Decreased Stroke Volume and Venous Return in School Children with Postural Tachycardia Syndrome.

In postural tachycardia syndrome (POTS), a subtype of orthostatic intolerance, the changes in hemodynamics due to postural changes are poorly understood. We speculated that inappropriate venous return, which may occur in the upright position in patients with school-aged POTS, could be detected by echocardiography. Our prospective study was conducted with 100 POTS patients (45 boys and 55 girls), aged 13.1 ± 1.5 years and 52 age- and sex-matched healthy subjects (control). Echocardiography was performed in the supine and sitting positions. Cardiac parameters [stroke volume index, cardiac index, heart rate, and the maximum inferior vena cava diameter (max IVC)] were evaluated in addition to pulse pressure. Unlike the control subjects, POTS patients demonstrated decreased stroke volume index (P = 0.02) and max IVC (P < 0.01) irrespective of posture. The rates of max IVC change did not differ between control and POTS groups. The enrolled POTS patients were divided into two subgroups [dilatation (n = 57) and contraction (n = 43)] based on whether the change rate of max IVC was less than zero or not. The contraction group showed a significantly higher heart rate than the dilatation group with respect to posture (P = 0.03), indicating the poor response of peripheral vessels in the lower limbs only in the contraction group. In conclusion, echocardiographic assessment detected decreased stroke volume and venous return in POTS. The changes in max IVC in response to postural changes may indicate an underlying pathophysiology in POTS.

Normal reference values for left atrial strains and strain rates in school children assessed using two-dimensional speckle-tracking echocardiography.

Left atrium (LA) function is a known predictive marker of heart failure in adults. Few reports of LA function analyses using LA strain (ɛ) and strain rate (SR) measurements in children exist. Thus, this study aimed to determine normal reference values for LA ɛ and SR in healthy school children and to investigate methods of interpreting LA function data based on maturational changes using two-dimensional speckle-tracking echocardiography (2DSTE). We recruited 112 healthy school children (median age 12.0 years; range 6-16 years). LA ɛ and SR were investigated using 2DSTE multi-vendor analysis software (TomTec Imaging Systems, Germany) and compared to Doppler parameters and LA volumes measured by the conventional method. The onset of the P wave was selected as the reference point for the LA ɛ analysis. Normal ranges of LA ɛ [reservoir (ɛRS), conduit (ɛCD), or contractile (ɛCT)] and positive SR (SRPOS), early negative SR (SREN), and late negative SR (SRLN) were obtained using Z-score models via the lambda-mu-sigma method. According to the Z-score curves, all ɛ showed slight falling or continuous flat lines against age, body surface area (BSA), or heart rate (HR); however, ɛ CT showed modestly positive associations with HR. As for SR, the Z-score curves showed falling lines against age and BSA. In contrast, Z-score curves for SREN and SRLN showed rising lines against HR. SREN was independent of E/e' and was negatively correlated with LA volume indexed against BSA. This study demonstrated the normal reference values for LA ɛ and SR using 2DSTE in school children. The present results recommended that LA ɛ should be evaluated together with changes in LA SR for accurate assessment, considering maturational changes including age, BSA, and HR in school children.