RESUMO
We describe two cases of secondary prevention subcutaneous implantable cardioverter defibrillator (S-ICD) implantation and subsequent S-ICD electrode displacement which initially went undetected. One presentation was a result of a coincidental chest x-ray for respiratory exacerbation and another with an untreated episode highlighted via remote monitoring, both patients were booked to clinic for further investigation. Our findings highlighted had there been a comparison of the existing subcutaneous electrogram (S-ECG) to captured S-ECGs at time of implant the electrode displacement would have been detected beforehand. This underpins the importance of introducing the simple management strategy into routine follow-up.
RESUMO
BACKGROUND: Focal and rotational activations have been demonstrated in atrial fibrillation (AF), but their relationship to each other and to structural remodeling remains unclear. OBJECTIVE: The purpose of this study was to assess the relationship of focal and rotational activations to underlying low-voltage zones (LVZs) (<0.5 mV) and to determine whether there was a temporal (≤500 ms) and spatial (≤12 mm) relationship between these activations. METHODS: Patients undergoing catheter ablation for persistent AF were included. All patients underwent pulmonary vein isolation. Unipolar signals were collected to identify focal and rotational activations using a wavefront propagation algorithm. RESULTS: In 40 patients, 105 activations were identified (57 [54.3%] focal; 48 [45.7%] rotational). Rotational activations were co-localized to LVZs (35/48 [72.9%]) whereas focal activations were not (11/57 in LVZ [19.3%]; P <.001). The proportion of the left atrium occupied by LVZs predicted rotational activations occurrence (area under the curve 0.96; 95% confidence interval 0.90-1.00; P <.001). In patients with a relatively healthy atrium, in which the atrium consisted of ≤15% LVZs, only focal activations were identified. Thirty-two of the 35 rotational activations (91.4%) located in LVZs also showed a temporal and spatial relationship to a focal activation. The presence of a LVZ within 12 mm of the focal activation was a strong predictor for whether a paired rotational activation would also occur in that vicinity. CONCLUSION: Rotational activations are largely confined to areas of structural remodeling and have a clear spatial and temporal relationship with focal activations suggesting they are dependent on them. These novel mechanistic observations outline a plausible model for patient-specific mechanisms maintaining AF.