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The 12-Lead Option
12-16
Sampling Characteristics of the 12-Lead Option
Physiological factors such as breathing can cause variation in amplitudes of heart
beats, independent of the heart rate. In addition, sampled systems (as opposed to
continuous systems) may show changes in the apparent height of the R-wave when
sampling of the R-wave occurs slightly off-peak. Because the sampling rate and the
heart rate are asynchronous, the time between the peak and an adjacent sample can
vary from one QRS complex to the next. This results in a slight variation of
displayed QRS amplitude. This effect is more pronounced with narrower signals,
more commonly found in some pediatric electrocardiograms and in pacemaker
pulses. The CodeMaster 100 with 12-Lead option minimizes this effect by:
• using an integrating-type A/D converter
• sampling all leadwires simultaneously
• oversampling the signals
• processing the oversampled signals with appropriate digital signal processing
techniques
Identifying Storage Problems
The following table shows symptoms and solutions to problems that can occur when
storing an ECG.
Table 12-9 Storage Problems and Solutions
Message Likely Cause Possible Solutions
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