A trial randomised 2,234 patients presenting with syncope to immediate ambulatory electrocardiographic monitoring or standard care, with 1,970 contributing to the primary analysis. The outcome was patient-reported syncope episodes at one year.
The mean number of episodes was 1.37 in the monitored group and 1.58 in the standard-care group, an incidence rate ratio of 0.89 with a confidence interval from 0.68 to 1.18 and a P value of 0.42. Adverse events were reported in 49 monitored patients against 8 in standard care, with one serious event in each arm — most of the excess being the nuisance of wearing a monitor rather than harm from it.
The result is worth reading precisely. Monitoring is a diagnostic intervention, and diagnosing an arrhythmia only prevents syncope if it leads to treatment that works. This trial measured the whole chain, and the chain did not deliver. It does not mean monitoring never helps — in a patient with structural heart disease or exertional syncope the pretest probability is entirely different — but it does undercut monitoring everyone who presents.
- Patient-reported episodes, which is the outcome that matters and the noisiest to measure
- Standard deviations exceeded the means, so a few patients had very many episodes
- Tests the whole chain: monitor, diagnose, treat, prevent recurrence
- Says nothing about high-risk syncope, where the question is not recurrence but death
- The excess adverse events are largely the burden of wearing the device
The statistics, in plain English
An incidence rate ratio of 0.89 with an interval of 0.68 to 1.18 includes 1.0, so no effect was shown. Note the standard deviations — 5.10 and 8.56 against means near 1.4 — which say the distribution is dominated by a small number of patients with very frequent syncope. Counting events in a distribution shaped like that needs a large trial to say anything, and 2,234 patients was enough here only to exclude a large benefit.
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