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AP EXAM 4 > LECTURE 24 10/31/22 (LECTURE 12 SLIDES: THE NORMAL ELECTROCARDIOGRAM) > Flashcards

LECTURE 24 10/31/22 (LECTURE 12 SLIDES: THE NORMAL ELECTROCARDIOGRAM) Flashcards

1
Q

A large QRS complex will indicate the lead/electrode is closer to the heart.

What is another indication for large magnitude of the QRS complex or high voltage EKG?

A

The lead could be actually picking up more cardiac tissue

Hypertrophy of the ventricular wall will give us more tissue to depolarize. More tissue depolarization will lead to a QRS complex greater than 2.0 mV*** (14:15)

**This is in regards to the bipolar leads/ frontal plane

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2
Q

Per lecture, everyone has some form of ____________ when they reach the age of 30 to 40 that will lead to increase afterload and resulting in some LVH.

A

Aortic Stenosis (15:15)

This will result in a high voltage QRS complex.

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3
Q

What will indicate the entire ventricle has been depolarized on a EKG?

What will roughly indicate the amount of time the ventricles are squeezing on a EKG?

A

ST segment/ 0.16 seconds(15:55)

QT interval/ 0.35 seconds (16:00)

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4
Q

Compare the bipolar and precordial leads in terms of how the leads are viewing the heart?

A

The bipolar leads (3-limb leads) are looking at activity of the heart from the frontal plane.

The precordial leads (V1-V6) will give us a little bit more information because they are sitting right on top of the heart and the lateral side. So they are looking at activity of the heart from front to back. (17:30)

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5
Q

When graphing paper is fed through an EKG machine, what is the paper feed rate/spin rate?

What is the length of one little box? Time?

What is the length of one big box? Time?

How many little boxes make up a one second EKG feed? Big boxes in one second?

A

25 mm/second (18:43)

1 mm/ .04 seconds

5 mm/ .20 seconds

25 little boxes/ 5 big boxes

(19:30)

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6
Q

How many horizontal little boxes are in 5 second EKG paper feed?

How many big boxes?

How many mm of paper has been fed?

A

125 little boxes
(5 secs/0.04 secs per little box)

25 big boxes
(5 secs/0.20 secs per big box)

125 mm of paper
(25 mm per sec x 5 sec)

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7
Q

What is the RR interval?

How long is a perfect RR interval?

How do you calculate HR using the RR interval?

How many small boxes are between a perfect R-R interval?

A

RR interval is the period of time between two R-waves.

0.83 seconds

60 seconds/ RR interval = BPM
(60 secs / 0.83 secs) = 72 bpm

21 small boxes
(0.83/.04 = 20.75)

(21:00)

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8
Q

What direction are the three “eye balls” looking at in the bipolar leads?

If you plot this out, what shape do you get? What the angle in each corner?

A

Lead 1 Eyeball: Looking across left to right.

Lead 2 Eyeball: looking up from left leg to right arm.

Lead 3 Eyeball: looking up from left leg to left arm. (24:00)

Equilateral Triangle, 60 degrees in each corner.
180 degrees total (24:45)

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9
Q

In a completely healthy 30-year-old, which bipolar limb lead will display the largest magnitude of the QRS complex?

The voltage seen in this lead should correlate with the sum of what values?

What law is this?

A

Lead II

The deflection of the QRS complex in lead II should equal the sum of the deflection of the QRS complex in lead I and III.
(25:55)

Einthoven’s Law
Lead I + Lead III = Lead II

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10
Q

How do you calculate the magnitude of a QRS deflection?

A

R-wave value subtracted from value of Q or S wave (whichever one is lower).

This value will be the deflection of the QRS complex.

(27:20)

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11
Q

Where did the ‘K’ come from in EKG?

A

Willem Einthoven developed the basics of the modern EKG. At the time, the language used in most scientific journals was German so the term was spelled with a K. The K has stuck in common practice and despite the English spelling, we use the abbreviations EKG and ECG interchangeably now. (28:15)

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12
Q

If Einthoven’s triangle is broken down into vectors. Where is the start point or 0 degree located?

A clockwise movement from the start point to end point will be how many degrees?

What about counter clockwise?

A

The eyeball (positive electrode) of Lead I.

+180 degrees going clockwise

-180 degrees going counter clockwise

(30:00)

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13
Q

How many degrees are between the positive electrode of lead I to the negative electrode of lead II?

A

-120 degrees

(31:30)

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14
Q

How many degrees is the mean electrical axis of the heart?

A

Mean electrical axis is +59 degrees heading toward the positive end (eyeball) of lead II. (32:30)

Normal electrical axis is pointed to the left foot (57:59)

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15
Q

What does the mean electrical axis tell you?

A

Mean electrical axis is referring to which direction and how much magnitude do we have of depolarization during the normal action potential in the heart. (32:45)

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16
Q

What represents the average sum of all of the waves of depolarization that are occurring simultaneously.

A

Mean Electrical Axis (34:34)

Some of all currents averaged out.

17
Q

As depolarization moves through the septum, the length of the red arrow indicates what?

What lead is the current pointing to?

What kind of deflection will this result in?

A

The length red arrow indicates the amount of current is going through the septum at that point in time. (37:38)

Current is pointing to lead II.

Small positive deflection.

18
Q

What is going on in this picture?

A

The depolarization is around the halfway point.
The red arrow is pointing to the left leg, the increase length of arrow indicates more current.
This correlates with a larger positive deflection. (39:00)

19
Q

What is going on in this picture?

A

The depolarization is beyond the halfway point.

There is still positive deflections, but going down now. QRS complex has peaked, but still above base line.

Current is still moving toward the left foot. (40:35)

20
Q

What is going on in this picture?

A

The heart is almost completely depolarized, the only place left on the heart the is far left lateral ventricle.

The current will now move to the only area that has yet to be depolarized (only positive charge spot left on the heart).

Current now is pointed toward the left shoulder.

(42:42)

21
Q

Why are there negative deflections in lead II and III, but a positive deflection on lead I?

A

The current is moving toward the only positive charge (non-depolarized) left on the heart which is toward the left shoulder.

The current is moving toward the eyeball of lead I, causing a positive deflection/ above baseline.

The current is moving away from the eyeballs of lead II and III which will cause a negative deflection/ below baseline. (42:35)

22
Q

When will a lead not see a current?

A

If the movement of a current is perpendicular of the eyeball, it will register as 0 deflection.

If a cell is completely depolarized, repolarized, or at rest. There will be no current, and 0 deflection as well.

(47:21)

23
Q

What is going on in this picture? (Insert 1E)

A

The entire ventricle has been depolarized.

Since the ventricles are now at the same electrical state there should be no current. Eyeballs will register a 0 deflection reading. (49:45)

24
Q

Large current (arrow) will result in a _______ deflection.

A small current will result in a _____deflection.

A

Large deflection

Small deflection

**Now whether these deflections are positive or negative will depend on direction of the arrow/current.
(52:23)

25
Q

What are the two types of deviation for the mean electrical axis?

A

Deviation to the left side of the body.

Deviation to the right side of the body.

(58:00)

26
Q

What is the reading Lead I’s QRS magnitude deflection?

What is the reading of Lead III’s QRS magnitude deflection?

Estimate the mean electrical axis.

What kind of axis shift is this and cause of this shift?

A

Lead I: +1.5 mV

Lead III: -1.0 mV

Mean arterial axis is the intersection point of Lead I and III. (-10 to -15 degrees)

Left axis shift caused by LVH. (93:00)

27
Q

How does obesity cause a shift in mean electrical axis?

A

Obese individuals will have a large amount of adipose tissue that will cause abdomen to be shifted up and push against the diaphragm. The force of the diaphragm will angle the apex of the heart to the left side of the body.

This will cause a left axis deviation on the bipolar limb leads. (96:24)

28
Q

How will the mean electrical axis differ in an individual sitting up and laying down.

A

When the patient lays down the abdomen will apply pressure to the diaphragm. The force of the diaphragm will nudge the heart the up.

This will cause a slight left shift to the mean electrical axis (97:21)

29
Q

How will the mean electrical axis be affected in paralyzed patients?

A

Paralyzed patients will have low lung volume will cause the diaphragm to be higher up nudging the heart to cause a left shift to the mean electrical axis (98:02)

At a deep exhalation, we would have a low lung volume and plenty of room for the heart to shift to the left side of the body.

30
Q

How will the mean electrical axis be affected with hypertrophy of one side of the heart.

A

A thickened left ventricular wall means more area for the current to move through, specifically current coming from the right side of the heart. This will result in a left shift to the mean electrical axis. (98:10)

31
Q

How will the mean electrical axis be affected with a left bundle branch block?

A

A left BBB will delay the depolarization to the left side of the heart. This will give the left side of the heart extra time seeing current from the right side of the heart that has already depolarized. This will result in a left shift to the mean electrical axis. (99:00).

32
Q

What are factors stated in lecture that can shift the mean electrical axis to the left?

A
  1. Old Age
  2. Ventricular Hypertrophy (aortic stenosis, systemic hypertension)
  3. Ischemia to left side of the heart.
  4. Left Bundle Branch Block
  5. Low Lung Volume
  6. Laying Down
  7. Being Obese

(100:00)

33
Q

How will really deep inspiration or over inflated lungs affect the mean electrical axis.

A

It would cause the apex of the heart to point straight down causing a right shift to the mean electrical axis. (106:00)

34
Q

What is the reading Lead I’s QRS magnitude deflection?

What is the reading of Lead III’s QRS magnitude deflection?

Estimate the mean electrical axis.

What kind of axis shift is this and cause of this shift?

A

Lead I: -2.2 mV

Lead III: 1.3 mV

Mean arterial axis is the intersection point of Lead I and III. (170 degrees)

Right axis shift caused by hypertrophy of right ventricle. (111:49)

35
Q

What are factors stated in lecture that can shift the mean electrical axis to the right?

A
  1. Hypertrophy of the right ventricle (pulmonary hypertension, pulmonary valve stenosis, inter-ventricular septal defect).
  2. COPD
  3. Hyperinflation of the lungs/ Deep inspiration.
  4. Right Bundle Branch Block
  5. Very thin people will have right pointed to right side of the body
  6. Young People

(112:09)

36
Q

What does a left bundle branch block look like in Lead V1?

What does a left bundle branch block look like in V6?

A

Lead V1 has a wide negative S wave.

Lead V6 has a “rabbit ear” pattern.

(115:03)

AP EXAM 4 (8 decks)

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