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ECG display requirements

Scope​

This specification gives the user requirements of the ECG display of the Generic Viewport: what a clinician sees, and what a clinician can do. It names no class, file or algorithm. The deprecated ECG display does not meet ECG-U-3, ECG-U-7 and ECG-U-8.

The code design is in the Generic Viewport code design, section GENVIEW-ECG. That section can change when a better design appears.

Change rule: change a requirement of this document only when the requirement describes the behaviour wrongly, or when the intended behaviour for the clinician changes. An implementation that is inconvenient is not a reason to change a requirement.

Paper scale and grid​

  • ECG-U-1 By default, the record fits the viewport, and the sweep speed is 25 mm/s. The clinician can set the sweep speed in mm/s and the sensitivity in mm/mV. With a set sensitivity, the trace has the shape of a paper ECG at that sweep speed and sensitivity, at each zoom.
  • ECG-U-2 A minor block of the grid is one paper millimetre, and a major block is five minor blocks. In time, a minor block is 1/sweep speed seconds, for example 0.04 s at 25 mm/s. With a set sensitivity, a minor block in amplitude is 1/sensitivity mV, for example 0.1 mV at 10 mm/mV. The grid covers the whole viewport. The mV labels on the grid are off by default, and the application can show them.
  • ECG-U-3 Each lead shows its amplitude from its own channel sensitivity. An amplitude that the clinician reads or measures in mV on a lead is the value that the device recorded on that lead.

Layout and navigation​

  • ECG-U-4 By default, a record of 8 or more leads and at least 5 s opens in 3x4 with a rhythm strip of lead II. Another record opens with one lead in each row. Each record gets its own default. The clinician can select a trace layout, for example 12x1, 6x2, 3x4 or 3x4 with a rhythm strip. In a layout with more than one column, each column shows its own time window of the record.
  • ECG-U-5 Each trace shows the label of its lead.
  • ECG-U-6 When the clinician hides a lead, no other lead moves in time or to another column. In a layout with one lead for each row, the rows below the hidden lead move up.
  • ECG-U-7 The clinician can scroll the time window through the record.

Annotations​

  • ECG-U-8 An annotation stays on the lead where the clinician made it. When the clinician hides that lead, the annotation does not show. The annotation shows again when the lead shows. The annotation is not lost. An annotation on a rhythm strip shows on its lead in a layout with no rhythm strip.
  • ECG-U-9 An annotation shows in every viewport that shows the same ECG.

Waveform groups​

  • ECG-U-14 An ECG can hold more than one waveform group, for example a rhythm group and a median beat. By default, the clinician sees the rhythm group: the group with the label RHYTHM or CONTINUOUS, else the longest group. The application can show another group. A measurement uses the group that shows.

Measurements of the device​

  • ECG-U-10 The application can show the global measurements that the device recorded, for example the heart rate and the QT interval, each with its unit. A value for one lead, or a marker on the trace, is not a global measurement.
  • ECG-U-11 The application can show the findings that the device recorded, for example "Sinus rhythm". A marker on the trace, for example "QRS onset", is not a finding.