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Interactions between pharmacologic and nonpharmacologic antiarrhythmic therapy
1Department of Medicine, University of Washington, Harborview Medical Center, Seattle 98104, USA.
Insights
The optimal treatment for ventricular arrhythmias using antiarrhythmic drugs and implantable cardioverter-defibrillators (ICDs) remains unclear. Combining therapies offers benefits like improved tolerance but carries risks, necessitating careful monitoring and electrophysiologic testing.
Area of Science:
- Cardiology
- Electrophysiology
- Pharmacology
Background:
- The optimal initial treatment strategy for serious ventricular arrhythmias, whether antiarrhythmic drugs or implantable cardioverter-defibrillators (ICDs), is not established.
- Many patients with ventricular arrhythmias are treated with both antiarrhythmic drugs and ICDs, though the frequency of this combined approach has decreased over time.
Purpose of the Study:
- To review the beneficial and adverse interactions between antiarrhythmic drugs and ICDs in patients with ventricular arrhythmias.
- To highlight the importance of careful consideration and monitoring when combining these treatment modalities.
Main Methods:
- Literature review and synthesis of existing studies on antiarrhythmic drug and ICD combination therapy.
- Analysis of reported benefits and drawbacks of combined pharmacologic and device therapy for ventricular arrhythmias.
Main Results:
- Beneficial interactions include improved hemodynamic tolerance, enhanced pacing/cardioversion success, reduced drug side effects, fewer arrhythmia episodes, and prevention of supraventricular arrhythmias.
- Adverse interactions involve slowed ventricular tachycardia detection, increased defibrillation/pacing thresholds, worsened hemodynamic tolerance, lengthened cardiac intervals, and reduced electrogram size, potentially leading to detection failure.
Conclusions:
- Combining antiarrhythmic drugs and ICDs can offer significant benefits but also presents considerable risks.
- Caution is advised when using both therapies concurrently, and repeat electrophysiologic testing is often required after initiating antiarrhythmic drug therapy in patients with an ICD to ensure efficacy and safety.
Abstract:
Whether patients with serious ventricular arrhythmias should be treated first with antiarrhythmic drugs or an implantable cardioverter-defibrillator (ICD) is not known. Many patients are ultimately treated with both an antiarrhythmic drug and on ICD. Early studies reported that 40-70% of patients who received an ICD were ultimately treated with an antiarrhythmic drug, although fewer patients are now being treated with both modalities. The beneficial interactions between antiarrhythmic drugs and an ICD are slowing of ventricular tachycardia, which yields improved hemodynamic tolerance; improved antitachycardia pacing and low energy cardioversion success; lowering of antiarrhythmic drug doses, which reduces the risk of side effects; limiting the number of arrhythmia episodes, which minimizes patients discomfort and prolongs ICD battery life; and preventing or slowing supraventricular tachyarrhythmias, which reduces the number of inappropriate shocks from the ICD. The disadvantages of combining pharmacologic therapy and the use of an ICD are the cost and side effects of both therapies. Adverse interactions between an ICD and antiarrhythmic drugs include slowed ventricular tachycardia, which may lead to failure to detect the arrhythmia; increased defibrillation and pacing thresholds; worsened hemodynamic tolerance of ventricular tachycardia; lengthened PR, QRS, or QT intervals causing multiple counting; and decreased size of the intracardiac electrogram, leading to failure to detect the ventricular tachycardia or fibrillation. Caution must be used when combining pharmacologic therapy with an ICD. Repeat electrophysiologic testing is frequently necessary after the initiation of antiarrhythmic drug therapy in a patient with an ICD to ensure successful therapy with the ICD.