Factors related to AF originating from the SVC
Several previous studies have elucidated the relationship between some
factors and AF originating from the SVC (SVC-AF). Almost all of these
studies used pacing and/or drugs to induce SVC-AF. An anatomical report
showed that SVC-AF is more likely to occur in patients with a smaller LA
diameter 17. In a report on clinical features, SVC-AF
tends to be more common in female patients, those with a lower body mass
index, and those with certain genes (rs2634073 and rs6584555)18. The electrical characteristics were that SVC-AF is
more common in patients with long SVC sleeves (>30 mm12,13), SVC firing is more likely to occur in patients
with long SVC sleeves (>37 mm) or long SVC diameters
(>17 mm) 19, and SVC-AF is more common in
cases with a large potential (>1 mv 12).
In our electrophysiological study, the relationship between the SVC-ERP
and SVC-AF was clarified. To the best of our knowledge, there are no
reports that have examined the relationship between the SVC-ERP and
SVC-AF. Our study revealed that the shorter the SVC-ERP, the more likely
SVC-AF occurred at pacing, while the dispersion of the SVC-ERP did not
contribute.
The present study revealed that the SIG had a higher proportion of
patients with persistent AF. Past animal experiments using goats
reported that AF leads to a marked shortening of the atrial ERP20, and this electrophysiological change is called
electrical remodelling. Another previous study reported that electrical
remodelling may also occur in the human SVC 16. Our
study revealed the concordant result; patient with persistent AF had a
shorter SVC-ERP than those with paroxysmal AF (240.0±37.6 vs 295.7±31.7
ms, p=0.002). We assumed that persistent AF caused the SVC sleeve to
have a stronger electrical remodelling than that caused by paroxysmal
AF, resulting in the acquisition of a shorter SVC-ERP and a greater
vulnerability to pacing from the SVC.
Although previous studies using the same rapid electrical stimuli
reported that the length of the SVC sleeve was longer in the SIG13, we did not find a difference between the two
groups. The possible reason was that we selected only patients who could
measure the SVC-ERP in all three portions. As a result of selecting a
population with a relatively long SVC sleeve length, there may be no
difference between the two groups in the present study.
A previous study reported that SVC firing is more likely to occur in
patients with long SVC sleeves (>37 mm) or long SVC
diameters (>17 mm) 19. Our study also
revealed that the longer diameter of the SVC was significantly longer in
the SIG (27.4±4.3 vs. 22.9±4.6 mm, p=0.03) compared to that of the
non-SIG. Furthermore, we found that the SVC-ERP was significantly
associated with pacing inducibility of AF after adjustment for the
longer diameter of the SVC (adjusted odds ratio: 0.96 [1-ms
increments], 95% confidence interval: 0.93–0.99; p=0.01). It was
suggested that the SVC-ERP was also a factor related to SVC-AF.