Abstract
Orthostatic fluid shifts reduce the effective circulating volume and thus contribute to syncope susceptibility. Recurrent syncope has a devastating impact on quality of life and is challenging to manage effectively. To blunt orthostatic fluid shifts, static calf compression garments are often prescribed to patients with syncope, but have questionable efficacy. Intermittent calf compression, which mimics the skeletal muscle pump to minimize pooling and filtration, holds promise for the management of syncope. We aimed to evaluate the effectiveness of intermittent calf compression for increasing orthostatic tolerance (OT; time to presyncope). We conducted a randomized single-blind crossover study, in which participants (n = 21) underwent three graded 60° head-up-tilt tests to presyncope with combined lower body negative pressure on separate days. Low frequency intermittent calf compression (ICLF; 4 s on and 11 s off) at 0–30 and 0–60 mmHg was applied during two tests and compared to a placebo condition where the garment was fitted, but no compression applied. We measured continuous leg circumference changes (strain gauge plethysmography), cardiovascular responses (finger plethysmography; Finometer Pro), end tidal gases (nasal cannula), and cerebral blood flow velocity (CBFv, transcranial Doppler). The 0–60 mmHg ICLF increased OT (33 ± 2.2 min) compared to both placebo (26 ± 2.4 min; p < 0.001) and 0–30 mmHg ICLF (25 ± 2.7 min; p < 0.001). Throughout testing 0–60 mmHg ICLF reduced orthostatic fluid shifts compared to both placebo and 0–30 mmHg ICLF (p < 0.001), with an associated improvement in stroke volume (p < 0.001), allowing blood pressure to be maintained at a reduced heart rate (p < 0.001). In addition, CBFv was higher with 0–60 mmHg ICLF than 0–30 mmHg ICLF and placebo (p < 0.001). Intermittent calf compression is a promising novel intervention for the management of orthostatic intolerance, which may provide affected individuals renewed independence and improved quality of life.
Highlights
Syncope, or fainting, refers to a transient loss of consciousness and postural tone due to cerebral hypoperfusion, characterized by a rapid onset, short duration and spontaneous recovery (Shen et al, 2017)
We evaluated the effect of intermittent compression on SAP throughout the initial 30 s of tilt to examine whether this intervention might be of benefit for the prevention of initial orthostatic hypotension (OH)
We demonstrated that intermittent calf compression from 0 to 60 mmHg (4 s on – 11 s off) effectively delays the onset of presyncope in healthy individuals
Summary
Fainting, refers to a transient loss of consciousness and postural tone due to cerebral hypoperfusion, characterized by a rapid onset, short duration and spontaneous recovery (Shen et al, 2017). Syncope is a heterogeneous condition caused by inadequate cardiovascular autonomic compensation for the gravitational fluid shifts that occur in Intermittent Calf Compression Delays Presyncope the upright position. In patients with orthostatic syncope, impaired autonomic control of vascular resistance and/or cardiac output culminates in global cerebral hypoperfusion (Hansson, 1979; Hainsworth, 2004). Clinical investigations for syncope are largely aimed at the differential diagnosis, ruling out serious or life-threatening conditions such as cardiac syncope, epilepsy, and transient ischemic attacks, with a low diagnostic yield (Mendu et al, 2009; Krahn et al, 2013). The fear of missing a serious underlying condition has led to a practice of over-investigating low-risk patients that is taxing on the healthcare system and causes unnecessary anxiety and uncertainty for patients and families
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