The following are key points to remember from this guideline comparison of the American College of Cardiology/American Heart Association/Heart Rhythm Society (ACC/AHA/HRS) and the European Society of Cardiology (ESC) Guidelines for the Diagnosis and Management of Syncope:

1. Syncope is a common clinical entity with variable presentations, and often an elusive causal mechanism, even after extensive evaluation. This review highlights both congruencies and differences between the most recent syncope guidelines (2017 ACC/AHA/HRS vs. 2018 ESC).
2. There were key differences noted in recommendations for patients with conduction disease, reflex syncope, and orthostatic hypotension. However, many of the treatment recommendations were grossly similar.
3. A notable discordancy between the two guidelines regarding conduction system disease is the presence of discrete recommendations in the European guidelines, and the lack of specific recommendations in the US guidelines. Rather, the US guidelines offer a Class I, Level of Evidence (LOE) C-EO recommendation for guideline-directed medical therapy for syncope due to bradycardia. The European guidelines, in contrast, offer several recommendations for pacing in conduction system disease, and while the European guidelines are slightly less supportive of empiric pacing in patients with syncope and bifascicular block (Class IIb), they offer a Class I recommendation for pacing with electrophysiological study (EPS)-guided therapy.
4. European guidelines also offer several specific recommendations for EPS, and present four specific recommendations for EPS indications and EPS-guided therapy. The European guidelines favor EPS in patients with an ischemic substrate (Class I), syncope with bifascicular block (Class IIa), or syncope accompanied by sinus bradycardia or palpitations (Class IIb) when syncope remains unexplained after noninvasive evaluation. In contrast, EPS is more broadly addressed in the US guidelines.
5. A striking discordancy between the two syncope guidelines is the recommendations for beta-blockers in the treatment of reflex syncope. The European guidelines assign a Class III recommendation, stating that there is no indication for beta-blockers in reflex syncope. The US guidelines, in contrast, state that beta-blockers might be reasonable in patients ≥42 years of age (Class IIb, LOE B-R).
6. Another difference is that the European guidelines provide Class IIb recommendations for pacing in patients >40 years of age with tilt-induced asystolic response and frequent unpredictable recurrent syncope, and in patients with clinical features of adenosine-sensitive syncope, without direct parallel US recommendations.
7. The European guidelines recommend patient education and reassurance for orthostatic hypotension, and the US guidelines recommend acute water ingestion for neurogenic orthostatic hypotension. This difference may in part be related to how neurogenic orthostatic hypotension is defined.
8. Both guidelines identify the need for studies aimed at understanding the underlying causes of syncope, and both target the need for improved diagnostic devices, preferably both wearable and multiparametric.
9. Even in the era of evidence-based medicine, practitioners will have slightly varied interpretations and opinions of similar data. Of note, despite key discordances, the two recent syncope guidelines are complementary.
10. Randomized trials and further translational investigations are needed to strengthen recommendations that are currently supported only with minimal evidence, and in areas of discrepancy between the guidelines.

Keywords: Adenosine, Arrhythmias, Cardiac, Bradycardia, Diagnostic Imaging, Electrophysiology, Evidence-Based Medicine, Hypotension, Orthostatic, Myocardial Ischemia, Reflex, Syncope, Syncope, Vasovagal

< Back to Listings