Atrial tachyarrhythmias with ultra-rapid ventricular response in patients with a structurally normal heart: a new and distinct entity in the spectrum of sudden cardiac death?

Abstract Background Sudden cardiac death (SCD) is linked to severe ventricular arrhythmias. While supraventricular arrhythmias are known to cause SCD in conditions like Wolff-Parkinson-White syndrome and complex congenital heart disease, the contribution of atrial tachyarrhythmias (ATA) to SCD in patients with otherwise normal hearts remains uncertain. Purpose To present data on resuscitated patients without structural heart disease (SHD), suffering from recurrent ICD shocks, that share common clinical and electrical features suggesting that ATAs can cause SCD. Methods We describe the clinical characteristics and ICD analysis of syncopal events terminated with shock delivery in 5 young SCD survivors without SHD. SHD was thoroughly excluded, including cardiac magnetic resonance imaging. Extensive electrophysiological testing and genetic analysis was also performed. Furthermore, we report the follow-up after ablation of the arrhythmia causing the syncopal episode. Results In five patients (4 male, 1 female; median age 23 years, range 15–47), surface ECGs during resuscitation initially suggested ventricular fibrillation. No SHD was found in all patients and no (likely) pathogenic variants were identified in genes related to inherited arrhythmia syndromes and genetic cardiomyopathies. After the initial event, all patients continued to experience adrenergically triggered syncopal arrhythmias, requiring ICD intervention. ICD tracing analysis showed ATAs (atrial fibrillation in four patients and atrial tachycardia in one) with ultra-rapid ventricular rates nearing 300 bpm, leading to these syncopal events. These clinical, hemodynamic and electrophysiological features could be repeated during electrophysiological study. ATA ablation effectively prevented further syncopal episodes and ICD shocks in all patients during a median follow-up of 34 months, with no sudden deaths reported. Conclusion A specific form of SCD related to ATAs with ultra-rapid ventricular response rates can be identified in patients with structurally normal hearts. Catheter ablation of the ATA appears to be a successful therapy for these patients.