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Atrial Electrophysiology (atrial + electrophysiology)

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Medical Sciences100%

Selected Abstracts

Pilot Study: Noninvasive Monitoring of Oral Flecainide's Effects on Atrial Electrophysiology during Persistent Human Atrial Fibrillation Using the Surface Electrocardiogram

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2005
Daniela Husser M.D.
Background: The relation between flecainide's plasma level and its influence on human atrial electrophysiology during acute and maintenance therapy of atrial fibrillation (AF) is unknown. Therefore, this study determined flecainide plasma levels and atrial fibrillatory rate obtained from the surface ECG during initiation and early maintenance of oral flecainide in patients with persistent lone AF and assessed their relationship. Methods and Results: In 10 patients (5 males, mean age 63 ± 14 years, left atrial diameter 46 ± 3 mm) with persistent lone AF, flecainide was administered as a single oral bolus (day 1) followed by 200,400 mg/day (days 2,5). The initial 300 mg flecainide bolus resulted in therapeutic plasma levels in all patients (range 288,629 ng/ml) with no side effects. Flecainide plasma levels increased on day 3 and remained stable thereafter. Day 5 plasma levels were lower (508 ± 135 vs 974 ± 276 ng/ml, P = 0.009) in patients with daily mean flecainide doses of 200 mg compared to patients with higher maintenance doses. Fibrillatory rate obtained from the surface electrocardiogram measuring 378 ± 17 fpm at baseline was reduced to 270 ± 18 fpm (P < 0.001) after the flecainide bolus but remained stable thereafter. Fibrillatory rate reduction was independent of flecainide plasma levels or clinical variables. Conclusion: A 300 mg oral flecainide bolus is associated with electrophysiologic effects that are not increased during early maintenance therapy in persistent human lone AF. In contrast to drug plasma levels, serial analysis of fibrillatory rate allows monitoring of individual drug effects on atrial electrophysiology. [source]

Surface Atrial Frequency Analysis in Patients with Atrial Fibrillation:

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2004
A Tool For Evaluating the Effects of Intervention
Introduction: The aims of this study were to evaluate (1) principal component analysis as a technique for extracting the atrial signal waveform from the standard 12-lead ECG and (2) its ability to distinguish changes in atrial fibrillation (AF) frequency parameters over time and in response to pharmacologic manipulation using drugs with different effects on atrial electrophysiology. Methods and Results: Twenty patients with persistent AF were studied. Continuous 12-lead Holter ECGs were recorded for 60 minutes, first, in the drug-free state. Mean and variability of atrial waveform frequency were measured using an automated computer technique. This extracted the atrial signal by principal component analysis and identified the main frequency component using Fourier analysis. Patients were then allotted sequentially to receive 1 of 4 drugs intravenously (amiodarone, flecainide, sotalol, or metoprolol), and changes induced in mean and variability of atrial waveform frequency measured. Mean and variability of atrial waveform frequency did not differ within patients between the two 30-minute sections of the drug-free state. As hypothesized, significant changes in mean and variability of atrial waveform frequency were detected after manipulation with amiodarone (mean: 5.77 vs 4.86 Hz; variability: 0.55 vs 0.31 Hz), flecainide (mean: 5.33 vs 4.72 Hz; variability: 0.71 vs 0.31 Hz), and sotalol (mean: 5.94 vs 4.90 Hz; variability: 0.73 vs 0.40 Hz) but not with metoprolol (mean: 5.41 vs 5.17 Hz; variability: 0.81 vs 0.82 Hz). Conclusion: A technique for continuously analyzing atrial frequency characteristics of AF from the surface ECG has been developed and validated. [source]

Relationship Between Connexins and Atrial Activation During Human Atrial Fibrillation

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2 2004
M.R.C.P., PRAPA KANAGARATNAM Ph.D.
Introduction: Gap junctional connexin proteins (connexin40 [Cx40], connexin43 [Cx43]) are a determinant of myocardial conduction and are implicated in the development of atrial fibrillation (AF). We hypothesized that atrial activation pattern during AF is related to connexin expression and that this relationship is altered by AF-induced remodeling in the fibrillating atria of chronic AF. Methods and Results: Isochronal activation mapping was performed during cardiac surgery on the right atria of patients in chronic AF (n = 13) using an epicardial electrode array. The atrial activation pattern was categorized using a complexity score based on the number of propagating wavefronts of activation and by grouping atria into those capable of uniform planar activation (simple) and those that were not (complex). The activation pattern was correlated with the levels of Cx43 and Cx40 signal measured by immunoconfocal quantification of biopsies from the mapped region. We studied the impact of electrical remodeling by comparing these findings with the unremodeled atria of patients in sinus rhythm during pacing-induced sustained AF (n = 17). In chronic AF, atria with complex activation had lower Cx40 signal than atria showing simple activation (0.013 ± 0.006 ,m2/,m2 vs 0.027 ± 0.009 ,m2/,m2, P < 0.02), with the relative connexin signal (Cx40/Cx40+Cx43) correlating with complexity score (P = 0.01, r =,0.74). This relationship did not occur in the unremodeled atria, and increased heterogeneity of distribution of Cx40 labeling in chronic AF was the only evidence of connexin remodeling that we detected in the overall group. Conclusion: The pattern of atrial activation is related to immunoconfocal connexin signal only in the fully remodeled atria of chronic AF. This suggests that intercellular coupling and pattern of atrial activation are interrelated, but only in conjunction with the remodeling of atrial electrophysiology that occurs in chronic AF. (J Cardiovasc Electrophysiol, Vol. 15, pp. 206-213, February 2004) [source]

Prolonged Atrial Action Potential Durations and Polymorphic Atrial Tachyarrhythmias in Patients with Long QT Syndrome

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2003
PAULUS KIRCHHOF M.D.
Introduction: Prolongation of the QT interval and torsades de pointes tachycardias due to altered expression or function of repolarizing ion channels are the hallmark of congenital long QT syndrome (LQTS). The same ion channels also contribute to atrial repolarization, and familial atrial fibrillation may be associated with a mutated KVLQT1 gene. We therefore assessed atrial action potential characteristics and atrial arrhythmias in LQTS patients. Methods and Results: Monophasic action potentials (MAPs) were simultaneously recorded from the right atrial appendage and the inferolateral right atrium in 10 patients with LQTS (8 with identifiable genotype) and compared to 7 control patients. Atrial arrhythmias also were compared to MAPs recorded in patients with persistent (n = 10) and induced (n = 4) atrial fibrillation. Atrial action potential durations (APD) and effective refractory periods (ERP) were prolonged in LQTS patients at cycle lengths of 300 to 500 msec (APD prolongation 30,41 msec; ERP prolongation 26,52 msec; all P < 0.05). Short episodes of polymorphic atrial tachyarrhythmias (polyAT, duration 4,175 sec) occurred spontaneously or during pauses after pacing in 5 of 10 LQTS patients, but not in controls (P < 0.05). P waves showed undulating axis during polyAT. Cycle lengths of polyAT were longer than during persistent and induced atrial fibrillation. Afterdepolarizations preceded polyAT in 2 patients. The electrical restitution curve was shifted to longer APD in LQTS patients and to even longer APD in LQTS patients with polyAT. Conclusion: This group of LQTS patients has altered atrial electrophysiology: action potentials are prolonged, and polyAT occurs. PolyAT appears to be a specific arrhythmia of LQTS reminiscent of an atrial form of "torsades de pointes."(J Cardiovasc Electrophysiol, Vol. 14, pp ***-***, October 2003) [source]

Atrial, SA Nodal, and AV Nodal Electrophysiology in Standing Horses: Normal Findings and Electrophysiologic Effects of Quinidine and Diltiazem

JOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2007
Colin C. Schwarzwald
Background: Although atrial arrhythmias are clinically important in horses, atrial electrophysiology has been incompletely studied. Hypotheses: Standard electrophysiologic methods can be used to study drug effects in horses. Specifically, the effects of diltiazem on atrioventricular (AV) nodal conduction are rate-dependent and allow control of ventricular response rate during rapid atrial pacing in horses undergoing quinidine treatment. Animals: Fourteen healthy horses. Methods: Arterial blood pressure, surface electrocardiogram, and right atrial electrogram were recorded during sinus rhythm and during programmed electrical stimulation at baseline, after administration of quinidine gluconate (10 mg/kg IV over 30 minutes, n = 7; and 12 mg/kg IV over 5 minutes followed by 5 mg/kg/h constant rate infusion for the remaining duration of the study, n = 7), and after coadministration of diltiazem (0.125 mg/kg IV over 2 minutes repeated every 12 minutes to effect). Results: Quinidine significantly prolonged the atrial effective refractory period, shortened the functional refractory period (FRP) of the AV node, and increased the ventricular response rate during atrial pacing. Diltiazem increased the FRP, controlled ventricular rate in a rate-dependent manner, caused dose-dependent suppression of the sinoatrial node and produced a significant, but well tolerated decrease in blood pressure. Effective doses of diltiazem ranged from 0.125 to 1.125 mg/kg. Conclusions and Clinical Importance: Standard electrophysiologic techniques allow characterization of drug effects in standing horses. Diltiazem is effective for ventricular rate control in this pacing model of supraventricular tachycardia. The use of diltiazem for rate control in horses with atrial fibrillation merits further investigation. [source]

Pilot Study: Noninvasive Monitoring of Oral Flecainide's Effects on Atrial Electrophysiology during Persistent Human Atrial Fibrillation Using the Surface Electrocardiogram

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2005
Daniela Husser M.D.
Background: The relation between flecainide's plasma level and its influence on human atrial electrophysiology during acute and maintenance therapy of atrial fibrillation (AF) is unknown. Therefore, this study determined flecainide plasma levels and atrial fibrillatory rate obtained from the surface ECG during initiation and early maintenance of oral flecainide in patients with persistent lone AF and assessed their relationship. Methods and Results: In 10 patients (5 males, mean age 63 ± 14 years, left atrial diameter 46 ± 3 mm) with persistent lone AF, flecainide was administered as a single oral bolus (day 1) followed by 200,400 mg/day (days 2,5). The initial 300 mg flecainide bolus resulted in therapeutic plasma levels in all patients (range 288,629 ng/ml) with no side effects. Flecainide plasma levels increased on day 3 and remained stable thereafter. Day 5 plasma levels were lower (508 ± 135 vs 974 ± 276 ng/ml, P = 0.009) in patients with daily mean flecainide doses of 200 mg compared to patients with higher maintenance doses. Fibrillatory rate obtained from the surface electrocardiogram measuring 378 ± 17 fpm at baseline was reduced to 270 ± 18 fpm (P < 0.001) after the flecainide bolus but remained stable thereafter. Fibrillatory rate reduction was independent of flecainide plasma levels or clinical variables. Conclusion: A 300 mg oral flecainide bolus is associated with electrophysiologic effects that are not increased during early maintenance therapy in persistent human lone AF. In contrast to drug plasma levels, serial analysis of fibrillatory rate allows monitoring of individual drug effects on atrial electrophysiology. [source]