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. 1998 Dec;80(6):596–600. doi: 10.1136/hrt.80.6.596

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

B Mtinangi 1, R Hainsworth 1
PMCID: PMC1728858  PMID: 10065030

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.
Conclusions—Exercise training has a role in the management of patients with syncope and poor orthostatic tolerance. It improves symptoms and increases orthostatic tolerance without increasing resting blood pressure.

 Keywords: orthostasis;  syncope;  baroreceptors;  exercise

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Figure 1  .

Figure 1  

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Relations between heart rate and oxygen consumption during exercise in one of the patients before and after undertaking the training programme. The lines are the linear regression and show the lower heart rates after training, at corresponding levels of oxygen consumption.

Figure 2  .

Figure 2  

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Values of heart rate taken from the regression lines (for example, fig 1) at values of oxygen consumption (V̇O2) of 1.5 l/min. Points shown are values before and after training. Solid points with bars are the means with SE from all points. The dashed lines are the data from the two subjects in whom the change in the elevation of the regression line did not reach statistical significance. After training, all patients had lower values of heart rate at a V̇O2 of 1.5 l/min.

Figure 3  .

Figure 3  

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Values of plasma volume before and after training. Points joined by dashed lines are from patients who failed to show a significant change in the slope of the heart rate to V̇O2 relation.

Figure 4  .

Figure 4  

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Values of orthostatic tolerance (time to presyncope) in patients before and after training. The stages of the test were: 0-20 minutes, head up tilt; 20-30 minutes, tilt and lower body suction at −20 mm Hg; after 30 minutes, tilt and lower body suction at −40 mm Hg. Dashed lines are from patients failing to show significant change in heart rate to V̇O2 relation. All other patients showed increased tolerance, with eight changing up to the next stress level.

Figure 5  .

Figure 5  

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Relation between change in orthostatic tolerance and change in plasma volume. Note that all patents who showed increases in plasma volume of 150 ml or more showed increases in orthostatic tolerance.

Figure 6  .

Figure 6  

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Effects of training on baroreceptor sensitivity. Baroreceptor sensitivity decreased in all patients, although in one of those who did not show a significant change in the heart rate/V̇O2 slope, baroreceptor sensitivity did not change outside the error of the method.

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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