Initial orthostatic hypotension among patients with unexplained syncope: An overlooked diagnosis?

BACKGROUND

Initial orthostatic hypotension (IOH) is a clinical syndrome of transient orthostatic hypotension that is defined as a drop in blood pressure of >40 mm Hg systolic and/or >20 mm Hg diastolic within 15 s after standing, accompanied by symptoms of cerebral hypoperfusion, but without sustained orthostatic hypotension (blood pressure decrease >20/10 mm Hg after 1-3 min of standing). As the etiology of syncope remains unknown in a large proportion of patients, we hypothesized that IOH is highly prevalent among patients with unexplained syncope.

METHODS

We studied 250 consecutive outpatients with unexplained syncope that were evaluated in the syncope-unit of our tertiary referral hospital. We measured hemodynamic changes in response to active standing using a beat-to-beat blood pressure measurement device, first after lying supine for >5 min and then after squatting for 30 s.

RESULTS

11.2% of the patients were diagnosed with syncope due to IOH, with a mean fall in blood pressure of 47.4 ± 12.5/29.0 ± 10.7 mm Hg within 15 s after standing up. Therefore, IOH was the second commonest cause of syncope in our cohort. 46.2% of the patients diagnosed with syncope due to IOH used antihypertensive drugs, mostly betablockers (41.6%) and/or tamsulosin (24.9%). The squatting-to-standing-test in addition to the lying-to-standing-test resulted in only 3 additional patients diagnosed with syncope due to IOH.

CONCLUSIONS

IOH is highly prevalent among patients with previously unexplained syncope. Therefore, beat-to-beat blood pressure measurement should be considered in patients with unexplained syncope.