Improvement in low upright baroreflex sensitivity is associated with positive clinical effect of orthostatic training.

Abstract

To assess the clinical efficacy of orthostatic training (OT) and its effect on the autonomic activity. OT was performed in 38 patients (13 males, age 36.4 ± 15.2 years). Baroreflex sensitivity (BRS), heart rate variability, and quality of life (SF 36) were assessed before and after 6 months of OT. Patients with no recurrence of syncope and reduction of the presyncope number to one-third or less were classified as responders. Compliance to OT was low. Only 55% (38 from 69 patients) completed the training programme; 28 patients were responders (74%) and 10 patients were nonresponders. Before OT, BRS in upright position was lower in responders than in nonresponders (sitting: 8.05 ± 3.94ms/mm Hg vs 12.51 ± 5.3ms/mm Hg, P=0.04, standing: 5.08 ± 2.34ms/mm Hg vs 7.54 ± 2.16ms/mm Hg, P=0.02). After OT, BRS increased in responders (sitting: 8.05 ± 3.94ms/mm Hg to 9.31 ± 4.49ms/mm Hg, P=0.05; standing: 5.08 ± 2.34ms/mm Hg to 5.96 ± 2.38ms/mm Hg, P=0.03). No differences in supine BRS were observed. In responders, low frequency (LF) and high frequency (HF) power in sitting and standing positions significantly increased after OT (P<0.05). In nonresponders, there was no significant rise in BRS, LF, and HF after OT. A significant increase in quality of life was noted in responders, but not in nonresponders. OT reduced symptoms in 74% patients who trained regularly. However, the compliance to training was low. Possible mechanism of OT is reconditioning effect on baroreceptor reactivity in upright position.