Electrophysiological effects of ethmozine in perfused rabbit hearts

1985 ◽  
Vol 63 (11) ◽  
pp. 1418-1422 ◽  
Author(s):  
Peter E. Dresel ◽  
A. Ogbaghebriel ◽  
R. Abraham
Keyword(s):  
Refractory Period ◽  
Conduction Block ◽  
Cardiac Conduction ◽  
Effective Refractory Period ◽  
Conduction Time ◽  
Coupling Interval ◽  
Cycle Lengths ◽  
Significant Change ◽  
High Concentrations ◽  
Electrophysiological Effects

His-bundle electrocardiography was used to evaluate the effects of ethmozine on cardiac conduction in isolated perfused rabbit hearts electrically driven at cycle lengths of 320 and 250 ms. There was no significant change in conduction until high concentrations of ethmozine were reached. His-Purkinje and atrioventricular (AV) nodal conduction were slowed significantly at 0.1 μg/mL and atrial conduction at 1.0 μg/mL. Conduction block occurred at 10.0 μg/mL in all the hearts treated. Effects of the drug (0.1 and 0.01 μg/mL) on conduction of extrasystoles were also studied in hearts driven at a basic cycle length of 270 ms. No significant change was observed in atrial conduction of extrasystoles throughout the coupling intervals tested at both concentrations. Ethmozine (0.01 and 0.1 μg/mL) caused slowing of His-Purkinje conduction of extrasystoles but the effect of the drug did not change as a function of the coupling interval. An interval-dependent increase in AV-nodal conduction time was observed, with the maximum slowing of conduction occurring at coupling intervals close to the effective refractory period of the AV node. AV-nodal functional refractory period was increased significantly by ethmozine (0.01 and 0.1 μg/mL). The effective refractory period was significantly increased only at the higher concentration.

Effects of infarction, procainamide, coupling interval, and cycle length on refractoriness of extrastimuli

1985 ◽  
Vol 248 (5) ◽  
pp. H606-H613
Author(s):  
F. E. Marchlinski ◽  
M. E. Cain ◽  
R. A. Falcone ◽  
R. F. Corky ◽  
J. F. Spear ◽  
...  
Keyword(s):  
Refractory Period ◽  
Cycle Length ◽  
Narrow Range ◽  
Left Ventricular ◽  
Effective Refractory Period ◽  
Stimulation Site ◽  
Refractory Periods ◽  
Coupling Interval ◽  
Cycle Lengths ◽  
Site Of Stimulation

The effects of prematurity, cycle length, site of stimulation, and procainamide on ventricular refractoriness following an extrastimulus (S2) were assessed in 10 dogs with and 10 dogs without infarction. Extrastimuli were introduced at preselected coupling intervals (S1-S2) from normal right and left ventricular sites and from left ventricular sites of infarction during drive cycle lengths (S1-S1) of 350 and 250 ms. At each S1-S2 interval, the effective refractory period of S2 was determined by introducing a second extrastimulus (S3). At all stimulation sites, cycle lengths, and before and during infusion of procainamide (mean concn 18.6 +/- 3.5 micrograms/ml), shortening (greater than 10 ms change) in refractoriness was most marked over a narrow range of closely coupled S1-S2 intervals. Regardless of stimulation site, the effective refractory period of S2 was less during a cycle length of 250 ms compared with a cycle length of 350 ms. In dogs without infarction, the effective refractory periods of S2 from left ventricular sites tended to be longer than from right ventricular sites, particularly during procainamide administration. The refractory period of S2 at sites of infarction did not differ consistently from those at normal sites. Finally, at all stimulation sites and cycle lengths, procainamide prolonged refractoriness of S2 at each S1-S2 interval and blunted the total shortening in refractoriness in response to S2.

Effects of Halothane and Enflurane on Ventricular Conduction, Refractoriness, and Wavelength 

1999 ◽  
Vol 91 (6) ◽  
pp. 1873-1873 ◽  
Author(s):  
Antoine G. Aya ◽  
Jean E. de La Coussaye ◽  
Emmanuelle Robert ◽  
Jacques Ripart ◽  
Jean-Yves Lefrant ◽  
...  
Keyword(s):  
Conduction Velocity ◽  
Refractory Period ◽  
Conduction Block ◽  
Effective Refractory Period ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Rr Interval ◽  
Sinus Cycle Length ◽  
Epicardial Layer ◽  
Ventricular Conduction

Background Effects of halothane and enflurane on ventricular conduction, anisotropy, duration and dispersion of refractory periods, and wavelengths were studied, and putative antiarrhythmic or arrhythmogenic properties on ventricles were discussed. Methods High-resolution epicardial mapping system was used to study the effects of 1, 3, and 5 vol% halothane and enflurane in 30 isolated rabbit hearts. Ten hearts were kept intact to study the effects on spontaneous sinus cycle length (RR interval), perfusion pressure, and the occurrence of spontaneous dysrhythmias. In 20 other hearts, a thin epicardial layer was obtained (frozen hearts) to study ventricular conduction velocity, ventricular effective refractory period (VERP in four sites) and wavelengths. Results Halothane induced a concentration-dependent lengthening of RR interval, whereas enflurane did not. Both agents slowed longitudinal and transverse ventricular conduction velocity with no anisotropic change. Ventricular effective refractory period was prolonged at 1 vol% and was shortened at higher concentrations, with no significant increase in dispersion. Ventricular longitudinal and transverse wavelengths decreased in a concentration-dependent manner. Although changes in wavelengths could express proarrhythmic effects of volatile anesthetics, no arrhythmia occurred in spontaneously beating hearts or in frozen hearts. Conclusions The ventricular electrophysiologic effects of halothane and enflurane were slight, suggesting that both agents are unable per se to induce functional conduction block and therefore reentrant ventricular arrhythmias.

scholarly journals Ionic mechanisms of electrophysiological heterogeneity and conduction block in the infarct border zone

2010 ◽  
Vol 299 (5) ◽  
pp. H1588-H1597 ◽  
Author(s):  
Keith F. Decker ◽  
Yoram Rudy
Keyword(s):  
Refractory Period ◽  
Conduction Block ◽  
Border Zone ◽  
Effective Refractory Period ◽  
Diastolic Interval ◽  
Primary Determinant ◽  
Healing Phase ◽  
Ionic Mechanisms ◽  
Infarct Border Zone ◽  
Vulnerable Window

The increased incidence of arrhythmia in the healing phase after infarction has been linked to remodeling in the epicardial border zone (EBZ). Ionic models of normal zone (NZ) and EBZ myocytes were incorporated into one-dimensional models of propagation to gain mechanistic insights into how ion channel remodeling affects action potential (AP) duration (APD) and refractoriness, vulnerability to conduction block, and conduction safety postinfarction. We found that EBZ tissue exhibited abnormal APD restitution. The remodeled Na+ current ( INa) and L-type Ca2+ current ( ICa,L) promoted increased effective refractory period and prolonged APD at a short diastolic interval. While postrepolarization refractoriness due to remodeled EBZ INa was the primary determinant of the vulnerable window for conduction block at the NZ-to-EBZ transition in response to premature S2 stimuli, altered EBZ restitution also promoted APD dispersion and increased the vulnerable window at fast S1 pacing rates. Abnormal EBZ APD restitution and refractoriness also led to abnormal periodic conduction block patterns for a range of fast S1 pacing rates. In addition, we found that INa remodeling decreased conduction safety in the EBZ but that inward rectifier K+ current remodeling partially offset this decrease. EBZ conduction was characterized by a weakened AP upstroke and short intercellular delays, which prevented ICa,L and transient outward K+ current remodeling from playing a role in EBZ conduction in uncoupled tissue. Simulations of a skeletal muscle Na+ channel SkM1- INa injection into the EBZ suggested that this recently proposed antiarrhythmic therapy has several desirable effects, including normalization of EBZ effective refractory period and APD restitution, elimination of vulnerability to conduction block, and normalization of conduction in tissue with reduced intercellular coupling.

Effects of Propofol or Isoflurane Anesthesia on Cardiac Conduction in Children Undergoing Radiofrequency Catheter Ablation for Tachydysrhythmias

1995 ◽  
Vol 82 (4) ◽  
pp. 884-887. ◽  
Author(s):  
J. Lavoie ◽  
E. P. Walsh ◽  
F. A. Burrows ◽  
P. Laussen ◽  
J. A. Lulu ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Catheter Ablation ◽  
Refractory Period ◽  
Radiofrequency Catheter Ablation ◽  
Statistical Significance ◽  
Cardiac Conduction ◽  
Effective Refractory Period ◽  
Isoflurane Anesthesia ◽  
Electrophysiology Study ◽  
Significant Difference

Background To determine suitability for ablation procedures in children, two commonly used anesthetic agents were studied: propofol and isoflurane. Methods Twenty patients presenting for a radiofrequency catheter ablation procedure were included and randomly assigned to two groups. A baseline electrophysiology study was performed during anesthesia with thiopental, alfentanil, nitrous oxide, and pancuronium in all patients. At the completion of the baseline electrophysiology study (EPS), 0.8-1.2% isoflurane was administered to patients in group 1 and 2 mg/kg propofol bolus plus an infusion of 150 micrograms.kg-1.min-1 was administered to patients in group 2. Nitrous oxide and pancuronium were used throughout the procedure. After 30 min of equilibration, both groups underwent a repeat EPS. The following parameters were measured during the EPS: cycle length, atrial-His interval, His-ventricle interval, corrected sinus node recovery time, AV node effective refractory period, and atrial effective refractory period. Using paired t tests, the electrophysiologic parameters described above measured during propofol or isoflurane anesthesia were compared to those measured during baseline anesthesia. Statistical significance was accepted as P < 0.05. Results There was no statistically significant difference in the results obtained during baseline anesthesia when compared with those measured during propofol or isoflurane anesthesia. Conclusions Neither propofol nor isoflurane anesthesia alter sinoatrial or atrioventricular node function in pediatric patients undergoing radiofrequency catheter ablation, compared to values obtained during baseline anesthesia with alfentanil and midazolam.

Facilitated ventriculoatrial conduction: effects of sequential pacing interval and basic cycle length

1995 ◽  
Vol 268 (1) ◽  
pp. H384-H390
Author(s):  
A. F. Kuguoglu ◽  
D. W. Wallick ◽  
P. J. Martin
Keyword(s):  
Refractory Period ◽  
Cycle Length ◽  
Effective Refractory Period ◽  
Conduction Time ◽  
Time Intervals ◽  
Av Node ◽  
Anesthetized Dogs ◽  
Alpha Chloralose ◽  
Retrograde Conduction ◽  
Basic Cycle Length

We studied 1) the effects of pacing interval, 2) the timing of atrioventricular sequential pacing, and 3) the effects of successive premature intervals on retrograde conduction of the atrioventricular (AV) node in open-chest alpha-chloralose-anesthetized dogs. The ventricles and atria were sequentially paced at one of three levels of basic cycle length and one of six sequential time intervals (V1-A1) for three basic cycles (V1-V1). Then a premature ventricular impulse was introduced at various V1-V2 intervals, and the resultant retrograde conduction time (V2-A2 interval) was measured. Successive V1-V2 intervals were applied in an incremental or a decremental fashion. The V1-V2 intervals ranged from V1-V1 to V1-V2, at which the retrograde conduction was blocked. For each level of the above three factors, we plotted retrograde conduction time (V2-A2) as a function of the various premature intervals (V1-V2). We found that the time between atrial and ventricular activations was the most important factor in determining V1-V2 and in decreasing the effective refractory period of the AV node during retrograde conduction.

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