Response to Letter by Gladstone et al
In order to increase the chance of detecting asymptomatic atrial fibrillation (AF) in patients with a recent stroke, ECG monitoring should be performed for prolonged periods, but only in selected patients with increased risk of AF.1 In the EMBRACE pilot study, monitoring all patients with cryptogenic stroke for periods up to 30 days is expected to confirm the value of screening patients for longer periods.2 Other investigators have even proposed to implant a device recording the cardiac rhythm during up to 3 years in similar patients. The new Reveal XT (Medtronic Inc) is an implantable event triggered recorder which detects and monitors atrial and ventricular tachycardias. Using a special algorithm, the device is able to detect AF on a beat-to-beat irregularity analysis of successive RR-intervals. AF episodes and their time of onset and duration, as well as AF burden are available for the clinicians. Ongoing studies and registries are evaluating the use of such implantable loop recorders for the diagnosis of oligosymptomatic AF in patients with a recent stroke and in patients after catheter ablation of AF. However, the diagnostic value and the cost-efficiency of systematic long-term cardiac rhythm recording will need to be compared with other strategies. It is likely that the economic burden of long-term ECG recording will limit its use if it is proposed for all patients without any risk stratification. When risk stratification is performed using 24-hour ECG recordings to analyze the number of supraventricular premature depolarizations, only a fourth of patients with a recent stroke need to be investigated with longer recording.3 Using serial 7-day recordings AF was detected in 26% of the patient with 70 or more supraventricular premature depolarizations per 24 hours versus 6.5% of the other patients.2 Another advantage of the serial 7-day recording is that cardiac monitoring can be interrupted when AF is detected. All in all, this method will generate substantially lower costs than while screening all patients without any distinction of their risk profile. Ultimately, there is a need to detect AF in patients at risk of AF before they experience a stroke, and in this setting cost efficient strategies will be necessary.
Wallmann D, Tüller D, Wustmann K, Meier P, Isenegger J, Arnold M, Mattle HP, Delacrétaz E. Frequent atrial premature beats predict paroxysmal atrial fibrillation in stroke patients: an opportunity for a new diagnostic strategy. Stroke. 2007; 38; 2292–2294.
Gladstone DJ, Blakely J, Dorian P, Spring M, Fang J, Silveret JL, Kapral MK. Detecting paroxysmal atrial fibrillation after ischemic stroke and TIA: If you don’t look, you won’t find. Stroke. 2008; 39: e78–e79.
Wallmann D, Tüller D, Kucher K, Fuhrer J, Arnold M, Delacrétaz E. Frequent atrial premature contractions as a surrogate marker for paroxysmal atrial fibrillation in patients with acute ischemic stroke. Heart. 2003; 89: 1247–1248.