Using Consumer-Wearable Activity Trackers for Risk Prediction of Life-Threatening Heart Arrhythmia in Patients with an Implantable Cardioverter-Defibrillator: An Exploratory Observational Study

Figures

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  Figure A1. Observation time intervals. Fitbit-monitored days (green) and events (magenta) are depicted on a timeline. The first and last event days delimit the event observation time interval. The first and last Fitbit monitoring days delimit the Fitbit observation time interval. The first event or first Fitbit-monitored day (whichever occurs first) and the last event or last Fitbit-monitored day (whichever occurs last) delimit the total observation time interval.

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  Figure A2. Daily life behaviors (bars) and VA events (strokes) observed in the Fitbit monitoring time interval for Patient 4; (a) steps; (b) physical activity—sedentary awake includes non-measured and measured-as-sedentary durations excluding measured sleep—and sleep duration; (c) heart rate.

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  Figure A3. Daily life behaviors (bars) and VA events (strokes) observed in the Fitbit monitoring time interval for Patient 12; (a) steps; (b) physical activity—sedentary awake includes non-measured and measured-as-sedentary durations excluding measured sleep—and sleep duration; (c) heart rate.

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  Figure A4. Daily life behaviors (bars) and VA events (strokes) observed in the Fitbit monitoring time interval for Patient 18; (a) steps; (b) physical activity—sedentary awake includes non-measured and measured-as-sedentary durations excluding measured sleep—and sleep duration; (c) heart rate.

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  Figure 1. Data validation for days, weeks, and periods for one combination of scenarios: at least four hours of physical activity data between 8 a.m. and 8 p.m. for valid days, at least four valid days for valid weeks, and at least 50% valid weeks for valid periods. Days (depicted in green in the top left) contain physically active or inactive time (physically active time is depicted with solid blue, while physically inactive time is depicted with pale blue). If at least 50% of the time between 8 a.m. and 8 p.m. is active, the day is valid. Weeks (depicted in yellow in the top center) contain seven days (valid days are depicted with solid green, while invalid days are depicted with pale green). If the week has at least four valid days, that week is valid. Periods (in orange in the top right) contain 1–8 weeks (valid weeks are depicted with solid yellow, while invalid weeks are depicted with pale yellow). If at least 50% of the weeks of a period are valid, the period is valid. The figure then shows examples of valid and invalid days (bottom left), weeks (bottom center), and periods (bottom right).

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  Figure 2. Data aggregations over valid days, valid weeks, and valid periods. A day (depicted in green in the top left) contains 96 15-min intervals (depicted in blue; the intervals with a value are solid blue, while those without a value are pale blue). A daily aggregate (in green in the bottom left) is constructed from the 15-min intervals with values. A week (depicted in yellow in the top center) contains seven days (in green; the valid days are solid green, while those invalid are pale green). A weekly aggregate (depicted in yellow in the bottom center) is constructed from the daily aggregates of the valid days. A period (in orange in the top right) contains 1–8 weeks (depicted in yellow; the valid weeks are solid yellow, while those invalid are pale yellow). A period aggregate (depicted in orange in the bottom right) is constructed from the weekly aggregates of the valid weeks. The period aggregate is then used for the inferential analysis.

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  Figure 3. Case-crossover analysis: case and control periods for a combination of scenarios: an arbitrary scenario for valid days, at least four valid days for valid weeks, and at least 50% valid weeks for valid periods. Periods (depicted with orange contour) contain valid weeks (depicted with strong yellow contour and fill) and invalid weeks (depicted with pale yellow contour only). Week validity depends on having at least four valid days (depicted with strong green contour and fill) and at most three invalid days (depicted with pale green contour only). Case periods are followed by an event on the next day (depicted by a magenta vertical line). Events on the following day do not follow control periods. Valid periods (depicted with strong orange contour and fill) are either case periods (above the timeline of wearable monitoring) or control periods (below the timeline). Invalid periods are neither case periods nor control periods. The analysis uses all patients’ case and control periods.

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  Figure 4. Periods in separate and combined models for a fixed duration of four weeks. Periods (depicted in orange) span across 1–8 weeks (depicted in yellow). For the separate models, only periods of precisely four weeks are included. For the combined models, periods of up to 4 weeks (precisely one week, and precisely two weeks, and precisely three weeks, and exactly four weeks) are included.

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  Figure 5. Odd ratios obtained from the separate models for 1000 extra steps, 15 extra minutes of physical activity or sleep, and 10 extra beats per minute for the heart rate. The separate Fitbit measurement periods of 1, 2, … 8 weeks are depicted on top. Below, informative estimations of the odd ratios are represented. For all results, p < 0.05. Periods in the separate models (depicted in yellow as sequences of weeks) are followed by potential events (depicted at the end of the yellow sequences). ORs are depicted as bars: OR > 1 (red and upwards) and OR < 1 (green and downward). Bar height corresponds to the distance between the OR and 1.

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  Figure 6. Odd ratios obtained from the combined models for 1000 extra steps, 15 extra minutes of physical activity or sleep, and 10 extra beats per minute for the heart rate. The combined Fitbit measurement periods of 1, 1–2, …, 1–8 weeks are depicted on top. Below, informative estimations of the odd ratios are represented. For all results, p < 0.05. All periods in the combined models (depicted in yellow as sequences of weeks and stacked for each maximum duration of 1, 2, …, 8 weeks) are followed by potential events (depicted at the end of the yellow sequences). ORs are depicted as bars: OR > 1 (red and upwards) and OR < 1 (green and downwards). Bar height corresponds to the distance between the OR and 1.