Discussion
We encountered two cases of cardiac arrest in patients with persistent AF with SVR after electrical cardioversion for rhythm control. Both patients had tolerable LV function and NYHA class II to III dyspnea despite being on medication. Although their AF showed SVR, and NSVT was also identified, pacemaker or ICD implantation was not indicated. Thus, rhythm control strategy could be selected according to the current guideline.3 However, the patients suffered critical arrhythmic complications.
The risk of arrhythmic complications of rhythm control in AF patients with bradyarrhythmia has been pointed out since the past,4, 5 and current guidelines recommend avoiding pharmacological cardioversion in patients with SSS or AV conduction disturbances.3 However, guidelines do not provide a distinct recommendation for electrical cardioversion in patients with AF with SVR, and the outcome of rhythm control is unknown for this sub-population.3 Moreover, in patients with no previous history of SSS or AV conduction disturbances, the assessment of the functional status of the SA node or AV node before cardioversion is challenging.6 Thus, a dilemma arises in the decision of the rhythm control in patients with symptomatic AF with SVR.
The effect of ventricular rate on the outcome of electrical cardioversion remains controversial. Shin et al. reported that patients with lower heart rates before cardioversion were more likely to have bradyarrhythmic events, but Jussi et al. reported that a lower ventricular rate does not affect the success of cardioversion or predispose to complications including bradyarrhythmia.7, 8 And, there are emerging data that rhythm control including catheter ablation in cases of predominant AF and secondary sinus nodal dysfunction can lead to resolution of the bradyarrhythmia.9 In this respect, rhythm control strategy could be selected in patients with AF with SVR. However, meticulous evaluations including history taking, physical examination, ECG, chest radiography, 24-hour Holter recording, TTE, and treadmill test should be performed before rhythm control strategy. Additionally, NSVT was documented in both patients, which might be an ominous sign of critical arrhythmic events. However, the effect of rhythm control in AF patients with NSVT has not yet been investigated.