Abstract
Objectives: This study aims to investigate the diurnal variability of heart rate (HR) increment after standing (ΔHR) in pediatric postural tachycardia syndrome (POTS) and explore appropriate cutoff values of ΔHR at different times for the POTS diagnosis.Materials and Methods: Seventy-eight patients (9–14 years) who presented with orthostatic intolerance symptoms were enrolled. Forty-three patients were diagnosed as POTS (ΔHR ≥40 bpm), and 35 patients were assigned to the non-POTS group (ΔHR <40 bpm). Twenty-six healthy children served as the control group. All subjects completed three standing tests in the morning, afternoon, and evening. Orthostatic HR parameters were analyzed to predict the diagnosis of POTS. Additionally, 41 patients were recruited as an external validation group.Results: Orthostatic HR increments in both the POTS and non-POTS groups exhibited diurnal variability, which was markedly larger in the morning (P < 0.05), whereas it did not differ with the time of day in the control group. Among the POTS patients, 100% met the diagnostic criteria for POTS in the morning, 44.2% in the afternoon, and 27.9% in the evening. Almost half of the POTS patients (51.2%) displayed a positive result only in the morning standing test. However, in the three standing tests at different times, ΔHR from 1 to 10 min after standing and ΔHRmax were the highest in the POTS group compared with in the non-POTS and control groups (P < 0.05). Furthermore, the maximum ΔHR (ΔHRmax) and ΔHR at 5 and 10 min in the afternoon and evening standing tests yielded moderate predictive values for the POTS diagnosis. The external validation test showed that the afternoon ΔHRmax ≥30 bpm to diagnose POTS yielded sensitivity, specificity, and accuracy of 85, 71.4, and 78%, respectively, and the evening ΔHRmax ≥25 bpm yielded sensitivity, specificity, and accuracy of 85, 76.2, and 80.5%, respectively.Conclusions: The orthostatic HR increment exhibits diurnal variability in children and adolescents with POTS that may affect the diagnosis of POTS. Supplementary criteria are proposed for the POTS diagnosis based on diurnal variability.
Highlights
Postural tachycardia syndrome (POTS) is a common form of pediatric orthostatic intolerance (OI), characterized by an excessive heart rate (HR) increment after standing and chronic day-to-day OI symptoms, such as dizziness, headache, palpitations, chest discomfort, blurred vision, profuse perspiration, and even syncope [1]
We suggest that orthostatic HR increment ≥30 bpm in the afternoon standing test and orthostatic HR increment ≥25 bpm in the evening standing test could be considered as POTS, combined with clinical symptoms
We showed that the orthostatic HR increment exhibited diurnal variability in children and adolescents with OI, with a peak in the morning
Summary
Postural tachycardia syndrome (POTS) is a common form of pediatric orthostatic intolerance (OI), characterized by an excessive heart rate (HR) increment after standing and chronic day-to-day OI symptoms, such as dizziness, headache, palpitations, chest discomfort, blurred vision, profuse perspiration, and even syncope [1]. Many POTS patients have high plasma norepinephrine levels and excessive sympathetic activation upon standing [2, 3]. Almost every physiological system has some degree of the circadian rhythm Many cardiovascular parameters, such as HR, blood pressure (BP), plasma catecholamine concentrations, and sympathetic activity, show distinct circadian rhythm, increasing significantly during the day and decreasing during the night [4]. Various cardiovascular events, such as arrhythmias, angina pain, myocardial infarction, stroke, sudden cardiac death, and syncope, exhibit diurnal patterns with morning peaks [5, 6]. Some patients who meet the criteria for POTS in the morning do not always meet the criteria in the afternoon or the evening
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