Background
Stroke is one of the leading causes of morbidity and mortality. Identification of the underlying etiology is of major importance in order to prevent stroke recurrence. However, in 30-40% of strokes, the exact etiology remains undetermined. Silent paroxysmal atrial fibrillation (AF) is recorded in 9 up to 30% of strokes with unknown etiology. Current guidelines recommend 24-h Holter monitoring for AF detection in patients with stroke of unknown cause. Prolonged ECG monitoring after stroke is associated with greater chance to detect AF.
Signal averaged electrocardiography (SAECG) is a high-resolution electrocardiographic technique that detects conduction abnormalities in the atria. SAECG, by recording microvolt amplitude atrial signals, allows for more accurate analysis of the P wave and, possibly, prediction of AF.
Study aims
This research proposal aims to investigate whether SAECG P wave analysis may identify early changes in left atrial functional/electrical substrates and predict the occurrence of AF in patients with stroke of unknown cause implanted with an ECG loop recorder.
Methods
Cases will consist of patients with confirmed cerebral ischemia of unknown cause implanted with an ILR for long-term rhythm monitoring.
Medical history, resting 12-lead ECG, echocardiogram and SAECG will be recorded before ILR implantation. The primary end-point of the study will be the occurrence of symptomatic or asymptomatic atrial fibrillation as recorder by the ILR over a follow-up period of 24 to 36 months.
Perspectives
Silent AF in patients with previous stroke is a crucial finding, as it allows to start anticoagulation therapy and prevent cerebrovascular accidents. However, a strategy based on the widespread use of ILR with home monitoring of cardiac arrhythmia drains substantial economic and human resources. The availability of predictors of AF in cryptogenic stroke may allow to select patients more likely to benefit from an implantable event recorder.
Preliminary results
To test the rate of events and the population size needed to test the hypothesis, we performed a retrospective analysis of consecutive patients with cerebral ischemia of unknown origin implanted with an ECG loop recorder at our institution between January 2018 and November 2019. Seventeen patients with cryptogenic cerebral ischemia have been implanted. In 8 out of 17 patients (47%) previously undiagnosed AF was identified and anticoagulation started. The median time to diagnosis was 7 weeks (range 2-26).
With such an high rate of events in well selected candidates, our study will be powered to detect even small effects of clinical or ECG prognosticators on the risk of AF.
Perspectives
Silent AF detection in patients with previous stroke of unknown origin is a crucial finding, as it allows to start anticoagulation therapy and prevent a second cerebrovascular accident. However, a strategy based on the widespread use of implantable loop recorders drains many economic and human resources. Indeed, costs include not only the recorder per se, but also all the resources needed to setup an effective home monitoring activity, that can last for months or years.
In this view, the availability of predictors of AF in cryptogenic stroke may allow to select patients more likely to benefit from an implantable event recorder.