Abstract: Objective: To explore the clinical characteristics of the co-morbidity of vasovagal syncope (VVS) and postural tachycardia syndrome (POTS) with allergic diseases in children. Methods: A re-trospective analysis was launched to summarize the clinical data of children with VVS and POTS. They were divided into allergic group and non-allergic group according to the history of allergic diseases. The participants’ clinical characteristics were compared between allergic group and non-allergic group using independent sample t test or rank sum test; composition comparisons were completed by Chi-square test. Bi-variate correlation analysis was used to explore the association between eosinophil percentage/count and symptom scores/frequency of syncope episodes. A P value <0.05 was defined as statistically significant. Results: Sixty-seven children complaining of orthostatic intolerance (43 patients diagnosed as VVS and 24 cases diagnosed as POTS) were enrolled. Totally 21 cases (31%) had allergic diseases, including allergic rhinitis, atopic eczema, asthma, as well as food allergy. And allergic rhinitis is the most common co-morbidity. There were no significant differences between the two groups in age, gender ratio, height, body weight and basement blood pressure. Compared with the non-allergic group, the allergic group showed later onset age (year) (11±2 vs. 9±3, P<0.05) of orthostatic intolerance and shorter course of the diseases (month) [8.0 (0.1, 0.1) vs. 24.0 (0.1, 144.0), P<0.05]. The frequency of syncope episodes in the allergic group among VVS children (times per month) [2.50 (0.08, 30.00) vs. 0.25 (0.03, 5.00), P<0.05] was much higher than that in the non-allergic group. Additionally, the eosinophil percentage (%) [3.50 (0.70, 0.59) vs. 1.65 (0.30, 6.20), P<0.001] and eosinophil count (×10⁹) [0.18 (0.05, 0.71) vs. 0.10 (0.02, 0.38), P<0.001] were increased in the allergic group. However, there were no remarkable differences in the results of head-up tilt test in children with VVS or in the maximum change of heart rate during standing test in children with POTS were involved. Conclusion: Allergic diseases are common co-morbidities in children with both VVS and POTS. Allergic rhinitis is the most common co-morbidity. Children with co-morbidity of VVS/POTS and allergic diseases had a later onset of symptoms of orthostatic intolerance, and were more likely to be hospitalized for intensive attacks of symptoms during a short period when compared with those without allergic diseases. Children diagnosed as VVS combined with allergic diseases had more frequent episodes of syncope.

Key words: Syncope, vasovagal, Postural orthostatic tachycardia syndrome, Orthostatic intolerance, Allergy