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Ventricular Depolarization (ventricular + depolarization)
Selected AbstractsDynamics and Rate-Dependence of the Spatial Angle between Ventricular Depolarization and Repolarization Wave Fronts during Exercise ECGANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2010Tuomas Kenttä M.Sc. Background: QRS/T angle and the cosine of the angle between QRS and T-wave vectors (TCRT), measured from standard 12-lead electrocardiogram (ECG), have been used in risk stratification of patients. This study assessed the possible rate dependence of these variables during exercise ECG in healthy subjects. Methods: Forty healthy volunteers, 20 men and 20 women, aged 34.6 ± 3.4, underwent an exercise ECG testing. Twelve-lead ECG was recorded from each test subject and the spatial QRS/T angle and TCRT were automatically analyzed in a beat-to-beat manner with custom-made software. The individual TCRT/RR and QRST/RR patterns were fitted with seven different regression models, including a linear model and six nonlinear models. Results: TCRT and QRS/T angle showed a significant rate dependence, with decreased values at higher heart rates (HR). In individual subjects, the second-degree polynomic model was the best regression model for TCRT/RR and QRST/RR slopes. It provided the best fit for both exercise and recovery. The overall TCRT/RR and QRST/RR slopes were similar between men and women during exercise and recovery. However, women had predominantly higher TCRT and QRS/T values. With respect to time, the dynamics of TCRT differed significantly between men and women; with a steeper exercise slope in women (women, ,0.04/min vs ,0.02/min in men, P < 0.0001). In addition, evident hysteresis was observed in the TCRT/RR slopes; with higher TCRT values during exercise. Conclusions: The individual patterns of TCRT and QRS/T angle are affected by HR and gender. Delayed rate adaptation creates hysteresis in the TCRT/RR slopes. Ann Noninvasive Electrocardiol 2010;15(3):264,275 [source] Spatial QRS-T angle: association with diabetes and left ventricular performanceEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 9 2006Ch. Voulgari Abstract Background, The spatial QRS-T angle obtained by vectorcardiography is a combined measurement of the electrical activity of the heart and predicts cardiovascular morbidity and mortality. Disturbances in repolarization and depolarization are common in diabetes. No data, however, exist on the effect of diabetes on QRS-T angle. In this study we examined differences in QRS-T angle between type 2 diabetic and non-diabetic subjects; in addition, the potential relationship between QRS-T angle and left ventricular performance as well as glycaemic control were also examined. Patients and methods, A total of 74 subjects with type 2 diabetes and 74 non-diabetic individuals, matched for age and sex with the diabetic subjects were examined. All subjects were free of clinically apparent macrovascular complications. Spatial vectorcardiogaphic descriptors of ventricular depolarization and repolarization were reconstructed from the 12-electrocardiographic leads using a computer-based electrocardiogram. Left ventricular mass and performance were measured using M-mode and Doppler echocardiography. Results, QRS-T angle values were higher (by almost 2-fold) in the diabetic in comparison with the non-diabetic subjects (P < 0·001). After multivariate adjustment, QRS-T angle was independently associated with age (P = 0·01), HbA1c (P = 0·003), and low-density lipoprotein cholesterol levels (P = 0·04) in the non-diabetic, and with HbA1c (P = 0·03) as well as Tei index (P = 0·003) in the diabetic subjects. Conclusions, The spatial QRS-T angle is high in subjects with type 2 diabetes and is associated with glycaemic control and left ventricular performance. The prognostic importance of the higher spQRS-T angle values in subjects with diabetes remains to be evaluated in prospective studies. [source] Electrocardiographic Alterations during Hyperinsulinemic Hypoglycemia in Healthy SubjectsANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2008Tomi Laitinen M.D. Background: We evaluated the arrhythmogenic potential of hypoglycemia by studying electrocardiographic (ECG) changes in response to hyperinsulinemic hypoglycemia and associated sympathoadrenal counterregulatory responses in healthy subjects. Methods: The study population consisted of 18 subjects, aged 30,40 years. Five-minute ECG recordings and blood samplings were performed at baseline and during the euglycemic and hypoglycemic hyperinsulinemic clamp studies. PR, QT, and QTc intervals of electrocardiogram and ECG morphology were assessed from signal-averaged ECG. Results: Although cardiac beat interval remained unchanged, PR interval decreased (P < 0.01) and QTc interval (P < 0.001) increased in response to hyperinsulinemic hypoglycemia. Concomitant morphological alterations consisted of slight increases in R-wave amplitude and area (P < 0.01 for both), significant decreases in T-wave amplitude and area (P < 0.001 for both), and moderate ST depression (P < 0.001). Counterregulatory norepinephrine response correlated with amplification of the R wave (r =,0.620, P < 0.05) and epinephrine response correlated with flattening of the T wave (r =,0.508, P < 0.05). Conclusions: Hyperinsulinemic hypoglycemia with consequent sympathetic humoral activation is associated with several ECG alterations in atrioventricular conduction, ventricular depolarization, and ventricular repolarization. Such alterations in cardiac electrical function may be of importance in provoking severe arrhythmias and "dead-in-bed" syndrome in diabetic patients with unrecognized hypoglycemic episodes. [source] Prognostic Significance of QTc Interval for Predicting Total, Cardiac, and Ischemic Heart Disease Mortality in Community-Based Cohort from Warsaw Pol-MONICA PopulationANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 4 2000Aleksandra Pytlak M.D. Background: QT interval in resting electrocardiogram (ECC) is a sum of ventricular depolarization and repolarization time. Its prolongation is associated with a worse prognosis for survival due to a high incidence of severe ventricular arrhythmias. Methods: The random sample of the Warsaw Pol-MONICA population consisting of 2646 men and women, aged 35,64, screened in 1984, was followed-up until 1996. All deaths and their causes were registered based on death certificate diagnosis. QT interval was measured manually in three consecutive QRST complexes in each ECG and corrected using Bazett's formula (QT corrected: QTc). For statistical analyses the mean value of 3 QTc measurements were used. To assess the relationship between QTc and mortality, the Cox proportional hazards model with stepwise selection of variables was used. Results: Out of the screened sample, 459 persons died (309 men, 150 women), 226 due to cardiovascular diseases (CVD) (162 men, 64 women), and 81 due to ischemic heart disease (IHD) (59 men, 22 women). Both men and women who died were significantly older at baseline and had significantly longer mean QTc as compared to survivors (men: 457 ms vs 446 ms, P = 0.0001; women: 469 ms vs 459 ms, P = 0.001). Among men, after adjustment for confounding variables, mean QTc was significantly associated with total and CVD mortality, and in women, with CVD and IHD mortality. The risk of death rose with an increase in QTc duration. In men, with every increase in QTc by 20 ms, the risk of all causes of death rose by 11% (95% CI: 1.04,1.18), CVD death by 9% (95% Cl: 1.01,1.19), and IHD death by 11 % (95%: 0.97,1.28). In women, the risk of all-cause death increased by 9% (95% CI: 0.98,1.21), CVD death by 21% (95% Cl: 1.02,1.43), and IHD death by 41% (95% Cl: 1.08,1.85). Conclusion: QTc interval was significantly related to all cause, cardiovascular and ischemic heart disease. The risk of death increased with longer QTc duration. A.N.E. 2000;5(4):322,329 [source] | ||||||||||