Heart Rate Variability During Sleep in Patients with Vasovagal Syncope

Venous capacitance and venous return in young adults with typical vasovagal syncope: a cross-sectional study

Vasovagal syncope (VVS) has a high prevalence in the general population and is associated with potential complications. There is limited information on the possible association between venous capacitance (VC) and venous return (VR), important determinants of preload and VVS. Since the tilt test was reported to yield a high rate of false positive results, the aim of this study was to evaluate whether abnormal VC and VR at baseline could predispose individuals to VVS.To this end, 88 young, healthy volunteers were recruited and classified to 26 (29.5%) who experienced typical VVS and 62 (70.5%) who did not. VC and VR were evaluated with a commercial device and plethysmography applied to the elevated legs. Maximum venous outflow (MVO), segmental venous capacitance (SVC) and MVO/SVC ratio were calculated and averaged.No significant differences between MVO (5.0±0.5 vs 5.6±0.8, p>0.05), SVC (6.0±0.5 vs 6.3±0.8, p>0.05) or MVO/SVC ratio (0.83±0.02 vs 0.86±0.03, p>0.05) were observed for the non-VVS and VVS volunteers, respectively. There was a significant association between a higher MVO and SVC values and a larger decrease in diastolic blood pressure with standing, although correlations were weak (R²=0.0582 and 0.0681, respectively).In conclusion, at baseline, VC and VR are not impaired in healthy volunteers with a history of VVS. It remains unknown if similar results would be found in patients with cardiovascular comorbidities. Also, the sensitivity of VC and VR evaluations to identify a predisposition for VVS following physiological provocations merits further study.

Management of sleep apnoea syndrome (SAS) in patients with vasovagal syncope (VVS): a protocol for the VVS-SAS cohort study

INTRODUCTION

Recurrent vasovagal syncope (VVS) is associated with decreased quality-of-life and frequent use of emergency services. The evidence base for causality, diagnostic procedures and potential VVS treatments is poor. Scattered observations in the literature suggest a link between respiratory disturbances during sleep and VVS. Empirical observations lead us to further hypothesise that the appropriate management of sleep apnoea syndrome (SAS) may help resolve comorbid recurrent VVS in certain patients. We therefore designed this pilot study to provide a framework for the observation of changes in outcomes accompanying the deployment of SAS treatments in patients with VVS.

METHODS AND ANALYSIS

This is a multicentre, registry-based study whose primary objective is to evaluate the effect of SAS management on the number of syncope/presyncope episodes in a population suffering from both VVS and SAS. To this effect, syncope rates prior to the treatment of SAS will be compared with those occurring after the initiation of the latter. In addition, yearly assessments will collect data for echocardiography, polysomnography, Holter monitoring, table tilt tests, multiple sleep latency tests, SAS management parameters and questionnaires describing fatigue, depression and quality-of-life. Sixty patients will be included with a minimum follow-up period of 12 months. The primary analysis will use comparisons of centrality for paired data to describe the changes in syncope rates before versus after the initiation of SAS management. Longitudinal data will be analysed using mixed models with patients set as a random effect. Subgroup analyses will be performed for SAS-treatment adherence and efficacy.

ETHICS AND DISSEMINATION

The VVS-SAS registry was approved by an ethics committee (Comité pour la Protection des Personnes Ile-de-France VI, Reference number CPP/2-18) in accordance with French law. The princeps publication will present before-after SAS management results and longitudinal analyses.

TRIAL REGISTRATION NUMBER

NCT04294524. Pre-results.

Heart rate recovery and diastolic blood pressure ratio on the treadmill test predict an induction and recurrence of vasovagal syncope

BACKGROUND/AIMS

The induction and recurrence of syncope is a concerning situation that could be unpredicted in the vasovagal syncope (VVS). We investigated a simple predictor for the induced and recurrent VVS during Head-Up table-tilt Test (HUT) and clinically follow-up.

METHODS

The 143 consecutive patients with VVS (age 31 ± 19 years, 33 male) who referred by a cardiologist or neurologist and had undergone an echocardiogram, HUT, and a treadmill exercise test (TMT) were recruited and clinically follow-up. Patients were divided into two groups based on the result of HUT and TMT. The data was analyzed and compared between VVS patients and control 141 patients without VVS who were enrolled in the same study period (age 40 ± 5 years, 117 male).

RESULTS

The heart rate recovery (HRR), recovery systolic blood pressure (RecSBP), recovery diastolic blood pressure (RecDBP), HRR/RecSBP and HRR/RecDBP were significantly different between controls and VVS during the TMT. Within VVS, even if, baseline characteristics were similar between negative and positive HUT (n = 92 vs. n = 51). HRR (31 ± 10 vs. 35 ± 10), HRR/RecSBP (0.24 ± 0.09 vs. 0.28 ± 0.09) and HRR/RecDBP (0.49 ± 0.18 vs. 0.58 ± 0.19) were significantly different between negative and positive HUT results. Especially, HRR/RecSBP and HRR/RecDBP were significantly correlated with induced syncope with a sensitivity and specificity ([60%, 83%] cut-off, 0.31; [72%, 80%] cut-off, 0.63). In the Cox regression, HRR/ RecDBP were significantly associated with recurrence of VVS with hazard ratio of 3.29 (confidence interval, 0.95 to 11.3; p = 0.049).

CONCLUSION

HRR/RecDBP may be a useful predictor for induction during HUT and recurrence during follow-up in the VVS.

Effects of sildenafil on autonomic nervous function during sleep in obstructive sleep apnea

OBJECTIVE

To evaluate the effects of sildenafil on the autonomic nervous system in patients with severe obstructive sleep apnea.

METHODS

Thirteen male patients with severe obstructive sleep apnea (mean age 43+/-10 years with a mean body mass index of 26.7+/-1.9 kg/m(2)) received a single 50-mg dose of sildenafil or a placebo at bedtime. All-night polysomnography and heart rate variability were recorded. Frequency domain analysis of heart rate variability was performed for the central five-minute sample of the longest uninterrupted interval of slow wave and rapid eye movement sleep, as well as for one-minute samples during apnea and during slow wave and rapid eye movement sleep after resumption of respiration.

RESULTS

Compared to the placebo, sildenafil was associated with an increase in the normalized high-frequency (HF(nu)) components and a decrease in the low/high-frequency components of the heart rate variability ratio (LF/HF) in slow wave sleep (p<0.01 for both). Differences in heart rate variability parameters between one-minute post-apnea and apnea samples (Delta = difference between resumption of respiration and apnea) were assessed. A trend toward a decreasing magnitude of DeltaLF activity was observed during rapid eye movement sleep with sildenafil in comparison to placebo (p=0.046). Additionally, DeltaLF/HF in SWS and rapid eye movement sleep was correlated with mean desaturation (s(R =) -0.72 and -0.51, respectively, p= 0.01 for both), and DeltaHF(nu) in rapid eye movement sleep was correlated with mean desaturation (s(R=) 0.66, p= 0.02) and the desaturation index (s(R=) 0.58, p = 0.047).

CONCLUSIONS

The decrease in arousal response to apnea/hypopnea events along with the increase in HF(nu) components and decrease in LH/HF components of the heart rate variability ratio during slow wave sleep suggest that, in addition to worsening sleep apnea, sildenafil has potentially immediate cardiac effects in patients with severe obstructive sleep apnea.

[Heart rate variability and vasovagal syncope]

OBJECTIVE

Tilt Table testing is widely used for the diagnosis and evaluation of vasovagal syncope. By evaluating the fluctuations of the autonomic nervous system that play an important role in syncope genesis, heart rate variability (HRV) can be considered as a tool of added value.

METHODS

We evaluated prospectively 123 patients admitted for recurrent syncope with a positive tilt Table testing. A time domain analysis of a 24 hours ambulatory electrocardiography was used in all patients to asses the particularities of their autonomic function. We compared their results with those obtained from a group of 82 healthy volunteers.

RESULTS

Statistical analysis of the results showed a significant increase of all HRV parameters in the group of vasovagal syncope compared to the healthy volunteers. SDNNidx (58 vs 42; p < 0.001), rMSSD (40 vs 27; p < 0.001), SDNN (102 vs 83; p < 0.001), SDANN (79 vs 67; p< 0.001), pNN50 (11 vs 4.9; p <0.001).

CONCLUSION

Time domain analysis of heart rate variability reveals increased values in patients with vasovagal syncope. It seems to be an interesting, easy and complementary test in the evaluation of syncope of unknown etiology.