Definition of success
Procedural success varies substantially depending on how success is
defined. The first 90 days following ablation, termed the blanking
period, are characterized by a high burden of atrial arrhythmias
resulting from atrial inflammation which does not necessarily portend a
reduction in long term success and is frequently not used clinically or
in research studies to indicate treatment failure. While one 30 second
episode of AF over the course of a year, excluding the blanking period,
technically constitutes treatment failure to maintain sinus rhythm, this
low burden of AF is arguably clinically irrelevant to the individual
patient and does not increase stroke risk17. AF burden
reduction18 and improvement in quality of life
(QoL)7 may be more clinically relevant endpoints.
Clinical trials such as CIRCA Dose used insertable cardiac monitors
(ICMs) for AF monitoring post-ablation and showed a reduction in AF
burden by 99% even though almost half had one or more AF recurrences at
12 months18. Using a real-world dataset of 665
patients with a cardiac implantable electronic device (CIED) having
undergone an AF catheter ablation, we showed that AF free survival at 1
year post-blanking period for patients with paroxysmal AF varied from
28.2 to 72.1% for AF events >6 min and >24
hrs, respectively, despite a 99.6% reduction in AF burden, and AF free
survival at 1 year for patients with persistent AF varied from 24.9 to
60% for AF events >6 min and > 7 days with
>23hrs, respectively, despite a 99.3% reduction in AF
burden (Figure 1)19. These findings were similar to
those found in the LINQ AF study in which 419 patients that had an ICM
implanted following AF catheter ablation had a success rate that varied
from 46 to 79%, depending on what threshold was used to define success.
A rational approach to AF detection post-intervention should rest in
part on the minimal duration of AF associated with major events, with
stroke constituting the most feared consequence of the disease. While AF
burden has been directly correlated with stroke
risk20–23, the exact duration of AF that is required
to increase the risk of stroke is still being debated. In a sample of
725 patients with implanted pacemakers, Capucci and colleagues showed
that the risk of stroke was increased with AF episodes
>24hrs24. The TRENDS
study25, which subsequently enrolled 2486 patients
with CIEDs, found that only AF episodes >5.5 hours over a
30-day rolling window were associated with an increased risk of
thromboembolic events (HR 2.2). The initial analysis of the ASSERT
trial, which enrolled 2580 patients with CIEDs, found that AF events
>6 minutes in duration increased the risk of stroke or
systemic embolization (HR 2.49)26. However, a
subsequent analysis of the ASSERT data showed that only AF events
> 24 hours were associated with an increased stroke risk
(HR 3.24) and that patients with <24hrs of AF had the same
stroke risk as those without AF27. What further
complicates the issue is the observation that the association between AF
duration and stroke may be dependent on the individuals underlying risk
factors. A study of 21 768 non-anticoagulated patients with CIEDs
demonstrated a clear interaction between AF duration and
CHA2DS2-VASc score, such that patients
with a CHA2DS2-VASc score of 2 required
> 23.5hrs of AF but those with a
CHA2DS2-VASc score of 4 required only
>6min of AF to have a stroke risk >1%, the
threshold some suggest is the “tipping point” for
anticoagulation20.