ECG Features

• Normal rate (60-100 beats/min in adults), sinus rhythm, and normal axes
• P wave: normal axis (0° to +75°, upright in I and II, inverted in aVR) and same morphology
• PR interval: 120-200 ms
• QRS complex: normal axis (-30° to +110°) and duration (<120 ms)
• ST segment: typically isoelectric with <1 mm of elevation or depression in limb leads
• T wave: upright in I, II, and V3-V6 with normal asymmetric morphology