PAF patients with an AF recurrence after treatment showed significant higher cfc-mtDNA levels for both COX3 and ND1 compared to control patients (and borderline significant compared to PAF without an AF recurrence after treatment, p = 0.054 for COX3 and p = 0.053 for ND1), while LS-PeAF patients with an AF recurrence showed significant lower cfc-mtDNA levels compared to control patients (Figure 4A,B, Figure S4). Here, MT-ND1 is linked to atrial fibrillation.