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.