Leg crossing improves orthostatic tolerance in healthy subjects: a placebo-controlled crossover study

Abstract

Vasovagal syncope is the most common cause of transient loss of consciousness, and recurrent vasovagal fainting has a profound impact on quality of life. Physical countermaneuvers are applied as a means of tertiary prevention but have so far only proven useful at the onset of a faint. This placebo-controlled crossover study tested the hypothesis that leg crossing increases orthostatic tolerance. Nine naïve healthy subjects [6 females, median age 25 yr (range 20-41 yr), mean body mass index 23 (SD 2)] were subjected to passive head-up tilt combined with a graded lower body negative pressure challenge (20, 40, and 60 mmHg) determining orthostatic tolerance thrice, in randomized order: 1) control, 2) with leg crossing, and 3) with oral placebo. Blood pressure (Finometer), heart rate, and changes in thoracic blood volume (impedance), stroke volume, and cardiac output (Modelflow) were followed during orthostatic stress. Primary outcome was time to presyncope (systolic blood pressure </=85 mmHg, heart rate >/=140 beats/min). With leg crossing, orthostatic tolerance increased from 26 +/- 2 to 34 +/- 2 min (placebo 23 +/- 3 min, P < 0.001). During leg crossing, mean arterial pressure (81 vs. 81 mmHg) and cardiac output (95 vs. 94% supine) remained unchanged; heart rate increase was lower (13 vs. 18 beats/min, P < 0.05); stroke volume was higher (79 vs. 74% supine, P < 0.05); and there was a trend toward lower thoracic impedance. Leg crossing increases orthostatic tolerance in healthy human subjects. As a measure of prevention, it is a worthwhile addition to the management of vasovagal syncope.

2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society

“…This is particularly true in the pediatric population, where significant overlap exists in the clinical presentation of patients with V VS and arrhythmic syncope. 313,314 Attention to the triggers and presence of palpitations preceding syncope onset have been helpful in diagnosing an arrhythmic etiology. 315 Patients with LQTS and syncope should adhere to the lifestyle changes previously published, including avoidance of strenuous activity in LQTS1, and drugs known to prolong QT interval in all patients with LQTS.…”

Effects of pericardial constraint and ventricular interaction on left ventricular hemodynamics in the unloaded heart

“…Steady-state cardiac output and SV were measured at baseline and Ϫ30 mmHg LBNP by thermodilution (9). Modelflow SV at Ϫ30 mmHg LBNP was calibrated against the thermodilution method during steady-state Ϫ30 mmHg LBNP as previously reported (6,24,31,45). During LBNP release, beat-to-beat finger pressure waveforms were recorded (21).…”

Neurogenic orthostatic hypotension: chasing “the fall”

“…Manoeuvres which involve enhancing the skeletal muscle pump activity, such as standing and sitting cross legged,55 56 result in more blood being pumped back to the heart. The same effect can be obtained passively by using waist-high lower limb elastic stockings, and positive gravity suits.…”