Shruti Sonni, MD

A well known cause of cryptogenic stroke is intermittent atrial fibrillation (AF). Different cardiac monitors have been used for varying amounts of time to detect AF, with low sensitivities. Ritter et al. implanted 60 patients with acute cryptogenic stroke with insertable cardiac monitors (ICM) for a minimum of 12 months, and set them up with 7-day Holter monitors as well. Intermittent AF was identified in 10 patients with ICM between 1- 556 days after implantation, only one of which was also found on Holter monitoring. The authors concluded that ICM implantation was feasible, safe and had a higher diagnostic yield than 7-day Holter monitoring.

The ideal duration of ICM is yet to be determined. Often patients with ICMs and their physicians choose to leave the monitor in for a prolonged period of time, likely due to the convenience aspect, making one wonder about the cost-effectiveness of this diagnostic service. However, compliance is superior to the 7-day Holter group, making efficacy of prolonged (30 day) Holter monitoring perhaps even more questionable. Although minimally invasive, it may be a good idea to use ICMs after a negative study with 7-day Holter monitoring, to possibly spare 1 in 10 patients the implantation procedure. The authors also identify an important clinical question- are few minutes of AF identified on ICM as much a risk for stroke, and do these patients deserve treatment with anticoagulation? Hopefully the TRACK-AF study, a prospective study by this group, will provide more answers.