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CP1.06_Cardio_ZACHOW > Lecture 3 (ECGs) > Flashcards

Lecture 3 (ECGs) Flashcards

1
Q

Route of Electrical Conductance through Heart:

A
  1. SA node receives impulse from ANS afferents; pacemaker AP fires.
  2. Atrium depolarize and contract.
  3. AP reaches AV node. AV nodal delay occurs.
  4. AP travels through bundle of His to enter ventricles.
  5. AP travels to Purkinje fibers and then to ventricular myoctes.
  6. Ventricular depolarization and contraction occurs.
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2
Q

What fibers serve as a conduit to ventricular myocytes and coordinate ventricular contraction?

A

purkinje fibers from bundle of His.

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3
Q

Draw circle with limb leads and angles from heart:

A
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4
Q

V-leads: number and what part of the heart they are analyzing:

A
  • V1: Right ventricle
  • V2: Right ventricle
  • V3: Interventricular septum
  • V4: Interventricular septum
  • V5: Left ventricle
  • V6: Left ventricle
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5
Q

Limb leads: circle with degrees and part of heart being analyzed:

A
  • aVL: left upper lateral
  • I: left lateral
  • II: left lower lateral:inferior
  • aVF: apex:inferior
  • III: right lower later:inferior
  • aVR: right upper lateral
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6
Q

Label the waves:

A
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7
Q

Label the segments/intervals:

A
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8
Q

Order of waves on an ECG in normal sinus rhythm:

A
  • PQRST.
  • One P per QRS interval.
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9
Q

The P wave on an ECG represents:

A

atrial depolarization

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10
Q

Is atrial repolarization visible on an ECG?

A
  • No.
  • atrial repolarization is “buried” in QRS complex.
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11
Q

Location of PR interval on ECG and representation:

A
  • Start of P wave to beginning of Q wave.
  • Represents velocity of AV nodal conduction.
  • Length increased by heart block/PSNS.
  • Length decreased by SNS.
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12
Q

The QRS complex on ECG represents:

A

ventricular depolarization

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13
Q

Location of QT interval on ECG and representation:

A
  • Start Q wave to end T wave.
  • Represents entire period of ventricular depolarization and repolarization.
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14
Q

Location of ST segment on ECG and representation:

A
  • End of S wave to start of T wave.
  • Represents when ventricles are depolarized.
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15
Q

The T wave on ECG represents:

A

Ventricular repolarization.

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16
Q

When does SA nodal firing occur in relation to an ECG?

A
  • BEFORE the P wave.
  • P wave represents atrial depolarization.
  • SA nodal firing triggers atrial depolarization.
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17
Q

Steps in reading ECG (5):

A
  • Step 1: rhythm (atrial and ventricular). Consistent? Evenly spaced?
  • Step 2: rate (atrial and ventricular). Always start with ventricular.
  • Step 3: P waves. Present? At start of PQRST? One P wave before each QRS?
  • Step 4: PR interval. Increased (heart block/PSNS)? Decreased (SNS)?
  • Step 5: QRS segment. Wide? Narrow?
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18
Q

Effects of more muscle mass on an ECG (2):

A
  1. Greater deflection (more voltage)
  2. Longer intervals (more time to travel through)
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19
Q

One small box on an ECG in the vertical direction represents:

A

voltage (1mV)

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20
Q

One small box on an ECG in the horizontal direction represents:

A

time (0.04 seconds)

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21
Q

One large box on an ECG in the horizontal direction represents:

A

time (0.02 seconds)

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22
Q

Direction of depolarization for an upward deflection on an ECG:

A
  • depolarization is moving TOWARD measuring lead.
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23
Q

Direction of depolarization for a downward deflection on an ECG:

A
  • depolarization is moving AWAY from measuring lead.
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24
Q

Direction of depolarization when equal positive and negative deflection on ECG:

A
  • depolarization is moving PERPENDICULAR to measuring lead.
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25
Q

The first upward wave in a QRS complex is always which wave?

A
  • R wave.
  • Negative S wave always follows.
  • Q wave does not always have to be present.
26
Q

Direction of depolarization of an upward (positive) QRS:

A
  • depolarization toward measuring lead.
27
Q

Direction of depolarization of a downward (negative) QRS:

A

depolarization away from measuring lead.

28
Q

Direction of depolarization of an isoelectric QRS:

A

depolarization perpendicular to measuring lead.

29
Q

Limb leads I and II should always have (in a healthy heart):

A
  1. upward (positive) QRS complex deflection
    • ventricular depolarization
  2. upward (positive) T wave deflection
    • ventricular repolarization
30
Q

Limb lead aVR should always have (in a healthy heart):

A
  • Downward (negative) QRS complex deflection
  • Downward (negative) T wave deflection
31
Q

Left axis deviation (LAD):

A
  • a mean axis more negative than -30 degrees
  • left of aVL lead.
32
Q

Right axis deviation (RAD):

A
  • a mean axis greater than 90 degrees.
  • left of aVF lead.
33
Q

A normal mean axis is in between:

A
  • 0 to 90 degrees; usually 50-60 degrees.
34
Q

Three steps in determining the mean axis (left or right axis deviation):

A
  1. Inspect leads I and II. If both upward, normal. If not, Step 2.
  2. Find most isoelectric limb lead. Mean axis perpendicular to this lead.
  3. Find lead perpendicular to isoelectric lead (Step 2). If QRS upward in this lead, axis toward lead. If QRS downward in this lead, axis away from lead.
35
Q

Causes of left axis deviation:

A
  • left ventricular hypertrophy
  • aortic valve stenosis
  • hypertension

MORE MUSCLE MASS = MORE DEPOLARIZATION

36
Q

Causes of right axis deviation:

A
  • right ventricular hypertrophy
  • pulmonary hypertension
  • pulmonic valve stenosis

​MORE MUSCLE MASS = MORE DEPOLARIZATION

37
Q

What do electrocardiograms (ECGs) represent?

A
  • cardiac electrical activity only
  • DO NOT REFLECT CARDIAC MECHANICS
38
Q

Neurotransmitters and receptors used by the PSNS and SNS to mediate SA nodal firing and overall effect:

A
  • SNS: Norepi acting on β1 adrenoreceptors. Increase firing/HR.
  • PSNS: ACh acting on CM2 receptors. Decrease firing/HR.
39
Q

What is the red box indicating?

A
  • SA nodal firing
    • occurs before P wave (atrial depolarization).
    • mediated by SNS and PSNS.
40
Q

How does the PSNS slow heart rate (specifically):

A
  1. ACh binds to CM2 receptors.
  2. CM2-R activation causes opening of K+ channels and K+ efflux.
  3. RMP lowered, takes longer to reach threshold.
  4. HR decreases.
41
Q

What leads should the P wave be analyzed on?

A

Leads II and V1.

42
Q

What do the upstrokes and downstrokes of the P wave represent, and what leads should the P wave be analyzed on?

A
  • Leads II and V1.
  • Upstroke: right atrium depolarization.
  • Downstroke: left atrium depolarization.
43
Q

If the upstroke and downstroke of the P waves are not equal in magnitude, what may be present?

A
  • atrial hypertrophy in the larger magnitude stroke.
  • upstroke: right atrium
  • downstroke: left aftrium
44
Q

What qualifies normal sinus rhythm?

A
  • HR between 60-100 BPM.
  • PQRST; one P per QRS.
45
Q

What does the red box indicate, and what is this depolarization dependent on?

A
  • P wave
  • Sodium-dependent depolarization (myocardium plateau potentials)

ALWAYS CHECK UPSTROKE VERSUS DOWNSTROKE FOR ATRIAL HYPERTROPHY

46
Q

What does the red box indicate, and what is this depolarization dependent on?

A
  • AV nodal delay
    • time it takes to relay depolarization from the atrium to the ventricles through AV node.
  • calcium-dependent depolarization (AV node = pacemaker cells)
47
Q

What does the red box indicate, and what is this depolarization dependent on?

A
  • QRS complex (ventricular depolarization)
  • sodium-dependent depolarization
48
Q

The QRS complex on an ECG is directly measuring the function of:

A
  • conductive hardware of the heart: bundle branches, Purkinje fibers, and ventricular myocardium.
  • Wider QRS: slower conductance.
49
Q

Normal and abnormal QRS segment lengths:

A
  • Normal:
    • Start of Q to end of S is <3 small boxes (120msec).
  • Abnormal:
    • Start of Q to end of S is >3 small boxes (120msec).
50
Q

An abnormally long QRS (>3 small boxes; 120msec) may be indicative of:

A
  • defect in fast conducting pathway.
  • left or right bundle branch block.
51
Q

When does the aortic valve open on an ECG?

A
  • ST interval.
  • Systolic ejection occurs during ST interval.
52
Q

When does the aortic valve shut on an ECG?

A
  • end of T wave following slow ejection.
53
Q

When does the mitral valve open on an ECG?

A
  • Between T wave and P wave after isovolumetric relaxation.
54
Q

When does the mitral valve shuts on an ECG?

A
  • R wave of QRS complex.
55
Q

When does diastole occur on an ECG?

A
  • End of T wave to start of R wave.
56
Q

When does isovolumetric contraction occur on an ECG?

A
  • QRS complex and S wave.
57
Q

When does systolic ejection (overall, rapid and slow) occur on an ECG?

A
  • ST interval.
    • rapid ejection: start of ST interval.
    • slow ejection: T wave.
58
Q

When does isovolumetric relaxation occur on an ECG?

A

after T wave.

59
Q

When does systole occur on an ECG?

A
  • R wave to end of T wave.
60
Q

How to determine heart rate on ECG:

A
  1. Start with R wave nearest gridline.
  2. Count subsequent gridlines:
    • 300, 150, 100, 75, 60, 50 BPM.
  3. Find where next R wave sits.
61
Q

Heart Rate: Normal, bradycardia, and tachycardia values:

A
  • Normal: 60-100 BPM
  • Bradycardia: <60 BPM
  • Tachycardia: >100 BPM

CP1.06_Cardio_ZACHOW (10 decks)

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