The effect of basic cycle length stimuli on effective refractory period measurement

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.

Download Full-text

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

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1985.248.5.h606 ◽

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.

Download Full-text

Is the Ventricular Effective Refractory Period Different When Determined by Incremental Versus Decremental Scanning?: The Effect of Pacing Cycle Length, d-Sotalol, and Levcromakalim

Pacing and Clinical Electrophysiology ◽

10.1111/j.1540-8159.1994.tb03805.x ◽

1994 ◽

Vol 17 (11) ◽

pp. 2084-2089 ◽

Cited By ~ 3

Author(s):

HENDRIK M. LEERSSEN ◽

MARC A. VOS ◽

KAREL DULK ◽

JOLANDA ZANDE ◽

HEIN J. WELLENS

Keyword(s):

Refractory Period ◽

Cycle Length ◽

Effective Refractory Period

Download Full-text

Comparison of the Effects of Racemic Bupivacaine, Levobupivacaine, and Ropivacaine on Ventricular Conduction, Refractoriness, and Wavelength

Anesthesiology ◽

10.1097/00000542-200203000-00021 ◽

2002 ◽

Vol 96 (3) ◽

pp. 641-650 ◽

Cited By ~ 24

Author(s):

Antoine G. M. Aya ◽

Jean E. de La Coussaye ◽

Emmanuelle Robert ◽

Jacques Ripart ◽

Philippe Cuvillon ◽

...

Keyword(s):

Conduction Velocity ◽

Refractory Period ◽

Cycle Length ◽

Left Ventricular ◽

Effective Refractory Period ◽

Potency Ratio ◽

Dependent Effect ◽

Intergroup Comparison ◽

Conduction Velocities ◽

Ventricular Conduction

Background The study was designed to compare the effects of equimolar concentrations of racemic bupivacaine, levobupivacaine, and ropivacaine on ventricular conduction, anisotropy, duration and homogeneity of refractoriness, and wavelengths, and to provide a potency ratio for effects on conduction velocity. Methods Isolated frozen rabbit hearts (which leave a thin layer of surviving epicardial muscle) were treated with 0.1, 1, and 10 mum racemic bupivacaine, levobupivacaine, or ropivacaine. Left ventricular longitudinal and transverse conduction velocities, anisotropic ratio, minimum pacing cycle length, use dependency, duration and dispersion of ventricular effective refractory period, and wavelengths were studied. A high-resolution mapping system was used for data acquisition. In addition to two-way analysis of variance for repeated measures, data for conduction velocities were fitted simultaneously using a nonlinear mixed-effect modeling program to allow intergroup comparison. Results Each agent induced a concentration- and use-dependent slowing of conduction velocities, with no change of the anisotropic ratio. The use-dependent effect of levobupivacaine is similar to that of racemic bupivacaine concerning longitudinal conduction velocity. Fitting of conduction velocities provided a racemic bupivacaine to levobupivacaine and to ropivacaine ratio of 1:1.38 for concentration effect at 1,000-ms pacing cycle length, and 1:0.74 for use-dependent effect at 600-ms pacing cycle length. Racemic bupivacaine and levobupivacaine prolonged the ventricular effective refractory period, whereas ropivacaine did not. No dispersion in ventricular effective refractory period values occurred. All three agents induced significant decreases in wavelengths. This effect was not different among groups. Conclusions Differences among racemic bupivacaine, levobupivacaine, and ropivacaine at equimolar concentrations are mainly caused by the use-dependent effects on conduction velocities and the concentration-dependent effects on ventricular effective refractory period. Therefore, one must take into account the corresponding pacing rates when comparing the potency ratios of local anesthetics.

Download Full-text

Parasympathetic effects on cardiac electrophysiology during exercise and recovery

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00825.2001 ◽

2002 ◽

Vol 282 (6) ◽

pp. H2091-H2098 ◽

Cited By ~ 43

Author(s):

Prince J. Kannankeril ◽

Jeffrey J. Goldberger

Keyword(s):

Sudden Cardiac Death ◽

Refractory Period ◽

Cardiac Death ◽

Cardiac Electrophysiology ◽

Cycle Length ◽

Recovery Period ◽

Left Ventricular ◽

Effective Refractory Period ◽

Av Block ◽

Sinus Cycle Length

Depressed parasympathetic tone is associated with an increased risk of sudden cardiac death. Exercise and the postexercise recovery period, which are associated with parasympathetic withdrawal, are high risk periods for sudden death. However, parasympathetic effects on cardiac electrophysiology during exercise and recovery have not been described. Electrophysiology studies were performed using noninvasive programmed stimulation (NIPS) in nine subjects (age 59 ± 18 yr) with implanted dual-chamber devices and normal left ventricular function during multiple bicycle exercise sessions. NIPS was performed at rest, during exercise, and in the early recovery period both before and after parasympathetic blockade with atropine. Parasympathetic effect was defined as the value of the parameter of interest in the absence of atropine minus the value of the parameter in the presence of atropine. During exercise, sinus cycle length, atrioventricular (AV) block cycle length, AV interval, and ventricular effective refractory period shortened; in recovery, the values were intermediate between the rest and exercise values ( P < 0.0001 by ANOVA). Parasympathetic effects on sinus cycle length, AV block cycle length, AV interval, and ventricular effective refractory period were 247 ± 140, 58 ± 20, 76 ± 20, and 8.6 ± 7.5 ms at rest, 106 ± 20, 37 ± 14, 24 ± 13, and 2.6 ± 7.8 ms during exercise, and 209 ± 114, 50 ± 23, 35 ± 21, and 9.5 ± 11.8 ms during recovery, respectively. There was poor correlation among the parasympathetic effects noted at the sinus node, AV node, and ventricle. Further work evaluating parasympathetic effects on cardiac electrophysiology during exercise and recovery in patients with heart disease is required to elucidate its role in modulating the risk of sudden cardiac death noted at these times.

Download Full-text

Dose-Dependent Effects of Ranolazine on Reentrant Ventricular Arrhythmias Induced After Subacute Myocardial Infarction in Rabbits

Journal of Cardiovascular Pharmacology and Therapeutics ◽

10.1177/1074248419858113 ◽

2019 ◽

Vol 25 (1) ◽

pp. 65-71 ◽

Cited By ~ 1

Author(s):

Vassileios Moschovidis ◽

Vassileios Simopoulos ◽

Soultana Stravela ◽

Konstantina Dipla ◽

Apostolia Hatziefthimiou ◽

...

Keyword(s):

Myocardial Infarction ◽

Ventricular Tachycardia ◽

Action Potential ◽

Refractory Period ◽

Ventricular Arrhythmias ◽

Cycle Length ◽

Sustained Ventricular Tachycardia ◽

Effective Refractory Period ◽

Monophasic Action Potential ◽

Coronary Artery Ligation

Ranolazine has been found to prevent ventricular arrhythmias (VAs) during acute myocardial infarction (AMI). This study aimed to investigate its efficacy on VAs induced several days post-MI. For this purpose, 13 anesthetized rabbits underwent coronary artery ligation. Ten of these animals that survived AMI were reanesthetized 3 to 7 days later for electrophysiologic testing. An endocardial monophasic action potential combination catheter was placed in the right ventricle for simultaneous pacing and recording. Monophasic action potential duration, ventricular effective refractory period (VERP), and VAs induced by programmed stimulation were assessed. Measurements were performed during control pacing, and following an intravenous infusion of either a low-dose ranolazine (2.4 mg/kg, R1) or a higher dose ranolazine (4.8 mg/kg cumulative dose, R2). During control stimulation, 2 animals developed primary ventricular fibrillation (VF), 6 sustained ventricular tachycardia (sVT), and 2 nonsustained VT (nsVT). R1 did not prevent the appearance of VAs in any of the experiments; in contrast, it aggravated nsVT into sVT and complicated sVT termination in 2 of 6 animals. Sustained ventricular tachycardia cycle length and VERP were only slightly decreased after R1 (112 ± 5 vs 110 ± 6 ms and 101 ± 11 vs 98 ± 10 ms, respectively). R2 suppressed inducibility of control nsVT, VF, and sVT in 2 animals. In 4 animals with still inducible sVT, R2 significantly prolonged VT cycle length by 150 ± 23 ms ( P < .01), and VERP by 120 ± 7 ms ( P < .001) versus control. In conclusion, R2 exerted antiarrhythmic efficacy against subacute-MI VAs, whereas R1 rather aggravated than prevented these arrhythmias. Ventricular effective refractory period prolongation could partially explain the antiarrhythmic action of R2 in this rabbit model.

Download Full-text

Estimating refractory periods during atrial fibrillation based on electrogram cycle lengths in a heterogeneous simulation setup

Current Directions in Biomedical Engineering ◽

10.1515/cdbme-2017-0181 ◽

2017 ◽

Vol 3 (2) ◽

pp. 317-320 ◽

Cited By ~ 3

Author(s):

Laura Unger ◽

Tobias Oesterlein ◽

Gunnar Seemann ◽

Olaf Dössel ◽

Peter Spector ◽

...

Keyword(s):

Atrial Fibrillation ◽

Refractory Period ◽

Cycle Length ◽

Spherical Model ◽

Effective Refractory Period ◽

Absolute Difference ◽

Sequential Approach ◽

Tissue Properties ◽

Refractory Periods ◽

Mapping Techniques

AbstractAcquiring adequate mapping data in patients with atrial fibrillation is still one of the main obstacles in the treatment of this atrial arrhythmia. Due to the lack of catheters with both a panoramic field of view and sufficient electrode density for simultaneous mapping, electrophysiologists are forced to fall back on sequential mapping techniques. But, because activation patterns change rapidly during atrial fibrillation, they cannot be mapped sequentially. We propose that mapping tissue properties which are time independent, in contrast, allows a sequential approach. Here, we use the shortest measured electrogram cycle length to estimate the effective refractory period of the underlying tissue in a simulation study. Atrial fibrillation was simulated in a spherical model of the left atrium comprised of regions with varied refractory period. We found that the minimal measured electrogram cycle length correlates with the effective refractory period of the underlying tissue if the regions with distinct refractory properties are large enough and if the absolute difference in effective refractory periods is sufficient. This approach is capable of identifying regions of lowered effective refractory period without the need for cardioversion. Those regions are likely to harbor drivers of atrial fibrillation, which emphasizes the necessity of their localization.

Download Full-text