What happens after cardioversion at 100 Joules (J) fails to revert the rhythm?

Management After Failed 100 J Cardioversion

When a cardioversion attempt at 100 J fails to revert the rhythm, the next step is to increase the energy level to 200 J or higher, as an initial shock of 100 J is often too low for effective cardioversion of atrial fibrillation. 1, 2

Energy Escalation Protocol

• Increase to 200 J for the second attempt, as higher initial energy is significantly more effective than lower levels 2, 3
• If 200 J is unsuccessful, escalate to maximum energy (typically 360 J) for subsequent attempts 3, 4
• Allow at least 1 minute between consecutive shocks to avoid myocardial damage 2
• Consider changing paddle position from anterior-lateral to anterior-posterior configuration, which has a higher overall success rate (87% vs 76%) 1

Pharmacological Augmentation

• If repeated external cardioversion attempts fail, consider administering antiarrhythmic medication before another attempt 1
• Ibutilide can be used to lower the defibrillation threshold in patients refractory to standard direct current cardioversion 1
• Amiodarone combined with cardioversion has shown improved maintenance of sinus rhythm compared to cardioversion alone 5

Alternative Approaches

• For patients in whom external cardioversion remains unsuccessful despite maximum energy and antiarrhythmic drugs, internal cardioversion may be considered 1, 6
• Internal cardioversion uses electrode catheters placed in the right atrium and coronary sinus, delivering energy directly to the heart 1
• Internal cardioversion has shown higher success rates (91% vs 67%) compared to external cardioversion in patients with refractory atrial fibrillation 7

Long-term Considerations

• Even with successful cardioversion, the rate of relapse is high unless antiarrhythmic drug therapy is given concomitantly 1
• Only 23% of patients remain in sinus rhythm after 1 year and 16% after 2 years without antiarrhythmic therapy 1
• For patients who relapse, repeated cardioversion with antiarrhythmic medication can result in sinus rhythm in 40% at 1 year 1

Safety Considerations

• Monitor for potential complications after cardioversion attempts, including:
  • Transient arrhythmias (ventricular and supraventricular premature beats, bradycardia, sinus arrest) 1, 3
  • Ventricular tachycardia or fibrillation, particularly in patients with hypokalemia or digitalis toxicity 1, 3
  • Thromboembolic events, especially if anticoagulation was inadequate 1
• For patients with implanted pacemakers or defibrillators, position paddles as distant as possible from the device, preferably in anterior-posterior configuration 1, 3
• Verify device function immediately before and after cardioversion 1

Special Situations

• For patients with long-standing persistent atrial fibrillation and significant cardiac remodeling, success rates are lower 5
• In highly symptomatic patients, infrequently repeated cardioversion can be an acceptable approach despite limited long-term efficacy 1
• High energy internal cardioversion may be considered as an alternative to AV junction ablation in selected patients with poorly tolerated chronic atrial fibrillation 6