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Tilt testing and neurally mediated syncope: too many protocols for one condition or specific protocols for different situations?

Angel Moya
DOI: http://dx.doi.org/10.1093/eurheartj/ehp290 2174-2176 First published online: 21 July 2009

Syncope, defined as a transient loss of consciousness due to transient global cerebral hypoperfusion, characterized by rapid onset, short duration, and spontaneous complete recovery, is a frequent symptom and can be attributed to different causes.1

The most common aetiology of syncope is a neurally mediated reflex that consists of a transient failure of the cardiovascular mechanisms that normally control haemodynamic stability. This reflex is usually triggered by different stimuli (afferent pathways), leading to sudden withdrawal of sympathetic activity and to an increase in parasympathetic nerve tone (efferent pathways), causing vasodilatation, with consequent hypotension, and bradycardia.

The clinical presentation of neurally mediated syncope is not usually uniform; however, it may manifest with different patterns. In some patients, it is initiated by clear adrenergic stimuli such as fear, pain, emotional distress, or medical instrumentation, whereas in others it develops after prolonged orthostatism, hypovolaemia, or carotid sinus stimuli. There are also many patients in whom reflex syncope develops without any apparent recognizable trigger. On the other hand, some patients complain of typical vegetative prodrome, whereas others develop sudden syncope without any warning symptom. In addition, although both mechanisms, hypotension and bradycardia, are, by definition, always present, the predominance of one or the other leads to the characteristic patterns of vasodepressor, mixed, or cardioinhibitory reflex syncope.2 Although all these situations share a common underlying mechanism, i.e. hypotension and bradycardia triggered by some afferent stimuli, these differences have a great impact on the diagnostic process and in therapeutic decisions. Whereas a syncopal episode in a young patient, with clear triggers and prodrome, is easy to diagnose and manage, sudden episodes, without recognizable triggers, particularly …

*Corresponding author. Tel: +34 932746166, Fax: +34 932746002, Email: 11193amm{at}comb.es; amoya{at}comb.es