Effects of acetylcholine, propranolol, and verapamil on sinus node refractoriness of the rabbit

1989 ◽  
Vol 67 (10) ◽  
pp. 1232-1239
Author(s):  
Charles R. Kerr
Keyword(s):  
Refractory Period ◽  
Sinus Node ◽  
Effective Refractory Period ◽  
Crista Terminalis ◽  
Premature Beats ◽  
Control State

At a critical premature interval, atrial premature beats encounter sinus node refractoriness and are blocked on entering and fail to reset the sinus node, resulting in interpolation of the premature beat. The transition from reset to interpolated response has been used to define the effective refractory period of the sinus node (SNERP). In an in vitro preparation of rabbit sinus node, we evaluated the effects of acetylcholine, propranolol, and verapamil on SNERP. Results obtained in the control state were compared with those obtained during superfusion with drugs, all of which prolonged refractoriness: acetylcholine from 233 ± 41 (SD) to 325 ± 88 ms; propranolol from 215 ± 60 to 241 ± 67 ms; and verapamil from 192 ± 69 to 254 ± 79 ms (p < 0.005 with all drugs). The site of block of premature beats was mapped between sinus node and crista terminalis with an intracellular microelectrode. All three drugs resulted in block of premature beats at sites farther from the primary pacemaker site. Thus, acetylcholine, propranolol, and verapamil prolong sinus node refractoriness.Key words: acetylcholine, propranolol, verapamil, sinus node, sinus node refractoriness.

Effects of propafenone on sinus node function in the rabbit heart

1990 ◽  
Vol 68 (7) ◽  
pp. 851-855 ◽  
Author(s):  
Charles R. Kerr
Keyword(s):  
Cycle Length ◽  
Sinus Node ◽  
Rabbit Heart ◽  
Conduction Time ◽  
Supraventricular Arrhythmias ◽  
Sinus Cycle Length ◽  
Cycle Lengths ◽  
Dose Dependent ◽  
Control State

Propafenone is a type 1C antiarrhythmic drug with efficacy for both ventricular and supraventricular arrhythmias. We investigated the effects of propafenone on properties of sinus node function in an in vitro preparation of rabbit sinus node and surrounding atrium. Spontaneous sinus cycle length (SCL), atriosinus conduction time (ASCT), and sinus node effective refractory period (SNERP) at multiple pacing cycle lengths were measured in the control state and during superfusion with propafenone (2.3 μM). SNERP prolonged from 175 ± 25 ms in the control state to 220 ± 45 ms (p < 0.001) with propafenone. ASCT also prolonged significantly (p < 0.01) from 50 ± 20 to 65 ± 20 ms whereas SCL did not change. In four experiments, multiple concentrations of propafenone were utilized and there appeared to be a dose-dependent prolongation of SNERP. Thus, propafenone has a significant effect on SNERP and ASCT in an isolated rabbit sinus node preparation.Key words: propafenone, sinus node, atrium.

scholarly journals Programmed deep septal pacing for the diagnosis of left bundle branch capture

2019 ◽  
Author(s):  
Marek Jastrzębski ◽  
Paweł Moskal ◽  
Aleksander Kusiak ◽  
Agnieszka Bednarek ◽  
Tomasz Sondej ◽  
...  
Keyword(s):  
Refractory Period ◽  
Pacemaker Implantation ◽  
Drive Train ◽  
Effective Refractory Period ◽  
Qrs Complex ◽  
Septal Pacing ◽  
Pacing Lead ◽  
Qrs Morphology ◽  
Premature Beats ◽  
Septal Myocardium

AbstractBackgroundDuring permanent deep septal pacing, it is important to confirm left bundle branch (LBB) capture.ObjectiveThe effective refractory period (ERP) of the working myocardium is different than the ERP of the LBB; we hypothesized that it should be possible to differentiate LBB capture from septal myocardial capture using programmed extra-stimulus technique.MethodsIn consecutive patients undergoing pacemaker implantation who received pacing lead in a deep septal position programmed pacing was delivered from this lead. Responses to programmed pacing were categorized on the basis of QRS morphology of the extrastimuli as: myocardial (broader QRS, often slurred), selective (narrower QRS, preceded by an isoelectric interval) or non-diagnostic (unequivocal change).ResultsProgrammed deep septal pacing was performed 269 times in 143 patients; in every patient with the use of an 8-beat basic drive train of 600 ms and when possible also during supraventricular rhythm. Responses diagnostic for LBB capture were observed in 114 (79.7%) of patients. Selective LBB paced QRS was more often seen when premature beats were introduced during the intrinsic rhythm rather than after the basic drive train. The average septal-myocardial refractory period was significantly shorter than the LBB refractory period: 263.0±34.4 ms vs. 318.0±37.4 ms.ConclusionsA novel maneuver for the diagnosis of LBB capture during deep septal pacing, was formulated, assessed and found as diagnostically valuable. This method, based on the differences in refractoriness between LBB and the septal myocardium is unique in enabling the visualization of components of the usually fused, non-selective LBB paced QRS complex.Graphical abstract

scholarly journals Translational Studies on Anti-Atrial Fibrillatory Action of Oseltamivir by its in vivo and in vitro Electropharmacological Analyses

2021 ◽  
Vol 12 ◽  
Author(s):  
Ryuichi Kambayashi ◽  
Hiroko Izumi-Nakaseko ◽  
Ai Goto ◽  
Kazuya Tsurudome ◽  
Hironori Ohshiro ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Refractory Period ◽  
Persistent Atrial Fibrillation ◽  
Effective Refractory Period ◽  
Conduction Time ◽  
Dependent Manner ◽  
Atrial Conduction Time ◽  
Atrial Effective Refractory Period

Oseltamivir has been shown to prolong the atrial conduction time and effective refractory period, and to suppress the onset of burst pacing-induced atrial fibrillation in vitro. To better predict its potential clinical benefit as an anti-atrial fibrillatory drug, we performed translational studies by assessing in vivo anti-atrial fibrillatory effect along with in vivo and in vitro electropharmacological analyses. Oseltamivir in intravenous doses of 3 (n = 6) and 30 mg/kg (n = 7) was administered in conscious state to the persistent atrial fibrillation model dogs to confirm its anti-atrial fibrillatory action. The model was prepared by tachypacing to the atria of chronic atrioventricular block dogs for &gt; 6 weeks. Next, oseltamivir in doses of 0.3, 3 and 30 mg/kg was intravenously administered to the halothane-anesthetized intact dogs to analyze its in vivo electrophysiological actions (n = 4). Finally, its in vitro effects of 10–1,000 μM on IK,ACh, IKur, IKr, INa and ICaL were analyzed by using cell lines stably expressing Kir3.1/3.4, KV1.5, hERG, NaV1.5 or CaV1.2, respectively (n = 3 for IK,ACh and IKr or n = 6 for IKr, INa and ICaL). Oseltamivir in doses of 3 and 30 mg/kg terminated the atrial fibrillation in 1 out of 6 and in 6 out of 7 atrial fibrillation model dogs, respectively without inducing any lethal ventricular arrhythmia. Its 3 and 30 mg/kg delayed inter-atrial conduction in a frequency-dependent manner, whereas they prolonged atrial effective refractory period in a reverse frequency-dependent manner in the intact dogs. The current assay indicated that IC50 values for IK,ACh and IKr were 160 and 231 μM, respectively, but 1,000 µM inhibited INa, ICaL and IKur by 22, 19 and 13%, respectively. The extent of INa blockade was enhanced at faster beating rate and more depolarized resting membrane potential. Oseltamivir effectively terminated the persistent atrial fibrillation, which may be largely due to the prolongation of the atrial effective refractory period and inter-atrial conduction time induced by IK,ACh and IKr inhibitions along with INa suppression. Thus, oseltamivir can exert a powerful anti-atrial fibrillatory action through its ideal multi-channel blocking property; and oseltamivir would become a promising seed compound for developing efficacious and safe anti-atrial fibrillatory drugs.

Stereospecific in vitro and in vivo effects of the new sinus node inhibitor (+)-S 16257

1997 ◽  
Vol 339 (1) ◽  
pp. 43-51 ◽  
Author(s):  
Catherine Thollon ◽  
Jean-Pierre Bidouard ◽  
Christine Cambarrat ◽  
Ludovic Lesage ◽  
Hélène Reure ◽  
...  
Keyword(s):  
Sinus Node ◽  
In Vivo Effects

Role of sinoatrial ring bundle in internodal conduction

1976 ◽  
Vol 231 (2) ◽  
pp. 319-325 ◽  
Author(s):  
M Hiraoka ◽  
T Sano
Keyword(s):  
Sinus Node ◽  
The Other ◽  
Wave Fronts ◽  
Av Node ◽  
Crista Terminalis ◽  
Main Route ◽  
Endocardial Surface ◽  
The Right ◽  
Activation Sequence

The role of the sinoatrial ring bundle (SARB) in internodal conduction was examined by the microelectrode technique in excised rabbit hearts. The spread of the sinus impluse to the surrounding tissues was shown to proceed anteriorly toward the right branch of the crista terminalis significantly faster than toward the other direction. Thus the right SARB and the right branch of the crista terminalis close to the sinus node were the earliest areas excited by the sinus impulse in the areas surrounding the sinus node. It was further shown that the activation sequence does not initiate from the right SARB to the right branch of the crista terminalis via the junction of these two structures. Cutting the SARB did not produce any delay in conduction from the sinus node to the atrioventricular (AV) node. The conduction velocity measured at the endocardial surface by two microelectrodes has proved that conduction in the crista terminalis was significantly faster than in the SARB. The upstroke of the action potential from the crista terminalis was also steeper than that from the SARB. These results suggest that the SARB is not the main route for impulse propagation from the sinus node to the AV node; the fastest internodal conduction therefore takes place with wide wave fronts, along the crista terminalis.

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