Objectives: Squatting is a potent physical maneuver to prevent syncope; however, a major drawback is that standing up from squatting is a large hemodynamic stressor that often causes new presyncopal symptoms. We tested the hypothesis that lower body skeletal muscle tensing (LBMT) attenuates the decrease of mean arterial blood pressure (MAP) upon standing from squatting when used as a maneuver to prevent vasovagal syncope.
Methods and results: In 18 patients (10 females and 8 males, median age 37.5 years) we followed continuous MAP, cardiac output (CO, by Modelflow) and total peripheral resistance (TPR) during tilt test-provoked pre-syncopal episodes. After standing up from squatting MAP decreased to a nadir of 64 +/- 4 mmHg (mean +/- SE), related to a reduction in CO 73 +/- 5% of supine values. Standing up with LBMT limited the reduction in CO (85 +/- 6 %, P < 0.05) and MAP nadir (to 76 +/- 3 mmHg; P < 0.05 compared to without LBMT) with fewer or no presyncopal symptoms. Standing up from squatting with and without LBMT did not affect TPR (99 +/- 5% vs. 101 +/- 7%).
Interpretation: LBMT is proposed as an effective follow-up maneuver to squatting when applied to prevent syncope.