ECG (Electrocardiogram) waves represent the electrical activity of the heart.brief overview: 1. P Wave Significance: Atrial depolarization (contraction). Normal Value: Duration < 0.12 sec (3 small squares), amplitude < 2.5 mm. 2. PR Interval Significance: Time taken for impulse to travel from atria to ventricles. Normal Value: 0.12–0.20 sec (3–5 small squares). 3. QRS Complex Significance: Ventricular depolarization (contraction). Normal Value: Duration < 0.12 sec, amplitude varies with leads. 4. ST Segment Significance: Represents early ventricular repolarization. Normal Value: Usually isoelectric (flat); elevation or depression indicates ischemia or infarction. 5. T Wave Significance: Ventricular repolarization. Normal Value: Upright in most leads; inversion or peaked waves may indicate pathology. 6. QT Interval Significance: Time for ventricular depolarization and repolarization. Normal Value: < 0.44 sec (varies with heart rate).