Diagnostic Challenges: Cryptogenic Ischemic Stroke
Pp. 216-232 (17)
Cryptogenic ischemic stroke defines the situation where the cause of the
thromboembolic event is not evident. Atrial fibrillation (AF) is a possible cause of
cryptogenic stroke, even if asymptomatic. AF is the most common arrhythmia, and its
incidence increases with age. AF is associated with an increased risk of ischemic stroke
and systemic embolism, independent of the type of AF and also of the symptoms
caused by the arrhythmia. The thromboembolic risk is associated to some clinical
variables like age, hypertension, heart failure, diabetes, previous stroke, vascular
diseases and gender. The mechanism of thrombosis in AF is complex, and comprises
blood stasis in the left atrial appendage, but also atrial and endothelial damage,
alteration of the extracellular matrix, and activation of humoral factors with
AF is often asymptomatic or “silent”, as demonstrated in many clinical situations.
Silent AF may be a frequent cause of otherwise unexplained stroke. The association
between stroke and silent AF was demonstrated in many trials, especially in patients
with an implanted device, like pacemakers, implantable cardiac defibrillators (ICD) and
cardiac resynchronisation therapy (CRT) devices, where a reliable report of the
arrhythmia is available. The best system to discover if a patient with cryptogenic stroke
has AF is the continuous monitoring with an implantable loop recorder. However, the
temporal relationship between AF and stroke is not often evident, so that the decision
to prevent thromboembolisms in patients with silent AF should be based on the
evaluation of risk with the appropriate score index. In the secondary prevention of
stroke and transient ischemic attack (TIA), however, anticoagulation is generally
indicated if a silent AF is demonstrated.
Atrial fibrillation, Cryptogenic stroke, Implantable defibrillators,
Implantable loop recorder, Left atrial appendage, Pacemaker, Silent atrial
fibrillation, Thromboembolic risk score, Thromboembolism.
Electrophysiology Unit, Multimedica IRCCS Sesto San Giovanni, Milan, Italy.