Detection of Subclinical Atrial Fibrillation in High-Risk Patients Using an Insertable Cardiac Monitor

Objectives: The study sought to determine the incidence of subclinical atrial fibrillation (AF) in high-risk patients and to compare the effect of continuous versus intermittent monitoring.

Background: AF often occurs in a subclinical form, which makes it difficult to detect. The authors do not know the incidence of subclinical AF among patients ≥65 years of age with hypertension and diabetes mellitus. This group of patients has increased risk of developing AF and in addition a high thromboembolic risk, if AF is present.

Methods: A total of 82 outpatients ≥65 years of age (median age 71.3 years [interquartile range [IQR]: 67.4 to 75.1 years]) with hypertension and diabetes mellitus, and no history of AF or any other cardiovascular disease, were consecutively included. All patients received an insertable cardiac monitor (ICM) and were followed for a median of 588 days (IQR: 453 to 712 days). We compared continuous monitoring with 72-h Holter monitoring 1 month after ICM insertion. The primary endpoint was AF ≥2 min for the ICM and AF ≥30 s for the Holter monitoring.

Results: During follow-up 17 (20.7%) patients were found to have subclinical AF detected by ICM with a median time to first detected episode of 91 days (IQR: 41 to 251 days) from inclusion. Only 2 (2.4%) patients also had AF episodes on the 72-h Holter monitoring. All detected episodes were completely asymptomatic.

Conclusions: The incidence of subclinical AF in this group of patients was surprisingly high. Continuous monitoring with ICM detected significantly more AF episodes than 72-h Holter monitoring. (Detection of Subclinical Atrial Fibrillation in High Risk Patients Using Implantable Loop Recorder; NCT02041832).