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Dysrhythmias after direct-current cardioversion
Insights
Direct-current (DC) countershocks effectively treat ventricular tachycardia/fibrillation (VT/VF) and atrial fibrillation (AF). Continuous cardiac rhythm analysis is crucial for automatic devices to manage postshock arrhythmias and ensure patient safety.
Area of Science:
- Cardiology
- Medical Devices
- Electrophysiology
Background:
- Direct-current (DC) countershocks are vital for treating life-threatening arrhythmias like ventricular tachycardia/fibrillation (VT/VF) and atrial fibrillation (AF).
- The efficacy of DC shocks and the occurrence of postshock arrhythmias are critical considerations for the development of automated external defibrillators (AEDs) and implantable cardioverter-defibrillators (ICDs).
Purpose of the Study:
- To analyze the success rates of transchest DC countershocks for induced VT/VF and AF.
- To investigate the relationship between clinical characteristics, arrhythmia types, and the incidence of postshock arrhythmias.
- To evaluate the impact of antiarrhythmic drugs on postshock rhythm disturbances.
Main Methods:
- Retrospective analysis of 112 DC shock episodes in 99 patients with induced VT/VF or AF.
- Correlation of clinical data and arrhythmia characteristics with DC shock success rates and postshock events.
- Assessment of asystole duration, recurrence of VT/VF, and development of bradyarrhythmias post-shock.
Main Results:
- The first DC shock successfully terminated 80% of VT/VF episodes, with all episodes resolved within four shocks.
- Asystole duration was significantly longer following VT/VF (1900 ms) compared to AF (1150 ms).
- VT/VF recurred in 26% of initially successful shocks, and bradyarrhythmias requiring pacing occurred in patients receiving antiarrhythmic drugs.
Conclusions:
- Transchest DC countershocks demonstrate high efficacy in terminating VT/VF and AF.
- Continuous cardiac rhythm monitoring post-discharge is essential for automatic devices to manage unsuccessful shocks or recurrent arrhythmias.
- Demand pacing capability is desirable in automated devices to address severe bradycardia in patients on antiarrhythmic medications.
Abstract:
The success rate of direct-current (DC) countershocks and postshock arrhythmias are of concern for the design of automatic devices. Results of 112 DC shocks for induced ventricular tachycardia/fibrillation (VT/VF) (n = 99) or atrial fibrillation (AF) were analyzed. Clinical and arrhythmia characteristics were related to the success rate of DC shocks as well as postshock arrhythmias. Sixty-one patients were men and 14 were women; mean age was 52 +/- 15 years. Coronary artery disease was present in 56 patients and cardiomyopathy in 4. The other patients had no apparent structural heart disease. The success rate of transchest DC shocks for VT and VF were identical. The first DC shock interrupted 80% of VT and VF episodes. All episodes were terminated by 4 or fewer DC shocks. A single DC shock changed morphologic pattern or rate of 4 episodes of VT. Asystole after VT/VF (1,900 +/- 960 ms) was longer than after atrial fibrillation (1,150 +/- 470 ms, p less than 0.01). VT/VF recurred (within 3 minutes) after 26 of 99 initially successful DC shocks, requiring repeat shocks in 2 cases. Sinus bradycardia (n = 18) or high degree atrioventricular block (n = 11) necessitated rate support pacing in 10 patients. Antiarrhythmic drugs did not prevent postshock tachycardias, but facilitated the development of bradycardias. In conclusion, reliable and continuous analysis of cardiac rhythm after discharge is mandatory to enable automatic devices to correct unsuccessful discharges or recurring VT/VF. In addition, demand pacing capability is desirable to prevent severe bradycardia after DC shocks in patients receiving antiarrhythmic drugs.