Exam 1 - ECG Interpretation

Question 1

what can an ECG NOT tell you?

Answer 1

information on the mechanical activity of the heart - strength of contraction

Question 2

what can an ECG tell you?

Answer 2

• info on chamber enlargement
• info regarding electrolyte concentrations
• info regarding myocardial hypoxia
• info about pericardial effusion
• info on conduction disturbances
• info on heart rate & rhythm

Question 3

if a BIC pen is 150mm in length, and the paper speed is 25mm/sec, how many seconds does 1 pen length represent?

Answer 3

6 seconds

Question 4

if a BIC pen is 150mm in length, and the paper speed is 50mm/sec, how many seconds does 1 pen length represent?

Answer 4

3 seconds

Question 5

how big are small & little boxes on ECG strips?

Answer 5

little boxes: 1x1mm
big boxes: 5x5mm

Question 6

what is the x-axis & y-axis on an ECG?

Answer 6

x-axis: time in mm/sec
y-axis: amplitude in mm/mv

Question 7

what is a normal heart rate for adult cats?

Answer 7

160-240 bpm

Question 8

what is a normal heart rate for adult dogs?

Answer 8

70-160 bpm

Question 9

what is a normal heart rate for toy breeds?

Answer 9

less than or equal to 180 bpm

Question 10

what is a normal heart rate for puppies?

Answer 10

less than or equal to 220 bpm

Question 11

what is a commonly seen arrhythmia in dogs? what about cats?

Answer 11

dogs - sinus arrhythmia

cats - sinus tachycardia

Question 12

at 25 mm/sec, how much time does 1 small box represent?

Answer 12

0.04 seconds

Question 13

at 50 mm/sec, how much time does 1 small box represent?

Answer 13

0.02 seconds

Question 14

what is a normal P wave interval in seconds for both dogs & cats?

Answer 14

less than or equal to 0.04 seconds

Question 15

what is a normal QRS interval for dogs <20kg? dogs over 20 kg? giant breeds?

Answer 15

< 20 kg: less than or equal to 0.05s

> 20 kg: less than or equal to 0.06s

giant breeds: less than or equal to 0.065s

Question 16

what is a normal QRS interval in cats?

Answer 16

less than or equal to 0.04s

Question 17

at 10mm/mv (standard), how many mv does 1 small box represent?

Answer 17

0.1mv

Question 18

what is a normal p wave amplitude in dogs & cats?

Answer 18

dogs: less than or equal to 0.4mv

cats: less than or equal to 0.2mv

Question 19

what is a normal r wave amplitude in cats?

Answer 19

less than or equal to 0.9mv

Question 20

what is a normal r wave amplitude for dogs <20kg? dogs over 20kg?

Answer 20

< 20 kg: less than or equal to 2.5mv

> 20 kg: less than or equal to 3.0mv

Question 21

what p wave duration meets the criteria for left atrial enlargement in both dogs & cats?

Answer 21

greater than 0.04 seconds

Question 22

what p wave amplitude meets the criteria for right atrial enlargement in dogs & cats?

Answer 22

dogs: greater than 0.4mv

cats: greater than 0.2mv

Question 23

what r wave amplitude in lead II meets the criteria for left ventricular enlargement in dogs & cats?

Answer 23

dogs <20kg: greater than 2.5mv

dogs >20kg: greater than 3.0mv

cats: > 0.9mv

Question 24

what are 4 criteria that support enlargement of the right ventricle seen on ecg?

Answer 24

1. s wave in lead I, II, & III
2. MEA to RV** only criteria for cats
3. s wave in lead III > lead II > lead I
4. s wave > r wave in lead II or s wave is > 0.7mv

Question 25

how is an instantaneous heart rate calculated from an ECG?

Answer 25

of boxes from r wave to r wave - multiply by the time (either 0.04 seconds or 0.02 seconds)

60 seconds/^^ = instantaneous heart rate

Question 26

what is the paper speed for horse ecgs?

Answer 26

12.5mm/sec, sensitivity 10mm/mv
0.08 sec/mm

Question 27

what is this & what is it associated with? how can you minimize or resolve it?

Answer 27

artifact - electrical interference, will not have an associated repolarization (if it mimics a QRS, won’t have a t wave)

unplugging, use a grounded outlet, keep patient on an insulated surface, & ensure good electrode contact on skin

Question 28

how can multiple leads help differentiate artifact from pathology on ecg?

Answer 28

artifact often won’t occur in 2 of 3 leads

Question 29

what must you rule out if suspecting artifact on an ecg?

Answer 29

ectopic p waves & QRS complexes

Question 30

what are ectopic complexes? what are their possible origins?

Answer 30

heart beats that don’t arise from the SA node

supraventricular or ventricular

Question 31

how can you tell the difference between SVPB & VPCs using morphology?

Answer 31

VPCs - usually wide & bizarre QRS, if in lead II & negative, LV origin, if in lead II & positive, RV origin, p waves not associated because they may be buried or superimposed on other parts

SVPB - normal/narrow QRS & mostly positive complex in lead II, P WAVES ARE ABSENT

Question 32

what is this?

Answer 32

ventricular premature complex - wide & bizarre QRS

Question 33

what is this?

Answer 33

PSVB - QRS is similar to sinus QRS morphology

Question 34

what are the hallmarks of afib seen on an ecg of a dog?

Answer 34

1. irregular
2. irregular
3. irregular
4. usually narrow
5. usually fast
6. no identifiable p waves

Question 35

what are the most likely etiologies of atrial fibrillation in dogs?

Answer 35

1. idiopathic or lone - not associated with structural heart disease
2. DCM
3. MMVD
4. HCM
5. hyperkalemia
6. hemangiosarcoma

Question 36

what is a fib?

Answer 36

no coordinated atrial contraction

Question 37

what arrhythmia is seen here?

Answer 37

atrial fibrillation