Syncope is defined as transient loss of consciousness (TLoC), due to cerebral hypoperfusion. Syncopal episodes come on rapidly and last only for a short time, with a spontaneous complete recovery. Presyncope is the feeling that one is about to lose consciousness, but without any actual TLoC; it should be investigated in the same way as syncope. This toolkit consists of a variety of ‘new and useful bits’ summaries, covering the differential diagnosis, clinical assessment, red flags and considerations to do with work and driving. More information is available in the various courses in our syncope hub. Referral to a syncope clinic may be appropriate, as they will have access to investigations such as tilt table testing and cardiac investigations which cannot be done in primary care. This may lead to treatment with medication such as fludrocortisone and midodrine, or occasionally pacing or ablation procedures - others are mentioned in the individual NUBs. Referral should be particularly considered where syncope occurs frequently, is associated with trauma (see top tips on falls and syncope) or affects the person’s occupation, as well as where there is diagnostic uncertainty. Commissioning GPs might want to think about whether they have a syncope clinic in their area and if not, how they could commission one, as they tend to lead to faster diagnosis and more cost-effective care. View the syncope basics NUB (‘new and useful bits’) and read about syncope in special situations – children, pregnant women and athletes.
Causes of syncope
Cardiac syncope This should be considered when there are red flags in the history or examination and an urgent cardiology referral should be arranged. Risk of overdiagnosis if there are incidental findings on ECG – an arrhythmia which is not accompanied by syncope may not be the cause of syncope which happens at another time. 24-hour ECG is generally unhelpful unless symptoms occur at least once per day.
PoTS Postural tachycardia syndrome is associated with a variety of co-morbidities, including long COVID, and should be considered when standing causes presyncope and tachycardia, with no fall in blood pressure. Syncope may also occur.
Orthostatic hypotension Significant drop in blood pressure which may be rapid or delayed and causes TLoC. Most commonly caused by medication, but other causes include volume depletion, autonomic failure and adrenal insufficiency.
Reflex syncope Any syncopal episode caused by a failure of autoregulation of blood pressure, causing a reduction in cerebral perfusion and TLoC. Commonly vasovagal, due to activation of the autonomic nervous system – can also be caused by carotid sinus stimulation due to neck pressure from a tight collar or when shaving.
View or download the syncope pathway, which can guide individual management as well as commissioning decisions.
View or download the syncope checklist, useful as a summary and while taking a history.