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  • 1
    Electronic Resource
    Electronic Resource
    Validation of ECG Indices of Ventricular Repolarization Heterogeneity: A Computer Simulation Study (2005)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 16 (2005), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Repolarization heterogeneity (RH) is functionally linked to dispersion in refractoriness and to arrhythmogenicity. In the current study, we validate several proposed electrocardiogram (ECG) indices for RH: T-wave amplitude, -area, -complexity, and -symmetry ratio, QT dispersion, and the Tapex-end interval (the latter being an index of transmural dispersion of the repolarization (TDR)). Methods and Results: We used ECGSIM, a mathematical simulation model of ECG genesis in a human thorax, and varied global RH by increasing the standard deviation (SD) of the repolarization instants from 20 (default) to 70 msec in steps of 10 msec. T-wave amplitude, -area, -symmetry, and Tapex-end depended linearly on SD. T-wave amplitude increased from 275 ± 173 to 881 ± 456 μV, T-wave area from 34 × 103± 21 × 103 to 141 × 103± 58 × 103μV msec, T-wave symmetry decreased from 1.55 ± 0.11 to 1.06 ± 0.23, and Tapex-end increased from 84 ± 17 to 171 ± 52 msec. T-wave complexity increased initially but saturated at SD = 50 msec. QT dispersion increased modestly until SD = 40 msec and more rapidly for higher values of SD. TDR increased linearly with SD. Tapex-end increased linearly with TDR, but overestimated it. Conclusion: T-wave complexity did not discriminate between differences in larger RH values. QT dispersion had low sensitivity in the transitional zone between normal and abnormal RH. In conclusion, T-wave amplitude, -area, -symmetry, and, with some limitations, Tapex-end and T-wave complexity reliably reflect changes in RH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.2005.40758.x
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  • 2
    Electronic Resource
    Electronic Resource
    Hypertensive Stress Increases Dispersion of Repolarization (2004)
    350 Main Street , Malden , MA 02148-5018 , USA and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Pacing and clinical electrophysiology 27 (2004), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Several electrocardiographic indices for repolarization heterogeneity have been proposed previously. The behavior of these indices under two different stressors at the same heart rate (i.e., normotensive gravitational stress, and hypertensive isometric stress) was studied. ECG and blood pressure were recorded in 56 healthy men during rest (sitting with horizontal legs), hypertensive stress (performing handgrip), and normotensive stress (sitting with lowered legs). During both stressors, heart rates differed 〈10% in 41 subjects, who constituted the final study group. Heart rate increased from 63 ± 9 beats/min at rest to 71 ± 11 beats/min during normotensive, and to 71 ± 10 beats/min during hypertensive stress (P 〈 0.001). Systolic blood pressure was 122 ± 15 mmHg at rest and 121 ± 15 mmHg during normotensive stress, and increased to 151 ± 17 mmHg during hypertensive stress (P 〈 0.001). The QT interval was larger during hypertensive (405 ± 27) than during normotensive stress (389 ± 26, P 〈 0.001). QT dispersion did not differ significantly between the two stressors. The mean interval between the apex and the end of the T wave (Tapex-Tend) of the mid-precordial leads was larger during hypertensive (121 ± 17 ms) than during normotensive stress (116 ± 15 ms, P 〈 0.001). The singular value decomposition T wave index was larger during hypertensive (0.144 ± 0.071) than during normotensive stress (0.089 ± 0.053, P 〈 0.001). Most indices of repolarization heterogeneity were larger during hypertensive stress than during normotensive stress. Hypertensive stressors are associated with arrhythmogeneity in vulnerable hearts. This may in part be explained by the induction of repolarization heterogeneity by hypertensive stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.2004.00692.x
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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