Conventional monitoring devices
Historically, post-intervention AF monitoring has been performed with
either periodic electrocardiograms (ECGs), external ambulatory ECG
monitors16 or CIEDs when present. External ambulatory
ECG monitors include continuous Holter monitors that record all ECG
data, event monitors that record patient events when manually triggered,
loop recorders that continuously monitor the patient’s rhythm and store
events that are either patient triggered or automatically triggered by
abnormal rhythms and real-time ambulatory telemetry that sends
continuous ECG recordings to a central monitoring station where
technicians can alert physicians in real time to events. CIEDs capable
of monitor AF recurrence and burden include ICMs as well as pacemakers
and implantable cardiac defibrillators with an atrial lead or with
atrial sensing poles on the ventricular lead.
Clinical practice guidelines recommend that for routine clinical care,
patients should have, at a minimum, an ECG at each follow up visit,
including at 3 months and then every 6 months for 2 years, with more
intense monitoring at the discretion of the provider. For the purposes
of clinical trials, guidelines recommend, in addition to ECGs at each
follow-up visit, a minimum of a 24hr Holter at the end of the follow-up
period (for paroxysmal AF) or every 6 months (for persistent AF) and
event monitoring done regularly and at the time of symptoms from the end
of the 3 months blanking period to end of follow-up (for paroxysmal AF)
or symptom driven event monitoring (for persistent AF).
Not surprisingly, the longer and more frequently you monitor for AF, the
more frequently it is discovered. This challenge is well illustrated by
the concept of AF density where intermittent monitoring has a low
sensitivity for detecting AF in individuals with infrequent episodes of
AF concentrated over short timeframes and are therefore less likely to
have AF detected with infrequent, intermittent monitoring.20 Consistent with this observation, a meta-analysis
of 66 AF ablation studies including a total of 6941 patients showed that
the method of AF detection was predictive of procedural success rather
than any specifics of the ablation procedure itself, with studies that
used CIEDs to monitor for AF recurrence showing the highest AF
recurrence rates. Using a monitoring strategy simulation in 665 patients
with CIEDs undergoing an AF ablation, we have shown that commonly used
strategies of external ambulatory monitoring have relatively low
sensitivity and negative predictive value in detecting post-ablation AF,
with a commonly used strategy of a single 7-day continuous Holter
monitor recording having <50% sensitivity in detecting AF
recurrence > 6min at 1 year (Figure 2)19.