Increased orthostatic tolerance following moderate exercise training in patients with unexplained syncope

Abstract

Objective-To determine whether a programme of simple, moderate exercise training increases blood volume and improves orthostatic tolerance in patients with attacks of syncope or near syncope related to orthostatic stress.Design-An open study in 14 patients referred with unexplained attacks of syncope, who were shown to have a low tolerance to an orthostatic stress test. Measurements were made of plasma and blood volumes, orthostatic tolerance to a test of combined head up tilt and lower body suction, and baroreceptor sensitivity by applying subatmospheric pressures to a chamber over the neck. Cardiorespiratory fitness was assessed from the relation between heart rate and oxygen uptake during a graded treadmill exercise test. Assessments were made before and after undertaking an exercise training programme (Canadian Air Force 5BX/XBX). Results-After the training period, 12 of the 14 patients showed evidence of improved cardiorespiratory fitness. All 12 patients were symptomatically improved; they showed increases in plasma and blood volumes and in orthostatic tolerance, and decreases in baroreceptor sensitivity. Despite the improved orthostatic tolerance, values of blood pressure both while supine and initially following tilting were lower than before training.

Guidelines on management (diagnosis and treatment) of syncope

“…increased dietary salt/electrolyte intake with fluids such as 'sport' drinks, salt tablets) or moderate exercise training [269][270][271][272] appear to be among the safest initial approaches (level B). Additionally, in highly motivated patients with recurrent vasovagal symptoms, the prescription of progressively prolonged periods of enforced upright posture (so-called 'tilt-training') may reduce syncope recurrence [273,274] (level B).…”

Assessment of capillary fluid shifts during orthostatic stress in normal subjects and subjects with orthostatic intolerance

“…This is presumably because, with a larger blood volume, more is available for filling the dependent capacitance vessels. It has also been shown that orthostatic tolerance improves if blood volume can be increased, for example by salt loading [4,5] or by exercise training [6].…”

Heart Rate Variability Assessment of the Effect of Physical Training on Autonomic Cardiac Control

“…18 It is said that postural changes, such as standing up, elicit sympathetic stimulation which, if attenuated, may be a marker of early sympathetic impairment. 44 However, it may also be an indication of exercise induced changes in the ANS. It is important to take cognisance of the fact that the orthostatic response can detect effects not visible in the supine position and that it can be a useful clinical tool to measure autonomic responsiveness, both in clinical medicine 45 and in exercise physiology.…”