Methods
Study Population: Using patient-level data from the
Optum® de-identified EHR dataset
from 01-01-2007-to 06-30-2019 linked with Medtronic cardiac implantable
electronic device (CIED) data, patients who underwent an AF ablation
procedure following CIED implantation were identified. Only the first AF
ablation procedure observed in the dataset was considered. Following a
90-day blanking period from the time of the first catheter AF ablation
procedure observed in the dataset, patient level daily AT/AF burden data
(collected by the CIED) was analyzed for AF recurrence using varying
definitions of recurrence, which were then compared against simulated
external monitoring strategies used clinically to detect recurrence.
Inclusion and Exclusion criteria: Patients were required to
have an AF ablation procedure (identified by the CPT codes 93656 &
93657), and only the patient’s first AF ablation procedure observed in
Optum® dataset was considered. Patients were also required to have a
Medtronic CIED capable of continuous AF monitoring implanted prior to
the AF ablation procedure, have at
least 6 months between first
record in the Optum EHR and the Medtronic CIED implant date, have daily
AT/AF burden available for every day during a period of 30 days prior to
AF ablation procedure, with at least one day having greater than 23
hours of available burden data, and have at least 1 daily AT/AF burden
measurement available after the end of the 90-day blanking period.
Medical history prior to AF ablation: History of hypertension,
prior stroke/TIA, heart failure, diabetes, and vascular diseases were
extracted from the Optum® EHR data based on the presence of diagnosis
codes (ICD-9/ICD-10) in the diagnosis table on or prior to the AF
ablation procedure date. The list of codes considered for each of these
conditions is available in Supplement Table 1.
AF type prior to AF ablation: Patients were classified as
having persistent AF if they had 7 consecutive daily AT/AF burden
> 23 hours in the 30 days prior to the AF ablation
procedure; all other patients were considered to have paroxysmal AF.
Atrial Fibrillation Recurrence: AF recurrence definitions
included daily AT/AF burden duration of at least 6 min, 1 hour, 6 hours,
12 hours, 23 hours, 7 consecutive days with >23 hours, and
a rolling 30-day average burden > 3.6 hours (0.5% burden).
Kaplan-Meier estimator was used to estimate the survival probability for
each recurrence definition post-ablation following a 90-day blanking
period.
Atrial Fibrillation Burden Reduction Following Ablation: Two
metrics were considered to quantify the change in AF burden following
ablation: percent of time in AT/AF and median daily AT/AF duration.
For each patient, the percent of time in AT/AF was computed as the
division of the total AT/AF burden hours by the total observed time,
while the median daily AT/AF was the median duration of the observed
daily AT/AF burden measurements. Both metrics were computed stratifying
by the time period with respect to ablation procedure: pre-ablation (all
observed daily AT/AF burden measurements 1 year prior to the AF ablation
procedure), and post ablation (all daily AT/AF burden measurements
observed between the days 90 and 455 (i.e. one-year post-blanking
period) post AF ablation).
Monitoring Strategy Simulation: Using daily AT/AF burden
measurements as the source of truth,
sensitivity and negative predictive value (NPV) were computed to assess
performance of various external AF monitoring strategies used in
clinical practice with respect to the detection of events of daily AT/AF
burden > 6 min, daily AT/AF burden > 6 hours
and daily AT/AF burden > 23 hours. The simulated monitoring
strategies were: 24-hour, 48-hour, 7-day, 21-day, 30-day, quarterly
24-hour, quarterly 48-hour, quarterly 7-day and monthly 24-hour
continuous external monitoring. All these monitoring strategies were
considered to occur within 1 year after the 90-day blanking period and
100% patient compliance with external monitoring was assumed. Only data
from patients who had uninterrupted daily AT/AF burden measurements
during this time period were included in the simulation. Lastly, a
bootstrap method (with 10,000 samples) was used to build 95% confidence
intervals (CI) for the performance metrics. The initial day of the AF
monitoring strategy was randomly assigned within the first two weeks
post blanking period for each patient.