Design projections for prospective studies evaluating the clinical effectiveness of cardiac arrest detection...

Recent developments have illustrated the feasibility of scalable out-of hospital cardiac arrest (OHCA) detection using consumer-wearable products. While initial evidence is promising, the real-world effectiveness of these technologies is unproven and design decisions to minimize false positives may constrain clinical impact. To support the real-world evaluation of these technologies, we analyzed registry data and evaluated strategies for a clinical trial.

We analyzed Emergency Medical Services (EMS)-treated and EMS-untreated cases in the British Columbia Cardiac Arrest Registry (2019-2020) who may have benefitted from cardiac arrest detection. Within strata formed by Age (0-35, 36-55, 56-65, 65+) and Sex, we estimated strata-specific treatment effects from recognition and calculated the required sample sizes for a set of potential primary clinical outcomes for a trial (survival to hospital discharge, initial shockable cardiac rhythm, EMS treatment). We compared this with population incidence to inform prospective recruitment requirements.

Within a population-at-risk of 9,739,356, 11,382 sentinel cases met criteria for inclusion. Strata-specific incidence ranged from 18.3 per 100,000 to 395 per 100,000. The most statistically efficient subgroup for a survival outcome was Males aged 56-65 (171,676 needed, total). For a trial outcome of EMS treatment or initial shockable rhythm, Males over 65 were the most efficient subgroup within which to test the intervention (7,608 and 66,962 needed, total respectively).

A prospective trial of OHCA detection technologies will require large recruitment targets. Subgroups with the highest estimated treatment effect are not those with the highest incidence. Large trials in the general population will require multiple centers and innovative recruitment strategies that may be aided by partnership with industry.