RESUMO
Despite clinical importance of ventricular repolarisation, it remains difficult to analyse. Conventionally, quantification of the electrocardiographic ventricular repolarization is usually performed with reference to axis of the T wave and QT interval duration. A variety of factors can prolong the QT interval, such as drug effects, electrolyte imbalances, and myocardial ischemia. The biggest risk with prolongation of the QT interval is the development of torsades de pointes. Commonly accepted reference ranges for the electrocardiogram (ECG) have been in use, with little change, for many years. Populations throughout the world present several differences: age, ethnic compositions, and are exposed to different environmental factors. Recent studies have reported reference data for QT interval in healthy population and have evaluated the influence of age, gender, QRS duration and heart rate on this interval. In this review, we address several issues relative to the measurement, and interpretation of QT interval and its adjustment for rate, age, gender and QRS duration.
Assuntos
Eletrocardiografia/normas , Eletrocardiografia/métodos , HumanosRESUMO
PURPOSE: Contrasting data exist about the hemodialysis induced changes of ventricular diastolic and systolic functions in adults. Few data in children with end-stage renal disease (ESRD) are reported. The aim of the present study was to evaluate the effect of a single hemodialysis (HD) session on left ventricular (LV) systolic and diastolic function using conventional pulsed-Doppler echocardiography and pulsed tissue Doppler imaging (TDI) in hemodialysis children. METHODS: Thirty-five children with chronic renal failure (15 males, aged 12.8+/-3.8 years) on maintenance hemodialysis underwent conventional 2D and Doppler Echo together with measurement of longitudinal mitral annular motion velocities. Echocardiographic parameters were obtained 30 minutes before and 30 minutes after HD. Paired data were compared. RESULTS: Hemodialysis led to reduction in LV end-diastolic volume (p=0.001), end-systolic volume (p=0.05), left atrium area (p<0.0001), peak early (E wave) transmitral flow velocity (p=0.005), peak S velocity of pulmonary vein flow (p=0.002), aortic time velocity integral (p<0.0001) and aortic ejection time (p<0.0001). No significant change in Tei Index was observed after HD. Regarding TDI measures, velocities were not affected by preload reduction. Only the early diastolic velocities on the septal side of the mitral annulus decreased significantly (p=0.001) and the systolic velocities on the lateral side of the mitral annulus increased significantly (p=0.042) after hemodialysis. CONCLUSIONS: Most of Doppler-derived indices of diastolic function are preload-dependent. TDI velocities and Tei Index were not or minimally affected by preload reduction in hemodialysis children.