Exam 2 – Cardio Ch 12

Question 1

What do you use to calculate the electrical axis of the heart?

Answer 1

Lead I, II and III

Question 2

What is the electrical axis of the heart based on?

Answer 2

Direction and voltage of tracing

Question 3

What is the electrical axis of the heart used to determine?

Answer 3

Determine potential diagnoses for problems in people

Question 4

Principles of Vectorial Analysis of EKG’s

Answer 4

The current in the heart flows from the area of depolarization to the polarized areas, and the electrical potential can be represented by a vector, with the arrowhead pointing in the positive direction

Question 5

What is the length of the vector proportional to?

Answer 5

The voltage of the potential by convention

Question 6

What does the instantaneous mean vector represent?

Answer 6

Generated potential at any instance

Question 7

What is the normal mean QRS vector?

Answer 7

59 degrees (in people)

Question 8

Define mean QRS vector

Answer 8

Average direction of vector during spread of depolarization wave through ventricles

Question 9

What is the mean vector go through?

Answer 9

The partially depolarized heart

Question 10

Look at axes of three bipolar and augmented leads

Answer 10

Look at axes of three bipolar and augmented leads

Question 11

What is the mean electrical axis averaged over the entire period of depolarization?

Answer 11

+59 degrees

Question 12

What is done with any area that is negative when determining voltage?

Answer 12

Any area that is negative is subtracted from the positive area

Question 13

Where do you draw a perpendicular line? (mean electrical axis)

Answer 13

Draw perpendicular line from end of each vector, and the intersection defines mean electrical axis

Question 14

In T wave (ventricular repolarization), what is the first area to repolarize?

Answer 14

Near the apex of heart

last areas to depolarize are first to repolarize

Question 15

In T wave (ventricular repolarization), what is the normal net charge?

Answer 15

Normally tends to have a net positive charge in people

positive, negative, or biphasic in dogs and cats, mostly negative in horses and cattle

Question 16

Where does atrial depolarization (P-wave) begin at?

Answer 16

Sinus node

Question 17

Where does atrial depolarization spread towards?

Answer 17

AV node

Question 18

What is the charge of the vector in atrial depolarization?

Answer 18

Positive vector in lead I, II and III

Question 19

Can you see the atrial repolarization? (atrial T wave)

Answer 19

No

Question 20

Why can you not see the atrial repolarization wave?

Answer 20

It is covered by the QRS complex

Atrial depolarization is slower than in ventricles, so first area to depolarize is also first to repolarize

Question 21

If you could see the atrial repolarization wave, what would the charge of the vector be?

Answer 21

Negative in all 3 leads

goes from negative to positive

Question 22

Why is atrial depolarization slower than in ventricles?

Answer 22

Atria have no purkinje system for fast conduction of depolarization signal

Question 23

What does a vectorcardiogram do?

Answer 23

Trace vectors throughout cardiac cycle

Question 24

When is the vector the largest in a vectorcardiogram?

Answer 24

When half of the ventricle is depolarized

Question 25

What is the zero reference point?

Answer 25

Phase 5 | When heart is fully depolarized

Question 26

Is a vectorcardiogram a continuous loop?

Answer 26

Yes. It outlines all areas that vector went throughout the heart

Question 27

What do some veterinary cardiologists use?

Answer 27

Cardiograms

Question 28

Look at plot of mean electrical axis of heart from two electrocardiographic leads

Answer 28

Look at plot of mean electrical axis of heart from two electrocardiographic leads

Question 29

What are factors that cause electrical axis deviations?

Answer 29

Changes in heart position | hypertrophy of left or right ventricle

Question 30

What causes a left shift in heart position?

Answer 30

``` Expiration Lying down (abdominal contents press upward against diaphragm) Excess abdominal fat (diaphragm normally press upward against heart all the time) ```

Question 31

What causes a right shirt in heart position?

Answer 31

End of deep inspiration Standing up Tall people

Question 32

What causes hypertrophy of left ventricle?

Answer 32

Hypertension (high arterial blood pressure) Aortic stenosis Aortic regurgitation causes slightly prolonged QRS (wide) and high voltage

Question 33

What type of shirt is hypertrophy of left ventricle?

Answer 33

Left axis shift

Question 34

What causes hypertrophy of right ventricle?

Answer 34

Pulmonary hypertension Pulmonary valve stenosis Interventricular septal defect All cause slightly prolonged QRS and high voltage

Question 35

What type of shirt is hypertrophy of right ventricle?

Answer 35

Right axis shift

Question 36

How does mild ischemia cause a T wave abnormality?

Answer 36

Mild ischemia in particularly in the apex of the heart in people prevents apex from repolarizing first T wave inverts

Question 37

What is a T wave abnormality?

Answer 37

Becomes abnormal when normal sequence of repolarizatoin does not occur

Question 38

How does digitalis toxicity cause a T wave abnormality?

Answer 38

Prolongs depolarization in certain parts of the heart and can cause a biphasic T wave

Question 39

How does digitalis toxicity relate to heart failure?

Answer 39

Digitalis binds to sodium and potassium receptors to slow calcium from leaving the cells Increased Ca results in stronger heartbeat

Question 40

How does arrhythmias relate to digitalis toxicity?

Answer 40

Slows the signals that start the SA node | Fewer signals, fewer arrhythmias

Question 41

What is a biphasic T wave?

Answer 41

Positive and negative deflection

Question 42

What is a inotropic cardiac drug propertiy?

Answer 42

Affects strength of contraction Mostly positive inotropic effect Stronger contractions

Question 43

What is a chronotropic drug property?

Answer 43

Affects rate of contraction can have positive and negative chronotropic effects Pacekeeping effects

Question 44

What is considered to be a high voltage EKG?

Answer 44

If sum of voltages of Leads I-III is greater than 4 mV

Question 45

What causes a high voltage EKG?

Answer 45

Most often causes by increased ventricular muscle mass (hypertension, marathon runner)

Question 46

What causes a prolonged QRS complex?

Answer 46

Cause is prolonged conduction of cardiac impulse through ventricles cardiac hypertrophy purkinje system block

Question 47

How does a prolonged QRS complex relate to a normal one?

Answer 47

Prolonged is wider

Question 48

What does it mean if a QRS exceeds normal?

Answer 48

Usual cause is conduction block

Question 49

What is a normal QRS time?

Answer 49

0.12 seconds in humans

Question 50

What is current of injury?

Answer 50

Current flows between pathologically depolarized and normally polarized areas, even between heartbeats

Question 51

What does damaged cardiac muscle remain?

Answer 51

Partially or totally depolarized all the times

Question 52

What does injured muscle emit?

Answer 52

Negative charges throughout each heart beat stays polarized/does not depolarize and contract

Question 53

What are causes of current of injury?

Answer 53

Local ischemia Mechanical trauma Infection

Question 54

How does local ischemia cause current of injury?

Answer 54

Caused by local coronary occlusions | Not enough nutrients available

Question 55

How does mechanical trauma cause current of injury?

Answer 55

Sometimes makes membranes so permeable that full repolarization cannot take place

Question 56

How does infection cause current of injury?

Answer 56

Damage muscle membranes

Question 57

What is the most common cause of current of injury?

Answer 57

Local ischemia

Question 58

What are causes of decreased voltages in standard bipolar limb leads?

Answer 58

Cardiac muscle abnormalities Conditions surrounding heart Anterior-posterior rotation of apex of heart

Question 59

What are some cardiac muscle abnormalities that cause decreased voltages in standard bipolar limb leads?

Answer 59

Old infarcts causing decreased muscle mass Low voltage EKG Prolonged QRS

Question 60

What are some conditions surrounding heart that cause decrease voltages in standard bipolar limb leads?

Answer 60

Fluid in pericardium Pleural effusions Emphysema