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Implantable loop recorder: evaluation of unexplained syncope
  1. R A Kennya,
  2. A D Krahnb
  1. aCardiovascular Investigation Unit, Royal Victoria Infirmary, Queen Victoria Road, Newcastle upon Tyne NE1 4LP, UK, bUniversity of Western Ontario, London Health Sciences Centre, University Campus, 339 Windermere Road, London, Ontario N6A 5A5, Canada
  1. Professor Kenny. email: R.A.Kenny{at}

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Syncope is a relatively common occurrence in the general population accounting for up to 6% of hospital medical admissions and at least 3% of accident and emergency visits each year.1 ,2 In a proportion of cases, syncope continues to pose a clinical dilemma despite the development of new diagnostic techniques. Mortality and serious morbidity associated with syncope are generally low overall but one year mortality is up to 33% in high risk groups of patients with a cardiac cause of symptoms.1 ,2 Recurrent syncope has additional deleterious effects on lifestyle, sense of physical wellbeing, and employment opportunities.3 Major obstacles to diagnosis are the intermittent nature of the symptoms, which are both periodic and often unpredictable, high spontaneous remission rates, and the lack of a diagnostic gold standard.

Despite the absence of a diagnostic gold standard for syncope and a paucity of data from randomised trials, several statements have emerged from a recent position paper on clinical guidelines from the American College of Physicians.4 In summary, these guidelines emphasise that:

  • history, physical examination, and electrocardiography are the core of the investigations of syncope (with a combined diagnostic yield of 50%)

  • neurological testing is rarely helpful unless additional neurological signs or symptoms are present (the diagnostic yield for electroencephalography, computed tomography, and Doppler ultrasound is only 6%)

  • and patients are at higher risk of adverse outcomes if heart disease is known or suspected, or if patients have explained syncope. It is recommended that these patients should have additional cardiac testing including echocardiography, stress testing, head up tilt testing, Holter monitoring or intracardiac electrophysiological studies, either alone or in combination, depending on the clinical …

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