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Interactions between implantable cardioverter-defibrillators and class III agents
1Department of Medicine, Allegheny University of the Health Sciences, Hahnemann Hospital, Philadelphia, Pennsylvania 19102-1192, USA.
Insights
Class III antiarrhythmic drugs are commonly used with implantable cardioverter-defibrillators (ICDs). These drugs can affect ICD effectiveness by altering defibrillation thresholds and ventricular tachycardia cycle length.
Area of Science:
- Clinical Electrophysiology
- Cardiology
- Pharmacology
Background:
- Implantable cardioverter-defibrillators (ICDs) effectively terminate ventricular arrhythmias.
- Many ICD patients (40-70%) require antiarrhythmic drugs to prevent recurrent arrhythmias.
- Class III antiarrhythmic agents are frequently prescribed due to their safety and efficacy.
Purpose of the Study:
- To evaluate the impact of Class III antiarrhythmic drugs on ICD function.
- To analyze how these drugs affect defibrillation threshold and ventricular tachycardia cycle length.
- To assess the proarrhythmic potential of Class III agents in ICD patients.
Main Methods:
- Review of existing animal and clinical studies on Class III antiarrhythmic drugs and ICDs.
- Analysis of drug effects on ventricular refractoriness and defibrillation threshold.
- Examination of drug-induced changes in ventricular tachycardia cycle length and proarrhythmic events.
Main Results:
- Pure Class III agents decrease defibrillation threshold in canine models.
- Sotalol consistently decreases defibrillation threshold in animal and clinical studies.
- Amiodarone shows variable effects on defibrillation threshold in animal models but increases it clinically; it moderately slows ventricular tachycardia cycle length.
Conclusions:
- Class III pharmacotherapy can be safely used with ICDs.
- Understanding drug interactions with ICDs is crucial for effective patient management.
- Potential proarrhythmic effects, such as torsade de pointes with sotalol or slowed VT below detection rates with amiodarone, must be considered.
Abstract:
Although implantable cardioverter-defibrillators (ICDs) can successfully terminate ventricular arrhythmias, antiarrhythmic drugs are often required to prevent recurrent events. Class III antiarrhythmic agents have emerged as the safest, most effective, and widely used agents in the 40-70% of ICD patients who require concomitant antiarrhythmic medication. Antiarrhythmic agents can influence the effectiveness of ICDs to terminate arrhythmias through their effect on defibrillation threshold. All class III agents share the ability to prolong ventricular refractoriness and those with "pure" class III activity consistently decrease defibrillation threshold in the normal canine heart model. Sotalol, amiodarone, and bretylium all have other Vaughan Williams class actions that influence their respective effects on defibrillation threshold. Sotalol has been associated with a decrease in defibrillation threshold in both animal and in clinical studies, whereas amiodarone has been associated with variable effects in animal models and an increase in defibrillation threshold in clinical studies. Additionally, antiarrhythmic agents may prolong ventricular tachycardia (VT) cycle length, which may affect the ability to pace terminate or cardiovert VT. Amiodarone has a moderate slowing effect on the VT cycle length. Finally, class III drugs also have proarrhythmic potential that may affect the defibrillator's function. Sotalol can be associated with dose-related torsade de pointes, whereas amiodarone may slow the VT cycle length below the tachycardia detection rate cutoff. In conclusion, class III pharmacotherapy can be safely administered in conjunction with ICD therapy as long as the interaction between these therapeutic modalities is appreciated.