Explain the ECG
Reading File
Finding Sources
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I have a clear view of the ECG. Let me provide a thorough systematic interpretation.
ECG Interpretation
Patient details (from the tracing):
- Age: 55 years | Date: 20/05/2026 | Time: 6:30 AM
- Paper speed: 25 mm/s | Gain: 5 mm/mV | Machine: Nidek ADS AC50
1. Rate
Counting R-R intervals on the rhythm strip (lead II), the ventricular rate is approximately 75–85 bpm — within normal limits.
2. Rhythm
- Regular R-R intervals throughout
- A P wave precedes every QRS → Normal sinus rhythm
3. Axis
- Lead I: upright QRS
- aVF: upright QRS
- → Normal axis (0° to +90°)
4. P Waves
- Present, upright in leads I, II, aVF
- Inverted in aVR (normal)
- Normal morphology and duration (~80–100 ms)
- Normal P waves
5. PR Interval
- Appears approximately 160–180 ms (3–3.5 small squares at 25 mm/s)
- Normal PR interval (120–200 ms)
6. QRS Complex
- Duration appears narrow (~80–100 ms) — no bundle branch block
- Prominent/tall R waves in V4–V6 with normal transition
- Deep S waves in V1–V2 progressing to taller R in V4–V5 — normal R-wave progression
7. ST Segment & T Waves
Examining each territory carefully:
| Territory | Leads | Findings |
|---|---|---|
| Inferior | II, III, aVF | ST segments appear isoelectric; T waves upright |
| Lateral | I, aVL, V5, V6 | ST isoelectric; T waves upright |
| Anterior | V1–V4 | V2–V3 show prominent biphasic/upright T waves with possible mild ST changes |
| Septal | V1–V2 | S waves present; no clear ST elevation |
Notable finding: In V2–V3, the T waves appear relatively tall/prominent and the ST segment shows a subtle upward curve. This raises the question of early repolarisation changes or anterior wall ischaemia — particularly significant in a 55-year-old.
There is no frank ST elevation or ST depression visible, but subtle changes in V2–V3 warrant correlation with symptoms and prior ECGs.
8. QT Interval
- Estimated QTc appears within normal range (~380–420 ms)
- No prolonged QT
9. Other Features
- No pathological Q waves identified (no evidence of old infarction)
- No delta waves (no pre-excitation)
- No voltage criteria for LVH (though limited by 5mm/mV gain — standard would be 10mm/mV; tall voltages may be masked)
- The reduced gain (5 mm/mV instead of standard 10 mm/mV) means all amplitudes are halved on paper — actual voltages are twice what is seen. This must be factored in when assessing for LVH or ST changes.
Summary / Impression
| Finding | Status |
|---|---|
| Rate | ~80 bpm — Normal |
| Rhythm | Normal sinus rhythm |
| Axis | Normal |
| PR interval | Normal |
| QRS duration | Normal (narrow) |
| ST segments | No frank elevation/depression; subtle anterior (V2–V3) changes |
| T waves | Upright; relatively prominent in V2–V3 |
| Q waves | Absent (no old MI) |
| QTc | Normal |
⚠ Clinical Caution
The ECG is recorded at half-standard gain (5 mm/mV). This reduces all deflections by 50% visually. Any ST changes or voltage abnormalities could be more significant than they appear. In a 55-year-old patient, subtle anterior T-wave and ST changes in V2–V3 must be:
- Correlated with clinical symptoms (chest pain, dyspnoea, diaphoresis)
- Compared with a prior ECG if available
- Followed by serial ECGs and troponin measurements if ischaemia is suspected
- A standard-gain (10 mm/mV) ECG should ideally be obtained for accurate assessment
Provisional interpretation: Normal sinus rhythm with no definitive acute ST-elevation changes. Anterior leads (V2–V3) warrant clinical correlation to exclude early ischaemia.
⚕️ This interpretation is for educational purposes. Final clinical decisions must be made by the treating physician with full patient context.
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