Open-Source ECG Viewer: How to Visualize and Analyze ECG Data

ECG Viewer Tutorial: Import, Filter, and Interpret 12‑Lead Traces

This tutorial walks through importing ECG data, applying common filters, and interpreting 12‑lead traces using a typical ECG viewer. Assumptions: you have a 12‑lead ECG file in a common format (EDF, DICOM-ECG, SCP-ECG, or CSV) and an ECG viewer application that supports lead mapping, filtering, and annotation.

1. Importing ECG data

1. Open your ECG viewer and choose Import or File → Open.
2. Select format: pick the correct file type (EDF, DICOM-ECG, SCP-ECG, CSV). If CSV, ensure columns map to leads and timestamps.
3. Map leads: confirm the viewer’s lead assignment matches the file (I, II, III, aVR, aVL, aVF, V1–V6). Remap if needed.
4. Set sampling rate: verify the sample frequency (commonly 250–1000 Hz) so timing and durations are accurate.
5. Confirm calibration: standard ECG calibration is 10 mm/mV and paper speed 25 mm/s (or 50 mm/s). Adjust viewer settings if the waveform amplitude or timing looks off.
6. Save session (optional) to preserve any initial mappings or metadata.

2. Basic viewer layout and controls

• Lead grid: displays simultaneous 12 leads—use this for overall rhythm and morphology.
• Single-lead zoom: isolates a lead for detailed measurement.
• Time cursor and markers: measure intervals (PR, QRS, QT) using cursors or built-in calipers.
• Amplitude scale: shows mV or mm; toggle calibration if needed.
• Annotation tools: mark beats, artifacts, or arrhythmias and add comments.

3. Filtering: remove noise without distorting ECG

Apply filters conservatively—overfiltering can alter diagnostic features.

1. Low‑pass filter (LPF): removes high‑frequency noise (muscle tremor). Typical cutoff: 40–150 Hz; commonly set to 100 Hz for diagnostic clarity.
2. High‑pass filter (HPF)/Baseline wander removal: removes slow baseline drift from respiration or movement. Use cutoff ~0.05–0.5 Hz; 0.05 Hz preserves ST segments better.
3. Notch filter: removes mains interference (50 or 60 Hz). Use only when necessary; it can introduce ringing.
4. Bandpass filtering: combined HPF + LPF (e.g., 0.05–100 Hz) is common.
5. Digital vs. analog filtering: prefer digital zero‑phase filters (no phase distortion) when available.
6. Artifact rejection: mark and exclude motion/lead-off segments rather than overfiltering.
7. Preview changes: always compare filtered vs. raw traces before final interpretation.

4. Measurements and automated analysis

• Heart rate: measure from RR intervals (continuous or median).
• PR