PDF: EMBRACE
(2014)Objective
To determine whether 30-day event-triggered ambulatory ECG monitoring is more effective than standard 24-hour Holter monitoring in detecting atrial fibrillation (AF) after cryptogenic stroke or TIA.
Study Summary
Intervention
30-day ambulatory ECG monitoring with an event-triggered loop recorder vs. conventional 24-hour Holter monitoring. All devices were analyzed centrally and blinded to study assignment.
Inclusion Criteria
Patients aged ≥55 with recent ischemic stroke or TIA (within 6 months) and no known atrial fibrillation, after standard workup ruled out major cardioembolic source. CHADS2 score ≥2 was required.
Study Design
Arms: 30-day ECG Monitoring vs. 24-hour Holter Monitoring
Patients per Arm: 30-day Monitoring: 286, 24-hour Holter: 277
Outcome
Bottom Line
30-day ambulatory ECG monitoring detected AF (≥30 sec) in 16.1% vs 3.2% with 24-hour Holter (absolute difference 12.9 percentage points; P<0.001; NNS=8). Prolonged monitoring nearly doubled anticoagulation rate at 90 days (18.6% vs 11.1%; P=0.01). AF detection was incremental: 2.2% at 24h rising to 14.8% by 4 weeks.
Major Points
- AF (≥30 sec) detected in 16.1% (45/280) with 30-day monitoring vs 3.2% (9/277) with 24-hour Holter — >5-fold increase (P<0.001; NNS=8).
- Anticoagulation at 90 days: 18.6% vs 11.1% (P=0.01). Switch from antiplatelet to anticoagulant: 13.6% vs 4.7% (P<0.001).
- AF detection incremental over time: 2.2% at 24h → 7.4% at 1 week → 11.6% at 2 weeks → 14.8% at 4 weeks.
- 59% of AF patients had ≥2 episodes; 64% had episode ≥2.5 minutes.
- Earlier monitoring (within 3 months of event) detected more AF: 18.5% vs 9.0% (P=0.049).
- 82% completed ≥3 weeks of monitoring (adherence).
- AF detected by clinical means alone in only 0.5% — monitors essential.
- 572 patients, 16 Canadian stroke centers, randomized open-label.
- Device: ER910AF event-triggered loop recorder with dry-electrode belt. ECG data transmitted transtelephonically.
- Challenged standard 24-48h monitoring practice; supported prolonged outpatient cardiac monitoring post-stroke.
Study Design
- Study Type
- Randomized controlled trial (investigator-initiated, open-label)
- Randomization
- Yes
- Blinding
- Open-label; ECG adjudicators blinded to patient demographics. 1:1, Web-based, variable block size.
- Sample Size
- 572
- Follow-up
- 90 days
- Centers
- 16
- Countries
- Canada, Ireland
Primary Outcome
Definition: Detection of AF ≥30 seconds within 90 days
| Control | Intervention | HR/OR | P-value |
|---|---|---|---|
| 9/277 (3.2%) | 45/280 (16.1%) | - (8.0-17.6 (absolute difference)) | <0.001 |
Limitations & Criticisms
- Cannot determine total AF burden — limited 2.5-minute recording capacity per episode.
- Monitoring started late (mean 75 days post-event) — earlier initiation may detect more.
- 30 days may underestimate true yield (implanted devices detect more with longer monitoring).
- Cryptogenic stroke heterogeneous — not all patients had intracranial imaging or TEE.
- Mild nondisabling strokes overrepresented (mRS ≤2: 94%).
- Open-label design (though ECG adjudicators blinded).
- 16% AF prevalence likely conservative underestimate.
- Detection of AF after stroke does not prove causation.
Citation
N Engl J Med 2014;370:2467-77.