0624 - Syncope: Cardiovascular and Neurological Perspectives

Question 1

What is Syncope?

Answer 1

Syncope - A sudden on brief loss of consciousness associated with a loss of postural tone, from which recovery is spontaneous. Caused by inadequate cerebral perfusion (low BP), and very serious if secondary to cardiac causes.

Question 2

What is presyncope?

Answer 2

Presyncope - Sensation of light-headedness preceding syncope.

Question 3

What is Orthostatic Hypotension?

Answer 3

Loss of BP on standing.
Characterised as drop in systolic BP≥20mmHg OR diastolic≥10mmHg OR mean arterial ≥ 10mmHg from lying to standing within 3 minutes.

Question 4

What are the 5 classic causes of syncope?

Answer 4

Neurally-mediated - 60% (vasovagal, carotid sinus, situational)
Orthostatic - 15% (Drug induced, volume depletion, autonomic failure)
Cardiac arrythmia - 10% (brady/tachy, channelopathies)
Cardiac structural - 5% (AMI, aortic stenosis, etc)
Idiopathic - 10%

Question 5

What are common cardiac causes of syncope?

Answer 5

Arrhythmia - sinus dysfunction, supra/ventricular tachy, channelopathies
Structural - AMI, aortic stenosis, cardiomyopathy, PE

Question 6

What are the three broad triggers for neurally-mediated syncope?

Answer 6

Central - emotional
Postural - prolonged upright
Situational - specific stimuli (e.g. micturition)

Question 7

What is the ‘chain’ that may lead to syncope?

Answer 7

Can start at any stage
Decreased venous return (hypovolaemia, impaired venous tone)
Decreased cardiac output (Pump Failure, arrhythmia)
Decreased cerebral perfusion (afterload reduction, impaired cerebral circulation)
Could also be a baroreceptor sensor problem.

Question 8

How can syncope be distinguished from seizure?

Answer 8

Shorter duration (seconds), with little confusion after the episode and not preceded by an aura. However, unlike seizures is often preceded by pain, fear, or prolonged standing.

Question 9

What are the key investigations in diagnosing the cause of syncope?

Answer 9

History, physical examination and ECG yield 50% of answers
Routine lab tests are low yield
Neurological tests (CT, EEG, doppler carotids) only if features suggest a neurological cause

Question 10

What investigations should you order if you suspect cardiac syncope?

Answer 10

If known to have cardiac disease/exertional, echo, stress test, holter.
If recurrent without underlying heart disease, loop ECG, tilt table.