Assessment of Midodrine in the Prevention of Vasovagal Syncope: The Prevention of Syncope Trial IV

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.