About 20% of adults faint recurrently. These patients are often highly symptomatic, have problems with employment and driving and have reduced quality of life. There are no therapies that have withstood the test of adequately designed and conducted randomized clinical trials. Midodrine is a prodrug whose metabolite is an alpha-1 adrenergic agonist that increases venous return to the heart and raises blood pressure. There is considerable lower level evidence that it might prevent vasovagal syncope.

The investigators will test the hypothesis that Midodrine prevents recurrences of syncope in patients with moderate to severe vasovagal syncope.

Inclusion Criteria:

• Patients will be eligible if they have:

  • ≥2 syncopal spells in the year preceding enrolment, and
  • ≥ -2 points on the Syncope Symptom Score for Structurally Normal hearts, and
  • Age ≥ 18 years with informed consent.

Exclusion Criteria:

• Patients will be excluded if they have:

  • other causes of syncope, such as ventricular tachycardia, complete heart block, postural hypotension or hypersensitive carotid sinus syndrome,
  • an inability to give informed consent,
  • important valvular, coronary, myocardial or conduction abnormality or significant arrhythmia,
  • hypertrophic cardiomyopathy,
  • a permanent pacemaker,
  • a seizure disorder,
  • urinary retention,
  • hypertension defined as >140/90 mm Hg,
  • hepatic disease,
  • glaucoma or
  • a 5-minute stand test resulting in diagnoses of Postural Orthostatic Tachycardia Syndrome or Orthostatic Hypotension.