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Cardiology > Chapter 4 : Vectors and the Basic Beat > Flashcards

Chapter 4 : Vectors and the Basic Beat Flashcards

1
Q

What is the sum of all ventricular vectors?

A

Electrical Axis

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2
Q

What do vectors represent?

A

Energy and direction

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3
Q

What are electrodes?

A

Sensing devices that pick up the electrical activity occurring beneath them

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4
Q

When a positive electrical impulse is moving away from the electrode the ECG machine converts it into a what?

A

Negative Wave

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5
Q

When a positive electrical impulse is towards from the electrode the ECG machine converts it into a what?

A

Positive Wave

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6
Q

What is the position for leads V1 and V2?

A

Each side of the sternum at fourth intercostal space

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7
Q

What is the position for lead V4?

A

Fifth intercostal space in the midclavicular line

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8
Q

What is the six limb leads? (Hexaxial system)

A

I, II, III, aVR, aVF, aVL

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9
Q

What is the lead aVR?

A

The augmented unipolar right arm lead faces the heart from the right side and is usually orientated to the cavity of the heart. Therefore, all the deflections P, QRS and T are normally negative in this lead

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10
Q

What is the lead aVF?

A

The augmented unipolar left leg lead, orientated to the inferior surface of the heart Precordial Chest Leads

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11
Q

What is the lead aVL?

A

The augmented unipolar left arm lead faces the heart from the left side and is orientated to the anterolateral surface of the left ventricle

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12
Q

How many degrees apart are all the leads using the haxaxial system?

A

30 degrees

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13
Q

The six limb leads view the heart at what angle?

A

Coronal

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14
Q

The six precordial leads view the heart at what angle?

A

Transverse

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15
Q

The Hexaxial System

A
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16
Q

What is the normal duration of the P wave?

A

0.08 to 0.11 seconds

17
Q

What does the P wave represent?

A

Electrical depolarization of the atria

18
Q

The axis of the P wave is usually directed in what direction?

A

Downward and to the left

19
Q

What does the TP wave represent?

A

Repolarization of the atria

It deflects in the opposite direction of the P wave but is usually not seen because it occurs at the same time as the QRS wave.

20
Q

If the PR segment is depressed more than 0.8mm it could be a sign of what?

A

Pericarditis or atrial infarct

21
Q

What happens in the PR segment?

A

The initiation of electrical impulse in the SA node up to the moment of ventricular depolarization

22
Q

What is the normal duration of the PR segment?

A

0.12 - 0.20 seconds (3 to 5 little boxes)

23
Q

What does the QRS complex represent?

A

Ventricular depolarization

24
Q

The Q wave can be present or absent

A
25
Q

Q wave significance

A

Can be benign, or it can be a sign of dead myocardial tissue. The Q wave is considered significant if it is 0.03 seconds or wider, or its height is equal or greater than 1/3 the height of the R wave.

If it meets that criteria it indicates a Myocardial Infarction (MI)

26
Q

What happens during the R wave peak time?

A

The amount of time it takes the electrical impulse to travel from the purkinje system in the endocardium to the surface of the epicardium immediately under an electrode.

27
Q

How long is the R wave peak time?

A

Up to 0.035 seconds in the right precordial leads (v1 and v2) because the right ventricle is thin compared to the left.

0.045 seconds in the left precordial leads (v5 and v6) because of the left ventricles thickness

28
Q

ST elevations?

A

It can vary up to 1mm from baseline in limb leads and 3mm in precordials.

Any ST elevation in a symptomatic patient should be considered significant and representative of myocardial injury or infarction.

29
Q

What does the T wave represent?

A

Ventricular repolarization

30
Q

Should the T wave be asymmetric or symmetric?

A

Asymmetric

31
Q

Why is the T wave in the same direction as the QRS if it represents repolarization?

A

The increased pressure on the endocardium during contraction, the repolarization wave travels in the opposite direction from the epicardium back to the endocardium.

32
Q

What does QTc stand for? And what is its purpose?

A

QT corrected interval

It is corrected for heart rate. As the heart rate decreases, the QT interval lengthens. And as the heart rate increases the QT interval shortens.

The QTc is less than 0.45 in males and 0.46 in females. Anything above this is considered prolonged. Considered at risk of lethal arrhythmias.

33
Q
A

Cardiology (41 decks)

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