Autonomic Nervous Function in Vasovagal Syncope of Children and Adolescents

Syncope is defined as a transient loss of consciousness due to global cerebral hypoperfusion, accompanied by loss of muscle tone and failure to maintain an active position. Vasovagal syncope (VVS) is the most common presentation of syncope, and its diagnostic criteria include:(1) absence of any other evident etiology for syncope or presyncope,(2) positive response to head-up tilt test with evident vasovagal reaction (hypotension and/or bradycardia), and (3) no concomitant chronic or acute disease [1, 2]. The onset of VVS peaks initially in childhood and adolescence, and accounts for 60%–70% of all syncopal cases. Clinicians pay great attention to syncope among children and adolescents, due to its high prevalence and its impact on patients’ quality of life. Affected individuals often experience mental stress, economic burdens, and accidental bodily injuries related to syncope [2]. While the pathogenesis of VVS is not fully understood, autonomic nervous dysfunction has been identified as a contributing mechanism. The examination of autonomic nervous function can provide important information about patients with syncope.

Hydrogen Sulfide Regulating Myocardial Structure and Function by Targeting Cardiomyocyte Autophagy

Objective： Hydrogen sulfide （H2S）, a gaseous signal molecule, plays a crucial role in many pathophysiologic processes in the cardiovascular system. Autophagy has been shown to participate in the occurrence of many cardiac diseases. Increasing evidences indicated that H,S regulates myocardial structure and function in association with the altered autophagy and plays a ＂switcher＂ role in the autophagy of myocardial diseases. The airn of this review was to summarize these insights and provide the experimental evidence that H2S targets cardiomyocyte autophagy to regulate cardiovascular function. Data Sources： This review was based on data in articles published in the PubMed databases up to October 30, 2017, with the following keywords： ＂hydrogen sulfide,＂ ＂autophagy,＂ and ＂cardiovascular diseases.＂ Study Selection： Original articles and critical reviews on H,S and autophagy were selected for this review. Results： When autophagy plays an adaptive role in the pathogenesis of diseases, H2S restores autophagy; otherwise, when autophagy plays a detrimental role, H2S downregulates autophagy to exert a cardioprotective function. For example, H2S has beneficial effects by regulating autophagy in myocardial ischemia/reperfusion and plays a protective role by inhibiting autophagy during the operation of cardioplegia and cardiopuhnonary bypass. H2S postpones cardiac aging associated with the upregulation of autophagy but improves the left ventricular function of smoking rats by lowering autophagy. Conclusions： H2S exerts cardiovascular protection by regulating autophagy. Cardiovascular autophagy would likely become a potential target of H2S therapy for cardiovascular diseases.

Gut microbiota analysis and its significance in vasovagal syncope in children

Background: Vasovagal syncope (VVS) is common in children and greatly affect both physical and mental health. But the mechanisms have not been completely explained. This study was designed to analyze the gut microbiota in children with VVS and explore its clinical significance. Methods: Fecal samples from 20 VVS children and 20 matched controls were collected, and the microbiota were analyzed by 16S rRNA gene sequencing. The diversity and microbiota compositions of the VVS cases and controls were compared with the independent sample t test or Mann-Whitney U test. The correlation between the predominant bacteria and clinical symptoms was analyzed using Pearson or Spearman correlation test. Results: No significant differences in diversity were evident between VVS and controls (P > 0.05). At the family level, the relative abundance of Ruminococcaceae was significantly higher in VVS children than in controls (median [Q1, Q3]: 22.10% [16.89%, 27.36%] vs. 13.92% [10.31%, 20.18%], Z=-2.40, P < 0.05), and LEfSe analysis revealed Ruminococcaceae as a discriminative feature (linear discriminant analysis [LDA] score > 4, P < 0.05). The relative abundance of Ruminococcaceae in VVS patients was positively correlated with the frequency of syncope (r= 0.616, P < 0.01). In terms of its correlation with hemodynamics, we showed that relative abundance of Ruminococcaceae was negatively correlated with the systolic and diastolic pressure reduction at the positive response in head-up tilt test (HUTT;r= -0.489 and -0.448, all P < 0.05), but was positively correlated with the mean pressure drop and decline rate (r= 0.489 and 0.467, all P < 0.05) as well as diastolic pressure drop and decline rate at the HUTT positive response (r= 0.579 and 0.589, all P < 0.01) in VVS patients. Conclusion: Ruminococcaceae was the predominant gut bacteria and was associated with the clinical symptoms and hemodynamics of VVS, suggesting that gut microbiota might be involved in the development of VVS.

Body mass index is a promising predictor of response to oral rehydration saline in children with vasovagal syncope

Background:Vasovagal syncope(VVS)greatly impairs quality of life.The therapeutic efficacy of oral rehydration saline(ORS)for unselected VVS patients is not satisfactory due to the diverse mechanisms of the disease.Body mass index(BMI)was demonstrated to reflect blood volume to a certain extent.Therefore,the present study explored the capability of BMI to predict the therapeutic response of children with VVS to ORS treatment.Methods:Seventy-four children with VVS who visited the Syncope Unit of Pediatrics at Peking University First Hospital from November 2010 to June 2019 receiving ORS treatment were enrolled for this retrospective case-control study.A comparison of demographic,clinical,and hemodynamic characteristics was performed between responders and non-responders.The correlation between baseline BMI and response time was analyzed.To determine the value of baseline BMI in predicting the therapeutic efficacy of ORS in children with VVS,a receiver operating characteristic curve analysis was performed.Results:Fifty-two children were identified as responders,and the remaining 22 children were identified as non-responders.The baseline BMI of the responders was much lower than that of the non-responders(16.4[15.5,17.8]kg/m2vs.20.7±3.6 kg/m2,P<0.001),and baseline BMI was positively correlated with response time in the head-up tilt test after adjusting for sex(r=0.256,95%confidence interval[CI]:0.067-0.439,P=0.029).The area under the receiver operating characteristic curve of baseline BMI was 0.818(95%CI:0.704-0.932,P<0.001),and an optimal cut-off value of 18.9 kg/m2 yielded a sensitivity of 83%and a specificity of 73%to predict the efficacy of ORS in VVS.Conclusion:Prior to treatment,baseline BMI is a promising predictor of response to ORS in children with VVS.

Orthostatic Intolerance and Coagulation Abnormalities:An Update

Orthostatic intolerance(OI)is a series of clinical symptoms that develop during long-term standing in the upright position,with clinical manifestations of frequent,recurrent,or persistent dizziness,fatigue,and heart palpitations with or without syncope.