Electrocardiogram ECG Part 1 Made for understanding. By Mandy Gutliph Stephanie Feldman. Electrocardiography or ECG is a important diagnostic tool for Veterinary Medicine. ECG’s measure the electrical activity of the heart.
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
By Mandy Gutliph
Electrocardiography or ECG is a important diagnostic tool for Veterinary Medicine.
ECG’s measure the electrical activity of the heart.
These measurements are called Lead Polarity and are represented by P,Q,R,S, and T (as shown below)
The P wave represents Atrial Depolarization The QRS wave represents Ventricular DepolarizationThe T wave represents Ventricular Repolarization
Your patient, any mammal, should be sedated or anesthetized for this procedure
THE ANIMAL MUST ALWAYS BE IN RIGHT LATERAL RECUMBENCY!
Use a rubber mat between metal tables and patient to prevent any electrical interference!
Black cable- Attaches to Left Front Leg!White cable- Attaches to Right Front Leg!Red cable- Attaches to Left Rear Leg!Green cable- Attaches to Right Rear Leg!
*Remember Snow (white) and Grass (green) are always on the ground (right side)
* Remember you always read the newspaper (black and white) at the beginning of the day (front legs)
You can change the Lead (I,II,III) to measure different parts of electrical activity (heart) to better diagnosis the patient.
Lead I- Causes the cables at the Right forelimb – Negative Pole Causes the cables on the Left forelimb – Positive Pole
Lead II – Causes the cable on the Right forelimb – Negative Pole Causes the cable on the Left hind limb – Positive Pole
Lead III- Causes the cable on the Left hind limb – Positive Pole Causes the cable on the Left forelimb – Negative Pole
The P wave or atrial depolarization is a small bump because the walls of the atria are thinner than the walls of the ventricle, therefore, the total amount of electrical activity is smaller than the ventricle, or QRS wave.
The individual squares measure time and amplitude.
This is a irregular rhythm
A. Heart rate B. Axis deviation C. conduction abnormalities D. All of the above
2) Which one of these important heart structures is not measured in an ECG?
A. AV Node B. SA Node C. Purkinje Fibers D. Posterior vena cava
3) The P wave represents Depolarization of:
A. Atria B. Ventricle C. Aorta D. vena cava
4) The QRS wave measures Depolarization of:
A. Atria B. Ventricle C. Aorta D. Vena cava
5) The T wave measures
A. Depolarization of the atria B. Depolarization of the ventricle C. Repolarization of ventricle
6) Lead II is:
A. + on Right Forelimb, - on Left forelimb B. – on right forelimb, + on left forelimb
C. – on right forelimb, + on left hind limb
By Mandy Gutliph
And Stephanie Feldman
1. The sensitivity setting- a setting of 1 makes a 1cm deflection of the pen, when the millivolt button is pushed.
The standard sensitivity is 1milivolt.
Remember that 1 millivolt = 1cm.
So you can change the sensitivity with the sensitivity selector to either 0.5cm or 2cm.
When you do this, then 1 millivolt = .5cm or 2cm.
This should be done if your waves are too small or too large to interpret.
Also, cats that are purring can cause this.
stimulation occurs through
the vagal nerve and lowers
the heart rate.
1. Count the R waves registering within 6 seconds and multiply by 10. (quick yet inaccurate method)
2. Count the number of large squares between two R waves and divide by 300. (this loosed accuracy when used to calculate fast heart rates and can only be used with regular rhythms)
3. Count the number of small squares between two R waves and divide by 1500. (most accurate method but can only be used with normal rhythms.)
By Mandy Gutliph
The second step is to determine whether the ventricles are activated from inside the ventricles; or from another location.
A QRS complex of normal duration is 0.04-0.06 seconds.
This indicates that waves are going along normal pathways (conduction tissues)
A QRS complex longer than 0.6 seconds has left normal pathways and occurs within Ventricular Myocardium.
When it takes longer this is called: Ventricular Complex; and causes the QRS complex to have a wide and bizarre appearance on the ECG
Ventricular Myocardium: muscular structure of the ventricle.
The third step is to determine the relationship between the P wave and the QRS complex.
Where's the P wave?
BAD! Asystole! No heartbeat!
The P-R interval may be short, normal or long depending on the origin of the premature beat.
Sites of origin are SA node or ectopic (displaced) locations in the atria.
It may or may no affect the QRS complex (ventricular contraction)
This happens when repolarization and depolarization occurring on a cell – to – cell basis within the myocardium. This looks very different from other QRS complex’s of sinus origin.
This can be determined by looking at lead II.
The QRS complex can either deflect downwards or upwards in Ventricular Premature Contraction.
Note how the backwards P wave is after the QRS complex
sinoatrial node is not functioning.