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Recording and Interpreting a 12-Lead ECG: Procedure and Analysis, Schemes and Mind Maps of Psychiatry

A step-by-step guide on how to record a 12-lead ecg, including patient preparation and electrode placement. It also explains the importance of each lead and how to interpret the resulting ecg waves, intervals, and potential abnormalities. This information is essential for healthcare professionals to diagnose various heart conditions.

What you will learn

  • What is the procedure for recording a 12-lead ECG?
  • What are the normal intervals for PR, QRS complex, and QT interval in an ECG?
  • How do the different leads of a 12-lead ECG look at the heart?

Typology: Schemes and Mind Maps

2021/2022

Uploaded on 09/27/2022

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kataelin 🇬🇧

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How to record a 12 lead ECG
Explain the procedure to the patient. Patient will have to remove the shirt to expose
the chest. Reassure that it will be painless and will only take a few minutes. Patient
should then be helped on the couch and asked to lie with legs and arms uncrossed.
Clean areas of electrode placement with alcohol wipes.
Place pads for limb and chest electrodes.
Limb leads are colour coded. Pneumonic Ride Your Green Bike will help you
remember how to place the leads. Start with the red lead and attach it to the
right wrist. Yellow is attached to the left wrist, green to the left leg and black
to the right leg.
Position of chest leads
o V1: Fourth intercostal space at the right sternal border. (First palpable
intercostals space, below the clavicle is the 2nd intercostal space.
o V2: Fourth intercostal space at the left sternal border
o V3: Midway between V2 and V4
o V4: Fifth intercostal space in the midclavicular line
o V5: Anterior axillary line at the same horizontal level as V4
o V6: Mid-axillary line at the same horizontal plane as V4 and V5
Switch on the machine, if it has a filter button press it to erase previously recorded
ECG. Record ECG.
How to read ECG
I will try to explain the important points in ECG as briefly and simply as I can. For
the OSCE you will obviously need to check the patient’s name, date of birth and date
when ECG was done.
ECG machines pick up electrical activity through 4 limb electrodes and 6 chest
electrodes and covert it into 6 limb leads (I, II, III, aVR, aVL and aVF) and 6 chest
leads (V1-V6)
Leads I and aVL look at the left side of the heart
Leads II, III and aVF look at the inferior surface of the heart
aVR is always negative as it looks at the heart from the position of the right
shoulder and electrical current moves away from it. The negative waves
confirm that the electrodes have been connected correctly
The 6 chest leads look at the heart in the horizontal plane, from the front and around
V1 and V2 give information about the right heart
V3 and V4 about the interventricular septum
V5 and V6 give information about the left side of the heart
Waves
P wave: represent atrial systole
QRS complex: ventricular systole
T wave: ventricular relaxation or diastole
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How to record a 12 lead ECG

Explain the procedure to the patient. Patient will have to remove the shirt to expose the chest. Reassure that it will be painless and will only take a few minutes. Patient should then be helped on the couch and asked to lie with legs and arms uncrossed.

  • Clean areas of electrode placement with alcohol wipes.
  • Place pads for limb and chest electrodes.
  • Limb leads are colour coded. Pneumonic R ide Y our G reen B ike will help you remember how to place the leads. Start with the red lead and attach it to the right wrist. Yellow is attached to the left wrist, green to the left leg and black to the right leg.
  • Position of chest leads o V1: Fourth intercostal space at the right sternal border. (First palpable intercostals space, below the clavicle is the 2nd^ intercostal space. o V2: Fourth intercostal space at the left sternal border o V3: Midway between V2 and V o V4: Fifth intercostal space in the midclavicular line o V5: Anterior axillary line at the same horizontal level as V o V6: Mid-axillary line at the same horizontal plane as V4 and V Switch on the machine, if it has a filter button press it to erase previously recorded ECG. Record ECG.

How to read ECG

I will try to explain the important points in ECG as briefly and simply as I can. For the OSCE you will obviously need to check the patient’s name, date of birth and date when ECG was done.

ECG machines pick up electrical activity through 4 limb electrodes and 6 chest electrodes and covert it into 6 limb leads (I, II, III, aVR, aVL and aVF) and 6 chest leads (V1-V6)

  • Leads I and aVL look at the left side of the heart
  • Leads II, III and aVF look at the inferior surface of the heart
  • aVR is always negative as it looks at the heart from the position of the right shoulder and electrical current moves away from it. The negative waves confirm that the electrodes have been connected correctly

The 6 chest leads look at the heart in the horizontal plane, from the front and around

  • V1 and V2 give information about the right heart
  • V3 and V4 about the interventricular septum
  • V5 and V6 give information about the left side of the heart

Waves

  • P wave: represent atrial systole
  • QRS complex: ventricular systole
  • T wave: ventricular relaxation or diastole
  • Atrial systole gets buried in the ventricular systole and therefore does not produce a wave form
  • Q waves: When heart muscles are damaged the electrical current does not pass through them and instead of upright R waves, downwards Q waves are produced

Intervals When ECG is recorded the paper speed is 25 millimetres/second so in 1 second ECG tracing covers 5 large squares or 1 large square is equal to 0.2 seconds and one small square is equal to 0.04 seconds.

  • PR interval is measured from the start of the P wave to the beginning of the QRS complex. The normal PR interval is 0.12 to 0.2 seconds or 3-5 small squares
  • Duration of QRS complex is normally 0.12 seconds or 3 small squares
  • QT interval is the time between the onset of depolarization to repolarization. It is affected by diet, gender, alcohol, time of the day, menstrual cycle and heart rate. QTc is the QT interval which has been corrected for the heart rate o QTc = QT msec/square root of RR I don’t know about you but I have limited mathematical skills and cannot calculate QTc with the above formula. An easier way is to calculate the RR interval (number of large squares) and if QT interval is longer than 50% of the RR interval (again check the number of large squares between beginning of Q and end of T) it is an indication that it is prolonged. You can then take out your calculator and do it properly Potential consequences of QT prolongation include torsade de pointes (syncope), ventricular fibrillation and sudden death. If QTc prolongation is associated with T wave changes refer to the cardiologist.

Heart rate Hear rate can be easily determined by counting the number of large squares between 2 consecutive QRS complexes (R-R interval). Normally the heart rate is between 60 and 100/min.

  • 1 large square: rate is 300/m
  • 2 large squares: rate is 150
  • 3 large squares: rate is 100
  • 4 large squares: rate is 75
  • 5 large squares: rate is 60 (1 QRS per second)
  • 6 large squares: rate is 50

Patient is said to be bradycardiac if under 60 and tachycardic if heart rate is more than

How to determine axis? Axis can be checked by looking at the direction of wave forms in leads I, II and III. A normal (11’o clock to 5 o’ clock axis means that current is flowing towards leads I, II and III and results in upward deflections in all 3.