Bogusław Mazurek

The head-up tilt table test (HUTT) with the upright phase is used to help determine an imbalance of the sympathetic nervous system that is related to abnormal electrocardiographic repolarization in children with vasovagal syncope (VVS) and also in patients with the long QT syndrome (LQTS). The study attempted to evaluate T wave morphology and QT and TpTe (Tpeak–Tend) intervals recorded in ECG during the HUTT for a more accurate diagnosis of children with VVS. The group investigated 70 children with a negative HUTT result: 40 patients with VVS and 30 healthy volunteers without syncope. The RR interval as well as TpTe, and QTc intervals were measured in lead V5 of electrocardiogram (ECG) on admission to the hospital and during three phases of the HUTT. In syncopal children, which included 23 children with bifid or flat T waves and 17 patients with normal T waves in the upright phase, the QTc and TpTe were longer (p < 0.001) compared to the other test phases and longer (p < 0.001) than in the control group, respectively, with the risk of arrhythmias. Only in the control group, the TpTe was shorter (p < 0.001) in the upright phase than in the other tilt phases. The TpTe in the upright phase (>70 ms) was a good discriminator, and was better than the QTc (>427 ms). Prolongation of electrocardiographic TpTe and QT intervals, in addition to the (abnormal T wave morphology recorded during the HUTT, are helpful for identifying VVS children more predisposed to ventricular arrhythmias with a latent risk of LQTS. Further studies are required to assess the value of these repolarization parameters in clinical practice.

Children who underwent surgery for complex congenital heart defects present worse exercise capacity than their healthy peers. In adults and adolescents, heart failure is assessed on the basis of clinical symptoms using the New York Heart Association (NYHA) score, while in an infant Ross scale; heart failure can also be evaluated by other parameters. The purpose of this study was to compare the degree of exercise tolerance in children after surgery for complex heart defects, assessed by the ratio of maximum oxygen uptake (VO2max) and the brain natriuretic peptide (N-terminal fragment of the prohormone brain-type natriuretic peptide [NT-proBNP]) concentration.The study group consisted of 42 children, ages 9 to 17 years (mean 14.00 ± 2.72). Among them there were 22 children with tetralogy of Fallot (ToF) after total correction, 18 children with transposition of the great arteries (d-TGA) after the arterial switch operation, and 2 children with single ventricle (SV) after the Fontan operation. All but 1 child were in NYHA class I. The control group consisted of 20 healthy children. Outcomes of interest were the ratio of VO2max, determined during ergospirometry, and the level of NT-proBNP. The statistical analysis was performed and the groups were considered significantly different for P < 0.05.There was no statistically significant correlation between NT-proBNP and maximum oxygen uptake (VO2) kg min in the study group compared with the control group.The VO2max in the test group had a mean value less (34.6 ± 8.0) than controls (38.4 ± 7.7), and the differences were statistically significant (P = 0.041). In contrast, the average concentration of NT-proBNP in the study group was higher than controls (117.9 ± 74.3 vs 18.0 ± 24.5), and these differences were statistically significant (P < 0.001).After operations for complex heart defects (ToF, TGA, and SV), children have worse heart function parameters and exercise capacity than the healthy population. To control this, we recommend postoperative ergospirometry and determination of NT-proBNP concentrations.