Electrocardiography

Question 1

What is the point of electrocardiopathy?

Answer 1

• Measures electrical activity of the heart
• Heart rate
• Conduction disturbances
  
  • Chamber enlargement
  • Electrolyte disturbances
  • Myocardial ischemia

Question 2

Normal conduction through the heart?

Answer 2

• Sino-atrial node
• AV node
• Bundle of His
• L and R bundle branches
• Purkinje fibers
• Rate depends on tone–SNS and PNS

Question 3

Normal EKG–what are the dif. waves?

Answer 3

Question 4

Which lead is the best regarding arrhythmias on an EKG?

Answer 4

Lead II

Question 5

What is the basic unit on EKG paper?

What does 1 cm equal? 1mm?

What dimensions are the tiny boxes? The big ones?

Answer 5

• Basic unit = 1mm
• 1 cm = 1 mV
• 1 mm = 0.1 mv
• Tiny box = 1x1mm
• Big box = 5x5 mm

Question 6

What artifact is this?

Answer 6

60 Hz interference

Question 7

What artifact is this?

Answer 7

Shivering

Question 8

What artifact is this?

Answer 8

Purring

Question 9

How do you determine HR from an EKG?

Answer 9

1. Determine speed (provided)
2. # of PQRST’s in ENTIRE strip
3. ^ convert to PQRST’s in 1 minute

Question 10

How do you find the mean electrical axis? Is it useful?

Answer 10

• Average direction of activation of ventricular myocardium during systole
• No–often inacurrate and can just use ultrasound instead

Question 11

How do you assess atrial size?

Answer 11

• P pulmonade (peak)
  
  • Too tall = right atrial enlargement
• P mitrale (mound)
  
  • Too wide = left atrial enlargement

Question 12

How do you assess ventricular size?

Answer 12

• QRS complex–septal and ventricular depolarization
• First neg. inflection = Q wave–don’t always get it, not unusual
• R wave too high = left ventricular enlargement
• Very deep S wave = right ventricular hypertrophy

Question 13

What is the most common EKG abnormality in cats?

Answer 13

Hypertrophic cardiomyopathy

Question 14

What is the most common cause of right atrial and right ventricular enlargement in dogs?

Answer 14

HEARTWORMS

Question 15

Right bundle branch block

Answer 15

• Deep S
• QRS prolonged
• R decreased
• Impulses come down –> jump from one cell to another via tight junctions–very slow –> QRS complex gets wider b/c process takes longer

Question 16

Left bundle branch block

Answer 16

• Wide QRS
• Normal height
• Infections, trauma
• Normal CO
• Blocks/VPDs
• Left atrium activated more slowly–look at septum via US

Question 17

Low voltage complexes

Answer 17

• <1 to 1.5 mV
• Obesity, pleural or pericardial effusion (picture), pneumothorax
• Hypothyroidism, or diffuse myocardial disease

Question 18

What does it mean if there’s depression of the whole S-T segment?

Answer 18

Entire heart is deprived of oxygen = PROBLEM

Question 19

How is the Q-T segment related to heart rate? What can it change with?

Answer 19

• Inversely proportional to heart rate
• Changes w/ K, Ca, drugs

Question 20

How tall is the T wave supposed to be?

Answer 20

• < 1/4 of the R wave (cats can be 1/3)
• No rules as to whether it should be +/-, but should be consistent
• If increased in amplitude (height) = hyperkalemia
  
  • Often due to hypertrophic cardiomyopathy