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ARTICLE CONTRIBUTORS

European Society of Cardiology

Clinical Articles, Lead Article

Loop recorders justified in syncope diagnoses

Diagnosis of neurally mediated syncope (NMS) can be confirmed with implantable loop recorders (ILR), according to a presentation at the Late Breaking Clinical Trials session II at EHRA EUROPACE 2013.

Using European Society of Cardiology (ESC) guidelines on Diagnosis and Management of Syncope,1 diagnosis of NMS could be confirmed with an ILR in 87% of patients, according to results from the ISSUE 3 registry.

ISSUE (International Study on Syncope of Uncertain aEtiology) was a prospective registry set up to analyse the diagnostic yield of ILRs in specific subgroups of patients with syncope of uncertain aetiology. The registry took place in Italy, Spain, Germany, France, Canada, The Netherlands and UK. For the ISSUE 3 registry, between July 2006 and November 2010, 504 patients with suspected NMS, according to criteria laid down in guidelines, had an implantable loop recorder (IRL) fitted.

Entry criteria included being older than 40 years and having experienced more than three episodes of syncope in the previous two years thought to be neurally mediated. Guidelines2 state that a likely diagnosis of NMS can be made when patients have a consistent history and competing diagnoses have been excluded.

Professor Michele Brignole (Osped-ali Tigullio, Genoa, Italy)

Professor Michele Brignole (Osped-ali Tigullio, Genoa, Italy)

Results show that a confirmed diagnosis could be achieved in 187 patients, with ILR findings in 162 of these patients (87%) being consistent with a likely diagnosis of NMS, and IRL findings in 25 patients (13%) allowing NMS to be ruled out. Of the 162 patients with IRL findings suggesting NMS 99 were found to be asystolic (where the heart stops beating for a short period of time) and 63 hypotensive (where blood pressure falls).

Altogether 52 patients received a pacemaker, of which 26 had a positive table tilt test result (TT+) and 26 patients a negative table tilt test (TT-) result. After 21 months the syncope recurrence rates were 55% (95% CI 29-85) in TT+ patients fitted with the pacemaker versus 5% ( 95%CI 1-32) in TT- patients fitted with the pace maker (p=0.004). When the recurrence rate of 55% in the TT+ patients was compared to 44 untreated patients (who acted as controls) who had recurrence rates of 64% the difference was not found to be statistically significant (p=0.75).

“By showing that NMS tilt-negative asystolic patients benefit most from cardiac pacing, the study inverts previous knowledge on indications for pacing. Prior to this registry, cardiac pacing for NMS had only been evaluated in patients with positive tilt test responses and no indications had existed for patients with negative tilt test results,” said presenter Professor Michele Brignole (Osped-ali Tigullio, Genoa, Italy).

For patients with negative table tilt tests, the observed 5% recurrence rate was similar to that observed for patients paced for cardiac intrinsic bradycardia. “Thus, pacemaker therapy can be offered to these patients with the same confidence as it can in patients with sick sinus syndrome or atrioventricular block (AV) block,” said Professor Brignole. “Such patients can be reassured that, after pacemaker implantation, they’ll likely be free from reoccurrences of syncope.”

But before pace maker therapy is offered to patients with TT+ even if they have experienced an asystolic response during the tilt test patience should be cautioned they may have reoccurances, he continued: “Although some benefits may still be possible in terms of reduced syncope burden, patients should be informed that they’ll likely have some recurrences despite pacing.”

Most of the misdiagnoses in the study were due to intrinsic cardiac arrhythmias which were largely unpredictable from baseline characteristics, he concluded: “This aspect, which has not yet been clarified in the literature, may be relevant in clinical practice,” he said, adding that it further justifies the usage of the ILR diagnostic tool.

References

1. Validation of the clinical diagnosis of neurally-mediated syncope. Presented by Michele Brignole.

2. Moya A, Sutton R, Ammirati F, et al. Guidelines for the diagnosis and management of syncope (version 2009) The Task Force for the Diagnosis and Management of Syncope of the European Society of Cardiology (ESC). Euro Heart J 2009;30:2631–71. http://dx.doi.org/10.1093/eurheartj/ehp298

Published on: July 30, 2013

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