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Related Concept Videos

Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers01:22

Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers

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Class I antiarrhythmic drugs are used to treat various types of arrhythmias or irregular heart rhythms. These drugs block the sodium (Na+) channels in the cardiac cells, thereby affecting the movement of electrical impulses across the heart. Class I antiarrhythmic drugs are divided into three subgroups: Class IA, Class IB, and Class IC, each with distinct mechanisms of action and effects on the heart.
Class 1A Antiarrhythmic Drugs: These drugs work by moderately blocking sodium channels,...
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Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers01:24

Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers

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Adrenergic stimulation generally impacts cardiac rate and rhythm. Specifically, stimulation of the β-adrenoceptors triggers an increase in intracellular calcium ion influx and pacemaker currents, which may cause arrhythmias. Catecholamines like adrenaline also demonstrate β2-adrenoceptor-mediated hypokalemia, impacting cardiac action potential and disrupting the normal cardiac rhythm. Class II antiarrhythmic drugs are β-adrenoceptor antagonists or β-blockers, which...
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Cardiac Action Potential01:30

Cardiac Action Potential

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Cardiac action potentials are essential for proper heart function, enabling the rhythmic contractions needed for adequate blood circulation. Nodal cells and Purkinje fibers, specialized for electrical conduction, generate these action potentials.
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
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Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers01:12

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Class III antiarrhythmic drugs are a group of medications that can prolong action potentials in the heart. They achieve this by blocking potassium channels or enhancing inward currents from sodium channels. However, these drugs have a unique property of "reverse use-dependence," which is most pronounced at slower heart rates and can lead to torsades de pointes—a specific type of arrhythmia. However, it is essential to note that excessive QT interval prolongation—a measure of...
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Mechanism of Cardiac Arrhythmias01:28

Mechanism of Cardiac Arrhythmias

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Arrhythmias are irregular heart rhythms occurring when the heart's electrical impulses become abnormal. These disturbances can lead to various symptoms, depending on their severity and the underlying cause. Some common factors contributing to arrhythmias include hypoxia, ischemia, electrolyte imbalances, excessive catecholamine exposure, drug toxicity, and muscle overstretching. Arrhythmias can be classified into two main types based on the rate and site of origin of abnormal heart rhythms.
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Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers01:20

Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers

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Class IV antiarrhythmic drugs, such as verapamil and diltiazem, block calcium channels. They primarily affect the heart, slowing the conduction in calcium-dependent tissues like the SA and AV nodes. These drugs manage reentrant supraventricular tachycardia (SVT) and reduce ventricular rate in atrial flutter/fibrillation.
Verapamil, a calcium channel blocker, inhibits calcium movement across myocardial cell membranes and vascular smooth muscle. This results in the dilation of coronary and...
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Submyocardial Pacing Threshold Distribution During Cold Saline Application; Exploring Reversible Arrhythmia

Osamu Saitoh1, Takumi Kasai1, Ayaka Oikawa1

  • 1Cardiovascular Research of Graduate School of Health Sciences, Niigata University School of Medicine, Niigata, Japan.

Pacing and Clinical Electrophysiology : PACE
|November 16, 2024
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Summary

Cold saline irrigation through a catheter can temporarily stop heart muscle signals, helping to find the best spot for radiofrequency ablation. This method shows promise for precise cardiac procedures.

Keywords:
cold saline mappingirrigation catheterrecoverable inhibition

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Area of Science:

  • Cardiac Electrophysiology
  • Minimally Invasive Cardiac Surgery
  • Medical Device Technology

Background:

  • Radiofrequency (RF) ablation is a key treatment for cardiac arrhythmias.
  • Precise targeting of ablation sites is crucial, especially near delicate cardiac structures.
  • Current methods for identifying optimal ablation sites may require further refinement.

Purpose of the Study:

  • To investigate the potential of cold saline application via an irrigation catheter to reversibly inhibit submyocardial excitation.
  • To determine if this method can aid in identifying ideal radiofrequency (RF) energy delivery sites around sensitive cardiac areas.
  • To assess the depth-dependent effects of cold saline on myocardial excitability.

Main Methods:

  • An open irrigation catheter was used to apply 4°C saline (20 mL/min) to porcine hearts.
  • Myocardial temperature 2 mm below the surface (Temp-BS) and pacing threshold increase (%increase-PT) were measured.
  • Pacing thresholds were assessed at varying depths using an electrode plunge needle near the ablation catheter.

Main Results:

  • Cold saline application reversibly inhibited submyocardial excitation, interrupting ventricular pacing capture.
  • The increase in pacing threshold was greatest at the myocardial surface and decreased with depth.
  • Significant pacing threshold increases (>150%) were observed at 2-3 mm depth, and (>120%) at 6-7 mm depth.

Conclusions:

  • Cold saline irrigation is a simple, reversible method to inhibit submyocardial excitation.
  • This technique shows potential for pre-determining optimal ablation sites in sensitive cardiac regions.
  • Further research and technological development are needed for clinical application.