Is the Adenosine Test Obsolete in the Clinical Assessment of Syncope of Unknown Origin?

Syncope is a common clinical condition affecting 50% of the general population; however, its exact pathophysiology and underlying mechanisms remain elusive. The adenosine test (ADT) has been proposed as a complementary diagnostic test in the work-up of syncope of unknown origin aiming to further elucidate the underlying pathogenetic mechanism of spontaneous syncope. Although ADT has not been endorsed by the recent European Society of Cardiology guidelines on syncope management, the use of a quick, safe and non-invasive test which can contribute to an accurate diagnosis and rationalised therapy, may deserve further consideration. This review summarises the evidence on the role of ADT in the investigation and management of syncope of unknown origin and highlights future perspectives in this area. The authors also analyse the current challenges and research targets on adenosine plasma levels and its receptors due to the involvement of the adenosine pathway in the ADT response.