Vasovagal Syncope: The Role of 24h Ambulatory Blood Pressure Monitoring

Abstract The haemodynamic mechanisms underlying vasovagal (reflex) syncope include hypotension and extrinsic asystole/bradycardia, corresponding to two distinct haemodynamic phenotypes of syncope, i.e., the hypotensive and the bradycardic phenotypes. The hypotensive phenotype is the most prevalent, being observed in the 83% of patients. Twenty-four-hour ambulatory blood pressure monitoring (ABPM) demonstrated high effectiveness in identifying the hypotensive phenotype in patients with suspected reflex syncope. The diagnosis of a hypotensive mechanism of syncope is supported by ABPM when one or more of the following criteria are present: Constitutional hypotension: 24-h systolic blood pressure (SBP) <105 mmHg in men and <98 in womenDrug-related hypotension: 24-h SBP <120 mmHgHypotensive episodes: ≥1 daytime SBP <90 mmHg or ≥2 daytime SBP <100 mmHgPostprandial hypotension: symptomatic SBP fall >20 mmHg or absolute value <90 mmHg within 75 min of meals ABPM also plays a key role in guiding therapy. In hypertensive patients with hypotensive syncope, deprescribing antihypertensive medications is indicated with the goal of increasing 24-hour average SBP to ≥ 134 mmHg and/or by at least ≥12 mmHg, without exceeding 140 mmHg (or <160 mmHg in frail older patients). In patients with drug-unrelated hypotension, lower-body elastic garments, fludrocortisone, or midodrine - prescribed singularly or in combination - may be considered and targeted to achieve a 24-hour average SBP ≥116 mmHg and/or an increase of at least ≥9 mmHg.