Search

Introduction: Multiple analysis techniques evaluate electrograms during atrial fibrillation (AF), but none have been established to guide catheter ablation. This study compares electrogram properties recorded from multiple right (RA) and left atrial (LA) sites. Methods: Multisite LA/RA mapping (281 ± 176/239 ± 166 sites/patient) was performed in 42 patients (30 males, age 63 ± 9 years) undergoing first (n = 32) or redo‐AF ablation (n = 10). All electrogram recordings were visually reviewed and artifactual signals were excluded leaving a total of 21 846 for analysis. Electrogram characteristics evaluated were cycle length (CL), amplitude, Shannon's entropy (ShEn), fractionation interval, dominant frequency, organizational index, and cycle length of most recurrent morphology (CLR) from morphology recurrence plot analysis. Results: Electrogram characteristics were correlated to each other. All pairwise comparisons were significant (p <.001) except for dominant frequency and CLR (p =.59), and amplitude and dominant frequency (p =.38). Only ShEn and fractionation interval demonstrated a strong negative correlation (r = −.94). All other pairwise comparisons were poor to moderately correlated. The relationships are highly conserved among patients, in the RA versus LA, and in those undergoing initial versus redo ablations. Antiarrhythmic drug therapy did not have a significant effect on electrogram characteristics, except minimum ShEn. Electrogram characteristics associated with ablation outcome were shorter minimum CLR, lower minimum ShEn, and longer mimimum CL. There was minimal overlap between the top 10 sites identified by one electrogram characteristic and the top 10 sites identified by the other 10 characteristics. Conclusion: Multiple techniques can be employed for electrogram analysis in AF. In this analysis of eight different electrogram characteristics, seven were poorly to moderately correlated and do not identify similar locations. Only some characteristics were predictive of ablation outcome. Further studies to consider electrogram properties, perhaps in combination, for categorizing and/or mapping AF are warranted. [ABSTRACT FROM AUTHOR]

The adoption of a holistic approach to root research, that is, one that takes into account all categories of root traits, from anatomy to root morphology, physiology and architecture, as well as interactions with the rhizosphere microbiota, was emphasised as a crucial step in facing the challenges posed by global change. Keywords: Ambassador Program; ISRR11; rhizosphere; root phenotyping; root traits; Rooting2021; roots EN Ambassador Program ISRR11 rhizosphere root phenotyping root traits Rooting2021 roots 2149 2154 6 08/22/22 20220915 NES 220915 Emerging frontiers: root and rhizosphere research in the context of global environmental chan... Natural ecosystems and agricultural production have been threatened by multifaceted global environmental changes. ISRR11, rhizosphere, root traits, Ambassador Program, root phenotyping, Rooting2021, roots Root biology never sleeps: 11th Symposium of the International Society of Root Research (ISRR11) and the 9th International Symposium on Root Development (Rooting2021), 24-28 May 2021. [Extracted from the article]

Oil-laden (OL) foams could serve an important role in various processes, particularly in enhanced oil recovery; however, OL foams are less studied than aqueous foams. In this work, the formation and stability of OL foam, by either sodium dodecyl sulphate (SDS) or Triton X-100 (TX-100) in water-pentane mixture, was evaluated. We first constructed a diagram of good and poor foaminess against pentane content in the mixture and aqueous surfactant concentration. It was shown that surfactant onset concentration for good foaming was increased with increasing pentane content. The result was fitted using a mathematical model that considers the surfactant dilution and adsorption effects by pentane. Foam height decay profiles were also monitored. Results indicated that SDS resulted in a more stable foam than TX-100 at the same critical micelle concentration (CMC). Depending on surfactant concentration, OL foams exhibited strikingly different stability behaviours. Pentane acted as an anti-foamer at surfactant concentrations at the CMC or lower. However, very high foam stability was displayed at high surfactant concentration (e.g., 3x CMC) and medium to high pentane contents; this is a result contradictory to the predication of entering, spreading, and bridging coefficients in the classic theory. The stable OL foams of this study could be attractive to potential foam applications. [ABSTRACT FROM AUTHOR]

Summary: Root system architecture (RSA) influences the effectiveness of resources acquisition from soils but the genetic networks that control RSA remain largely unclear.We used rhizoboxes, X‐ray computed tomography, grafting, auxin transport measurements and hormone quantification to demonstrate that Arabidopsis and Medicago CEP (C‐TERMINALLY ENCODED PEPTIDE)‐CEP RECEPTOR signalling controls RSA, the gravitropic set‐point angle (GSA) of lateral roots (LRs), auxin levels and auxin transport.We showed that soil‐grown Arabidopsis and Medicago CEP receptor mutants have a narrower RSA, which results from a steeper LR GSA. Grafting showed that CEPR1 in the shoot controls GSA. CEP receptor mutants exhibited an increase in rootward auxin transport and elevated shoot auxin levels. Consistently, the application of auxin to wild‐type shoots induced a steeper GSA and auxin transport inhibitors counteracted the CEP receptor mutant's steep GSA phenotype. Concordantly, CEP peptides increased GSA and inhibited rootward auxin transport in wild‐type but not in CEP receptor mutants.The results indicated that CEP–CEP receptor‐dependent signalling outputs in Arabidopsis and Medicago control overall RSA, LR GSA, shoot auxin levels and rootward auxin transport. We propose that manipulating CEP signalling strength or CEP receptor downstream targets may provide means to alter RSA. [ABSTRACT FROM AUTHOR]

Surface ECG f Wave Analysis X Introduction Dominant frequency (DF) analysis of electrocardiograms (ECGs) from patients with paroxysmal (PAF) and persistent (PeAF) atrial fibrillation has identified higher DFs in PeAF. We therefore hypothesized that among patients initially presenting to the emergency department (ED) with new onset AF, surface ECG features could differentiate PeAF from PAF. Methods and Results Initial 12-lead ECGs from patients presenting to the ED with a first episode of symptomatic AF were analyzed. Following QRS-T subtraction, fast Fourier transform (FFT) analysis of the AF fibrillatory waves was performed to measure DF and organization index (OI). Median DF of all leads and the DF in the lead with maximum OI were determined. Maximum f wave amplitude and vector magnitudes were measured. One hundred sixty-one patients (age 59 ± 16 years, 68% men) were included in this analysis, of whom 96 (58%) spontaneously converted to sinus rhythm within 7 days (PAF group). The remaining 65 patients underwent cardioversion or remained in AF (PeAF group). ECG features (DF, OI, f wave amplitude, and vector magnitude) did not differ among PAF and PeAF patients. Conclusions ECG features (DF, OI, amplitude, vector magnitude) do not differ among patients with PAF versus PeAF when the ECGs are obtained at the initial onset of symptoms. Thus, prior data showing higher DF in PeAF likely reflect electrophysiologic remodeling rather than a marker for any specific type of AF or extent of underlying substrate. [ABSTRACT FROM AUTHOR]

Dofetilide Effect on f Waves in AF Introduction The electrocardiogram (ECG) fibrillatory (f) wave characteristics in atrial fibrillation (AF) could provide important information regarding the efficacy of antiarrhythmic drug therapy. Methods and Results To measure the effects of dofetilide on the surface ECG f wave characteristics in patients with persistent AF, baseline and post-drug (2 hours after first dose and after multiple doses) ECGs in 31 patients with persistent AF admitted for dofetilide loading were evaluated. A QRST template subtraction algorithm was used to yield an atrial ECG. Fast Fourier transform analysis was performed to evaluate the maximum organizational index (OI), the dominant frequency (DF) in the lead with max OI, the median DF for all leads, and the vector magnitude f wave amplitude. Dofetilide reduced DF in the lead with the max OI (6.32 ± 0.98 Hz at baseline vs. 4.83 ± 0.63 Hz after final dose, P < 0.0001) and median DF (6.46 ± 0.87 Hz vs. 4.92 ± 0.62 Hz, P < 0.0001). Dofetilide also increased the maximum OI from 0.52 ± 0.11 at baseline to 0.59 ± 0.11 after final dose (P = 0.02). Of the 29 patients with long-term follow-up, the 22 (76%) with recurrent AF on dofetilide had a lower baseline DF in the lead with the max OI (6.01 ± 1.08 vs. 6.89 ± 0.46; P = 0.05). The change in DF after dofetilide did not correlate with the change in QTc interval. Conclusions The standard ECG can be used to assess atrial rate in AF. This may be useful to assess antiarrhythmic drug effects for treatment of AF. [ABSTRACT FROM AUTHOR]

Purpose: To use four-dimensional (4D) flow MRI to characterize and quantify 3D blood flow in the left atria (LA) of patients with a history of atrial fibrillation (AF). Materials and Methods: The 4D flow MRI was acquired in 19 volunteers (n = 9<30 years, n = 10>50 years) and 10 patients with AF (62 ± 9.6 years; n = 4 in persistent AF, n = 6 postintervention). The LA in each dataset was segmented, and intra-atrial blood flow velocity was quantified. Flow coherence was measured as the consistency of the net blood flow vector. Results: Quantification of atrial flow revealed significant differences in atrial hemodynamics between age groups. Postintervention AF patients had a mean blood flow of 0.22 ± 0.04 m/s, which was not significantly different than age-matched volunteers (0.21 ± 0.03 m/s). Patients with persistent AF had a mean blood flow of 0.13 ± 0.01 m/s, lower than AF patients in sinus rhythm (0.22 ± 0.04 m/s, P = 0.005), or age-matched volunteers (0.21 ± 0.03 m/s, P < 0.001). Flow coherence was significantly impaired in patients in AF. Conclusion: Flow-sensitive MRI shows that patients with a history of AF had global hemodynamics in the LA similar to those of age-matched volunteers. Additional studies with larger cohorts of AF patients and correlation with outcome are needed to further investigate the potential of atrial 4D flow MRI to flow patterns indicative of stroke risk in AF. J. Magn. Reson. Imaging 2013;38:580-587. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Baroreflex Response and AF Dominant Frequency. Introduction: Parasympathetic stimulation is known to promote atrial fibrillation (AF) through shortening of atrial refractory periods. We hypothesized that baroreflex-mediated parasympathetic stimulation via phenylephrine (PE) infusion would increase AF rate as measured by dominant frequency (DF). Methods and Results: The protocol was performed in 27 patients (24 M, 59 ± 1 years old) prior to AF ablation. For 10 patients in AF, PE was infused until systolic blood pressure increased ≥30 mmHg. Electrograms were recorded in the left atrium before and after PE. DFs of each recording were calculated offline. Atrial effective refractory periods (ERPs) were measured before and after PE in 11 patients who were in sinus rhythm during the procedure. DFs were also measured in 6 patients in AF before and after complete parasympathetic blockade with atropine (0.04 mg/kg). PE resulted in increased RR intervals during sinus rhythm (1,170 ± 77 to 1,282 ± 85 ms, P = 0.03) and AF (743 ± 32 to 826 ± 30 ms, P = 0.03), consistent with parasympathetic effect on the sinus and AV nodes, respectively. DFs were decreased by PE in the left atrium (6.2 ± 0.2 to 6.0 ± 0.2 Hz, P = 0.004). Correspondingly, atrial ERPs significantly increased from 218 ± 13 to 232 ± 11 ms (P = 0.04). Atropine resulted in a decreasing trend in DF in the left atrium (5.9 ± 0.1 to 5.8 ± 0.1 Hz, P = 0.07). Conclusions: Despite baroreflex-mediated parasympathetic effect, PE produced a slowing of AF along with lengthening of ERP, while parasympathetic blockade also slowed DF. It is therefore likely that the direct and indirect adrenergic effects of PE on atrial electrophysiology are more prominent than its parasympathetic effects. (J Cardiovasc Electrophysiol, Vol. 23 pp. 1045-1050, October 2012) [ABSTRACT FROM AUTHOR]

Background: There is a heightened risk of sudden cardiac death related to exercise and the postexercise recovery period, but the precise mechanism is unknown. We have demonstrated that sympathoexcitation persists for ≥45 minutes after exercise in normals and subjects with coronary artery disease (CAD). The purpose of this study is to determine whether this persistent sympathoexcitation is associated with persistent heart rate variability (HRV) and ventricular repolarization changes in the postexercise recovery period. Methods and Results: Twenty control subjects (age 50.7 ± 1.4 years), 68 subjects (age 58.2 ± 1.5 years) with CAD and preserved left ventricular ejection fraction (LVEF), and 18 subjects (age 57.6 ± 2.4 years) with CAD and depressed LVEF underwent a 16-minute submaximal bicycle exercise protocol with continuous ECG monitoring. QT and RR intervals were measured in recovery to calculate the time dependent corrected QT intervals (QTc), the QT-RR relationship, and HRV. QTc was dependent on the choice of rate correction formula. There were no differences in QT-RR slopes among the three groups in early recovery. HRV recovered quickly in controls, more slowly in those with CAD-preserved LVEF, and to a lesser extent in those with CAD-depressed LVEF. Conclusion: Despite persistent sympathoexcitation for the 45-minute recovery period, ventricular repolarization changes do not persist for that long and HRV changes differ by group. Additional understanding of the dynamic changes in cardiac parameters after exercise is needed to explore the mechanism of increased sudden cardiac death risk at this time. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the mechanomyographic (MMG) amplitude and mean power frequency (MPF) versus power output relationships for the vastus lateralis and rectus femoris muscles during incremental cycle ergometry between the piezoelectric contact sensor (HP) and the accelerometer (ACC) sensor. Nine men performed an incremental cycle ergometry test to voluntary exhaustion. Polynomial regression analyses on a subject-by-subject basis indicated that the relationship between the normalized MMG amplitude versus normalized power output was best fit with either a linear, quadratic, or cubic model. These patterns were consistent between sensors for each muscle for each subject. No consistent relationship was found for MMG MPF within subjects and between muscle groups. In addition, there were no significant sensor × power output interactions for normalized MMG amplitude or MPF. These results suggest that, for cycle ergometry, the HP and ACC sensors provide similar information for the interpretation of motor control strategies during continuous exercise. Muscle Nerve, 2010 [ABSTRACT FROM AUTHOR]

AF Electrogram Complexity. Introduction: Complex fractionated atrial electrograms (CFAE) have been identified as targets for atrial fibrillation (AF) ablation. Robust automatic algorithms to objectively classify these signals would be useful. The aim of this study was to evaluate Shannon's entropy (ShEn) and the Kolmogorov-Smirnov (K-S) test as a measure of signal complexity and to compare these measures with fractional intervals (FI) in distinguishing CFAE from non-CFAE signals. Methods and Results: Electrogram recordings of 5 seconds obtained from multiple atrial sites in 13 patients (11 M, 58 ± 10 years old) undergoing AF ablation were visually examined by 4 independent reviewers. Electrograms were classified as CFAE if they met Nademanee criteria. Agreement of 3 or more reviewers was considered consensus and the resulting classification was used as the gold standard. A total of 297 recordings were examined. Of these, 107 were consensus CFAE, 111 were non-CFAE, and 79 were equivocal or noninterpretable. FIs less than 120 ms identified CFAEs with sensitivity of 87% and specificity of 79%. ShEn, with optimal parameters using receiver-operator characteristic curves, resulted in a sensitivity of 87% and specificity of 81% in identifying CFAE. The K-S test resulted in an optimal sensitivity of 100% and specificity of 95% in classifying uninterpretable electrogram from all other electrograms. Conclusions: ShEn showed comparable results to FI in distinguishing CFAE from non-CFAE without requiring user input for threshold levels. Thus, measuring electrogram complexity using ShEn may have utility in objectively and automatically identifying CFAE sites for AF ablation. (J Cardiovasc Electrophysiol, Vol. 21, pp. 649-655, June 2010) [ABSTRACT FROM AUTHOR]

Introduction: Dominant frequency (DF) analysis of atrial electrograms has been used to characterize atrial fibrillation (AF). The aim of this study was to explore technical issues that may affect the estimation of local activation rate during AF using DF analysis. Methods and Results: Epicardial atrial electrograms recorded during AF from 10 dogs were used to evaluate the effects of unipolar versus bipolar recordings, bipolar electrode spacing, postrecording processing, far field ventricular depolarizations, ventricular template subtraction, and signal duration on DF analysis. Simulated electrograms were used to evaluate the effect of far field ventricular depolarizations and signal-to-noise ratio. DFs were compared with activation rates obtained by manual marking and the reproducibility of the DFs was evaluated. Bipolar electrograms were found to be preferable to unipolar electrograms. Preprocessing was a necessary step for bipolar signals, but also aided analysis of unipolar recordings. Ventricular far field depolarizations significantly affected DFs. Ventricular template subtraction helped DF analysis in signals with both minimal and significant ventricular components. A recording duration above 2 seconds was required for reliable DF measurements. Signal-to-noise ratios below 13 dB could also affect DF, particularly for signals with significant amplitude and frequency variation. Conclusions: Various factors affect DF analysis. Proper interpretation of DF analysis requires careful evaluation of the AF signals and robust processing techniques. [ABSTRACT FROM AUTHOR]

Dominant frequency analysis of atrial electrograms has been used to understand the pathophysiology of atrial fibrillation (AF). Although dominant frequency is an effective tool to estimate activation rate during AF, other factors besides activation rate may alter the results. Therefore, an adequate conceptual understanding of frequency domain analysis is required to properly use this technique and interpret the results. This review, while avoiding the use of formulas and equations, aims to explain fundamental theory of how signals can be decomposed into sine waves and how these sine waves relate to the activation rate detected from the electrograms. Through a series of examples and illustrations this relationship can be easily conceptualized. This will in turn allow the strengths and limitations of dominant frequency analysis to be better understood and improve its applicability to potential clinical usages. [ABSTRACT FROM AUTHOR]

Atrial Fibrillatory Wave Characteristics . Introduction: Fibrillatory waves on the surface ECG have been scrutinized to allow inferences about underlying mechanisms and pathophysiology, based on the premise that fibrillatory waves do not vary “randomly” but provide a consistent reflection of the underlying state of the atria in an individual patient. This premise is untested. Methods and Results: Ten standard ECGs were recorded over a 24-hour period in each of 20 clinically stable inpatients with atrial fibrillation. After QRS-T cancellation, the remainder fibrillatory waves were analyzed. Interpatient versus intrapatient differences in fibrillatory wave characteristics were evaluated by analysis of variance (ANOVA). The fibrillatory wave peak-to-peak amplitude of all the patients ranged from 0.06 to 0.35 mV, whereas 1 SD of the amplitude for each patient ranged from 0.004 to 0.053 mV. Short-term peak frequencies of all the patients ranged from 4.6 to 8.0 Hz, whereas 1 SD for each patient varied from 0.2 to 0.5 Hz. For these and all other parameters tested, interpatient differences were significantly greater compared to intrapatient differences (P < 0.0001). Conclusion: Fibrillatory wave characteristics are repeatable from ECG to ECG over 24 hours for clinically stable patients, whereas substantial differences are present between patients. Further study of the relationship of such characteristics to pathophysiology and management decisions is valid and warranted. (J Cardiovasc Electrophysiol, Vol. 15, pp. 911-917, August 2004) [ABSTRACT FROM AUTHOR]