OBJECTIVEThe study was designed to examine the effect of selective alpha1 receptor agonist midodrine hydrochloride in the treatment of children with postural orthostatic tachycardia syndrome.

METHODSFifty-five children (23 male, 32 female, age 5 - 19 yrs, mean age 12.3 +/- 3.1 yrs) who came from Peking University First Hospital were included in the study and clinical investigations as well as standing test, basic head-up tilt test and sublingual nitroglycerin-provocated head-up tilt test under quiet circumstance were conducted. They were randomly divided into treatment group (with midodrine hydrochloride and oral rehydration salt treatment) and control group (with oral rehydration salt treatment only). At last, the disease-free rate, improvement rate and effective rate of symptoms, and the rate of HUT from positive to negative response were compared between control group and treatment group. SPSS 10.0 software was used for the statistical analysis of these data.

RESULTSThe symptom improvement rate in treatment group was significantly higher than that of control group after three and six weeks of treatment (100.0% vs. 42.4%, P < 0.001; 100.0% vs. 42.4%, chi2 = 19.352, P < 0.001). The disease-free rate at follow-up end-point in treatment group was significantly higher than that of control group (77.3% vs. 27.3%, chi2 = 13.239, P < 0.001). The effective rate at follow-up end-point in treatment group was also significantly higher than that of control group (100.0% vs. 36.4%, chi2 = 22.647, P < 0.001). The rate of HUT changing from positive to negative response between two groups after three weeks of treatment was not significantly different (31.8% vs. 12.1%, P > 0.05), but it was significantly different (81.0% vs. 48.5%, P < 0.05) after six weeks of treatment.

CONCLUSIONSelective alpha1 receptor agonist midodrine hydrochloride is effective in the treatment of children with postural orthostatic tachycardia syndrome.