The effect of fludrocortisone and midodrine on ambulatory blood pressure biomarkers and symptoms of syncope.

INTRODUCTION

Fludrocortisone and midodrine are frequently used to raise blood pressure (BP) in patients with vasovagal syncope (VVS)/low BP phenotype and orthostatic hypotension (OH), despite limited supporting evidence. This study assesses changes in Ambulatory Blood Pressure Monitor (ABPM) biomarkers and symptoms of syncope after commencing/increasing fludrocortisone or midodrine.

METHODS

Patients attending a tertiary-referral falls & syncope unit and prescribed fludrocortisone/midodrine were included. ABPM at index visit and follow-up (after commencing/increasing fludrocortisone/midodrine) were analysed, with specific focus on biomarkers of syncope risk: overall systolic BP (sBP), minimum sBP, and 'dips' in sBP <100 mmHg. Symptoms of presyncope and syncope were assessed at follow-up. These variables were compared pre and post medication changes using paired t-tests.

RESULTS

110 patient reviews (median age 57.0 (95%CI 46.4-63.8) years, 77% female) were followed for median 4.0 (IQR 2.0-8.0) months. Of these, 52% (57/110) commenced/increased fludrocortisone, and 48% (53/110) commenced/increased midodrine. Fludrocortisone use was associated with significant increases in overall sBP, minimum sBP and reduction in sBP dips <100mmHg. Symptoms of presyncope improved in 73.7% participants commencing/increasing fludrocortisone. Only 9/27 outcomes reached statistical significance in participants commencing/increasing midodrine: overall sBP increase commencing midodrine, overall sBP increase increasing midodrine (including subgroup ≥65 years), overall sBP increase commencing/increasing midodrine (including subgroup ≥65 years), minimum sBP increase commencing midodrine (including subgroup <65 years), decrease in sBP dips <100mmHg in subgroup aged ≥65 years increasing midodrine, and decrease in sBP dips <100mmHg in subgroup ≥65 years commencing/increasing midodrine. Symptoms of presyncope improved in 64.2% participants commencing/increasing midodrine.

CONCLUSION

This study provides clinical data on the effectiveness of fludrocortisone and midodrine in patients with VVS/low BP phenotype and OH. Both fludrocortisone and midodrine significantly improved markers of future syncope risk, with fludrocortisone use showing a relatively greater effect.