Current technologies to prevent sudden cardiac death and the role of wearables in arrhythmia detection

The first part of this thesis compares the subcutaneous ICD (S-ICD) with the transvenous ICD (TV-ICD) and evaluates strategies to optimize S-ICD treatment. A sub-analysis of the PRAETORIAN trial showed that although overall complication rates were similar, TV-ICDs were associated with more severe complications, including more frequent invasive interventions, whereas the most common S-ICD complication was a pocket bleeding. Further research demonstrated that continuation of vitamin K antagonist therapy was an independent predictor of pocket bleedings compared with interruption before implantation, highlighting the need for S-ICD-specific perioperative antithrombotic guidelines.
The incidence of inappropriate shocks was comparable between devices, but their mechanisms differed. Interventions such as device reprogramming, medication adjustment, or invasive treatment significantly reduced the risk of recurrent inappropriate shocks. The PRAETORIAN score proved to be a reliable indicator of DFT success when calculated from correctly acquired chest radiographs. We further demonstrated that incorrect arm positioning can underestimate the score and that it should not be applied to chest radiographs obtained in the supine position.
The second part of this thesis investigated wearable technologies. The Apple Watch detected atrial fibrillation with high accuracy but generated many unclassifiable recordings. Repeating the measurement more than once after an unclassifiable result reduced diagnostic accuracy and increased false-positive results, supporting the recommendation to repeat the recording only once. A pilot study showed that a ring-based PPG sensor could accurately detect ventricular arrhythmias. Finally, white noise improved heart rate variability more than the music genres studied, suggesting potential applications for improving autonomic balance and reducing anxiety, which could be of interest for ICD patients who have experienced appropriate or inappropriate therapy while conscious.
Overall, this thesis provides new insights into current ICD therapy, identifies opportunities to optimize S-ICD treatment, and demonstrates the growing clinical potential of wearable technologies for arrhythmia detection and beyond.