5.2. Slow LACV as a marker of left atrial AF substrate
In this study, we found that a slow anterior LACV more accurately
predicted AF recurrence than any other previously reported predictor,
including AF type, left atrial size, and low-voltage-area existence.
This excellent predictive value of a slow LACV might be explained as
follows. First, conduction slowing is a direct measure of factors
associated with arrhythmia with the reentrant mechanism, such as rotor
during AF,12-14 and slow conduction zone during
regular atrial tachycardia.15 Second, as described in
the above paragraph, conduction slowing is a likely consequence of
atrial fibrosis, which could also provoke shortening of the refractory
period and triggered activity. Thus, a slow LACV possibly represents a
variety of electrophysiological characteristics which in concert render
the subject vulnerable to AF development. Third, this study measured
LACV from the start to the end of the left atrial propagation wave
front, which facilitates comprehensive assessment of left atrial
arrhythmogenicity. Anterior LACV was slower than posterior LACV,
irrespective of the presence of AF recurrence. A physiological slow
anterior LACV would be partially attributable to conduction slowing of
the anterior propagation wave perpendicularly crossing the
septo-pulmonary bundle.16 In addition, LACV slowing on
the anterior route more precisely predicted AF recurrence than that on
the posterior route. Left atrial fibrosis would progress initially in
the anterior-septal region before other regions, as reported in previous
studies which showed that low-voltage areas most commonly existed in the
anterior-septal region.8, 15 Several studies have
assessed atrial conduction disturbance using P-wave duration obtained by
surface signal-averaged electrocardiogram,5-7 and
found that P-wave prolongation was associated with AF recurrence after
PV. These results suggest that inter- and intra-atrial conduction
disturbances represent an arrhythmogenic substrate of AF. Our present
study using a recently available high-density mapping system confirms
these previously reported findings.