Effect of Pharmacological Interventions on Systolic Blood Pressure Drops (SynABPM 2 Proof-of-concept)

24-hour ambulatory blood pressure monitoring (ABPM) is able to detect systolic blood pressure (SBP) drops that allow to discriminate patients with reflex syncope from controls. One episode of daytime SBP <90 mmHg or one episode of daytime SBP <100 mmHg, if mean 24-hour SBP is <125 mmHg, is the best cut-off for the identification of reflex syncope patients with hypotensive susceptibility.

The hypothesis of the present proof-of-concept study is that a therapeutic strategy aimed to increase arterial blood pressure can prevent SBP drops and (hopefully) reduce syncope recurrences.

If the study hypothesis will be confirmed, the magnitude of increase of SBP needed to abolish SBP drops will be also assessed.

Inclusion criteria

Eligible patients were those who fulfilled all the following criteria:

• had received a diagnosis of reflex syncope
• had undergone an ABPM as part of the routine work-up of syncope in use in these hospitals that had shown one or more daytime SBP drop <90 mmHg or one or more daytime drops <100 mmHg in patients with average 24-hour SBP ≥125 mmHg
• had received instructions in order to abolish/reduce their antihypertensive therapy with the aim to prevent syncopal recurrences or had received active drug therapy, i.e., fludrocortisone, in order to increase their arterial blood pressure.
• had performed a second ABPM within 6 months from ABPM 1 in order to verify the effect of the prescribed change in therapy

Exclusion criteria

• Age <18 years
• Symptomatic orthostatic hypotension (defined as a symptomatic fall in SBP ≥20 mm Hg or a SBP decrease to <90 mmHg, as per the ESC guidelines;
• competing causes of syncope (i.e., syncope due to arrhythmias and structural cardiac diseases and non-syncopal causes of transient loss of consciousness as defined by ESC guidelines on syncope
• Severe structural heart disease, previous stroke or transient ischaemic attack