Ionic currents responsible for the generation of pace-maker current in the rabbit sino-atrial node.

Esaxerenone (ESAX; CS-3150, Minnebro®) is known to be a newly non-steroidal mineralocorticoid receptor (MR) antagonist. However, its modulatory actions on different types of ionic currents in electrically excitable cells remain largely unanswered. The present investigations were undertaken to explore the possible perturbations of ESAX on the transient, late and persistent components of voltage-gated Na+ current (INa) identified from pituitary GH3 or MMQ cells. GH3-cell exposure to ESAX depressed the transient and late components of INa with varying potencies. The IC50 value of ESAX required for its differential reduction in peak or late INa in GH3 cells was estimated to be 13.2 or 3.2 μM, respectively. The steady-state activation curve of peak INa remained unchanged during exposure to ESAX; however, recovery of peak INa block was prolonged in the presence 3 μM ESAX. In continued presence of aldosterone (10 μM), further addition of 3 μM ESAX remained effective at inhibiting INa. ESAX (3 μM) potently reversed Tef-induced augmentation of INa. By using isosceles-triangular ramp pulse with varying durations, the amplitude of persistent INa measured at high or low threshold was enhanced by the presence of tefluthrin (Tef), in combination with the appearance of the figure-of-eight hysteretic loop; moreover, hysteretic strength of the current was attenuated by subsequent addition of ESAX. Likewise, in MMQ lactotrophs, the addition of ESAX also effectively decreased the peak amplitude of INa along with the increased current inactivation rate. Taken together, the present results provide a noticeable yet unidentified finding disclosing that, apart from its antagonistic effect on MR receptor, ESAX may directly and concertedly modify the amplitude, gating properties and hysteresis of INa in electrically excitable cells.

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Linear transformations extract parameters of ionic currents and action potential features from pseudo-ECG in cardiomyocyte models

10.1063/5.0035269 ◽

2020 ◽

Author(s):

Salim Baigildin ◽

Konstantin Ushenin ◽

Aigul Fabarisova ◽

Marat Bogdanov ◽

Olga Solovyeva

Keyword(s):

Action Potential ◽

Ionic Currents ◽

Linear Transformations

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Effects of millimeter waves on ionic currents ofLymnaea neurons

Bioelectromagnetics ◽

10.1002/(sici)1521-186x(1999)20:1<24::aid-bem4>3.0.co;2-v ◽

1999 ◽

Vol 20 (1) ◽

pp. 24-33 ◽

Cited By ~ 21

Author(s):

S.I. Alekseev ◽

M.C. Ziskin

Keyword(s):

Millimeter Waves ◽

Ionic Currents

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Use of ionic currents to identify and estimate parameters in models of channel blockade

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1990.259.2.h626 ◽

1990 ◽

Vol 259 (2) ◽

pp. H626-H634

Author(s):

C. F. Starmer ◽

V. V. Nesterenko ◽

F. R. Gilliam ◽

A. O. Grant

Keyword(s):

Time Course ◽

Experimental Studies ◽

Ionic Currents ◽

Blocking Agent ◽

Model Parameters ◽

Protein Conformations ◽

Channel Blockade ◽

Channel Blocking ◽

Individual Contributions ◽

Modulated Receptor

Models of ion channel blockade are frequently validated with observations of ionic currents resulting from electrical or chemical stimulation. Model parameters for some models (modulated receptor hypothesis) cannot be uniquely determined from ionic currents. The time course of ionic currents reflects the activation (fraction of available channels that conduct in the presence of excitation) and availability of channels (the ability of the protein to make a transition to a conducting conformation and where this conformation is not complexed with a drug). In the presence of a channel blocking agent, the voltage dependence of availability appears modified and has been interpreted as evidence that drug-complexed channels exhibit modified transition rates between channel protein conformations. Because blockade and availability both modify ionic currents, their individual contributions to macroscopic conductance cannot be resolved from ionic currents except when constant affinity binding to a bindable site is assumed. Experimental studies of nimodipine block of calcium channels and lidocaine block of sodium channels illustrate these concepts.

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P957Characteristics of atrial tachycardia after mitral surgey via biatrial trans-septal approach using high density mapping system

EP Europace ◽

10.1093/europace/euaa162.222 ◽

2020 ◽

Vol 22 (Supplement_1) ◽

Author(s):

C Cataldi ◽

M Andronache ◽

R Eschalier ◽

F Jean ◽

R Bosle ◽

...

Keyword(s):

Atrial Tachycardia ◽

Sinus Node ◽

Pulmonary Veins ◽

High Density ◽

Congenital Defects ◽

Density Mapping ◽

Mapping System ◽

Oblique Incision ◽

Pace Maker ◽

The Right

Abstract Background The biatrial trans-septal approach (BTSa) ameliorates mitral valve (MV) exposure in difficult cases when routine left atriotomy doesnt"t allow it. Main steps are an oblique incision on the right atrium (RA), reaching medially the right pulmonary veins (PV), a septal incision from the fossa ovalis, extended up to reach the first incision, then on the left atrium (LA). Purpose We aim to study the arrhythmic burden in this post-surgical context, focusing on atrial tachycardia (AT), to investigate the complexity of several possible circuits. Methods All patients (>18yo) with previous MV surgery via BTSa for MV repair or replacement, who underwent ablation of AT from January 2017 to September 2019, were enrolled. Patients ablated for persistent or paroxysmal AF, or with AF during the index procedure were excluded. Patients with associated surgery on other valves or congenital defects, coronary, surgical or percutaneous rhythm interventions weren’t excluded. Electroanatomical mapping was created using 2 different high-density mapping system. Substrate and activation map and radio-frequency (RF) ablation (25-50W, Ablation Index target 400) were realized. Cartographies were analysed to evaluate AT re-entry circuit, critical isthmus (CI) location and characterization, atrial vulnerability. Procedural outcomes (AT termination, sinus rhythm (SR) restoration, anti-arrhythmic drugs (AAD) withdrawal), and peri-procedural complications were also evaluated. Results We enrolled 49 patients (median age 57 ± 15), finding a maximum of 5 AT per procedure (2 ± 1). A total of 112 AT were mapped: the majority (72%) were persistent AT, 8,2% common atrial flutter. Cycle length was 314 ± 74 msec, with proximal-distal activation of coronary sinus (78%). A multiple re-entry circuit was observed in 70% of index AT. We identified 152 critical isthmus (maximum 5 per procedure). Only 27,9% of our patients had a single CI; CTI was the most frequent one (n = 37), envolved in 33% of all AT, while BTS scars altogether were envolved in 65% AT. A complete AT circuit was mapped in the RA, the LA and both atria in respectively 49%, 11,5% and 39%AT. The distribution of CIs is shown in figure 1. Biatrial and left AT leads to superior procedure, RF and fluoroscopy duration (p <0,05). SR was restored in 93,4%of patients, requiring a DC shock in 4 cases. Immediate AAD withdrawal was achieved after 41%procedures. No pericardial, oesophageal, vascular or phrenic complication occurred. 4 pace-maker implantations were realized because of 3 interatrial, 2 AV block and a sinus node dysfunction. Conclusions AT occurring after a BTSa have a high prevalence of multiple re-entry circuits with multiple critical isthmus. Ablation in this context is feasible and safe but often requires a left atrial access. Mapping of both atria should be considered to identify critical isthmus and tailored ablation strategy. Abstract Figure 1. Critical Isthmus Distribution

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Laser treatment of benign prostatic hypertrophy

Urologia Journal ◽

10.1177/039156039606300113 ◽

1996 ◽

Vol 63 (1) ◽

pp. 77-80

Author(s):

S. Guazzieri ◽

W. Cecchetti ◽

M. Meneguolo ◽

G. D'incà ◽

R. Bertoldin

Keyword(s):

Laser Treatment ◽

Benign Prostatic Hypertrophy ◽

Prostatic Hypertrophy ◽

Laser Source ◽

Experimental Procedure ◽

The Usa ◽

Side Emission ◽

Pace Maker ◽

Stable Laser ◽

Good Flow

— Laser treatment of benign prostatic hypertrophy (BPH) has gradually become more widespread over the last few years. In the USA it is considered an alternative to endoscopic resection as far as insurance payments are concerned. Different methods are used but the most common and suitable one for urologists is the removal and coagulation of the prostatic tissue under visual control (VLAP or ELAP). The Authors report their personal experience in this type of treatment where good results are due to: 1) combination of a powerful, stable laser source 2) durable side-emission contact fibre 3) laser resector, which also in the absence of epicystostomy maintains a good flow during the operation. However, “laser resection” should still be considered an experimental procedure to be used for randomised protocols or on selected patients (high risk of bleeding, Jehovah's witnesses, carriers of pace-maker, etc.).

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