Initial orthostatic hypotension in teenagers and young adults

Abstract

Objective: To assess: (1) the frequency of an abnormally large fall in blood pressure (BP) upon standing from supine in patients with initial orthostatic hypotension (IOH); (2) the underlying hemodynamic mechanisms of this fall in BP upon standing from supine and from squatting.

Methods: In a retrospective study of 371 patients (≤30 years) visiting the syncope unit, the hemodynamic response to standing and squatting were studied in 26 patients who were diagnosed clinically with IOH, based on history taking only. In six patients changes in cardiac output (CO) and systemic vascular resistance (SVR) were determined, and the underlying hemodynamics were analyzed.

Results: 15/26 (58 %) patients with IOH had an abnormally large initial fall in systolic BP (≥40 mmHg). There was a large scatter in CO and SVR response after arising from supine [ΔCO at BP nadir median -8 % (range -37, +27 %); ΔSVR at BP nadir median -31 % (range -46, +10 %)]. The hemodynamic response after squatting showed a more consistent pattern, with a fall in SVR in all six patients [ΔCO at BP nadir median +23 % (range -12, +31 %); ΔSVR at BP nadir median -42 %, (range -52, -35 %)].

Interpretation: The clinical diagnosis of IOH is based on history taking, as an abnormally large fall in systolic BP can only be documented in 58 %. For IOH upon standing after supine rest, the hemodynamic mechanism can be either a large fall in CO or in SVR. For IOH upon arising from squatting a large fall in SVR is a consistent finding.

Keywords: Blood pressure; Cardiac output; Finapres; Initial orthostatic hypotension; Syncope; Vascular resistance.

Fig. 1

Flowdiagram of patient enrollment

Fig. 2

Initial BP responses upon arising from supine and squatting. The individual beat-to-beat systolic BP responses are given between the last 10 s of supine rest and squatting position until the first 20–30 s after arising. Asterisk patients with symptoms of light-headedness 5–10 s after arising. BP blood pressure

Fig. 3

Hemodynamic responses underlying the initial BP dip during active standing from supine (a) and from squatting (b). The CO and SVR responses are estimated by modeling flow from the arterial pressure waveform. SVR and CO are connected and given in percentages of change (from supine control or squat to the initial BP dip). BP blood pressure, CO cardiac output, SVR systemic vascular resistance

Fig. 4

Effect of buttock clenching in patient 3. Shown is the continuous BP during the last 10 s in supine position and the first 40 s while standing without muscle tension (a), moderate muscle tension (b) and maximal muscle tension (c). BP blood pressure

Fig. 5

Diagnostic algorithm of initial orthostatic hypotension. A typical clinical history is sufficient to diagnose initial orthostatic hypotension, if there is an absence of conventional orthostatic hypotension (systolic BP ≥20 mmHg and/or diastolic BP ≥10 mmHg <3 min of standing). The diagnosis becomes 100 % certain if an abnormally large fall in systolic BP (>40 mmHg) is documented <15 s of standing, accompanied with typical symptoms. BP blood pressure