Lecture 7 Cardiac

Question 1

Limb Lead I

Answer 1

Negative terminal is connected to the right arm
positive terminal is connected to the left arm
Looks at the heart form left to right

Question 2

Limb Lead II

Answer 2

Negative terminal of ECG is connected to the right arm
Positive terminal of ECG is connected to the left leg
Looks at heart form upper right to lower left

Question 3

Limb lead III

Answer 3

Negative terminal is connected to the left arm
Positive terminal is connected to the left leg
Looks at heart from the upper left to lower left

Question 4

Einthoven’s triangle

Answer 4

Two arms and left leg form apices of triangle

Question 5

Einthoven’s law

Answer 5

If the electrical potentials of any two of the three bipolar limb ECG leads are known at any given instant, the third can be determined by summing the first two

Question 6

Normally in the ventricles current flows?

Answer 6

form negative to positive primarily in the direction form the base of the heart toward the apex for most of the heart cycle until the very end

Question 7

In recording limb lead I: when the point where the right arm connects to the chest is negative with respect to the point where the left arm connects, the ECG records _______?

Answer 7

Positive

Question 8

In Limb lead II: when the right arm is negative with respect to the left leg the ECG records _________?

Answer 8

Positive

Question 9

Limb Lead III: When the left arm is negative with respect to the left leg, the ECG records _____?

Answer 9

Positive

Question 10

What is the angle for Lead I

Answer 10

0 degrees

Question 11

what is the angle for Lead II

Answer 11

60 Degrees

Question 12

what is the angle for Lead III

Answer 12

120 degrees

Question 13

In term of ECG the a vector is what

Answer 13

an arrow that points in the direction of the electrical potential generated by the current flow, with the arrowhead in the positive direction.
The length is proportional to the voltage of the potential

Question 14

When the vector in the heart is in a direction almost perpendicular to the axis of the lead, the voltage recorded in the ECG of this lead is very _____

Answer 14

low

Question 15

When the heart vector has almost the same axis as the axis of the lead, the _____ voltage of the vector is recorded

Answer 15

Entire

Question 16

What is the instantaneous mean vector

Answer 16

The summated vector of the generated potential at a particular instant

Question 17

_____ is horizontal and extends towards a person’s left side

Answer 17

Reference vector

Question 18

What is reference direction

Answer 18

0 degrees

reference vector is horizontal and extends towards a person’s left side

Question 19

what is the mean electrical axis of the heart

Answer 19

+ 59 degrees

Question 20

what results in the apex of the heart remaining positive with respect to the base of the heart

Answer 20

The average direction of the vector during spread of the depolarization wave through the ventricles

Question 21

T-Wave Vectorial Analysis

what repolarizes last

Answer 21

Endocardial areas

Question 22

T-Wave Vectorial Analysis

Ventricular vector during repolarization is toward ?

Answer 22

The apex of the heart

Question 23

The normal T-wave in all three bipolar leads is ______

Answer 23

Positive

Question 24

T-Wave Vectorial Analysis

what is the greatest portion of ventricular mass to repolarize first?

Answer 24

The entire outer surface of the ventricles, especially near the apex

Question 25

Atrial depolarization begins where

Answer 25

at the Sinus node

Question 26

The P-wave is normally ____ in all three leads

Answer 26

positive

Question 27

Vector direction of the P-wave is generally in what direction

Answer 27

direction of the axes of the three standard bipolar limb leads

Question 28

The spread of depolarization is slower where

Answer 28

In the atria than in the ventricles

Question 29

The Atrial T-wave is almost always obscured by what

Answer 29

The QRS complex

Question 30

what is the first area to become repolarized

Answer 30

The sinus node area

Question 31

At the beginning of repolarization the sinus node is ______ with respect to the rest of the atria

Answer 31

Positive

Question 32

A typical ECG may utilize how many leads

Answer 32

12 leads

Question 33

Each lead provides what

Answer 33

A different perspective on the voltage differences between areas of the heart

Question 34

In addition to the three conventional leads what are the additional leads in a common 12 lead

Answer 34

six standard leads (V1-V6) | three augmented leads (aVR, aVL, aVF)

Question 35

what is the mean electrical axis

Answer 35

is the direction of the electrical potential (negative to positive) form the base of the ventricles toward the apex 59 degrees

Question 36

what are some abnormal ventricular conditions that cause mean electrical axis deviation

Answer 36

``` Change in position of the heart in the chest hypertrophy of one ventricle bundle branch block fluid in pericardium pulmonary emphysema ```

Question 37

When is a high-voltage ECG said to occur and what is the most common cause

Answer 37

when the sum of the voltages of all the QRS complexes of the three standard leads is greater than 4 mV most common cause is hypertrophy of the ventricle

Question 38

What are the most common causes of decreased voltages in an ECG

Answer 38

cardiac myopathies, | caused by conditions surrounding the heart

Question 39

The normal QRS lasts how long

Answer 39

0.06 to 0.08 seconds

Question 40

Hypertrophy or dilation of the left or right ventricle can lead to the QRS?

Answer 40

being prolonged to 0.09 to 0.12 seconds (nl QRS duration is 0.06-0.09 seconds)

Question 41

what are some conditions that can cause bizarre patterns of the QRS

Answer 41

Destruction of cardiac muscle and replacement by scar tissue | multiple small local blocks in the conduction impulses at many points in the Purkinje system

Question 42

Different cardiac abnormalities cause part of the heart

Answer 42

To remain partially or totally depolarized all the time

Question 43

Current of injury flows?

Answer 43

between the pathologically depolarized and the normally polarized areas, even between heartbeats

Question 44

what are some abnormalities that cause current of injury

Answer 44

Mechanical trauma, infectious processes, Ischemia (most common cause)

Question 45

What is the most common cause for current of injury

Answer 45

Ischemia

Question 46

What are the effects of current of injury on QRS complex

Answer 46

Abnormal negative current flows from infarcted area and spreads toward the rest of the ventricles

Question 47

What is a J point

Answer 47

reference point for analyzing current of injury occurs at the very end of the QRS complex and is the point at which all parts of the ventricle, including the injured areas, have become depolarized