Evidence-based On-call

Syncope

Prognosis

Cardiac arrhythmias are a common cause of unexplained syncope and are more likely with ^a

Note:

A fifth of patients with unexplained syncope will go on to be diagnosed with a cardiac arrhythmia (20%: 95% CI: 15% to 25%) ^a

Lack of nausea and vomiting and an abnormal ECG increase the risk of an arrhythmia

Patient	Prognostic Factor	Outcome	CER	RR (95% CI)	NNF+ (95% CI)
unexplained syncope ^a	absence of nausea or vomiting before syncope independent	syncope due to cardiac arrhythmia at 12 months	20%	7.1 (1.6 to 33.3)	2 (1 to 12)
	abnormalities on ECG independent		20%	23.5 (7.0 to 78.7)	2 (1 to 2)