Device interrogations
We reviewed all available device interrogations for the 44 patients
included in this study, the dates of which ranged from 11/13/14 through
4/8/19. Devices included were single-chamber pacemakers, dual-chamber
pacemakers, single-chamber ICDs, biventricular pacemakers and
defibrillators, and subcutaneous ICDs. All interrogations, obtained both
in the ambulatory and inpatient settings, were reviewed. For each CIED,
the device type and implantation date were recorded. We calculated total
number of transmissions and monitoring hours for all patients in the
study. For VA analysis, the following were recorded: number of VT/VF
events, number of non-sustained VT (NSVT) events, and ventricular pacing
percentage. We defined VT as a wide-complex, regular tachycardia having
a duration greater than thirty seconds and/or requiring either
anti-tachycardia pacing (ATP) or ICD shock for termination. Thus, NSVT
was defined as a wide-complex regular tachycardia lasting at least three
beats but not meeting aforementioned VT criteria. For each NSVT, VT, and
VF episode, the following details were recorded: date, time, day of
week, duration, average atrial rate, average ventricular rate, and
therapy requirement (i.e. ATP, ICD shock, or both).
In order to compare overall VA burden between groups, we calculated the
total number of VA events divided by the product of the total number of
patients per group experiencing any VA event and total number of
monitoring hours for those patients. This resulted in events per
patient-hour for both individual patients and for each group. We chose
this calculation in order to account for the fact that patients
monitored for longer periods of time may represent a survival bias.
In an attempt to better categorize ventricular pacing data, four
quartiles for each group (0-25%, 26-50%, 51-75%, and 76-100%) were
created and represented the pacing percentage reported since last device
interrogation. Individual counts represented a device interrogation
reporting a particular ventricular pacing percentage in the range of the
specified quartile. Biventricular devices and subcutaneous ICDs were
excluded from ventricular pacing analysis.