms and 300 ms at any pacing site. Conclusion: The rate and direction-dependent reduction of the amplitude of atrial EGMs may explain, in part, the voltage discordance during SR and AF

Spatial and transmural repolarization, and dispersion of repolarization and late potentials evaluated using signal-averaged vector-projected 187-channel high-resolution electrocardiogram in Brugada syndrome

Background: Vector-projected 187-channel electrocardiograms (ECGs) were recorded in 45 patients with a Brugada-type ECG to evaluate spatial and transmural repolarization and dispersion of action potential duration in Brugada syndrome (BS). Methods: Corrected recovery time (RT-c, R wave peak to the first positive maximum derivative of the T wave with Bazett correction) and RT-c dispersion were calculated. The corrected T peak-end interval (T(p-e)-c, T wave peak to the end of the T wave with Bazett correction) and T(p-e)-c dispersion were calculated. Results: RT-c dispersion and T(p-e)-c interval were longer in patients with a type 1 ECG, but there was no significant difference in Tp-e dispersion between patients with a type 1 and those with a type 2/3 ECG. No significant correlation was noted between RT-c dispersion, T(p-e)-c dispersion, and symptoms. Late potentials (P=0.023) and a family history of sudden cardiac death (P=0.0017) were correlated with symptoms. Conclusions: Spatial dispersion of repolarization may constitute the electrocardiographic pattern of the Brugada type ECG and conduction disturbance in addition to repolarization abnormality may contribute to the development of malignant ventricular tachyarrhythmias