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Physiology > Exam 2 – Cardio Ch 12 > Flashcards

Exam 2 – Cardio Ch 12 Flashcards

1
Q

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

A

Lead I, II and III

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2
Q

What is the electrical axis of the heart based on?

A

Direction and voltage of tracing

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3
Q

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

A

Determine potential diagnoses for problems in people

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4
Q

Principles of Vectorial Analysis of EKG’s

A

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

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5
Q

What is the length of the vector proportional to?

A

The voltage of the potential by convention

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6
Q

What does the instantaneous mean vector represent?

A

Generated potential at any instance

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7
Q

What is the normal mean QRS vector?

A

59 degrees (in people)

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8
Q

Define mean QRS vector

A

Average direction of vector during spread of depolarization wave through ventricles

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9
Q

What is the mean vector go through?

A

The partially depolarized heart

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10
Q

Look at axes of three bipolar and augmented leads

A

Look at axes of three bipolar and augmented leads

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11
Q

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

A

+59 degrees

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12
Q

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

A

Any area that is negative is subtracted from the positive area

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13
Q

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

A

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

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14
Q

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

A

Near the apex of heart

last areas to depolarize are first to repolarize

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15
Q

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

A

Normally tends to have a net positive charge in people

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

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16
Q

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

A

Sinus node

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17
Q

Where does atrial depolarization spread towards?

A

AV node

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18
Q

What is the charge of the vector in atrial depolarization?

A

Positive vector in lead I, II and III

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19
Q

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

A

No

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20
Q

Why can you not see the atrial repolarization wave?

A

It is covered by the QRS complex

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

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21
Q

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

A

Negative in all 3 leads

goes from negative to positive

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22
Q

Why is atrial depolarization slower than in ventricles?

A

Atria have no purkinje system for fast conduction of depolarization signal

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23
Q

What does a vectorcardiogram do?

A

Trace vectors throughout cardiac cycle

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24
Q

When is the vector the largest in a vectorcardiogram?

A

When half of the ventricle is depolarized

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25
Q

What is the zero reference point?

A

Phase 5

When heart is fully depolarized

26
Q

Is a vectorcardiogram a continuous loop?

A

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

27
Q

What do some veterinary cardiologists use?

A

Cardiograms

28
Q

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

A

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

29
Q

What are factors that cause electrical axis deviations?

A

Changes in heart position

hypertrophy of left or right ventricle

30
Q

What causes a left shift in heart position?

A 
Expiration 
Lying down (abdominal contents press upward against diaphragm)
Excess abdominal fat (diaphragm normally press upward against heart all the time)
31
Q

What causes a right shirt in heart position?

A

End of deep inspiration
Standing up
Tall people

32
Q

What causes hypertrophy of left ventricle?

A

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

33
Q

What type of shirt is hypertrophy of left ventricle?

A

Left axis shift

34
Q

What causes hypertrophy of right ventricle?

A

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

35
Q

What type of shirt is hypertrophy of right ventricle?

A

Right axis shift

36
Q

How does mild ischemia cause a T wave abnormality?

A

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

37
Q

What is a T wave abnormality?

A

Becomes abnormal when normal sequence of repolarizatoin does not occur

38
Q

How does digitalis toxicity cause a T wave abnormality?

A

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

39
Q

How does digitalis toxicity relate to heart failure?

A

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

40
Q

How does arrhythmias relate to digitalis toxicity?

A

Slows the signals that start the SA node

Fewer signals, fewer arrhythmias

41
Q

What is a biphasic T wave?

A

Positive and negative deflection

42
Q

What is a inotropic cardiac drug propertiy?

A

Affects strength of contraction
Mostly positive inotropic effect
Stronger contractions

43
Q

What is a chronotropic drug property?

A

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

44
Q

What is considered to be a high voltage EKG?

A

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

45
Q

What causes a high voltage EKG?

A

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

46
Q

What causes a prolonged QRS complex?

A

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

47
Q

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

A

Prolonged is wider

48
Q

What does it mean if a QRS exceeds normal?

A

Usual cause is conduction block

49
Q

What is a normal QRS time?

A

0.12 seconds in humans

50
Q

What is current of injury?

A

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

51
Q

What does damaged cardiac muscle remain?

A

Partially or totally depolarized all the times

52
Q

What does injured muscle emit?

A

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

53
Q

What are causes of current of injury?

A

Local ischemia
Mechanical trauma
Infection

54
Q

How does local ischemia cause current of injury?

A

Caused by local coronary occlusions

Not enough nutrients available

55
Q

How does mechanical trauma cause current of injury?

A

Sometimes makes membranes so permeable that full repolarization cannot take place

56
Q

How does infection cause current of injury?

A

Damage muscle membranes

57
Q

What is the most common cause of current of injury?

A

Local ischemia

58
Q

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

A

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

59
Q

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

A

Old infarcts causing decreased muscle mass
Low voltage EKG
Prolonged QRS

60
Q

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

A

Fluid in pericardium
Pleural effusions
Emphysema

Physiology (70 decks)

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