Differential diagnosis
Type 1 Mixed
- heart rate falls to ≥ 40 beats/minute or
- heart rate falls to < 40 beats/minute for less than 10 seconds
- blood pressure falls before the heart rate falls
Type 2 A Cardioinhibition without asystole
- heart rate falls to < 40 beats/minute for more than 10 seconds
- asystole of > 3 seconds does not occur
- blood pressure falls before the heart rate falls
Type 2B Cardioinhibition with asystole
- asystole occurs for > 3 seconds
- blood pressure fall coincides with or occurs before the heart rate falls
Type 3 Vasodepressor
- heart rate does not fall more than 10% from its peak at the time of syncope Exception 1 Chronotropic Incompetence
Exception 1 Chronotropic Incompetence
- no heart rate rise during the tilt testing (i.e. less than 10% from the pre-tilt phase)
Exception 2 Excessive heart rate rise
- An excessive heart rate rise both at the onset of the upright position and throughout its duration before syncope (i.e. greater than 130 beats/minute)
Postural orthostatic tachycardia syndrome
Postural tachycardia in association with relatively mild hypotension is thought to represent a mild form of autonomic dysfunction rather than a variant of vasovagal syncope. Diagnosis is performed by means of tilt table testing, the syndrome is characterised as follows:
- heart rate increase of > 30 beats/minute (or a maximum heart rate of 120 beats/minute) during tilting
- no profound hypotension
- symptoms can include light-headed, fatigue, presyncope and dizziness
Carotid sinus hypersensitivity
The diagnosis of carotid sinus hypersensitivity is performed by means of carotid sinus massage:
- asystole of ≥3 seconds (cardioinhibitory subtype)
- fall in systolic blood pressure of ≥ 50 mmHg (vasodepressor subtype)
- asystole of ≥ 3 seconds + fall in systolic blood pressure of =50 mmHg (mixed subtype)