Detecting the undetectable: atrial fibrillation and recurrent stroke

This study examined whether continuous prolonged electrocardiography (ECG) monitoring would increase the detection rates of atrial fibrillation compared to standard ECG monitoring.

Atrial fibrillation, an arrhythmia (abnormal rhythm) of the heart where the atria (the chambers that receive blood into the heart) quiver instead of beat, is a leading preventable cause of recurrent (returning) stroke. In the absence of atrial fibrillation, a standard treatment of recurrent stroke is antiplatelet therapy (drugs that stop blood cells called platelets from sticking together and forming a blood clot). However, when atrial fibrillation is present, antiplatelet therapy is only modestly effective and anticoagulation (a therapy that interferes with blood clotting factors such as vitamin K) is strongly recommended instead.

However, as atrial fibrillation is often intermittent and asymptomatic (has no symptoms), it can be a silent risk factor that easily evades detection.  Therefore an unsolved problem is how to detect ‘covert’ atrial fibrillation in patients with stroke. In this study the researchers sought to detect atrial fibrillation in enrolled patients using 30-day continuous ECG monitoring versus the standard 24-hour ECG monitoring.

This study randomly assigned 572 patients into 2 groups. All patients were 55 years of age or older without known atrial fibrillation who had a cryptogenic ischemic stroke within the previous 6 months. The first group underwent continuous ECG monitoring (electrocardiograph; monitors the electrical activity of the heart) for 30 days. Recorders were attached to a nonadhesive belt worn around the chest to enable better compliance by the patients; this group was defined as the intervention group. The second group underwent conventional 24-hour ECG monitoring and was defined as the control group.

Following analysis, the 30-day ECG monitoring strategy was superior to 24-hour ECG monitoring for the detection of at least one episode of atrial fibrillation lasting 30 seconds or longer. Atrial fibrillation was detected in 45 of 280 patients (16.1%) in the intervention group, as compared with 9 of 277 (3.2%) in the control group. Prolonged monitoring was also superior for the detection of continuous atrial fibrillation lasting at least 2.5 minutes: in 28 of 284 patients (9.9%) in the intervention group versus 7 of 277 (2.5%) in the control group.

Due to the improved atrial fibrillation detection in the intervention group, the use of anticoagulant therapy tripled in this group. 13.6% of the intervention group switched from antiplatelet to anticoagulation therapy, compared to 4.7% of the control group.

This study concluded that continuous prolonged monitoring (30 day noninvasive ECG monitoring) significantly improves atrial fibrillation detection and treatment compared to the standard monitoring and clinical follow-up (24 hour ECG monitoring) among patients with a recent cryptogenic stroke who are 55 years of age or older.

Future studies are required to determine the extent of risk reduction associated with prolonged monitoring and its cost-effectiveness.

Though anticoagulant therapy is effective in preventing atrial fibrillation in patients with cryptogenic stroke, it should not be taken without physician consultation. Anticoagulants carry a higher risk of serious side effects including bruising, skin rash and bleeding in the brain, stomach and intestines.