Introduction of ECG a Basic Idea about ECG with general description of 12 Leads

** **

Connect leads:

**.**RA (Red) to right arm- • RL (Black) to right leg
- · LA (Yellow) to left arm
- · LL (Green) to left leg

**Connect the precordial leads ****Vi **– V 6 **as follows:**

** **

- ·
**Vi**to the right of sternum in the 4^{th}intercostal space - ·
**V**_{2}^{th}intercostal space - ·
**V**_{3}_{2}and V_{4} - ·
**V**_{4} - ·
**V**_{s}**and V**in the same line as V_{6}_{4}in anterior and mid axillary lines respectively.

·

The 12 leads are:

- – 3 standard limb leads L I, L II, L III
- – 3 augmented leads AVR, AVL, AVF
- – 6 precordial leads V1 to V6

Normal ECG consists of 12 leads recorded serially or simultaneously or in groups. In the above picture, 3 leads have been recorded at a time

• Look at the waves and intervals in the ECG.

- The first wave is the P wave.
- The next tall and narrow wave and often consistin RS wave followin which is the T
- From the beginning of P wave to beginning of QRS is the PR interval.
- · From the beginning of Q to the end of T is the QT interval.
- · From beginning of QRS to the end of QRS is the QRS interval.
- · From the end of R to the beginning of T is the ST segment.

- 1 mm = 0.04 see
- 5 mm = 0.2 see
- 1 mm = 0.1 mv

On the ECG paper, time is represented in seconds horizontally and voltage is represented in millivolts vertically.

- · 1 small square is 0.04 s horizontally and 0.1 mv vertically, if the paper speed is 25 mm/s.
- · This means that 10 mm = 1 mv.
- · 5 small squares = 5 x 0.04 = 0.2 s.
- · 1 big square = 0.2 s, 5 big squares = 0.2 x 5 = 1 sec.

- This is a Basic idea about ECG, with a introduction to measuring ECG .