Effect of adrenergic stimuli on electrocardiographic and vectorcardiographic characteristics of ventricular repolarization

: Autonomic effect of various stimuli on haemodynamic variables is usually tested by changes in blood pressure (BP) and/or heart rate (HR). It is known that increased sympathetic drive of ventricles can interfere with repolarization process. This study was focused on reactive changes of maximal spatial T vector (sTmax), R-R and QTc intervals, in relation to BP changes in 79 boys and men, averaged age 17 +/- 2 years, 36 from them were adolescents with elevated BP (high normal or hypertension I according to WHO/ISH 1999) (ZTK), 19 normotensives (NTK), and 24 normotensive sportsmen. R-R, QTc intervals and maximal spatial T vector were recorded by a PC (Cardiag METE, Prague) with Frank lead system while sitting in mid-respiratory position, during mental arithmetic (MA), after handgrip and during passive head-up tilting to 60 degrees. BP was measured simultaneously by a cuff sphygmomanometer, using phases 1 and 5 of Korotkoff sounds. MA resulted in significant BP increase in all subgroups, however the reactive changes of systolic BP as well as magnitude of R-R shortening, sTmax decline were about two times higher, and in the case of QTc lengthening three times higher in sportsmen. Handgrip provoked in all subgroups in average the less reactive changes of diastolic BP, sTmax, R-R, and QTc intervals. Head-up tilting evoked in all subgroups a significant increase of diastolic BP that was again higher in sportsmen vs. ZTK and NTK. R-R intervals became significantly (p < or = 0.02) and more often shortened in sportsmen vs. ZTK and NTK. Relatively more evident decline of sTmax (more than 20%) in ZTK was the highest change from all observed parameters to all tested stimuli. Our results indicate that for analysis of effect stimuli, which modulate balance in autonomic nervous system, it is helpful to pay attention also to the parameters of repolarization process that may represent a sensitive indicator of sympathetic tonization in myocardial ventricles.