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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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Arrhythmia is a condition characterized by an irregular heart rhythm, with ECG changes that differ based on its origin and nature. The types of arrhythmias discussed below include atrial, junctional, and ventricular arrhythmias.Atrial ArrhythmiasPremature Atrial Complexes (PACs): PACs are early atrial beats caused by stress, caffeine, alcohol, electrolyte imbalances, hypoxia, hyperthyroidism, or certain medications (e.g., bronchodilators and decongestants). The ECG shows early P waves with an...
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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.
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Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers01:22

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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.
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Electrocardiogram01:29

Electrocardiogram

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An electrocardiogram (ECG or EKG) is a critical diagnostic tool that records the electrical signals produced by the heart during each heartbeat. This recording is achieved through electrodes placed strategically on the arms, legs, and chest. The electrocardiograph amplifies these signals and produces 12 distinct tracings, offering a comprehensive understanding of the heart's electrical activity.
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Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers01:24

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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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Risperidone and corrected QT-interval prolongation in surface electrocardiogram.

F Ranjbar1, F Akbarzadeh, N M Ahmadi

  • 1Clinical Psychiatry Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.

Pakistan Journal of Biological Sciences : PJBS
|November 6, 2013
PubMed
Summary
This summary is machine-generated.

Risperidone, an antipsychotic, may significantly prolong the QT interval and increase QT dispersion in psychotic patients. Healthcare providers should monitor for cardiovascular risks associated with this medication.

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Area of Science:

  • Pharmacology
  • Cardiology
  • Psychiatry

Background:

  • Risperidone is an antipsychotic with suspected, yet limited, evidence of QT prolongation.
  • Cardiovascular risks associated with antipsychotics require ongoing investigation in diverse clinical settings.

Purpose of the Study:

  • To evaluate the effect of risperidone on QT interval lengthening in psychotic patients.
  • To assess risperidone's impact on corrected QT (QTc) interval and QTc dispersion.

Main Methods:

  • A controlled cohort study compared 120 patients receiving risperidone to 60 controls.
  • Electrocardiograms were taken at admission, one week, and discharge.
  • Corrected QT (QTc) interval and dispersion were calculated; data analyzed using multivariate longitudinal analysis.

Main Results:

  • Risperidone group showed a statistically significant QTc increment in V1 and V3 leads over time.
  • The control group did not exhibit significant changes in QTc measures.
  • Multivariate analysis revealed a significant difference in overall QTc trends between risperidone and control groups (p < 0.01).

Conclusions:

  • Risperidone may significantly affect the QT interval and QT dispersion.
  • Prolonged QTc is a potential cardiovascular risk indicator.
  • Clinicians should exercise caution when prescribing risperidone, monitoring for potential QT prolongation.