Electrocardiography

Question 1

The SA node is made up of __________ cells that spontaneously depolarize

Answer 1

Pacemaker

Question 2

The impulse from the SA node is conducted through the atria causing??

Answer 2

Myocyte depolarization then contraction (=atrial systole)

Question 3

Where does the electrical impulse travel after the AV node?

Answer 3

AV node —> bundle of His—> left and right bundle branches —> purkinje fibers —> ventricular depolarization and contraction

Question 4

What allows the impulse to travel through the heart?

Answer 4

Ion fluxes across the cell membranes

Question 5

Where are the EEG wires placed?

Answer 5

White -front right
Green- right hind
Black - left front
Red- left hind

Question 6

When an electrical impulse moves toward the positive pole, there will be a _________ deflection i the ECG

Answer 6

Upward

Question 7

When an electrical impulse moves toward a negative electrode, there will be a ________ deflection on the ECG

Answer 7

Downward

Question 8

What does lead 1 span?

Answer 8

Right front leg (-) to left front leg (+)

Question 9

Lead 2 spans??

Answer 9

Right front leg (-) to left hind leg (+)

Question 10

Lead 3 spans??

Answer 10

Left front leg (-) to left hind leg (+)

Question 11

P wave =

Answer 11

Atrial depolarization

Question 12

QRS =

Answer 12

Ventricular depolarization

Question 13

T wave =

Answer 13

Ventricular repolarization

Question 14

What is the PR interval?

Answer 14

Atrial depolarization and conduction through AV node

Question 15

What is the QT interval?

Answer 15

Ventricular depolarization and repolarization

Question 16

What is the R-R interval ?

Answer 16

Time between ventricular depolarizations

Question 17

What is the ST segment ?

Answer 17

Time between the end of ventricular depolarization and the beginning of repolarization

-normally isoelectric

Question 18

What is the PR segment ?

Answer 18

Time between end of atrial depolarization and the beginning of ventricular depolarization

-normally isoelectric

Question 19

If your paper speed is 25mm/sec, each small box is how many seconds?

Answer 19

0.04

Question 20

If your paper speed is 50mm/sec, each small box is how many seconds?

Answer 20

0.02sec

Question 21

On an ECG, what does the y-axis represent?

Answer 21

Voltage

Question 22

The height of the voltage on an ECG is determined by the ??

Answer 22

Amplitude calibration

Common amplitudes

• 10mm/mv -> small box 0.1mV
• 5mm/mv-> small box 0.2mV

Question 23

What does it mean to have a “narrow” ORS complex?

Answer 23

Normal duration

Cat < 40ms
Dog < 60ms

Question 24

What does it mean to have a “wide” QRS?

Answer 24

Prolonged duration

Cat >40ms
Dog >60ms

Question 25

What does it mean to have atrioventricular association?

Answer 25

The impulse that depolarizers the atria is the same impulse tat depolarizes the ventricles

Question 26

What two waves and which interval would help figure out if there is AV association?

Answer 26

Pwave and Rwave | PR interval

Question 27

What is a sinus rhythm?

Answer 27

Consecutive sinus complexes with regular RR and PR intervals 3 or more QRS complexes with the same morphology is a rhythm

Question 28

How do you calculate the heart rate if paper speed is 25mm/sec?

Answer 28

In 30boxes The number of QRS complexes x 10

Question 29

How do you calculate the heart rate if paper speed is 50mm/sec?

Answer 29

Number of QRS complexes in 30 boxes x 20 =bpm

Question 30

If the R-R intervals vary, then the rhythm is??

Answer 30

Irregular

Question 31

An abnormally high Pwave suggests?

Answer 31

Right atrial enlargement

Question 32

An abnormally this R wave suggests?

Answer 32

Left ventricular enlargement

Question 33

An abnormally high Swave suggests?

Answer 33

Right ventricular enlargement

Question 34

An abnormally wide duration can suggest??

Answer 34

1) chamber enlargement 2) bundle branch block 3) ectopic ventricular impulse

Question 35

What is the MEA?

Answer 35

Mean electrical axis - average direction of the electrical potential generated during a cardiac cycle

Question 36

What is a pause ?

Answer 36

If a QRS is “late” | Ie prolonged P-R interval

Question 37

There is a sinus arrhythmia if there is ______variation in R-R intervals with a pattern to the irregularity

Answer 37

>10%

Question 38

What is a respiratory sinus arrhythmia ?

Answer 38

HR accelerates during inspiration and slows during expiration -normal heart rate —> can be exaggerated in patients with certain respiratory diseases due to change in intrathoracic pressure

Question 39

What do you call the condition where there is variation in the site of impulse formation in/near the SA node

Answer 39

Wandering pacemaker

Question 40

What would you see on a ECG for wandering pacemaker?

Answer 40

Variation in P wave Consistent PR interval Rhythm is often RSA —> WP is normal in resting/calm dogs at clinic (PSNS > SNS)