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

AIM: To assess the clinical efficacy of orthostatic training (OT) and its effect on the autonomic activity. METHODS: 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. RESULTS: 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 ± 3.94 ms/mm Hg vs 12.51 ± 5.3 ms/mm Hg, P = 0.04, standing: 5.08 ± 2.34 ms/mm Hg vs 7.54 ± 2.16 ms/mm Hg, P = 0.02). After OT, BRS increased in responders (sitting: 8.05 ± 3.94 ms/mm Hg to 9.31 ± 4.49 ms/mm Hg, P = 0.05; standing: 5.08 ± 2.34 ms/mm Hg to 5.96 ± 2.38 ms/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. CONCLUSIONS: 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.

Clinical characteristics associated with bradycardia and asystole in patients with syncope undergoing long-term electrocardiographic monitoring with implantable loop recorder.

BACKGROUND: The aim of this retrospective single center cohort study was to assess the occurrence of bradycardia during implantable loop recorder (ILR) monitoring in patients with unexplained syncope and negative conventional testing and to identify clinical predictors of bradycardia and pacemaker implantation. METHODS: An ILR was implanted in 112 patients (31 men, 81 women, mean age 64 ±13 years) with syncope which was not explained after conventional diagnostic work-up. Clinical variables were compared between patients with and without pacemaker implantation. RESULTS: A diagnosis was made in 67 patients (60%), including non-arrhythmic (vasodepressor) syncope (27 patients), sinus bradycardia or asystole (23 patients), atrioventricular (AV) block (14 patients) and bradycardic atrial fibrillation (3 patients). The mean time to diagnosis was 233 ± 282 days. A pacemaker was implanted in 40 patients (36%). Male gender, age above 65 years, hypertension, presence of structural heart disease, absence of prodromal symptoms, trauma secondary to syncope, asymptomatic sinus bradycardia and first-degree AV block were clinical predictors of pacemaker implantation in univariate analysis. Of the independent predictive factors three remained significant in multivariate analysis: absence of prodromal symptoms before the loss of consciousness (odds ratio OR 3.38, p = 0.01, 95% confidence interval CI 1.24-9.20), male gender (OR 3.22, p = 0.01, 95% CI 1.26-8.20) and age >65 years (OR 2.94, p = 0.02, 95% CI 1.14-8.33). CONCLUSIONS: In patients undergoing ILR implantation bradycardia is a frequent finding despite the negative conventional diagnostic testing. Absence of prodromal symptoms, male gender and age >65 years are risk factors for bradycardia and pacemaker implantation.

Gene Polymorphism of the Adenosine A2a Receptor in Patients with Vasovagal Syncope.

BACKGROUND: Adenosine may play a role in the pathogenesis of vasovagal syncope (VVS). The aim of the study was to evaluate the adenosine A(2A) receptor gene 1083 T > C polymorphism in patients with syncope and its possible association with results of head-up tilt test (HUT). METHODS: Three hundred and forty-seven consecutive patients (mean age 47.3 ± 18.5 years, 132 men, 215 women) with one or more syncopal episodes underwent HUT as part of standardized diagnostic evaluation. HUT was positive in 207 patients (75 males, mean age 44.7 ± 18.6 years) and negative in 140 patients (58 males, mean age 48.17 ± 18.8 years). One thousand and eighty-three T > C single nucleotide polymorphism in the adenosine A(2A) receptor gene (rs5751876) was evaluated in 347 patients with syncope and in 85 subjects without history of syncope (54 men, mean age 41.7 ± 16.3). RESULTS: Adenosine A(2A) receptor 1083 T > C polymorphism was not associated with the positivity of HUT. Blood pressure and heart rate response to tilting was similar in all genotypes. Low frequency (LF) power was significantly lower in CC genotype compared to CT genotype in early phase of tilt (log LF 2.69 ± 0.61 vs 3.20 ± 0.60; P = 0.01) and at the time of syncope (log LF 2.60 ± 0.63 vs 2.77 ± 0.48; P = 0.04). CONCLUSIONS: Adenosine A(2A) receptor 1083 T > C polymorphism is not associated with the positivity of HUT and its proposed role in predisposition to VVS was not confirmed. CC genotype may be associated with lower sympathetic activity during HUT.