Noninvasive Characterisation of Short-and Long-Term Recurrence of Atrial Signals During Persistent Atrial Fibrillation

Propagation of electrical atrial activity (AA) during atrial fibrillation (AF) is a process characterized by different short- and long-term recurrence behaviours. Two antithetical (not mutually exclusive) hypotheses were proposed to noninvasively describe this nonstationary behaviour. The first hypothesis (H1) assumes a process with stationary spatial properties of AA propagation, but time-varying frequency properties, and vice versa for the second (H2). Based on H1 and H2, two phenomenological models were proposed, both able to replicate observations on AF patients, and a novel measure was introduced to assess the spatial variability of AA propagation (SVAAP) over short and long AA segments. Validity of the models was tested by looking at the relation between SVAAP-short and SVAAP-long on real observations from AF patients (high-density body surface potential maps recorded in 75 patients affected by persistent AF). H1 is confirmed if SVAAP-short is approximately equal to SVAAP-long. H2 if SVAAP-short is less than SVAAP-long. Results confirmed H2, showing that AA propagation during AF has strong nonstationary spatial properties. This could suggest new parameters to characterise AF substrate and predict therapy outcome.