Signal averaged ECG

T wave alternans Signal averaged ECG QRS duration Genetic markers Functional markers... 

Other noninvasive techniques to identify risk, such as baroreflex sensitivity, spectral turbulence (45 7), heart rate variability, T-wave altemans (48-51), QT interval prolongation, QT dispersion (52,53), and late potentials (by the signal averaged ECG) (54-56), have been considered in select patient populations (Table 14.2). AU have failed to live up to initial promises. 

More recently the high resolution ECG has been developed whereby the digitized ECG is signal averaged to reduce random noise [9,10]. This approach, coupled with postaveraging high-pass filtering, is used to... 

Neutral PU electrodes are also called indifferent or reference electrodes. A PU electrode may be more or less indifferent depending on its area and position with respect to signal sources. The ideal unipolar models presuppose an enormous spherical neutral electrode, infinitely far away and at zero potential. In a limited tissue volume such as the human body, the ideal indifferent electrode is not feasible, and we use flie concept of quality of an indifferent electrode. A practical approach is to take the average potential of several electrodes (e.g., Wilson s central terminal in ECG). It is not ideal to connect electrodes of different potentials resulting in exchange current flow between them, but each electrode may first be connected to a buffer amplifier. 

Fig. 1 Ensemble-averaged original signals (ECG, Plv, Pao, AZ) and the calculated (dPLv/dt, d PAc/dP, d Z/dP) signals. The pressure in the LV and aorta was recorded with the same catheter-tip manometer during different cardiac cycles with similar durations. For convenient presentation of the related blood volume changes, AZ curves and their derivatives, are inverted, i.e., the positive deflections of the curves correspond to the decrease in impedance.

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