Characterization of the critical cycle length of a left atrial driver which causes right atrial fibrillatory conduction

A stable rhythm of very short cycle length (CL) in the left atrium (LA) can cause fibrillatory conduction, particularly in the right atrium (RA). Fast Fourier transform (FFT) analysis reliably identifies LA to RA conduction path(s) during atrial fibrillation (AF). We tested the hypotheses that FFT analysis of atrial electrograms (AEGs) during AF simulation will reliably identify the critical LA driver CL that causes RA fibrillatory conduction (i.e., the critical conduction breakdown CL) and that a longer critical conduction breakdown CL is found in atria of abnormal (sterile pericarditis) compared to normal dogs. We paced from Bachmann´s bundle and the posterior-inferior LA at rapid rates to mimic an LA driver. During pacing, 4 sec of FFT analysis of 203 bipolar AEGs was performed and showed: 1) a single dominant frequency peak at the pacing CL in both atria when the atria followed the pacing in a 1:1 manner; 2) multiple and broad frequency peaks on the RA and parts of the LA at the conduction breakdown CL; and 3) the conduction breakdown CL is longer in pericarditis than normal dogs. FFT analysis allowed reliable detection of the critical CL of an LA driver that induces RA fibrillatory conduction.