|Transient Loss of Consciousness
|Carotid Sinus Syncope
Fainting is a protective mechanism in that it restores cerebral blood flow by the patient ending up on the floor with head and heart at same level. Do not prevent this.
- Standing leads to a reduced circulating volume
- Baroreceptors trigger the sympathetic system to increase stroke volume by contracting vigorously.
- Activation of C-fibres in the ventricular walls increases vagal stimulation
- There is bradycardia and/or hypotension known as the Bezold-Jarisch reflex.
- Neurocardiogenic syncope
- Simple faint
- Vagally mediated syncope
- Reflex syncope.
- Carotid sinus syncope: on turning the head or shaving the chin. Due to carotid sinus hypersensitivity, usually in the elderly.
- Cough syncope: after a paroxysm of coughing, usually in a patient with obstructive airways disease.
- Micturition syncope: commoner in men. Often at night when going to pass urine or during micturition itself.
- Large meals +/- alcohol, restaurant or pub
- Warm day and unpleasant event e.g. sight of blood
- Standing in church or other religious place or standing inline
- It is seen in all age groups and is a cause of syncope in the elderly.
- It is often brought on by pain, tiredness, heat, standing, Nitrates, blood loss.
- Patient may complain of initial buzzing in ears followed by nausea, sweating, dimming of vision and pallor followed by faint.
- Muscle tone and consciousness is lost and the patient falls.
- There may be jerking movements but these do not represent epilepsy.
- Tonic-clonic muscular contractions may occur as may Urinary incontinence which may be misdiagnosed as epilepsy.
- There are two main types of Neurocardiogenic syncope found at Head-Up Tilt Testing. This is usually carried out with a mechanised tilt table giving a head-up tilt of 60 degrees for 45 min, with continuous ECG and BP monitoring. Symptoms should correlate with investigated incidents. There are two types
- 1. Vasodepressor: Blood pressure drops 50 mmHg + syncope/pre syncope . Rx Fludrocortisone, stop diuretics, compression stockings thigh length. increased salt intake, Beta-blockers, SSRI's
- 2. Cardioinhibitory: Heart rate falls rate < 40 or pause > 3 secs+ syncope/pre syncope. HR drops before BP drops and treatment is a Pacemaker
Any sudden loss of consciousness without warning must be assumed to be a cardiac arrhythmia or a until proved otherwise. It has implications for those who wish to drive. Patient must be warned not to drive again until the diagnosis is established. They should inform DVLA.
Differentials and Causes
- Arrhythmia: profound bradycardia or tachycardia. Symptomatic palpitations can be a pointer but often are not present.
- Structural: e.g. outflow obstruction (notably aortic stenosis or hypertrophic cardiomyopathy), ischaemia, tamponade, pulmonary embolism.
- Neurological: seizures, stroke, TIA. Need good eye-witness account is key to the diagnosis. Jerky movements of the limbs, and even incontinence, can occur in a prolonged vasovagal attack, especially if the patient remains upright.
- Hypoglycaemia: well known in diabetics. On Insulin or Sulponylurea. Insulinoma is a rare cause
- Hyperventilation/anxiety: panic attack. Palpitations and might feel light-headed, or have a feeling of being distanced from the surroundings, chest pain and/or paraesthesiae with numbness in arms, hands or lips. Pallor and peripheral cyanosis can be striking in a full-blown attack. Circumstances provoking an attack can often be the same as for a faint (e.g. warm room, stressful situation).
- Orthostatic hypotension: elderly patients. Often caused by drugs, e.g. for hypertension, but don’t forget autonomic neuropathy and Parkinson’s disease.