ECG Interpretation | How to Interpret An ECG in 30 Seconds. ECG is the graphical representation of electrical potentials produced when the electric current passes through the heart. Before interpreting an ECG one must know details about the ECG paper, standardization and different waves in ECG. It is a matter of experience and pattern interpretation. This article deals with easy interpretation of an ECG.
ECG papers
- ECG paper is a graphical papers which has an X-axis and a Y—axis
- X—axis indicates time in second
- Y—Axis indicates amplitude/ Voltage in millivolt
- It consists of 2 type of square small @ large
- Small square is 1mm
- Large square is 5mm
- 1 large square = 5 small square
Voltage
Standard voltage of ECG recording is 1mv
- 1Mv = 10 mm / 10 small square = 2larg square
- Before interpreting the ECG first look for the voltage is 2 large square or not
- If voltage is 1 large square is the ECG is half voltage ECG
- Then voltage of P_QRST will Actually be double of what are u seeing
Heart rate
If rhythm is regular-
300
Heart Rate = ————————————————————————
Numbers of large square between two R-R interval
If rhythm is regular-
It calculate the number of R in 6 sec or 30 large square and multiply it with 10
If rhythm is irregular : numbers of R in 30 large square × 10
ECG Leads
Lead is nothing but like CC Camera. If you place 4 or 6 CC camera in 4 or 6 corner of your room and u sit in the middle of the room, the camera placed front of you it will take the picture of your front view and the camera placed behind of you will take the posterior view of your body. The side cameras will take left or right lateral surface of your body. Like this differents lead take picture of different parts (surface ) of the heart .such as inferior lead show the inferior surface of the heart
The standard ECG has 12 leads
1) Three bipolar standard limb leads- I, II and III.
2) Three unipolar augmented limb leads – aVL, aVF and aVR.
3) Six chest leads – V1, V2, V3, V4, V5 and V6.
In this picture we can see
- Lead I is most close proximity to lead AVL
- Lead III is close proximity to lead AVF
- Lead II is opposite to lead AVR
- Any change(like T –inversion ) in lead I will be found in lead AVL , and
- Change in lead III will be found in AVF
- What you get in lead II (positive R) will be opposite in lead AVR(negative R)
In this picture we can also see that II, III, AVF see the heart from inferior or ground so take picture of the inferior surface of the heart. That s why the are called inferior lead. Lead I and AVL are taking the picture from the side of body see the lateral part of the heart that’s why lead I and lead AVL are called Lateral lead
ECG Interpretation in 30 Seconds
| 1st seeIn lead IIRhythm |
If Regular —go next step
If irregular –it will be AF ,
· To confirm look for
Absent of p wave –if absent –then u r 100%
· If u confused about P wave present or not then look for
PR interval ,In sinus rhythm P is Isomorphic & PR is fixed before all R in lead II
|
| Next seeHeart Rate in lead II |
If heart rate is less 40
· exclude complete heart block
If your find ECG that
R-R interval equal and P-P interval equal but PR interval is not fixed
|
| NextMI
Try to find following :
· T inversion ,
· ST elevation
· Q wave
|
1st see ———–AVL , I —————acute lateral MI
|
Then ————-II , III , AVF —–acute inferior MI
| |
Then ————-V1 to V6 ————– acute extensive ant MI
| |
Then————–V 1—V 4—-Acute antero-septal MI
| |
Then ————-I, AVL , V5-V6 acute antero-lateal MI
| |
| Next see V 5 |
Tall R— LVH
(if with T- inversion or ST –depression then strain pattern )
Abnormal R or M pattern — — LBBB
|
| Next see V 2 |
Tall R— RVH
(if with T- inversion or ST –depression then strain pattern )
Abnormal R or RBBB
|
| Next seeI . II. IIICompare height of R |
to see axis deviation
Left axis…. R (+) in I & R (- ) II and III
Right axis…. R (-) in I & R (+ ) II and III
|
| Next seeV 1 to V 6 |
If R in V 6 < S in V 6 —– poor progression of R wave
|
References
ECG in MEDICAL PRACTICE – ABM Abdullah
Dr. Shahidullah Shamol (FCPS in Medicine)
Assistant Professor, Department of Medicine
Mymensingh Medical CollegeTimes New Roman
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