ECG / EKG Explained: What Your Heart Tracing Shows
By Dashvanth Healthcare Medical Team · Reviewed by our specialists · East Delhi
What Is an ECG?
An electrocardiogram (ECG or EKG) records the electrical activity of the heart via 10 electrodes placed on chest and limbs, producing a 12-lead tracing. It is a 10-second snapshot of heart rhythm and electrical function — painless, quick, and provides enormous diagnostic information.
What an ECG Detects
- Heart rhythm (normal sinus rhythm vs arrhythmia)
- Heart rate
- Heart attack — past or current (ST elevation/depression, Q waves)
- Conduction abnormalities (bundle branch blocks)
- Electrolyte imbalances (hyperkalaemia causes classic ECG changes)
- Heart muscle hypertrophy (LVH from hypertension)
- Pericarditis, cardiac tamponade
Understanding the Waves
- P wave: Atrial depolarisation (atria contract)
- PR interval: Normal 120–200 ms; Prolonged = heart block
- QRS complex: Ventricular depolarisation (ventricles contract); Widened = bundle branch block
- ST segment: Elevated = acute MI; Depressed = ischaemia
- T wave: Ventricular repolarisation; Inverted may indicate ischaemia
- QT interval: Prolonged = arrhythmia risk; affected by medications
Limitations
- Only 10 seconds — intermittent arrhythmias may be missed (need 24-hour Holter monitor)
- Normal ECG does NOT rule out heart disease (angiogram, echo needed for coronary and structural assessment)
I was told my ECG shows "ST changes" — should I be worried?
ST changes (elevation or depression) are significant and require urgent cardiologist evaluation. Other "changes" (minor T wave inversion, non-specific changes) are common, often benign, and need clinical correlation — not all ECG abnormalities indicate heart disease.
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