Heat syncope

Background

Variant of postural hypotension[1]
- Results from combination of volume depletion, decreased vasomotor tone and peripheral vasodilatation
- Often precipitated by rapid change in position during exercise
- Occurs in nonacclimatized patients during early stages of heat exposure (especially elderly)

Cardiovascular-mediated syncope
- Dysrhythmias:
  - WPW (pre-excitation)
  - Long QT Syndrome
  - Brugada Syndrome
  - Catecholaminergic polymorphic ventricular tachycardia
  - 2nd/3rd AV Block
  - Afib/aflutter
  - Vtach/torsades
  - Sick sinus syndrome
  - Arrhythmogenic right ventricular dysplasia
  - Short QT syndrome
- Cardiovascular disease
  - Valvular Disease (AS, MS, tricuspid stenosis)
  - Aortic Dissection
  - Myocardial Infarction
  - CHF
  - Hypertrophic Cardiomyopathy
  - PE
  - Pericardial Tamponade
  - Myxoma
  - Pulmonary Hypertension
  - Pacemaker malfunction
Neurally mediated syncope
- Vasovagal:
  - Fear, pain, emotion, valsalva, breath-holding spell
- Situational (associated with):
  - Coughing, micturition, defecation, vomiting, swallowing, postexercise
  - Carotid sinus stimulation
Orthostatic hypotension-mediated syncope:
- Volume depletion:
  - Dehydration (vomiting, diarrhea)
  - Hemorrhage, (Ectopic Pregnancy, Upper GI Bleed/Lower GI Bleeding, Abdominal Aortic Aneurysm)
  - Sepsis
- Autonomic Dysreflexia
- Autonomic failure due to meds
Other serious causes
- Stroke
- SAH
- TIA
- Vertebrobasilar Insufficiency
- Subclavian steal
- Heat syncope
- Hypoglycemia
- Hyperventilation
- Asphyxiation
- Seizure
- Narcolepsy
- Psychogenic (anxiety, conversion disorder, somatic symptom disorder)
- Toxic (drugs, carbon monoxide, etc.)

Waters T. Heat Emergencies In: Tintinalli's Emergency Medicine: A Comprehensive Study Guide. 7th ed. McGraw Hill Medical. 2011: 1339

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