Unrepresentative sample
The trial entered 446 overwhelmingly White and college-educated adults known to have symptomatic paroxysmal AFib who were “interested in testing a presumed AFib trigger they could readily introduce or withhold” and who owned a smartphone; the average age was 58 years, and 58% were men. The cohort was randomly assigned to the trigger-testing group or the control group, charged only with tracking their AFib.
Of the total, 320, or about 72%, completed the study; those who did not were mostly from the trigger-testing arm, leaving 136 in that group versus 184 patients in the control group.
Potential triggers that participants selected for tracking included, foremost, caffeine, alcohol, reduced sleep, and exercise, followed by lying on the left side, dehydration, large meals, and cold food or drink, the report noted.
Patients in the control group used the smartphone app and handheld ECG monitor (KardiaMobile, AliveCor) to document the duration and severity of AFib episodes daily and received data summary reports through the app weekly for 10 weeks. They then had the option to follow the trigger-testing protocol at least once.
Those in the trigger-testing group conducted their N-of-1 trials by exposing themselves to their chosen potential trigger during 3 separate weeks and avoiding the trigger during 3 other weeks, alternating each of the 6 weeks of trigger exposure or avoidance. They were instructed through the app to start the 6-week sequence with one or the other strategy randomly and to regularly track their AFib.
At the end of 6 weeks, each participant in the trigger-testing group had the opportunity to review their data for any potential trigger-AFib associations. They were then to use the next 4 weeks to enact lifestyle changes based on what they learned – as described in the report and on clinicaltrials.gov. They had the option of repeating the entire N-of-1 sequence at least one more time.
Participants in both the trigger-tracking and control arms were tested at baseline and at 10 weeks using the validated Atrial Fibrillation Effect on Quality-of-Life (AFEQT) questionnaire.
AFEQT scores didn’t change significantly over the 10 weeks in either arm, nor were they significantly different in one arm, compared with the other.
On the other hand, patients in the trigger-tracking arm reported significantly fewer daily AFib episodes during the final 4-week period of lifestyle changes based on their N-of-1 trial results, compared to the monitoring-only control group’s final 4 weeks.
The adjusted relative risk in the trigger-tracking arm was 0.60 (95% confidence interval, 0.43-0.83; P < .001), the difference driven by patients who selected alcohol, dehydration, or exercise for their trigger, Dr. Marcus reported.
Only alcohol intake emerged consistently as a significant predictor of risk for self-reported AFib episodes in a series of meta-analyses conducted using all of the individual N-of-1 trials that provided per-protocol data. The odds ratio was 1.77 (95% CI, 1.20-2.69).
I-STOP-AFib explored an important subject “that has been understudied,” Dr. Conen said. “The trial has some limitations that the authors address themselves, but hopefully it opens the path to future studies that can build upon this experience.”
Dr. Marcus reported receiving personal fees and equity interest from InCarda Therapeutics; personal fees from Johnson & Johnson; and grants from Baylis Medical, Medtronic, the National Institutes of Health, the Patient-Centered Outcomes Research Institute, and the California Tobacco-Related Disease Research Program.
A version of this article first appeared on Medscape.com.