Lower body muscle preactivation and tensing mitigate symptoms of initial orthostatic hypotension in young females.

Abstract

Initial orthostatic hypotension (IOH) is a form of orthostatic intolerance defined by a transient decrease in blood pressure upon standing. Current clinical recommendations for managing IOH includes standing up slowly or lower body muscle tensing (TENSE) after standing. Considering that IOH is likely due to a large muscle activation response resulting in excessive vasodilation with a refractory period (<2 minutes), we hypothesized that preactivating lower body muscles (PREACT) before standing would reduce the drop in mean arterial pressure (MAP) upon standing and improve presyncope symptoms. The purpose of this study was to provide IOH patients with effective symptom management techniques. Study participants completed 3 sit-to-stand maneuvers, including a stand with no intervention (Control), PREACT, and TENSE. Continuous heart rate and beat-to-beat blood pressure were measured. Stroke volume and cardiac output were then estimated from these waveforms. A total of 24 female IOH participants (mean ± SD: 32 ± 8 years) completed the study. The drops in MAP following PREACT (-21 ± 8 mm Hg; P <.001) and TENSE (-18 ± 10 mm Hg; P <.001) were significantly reduced compared to Control (-28 ± 10 mm Hg). The increase in cardiac output was significantly larger following PREACT (2.6 ± 1 L/min; P <.001) but not TENSE (1.9± 1 L/min; P = .2) compared to Control (1.4 ± 1 L/min). The Vanderbilt Orthostatic Symptom Score following PREACT (9±8 au; P = .033) and TENSE (8 ± 8 au; P = .046) both were significantly reduced compared to Control (14 ± 9 au). Both the drop in MAP and symptoms upon standing improved with either PREACT or TENSE. These maneuvers provide novel symptom management techniques for patients with IOH.