Hemodynamic Mechanisms Underlying Initial Orthostatic Hypotension, Delayed Recovery and Orthostatic Hypotension

Abstract

Objectives: Continuous noninvasive blood pressure (BP) measurement enables us to observe rapid changes in BP and to study underlying hemodynamic mechanisms. This study aimed to gain insight into the pathophysiological mechanisms underlying short-term orthostatic BP recovery patterns in a real-world clinical setting with (pre)syncope patients.

Setting and participants: In a prospective cohort study, the active lying-to-standing test was performed in suspected (pre)syncope patients in the emergency department with continuous noninvasive finger arterial BP measurement.

Measures: Changes in systolic BP, cardiac output (CO), and systemic vascular resistance (SVR) were studied in normal BP recovery, initial orthostatic hypotension, delayed BP recovery, and sustained orthostatic hypotension.

Results: In normal recovery (n = 47), ΔBP at nadir was -24 (23) mmHg, with a CO change of +10 (21%) and SVR of -23 (21%). In initial orthostatic hypotension (n = 7) ΔBP at nadir was -49 (17) mmHg and CO and SVR change was -5 (46%) and -29 (58%), respectively. Delayed recovery (n = 12) differed significantly from normal recovery 30 seconds after standing, with a ΔBP of -32 (19) vs 1 (16) mmHg, respectively. Delayed recovery was associated with a significant difference in SVR changes compared to normal recovery, -17 (26%) vs +4 (20%), respectively. There was no difference in CO changes. In sustained orthostatic hypotension (n = 16), ΔBP at 180 seconds after standing was -39 (21) mmHg, with changes in CO of -16 (31%) and SVR of -9 (20%).

Conclusions/implications: Hemodynamic patterns following active standing are heterogeneous and differ across orthostatic BP recovery patterns, suggesting that volume status, medication use, and autonomic dysfunction should all be taken into account when evaluating these patients. Moreover, results suggest that a delayed BP recovery is associated with an impaired increase in SVR in a significant proportion of individuals, implying that physicians treating older adults with hypertension should consider the possible negative effect of intensive hypertension treatment on initial orthostatic blood pressure control.

Keywords: Systemic vascular resistance; cardiac output; delayed blood pressure recovery; initial orthostatic hypotension; orthostatic blood pressure; orthostatic hypotension.