What question did this study set out to answer?

This research aims to determine how the timing of insertable cardiac monitor implantation affects atrial fibrillation detection after embolic strokes.

March 26, 2026

Timing of Insertable Cardiac Monitor Implantation After ESUS and Its Impact on Atrial Fibrillation Detection: A Target Trial Emulation Analysis

Key Result

Early implantable cardiac monitor insertion within 30 days after embolic stroke increased 30-day atrial fibrillation detection compared to delayed insertion (7.8% vs 1.6%, OR 4.49).

Key Points

This research aims to determine how the timing of insertable cardiac monitor implantation affects atrial fibrillation detection after embolic strokes.
Multicentre observational cohort study comparing early (≤30 days) and delayed (31–365 days) ICM implantation post-ESUS
Used inverse probability weighting to control for confounding factors
Measured AF detection at 30, 90, and 120 days post-implantation via weighted logistic regression and Poisson models
Early ICM implantation significantly increased AF detection within 30 days (7.8% vs 1.6%)
Higher detection rates per person-time were found in the early group (IRR 4.26)
Time-to-event analyses indicated faster AF detection rates with early implantation, with HRs showing significant benefits (HR 4.29, 30 days; HR 2.97, 90 days; HR 2.77, 120 days)

Structured PICO

Does early ICM implantation improve atrial fibrillation detection in patients with embolic stroke of undetermined source compared to delayed implantation?

Population

Patients with embolic stroke of undetermined source (ESUS) undergoing insertable cardiac monitor (ICM) implantation

Intervention

Early ICM implantation (≤30 days after the index event)

Comparator

Delayed ICM implantation (31–365 days after the index event)

Outcome

Atrial fibrillation (AF) detection within 30, 90, and 120 days after implantationsurrogate

Early implantation of cardiac monitors (≤30 days) after an embolic stroke of undetermined source significantly increases the early detection rate of atrial fibrillation compared to delayed implantation.

Main Result

Absolute Event Rate: 0% vs 0%

Abstract

Background. A substantial proportion of ischemic strokes remain classified as embolic stroke of undetermined source (ESUS) despite standard diagnostic evaluation. Prolonged cardiac monitoring with implantable cardiac monitors (ICMs) increases atrial fibrillation (AF) detection, but the optimal timing of ICM implantation after ESUS remains uncertain. Aims. To evaluate whether early versus delayed ICM implantation after ESUS influences AF detection and time to diagnosis. Methods. We conducted a multicentre observational cohort study emulating a target trial. Consecutive ESUS patients undergoing ICM implantation were classified as ICMEARLY (≤30 days) or ICMDELAYED (31–365 days) implantation after the index event. Inverse probability weighting was applied to adjust for baseline confounding. Primary and secondary outcomes included AF detection within 30, 90, and 120 days after implantation, assessed using weighted logistic regression, Poisson models for detection rates per person-time, Cox proportional hazards models, and restricted mean survival time (RMST). Sensitivity analyses included centre-level clustering and competing-risk models. Results. Among 333 patients (90 ICMEARLY, 243 ICMDELAYED), early implantation was associated with significantly higher AF detection within 30 days (7.8% vs 1.6%; OR 4.49, 95% CI 1.17–17.27; p=0.028) and higher detection rates per person-time (IRR 4.26, 95% CI 1.16–15.60; p=0.029). Consistent associations were observed at 90 and 120 days. Time-to-event analyses showed higher hazards of AF detection with early implantation (HR 4.29 at 30 days; HR 2.97 at 90 days; HR 2.77 at 120 days; all p<0.01). RMST analyses demonstrated progressively shorter time to AF diagnosis in the ICMEARLY group across multiple time horizons. Results were robust across sensitivity analyses. Conclusions. Early ICM implantation after ESUS is associated with higher and faster AF detection compared with delayed implantation. When ICM monitoring is indicated, avoiding unnecessary delays may substantially enhance diagnostic yield.

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