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Medical Physiology > Exam #2: Electrocardiography > Flashcards

Exam #2: Electrocardiography Flashcards

1
Q

What is depolarization?

A

Switching of charges on the cell membrane; positive outside relative to negative inside

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2
Q

How is current related to depolarization & repolarization? How is this related to the ECG tracing?

A
  • Current only flows when there is a depolarization or repolarization event
  • The ECG electrode can only detect current
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3
Q

By convention, flow of a positive ion away from the positive pole of an electrode appears as what? What about the opposite?

A
  • Away= negative deflection
  • Toward= positive deflection
Away= down 
Toward= up
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4
Q

What is the electrocardiogram?

A

A summation of all the depolarizations and repolarizations occurring in cardiac cells

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5
Q

What is the p-wave? What is the normal duration of the p-wave?

A
  • A summation of atrial myocyte depolarization

- 0.06-0.11 sec

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6
Q

What step theoretically comes before atrial depolarization?

A

SA node generation of impulse that CANNOT be seen on ECG

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7
Q

What does the PR interval correspond to? What is the normal duration of a PR interval?

A
  • Atrial myocyte plateau phase (Ca++ IN & K+ OUT)

- 0.12-0.2 sec

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8
Q

What causes the QRS complex? What is the normal duration of a QRS complex?

A
  • Ventricular depolarization

- 0.03-0.12 sec

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9
Q

What is the Q of the QRS? Define Q-wave.

A

Septal depolarization, which is positive current moving away from the positive electrode

Any negative defection before the R-wave is a Q-wave

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10
Q

What is the R of the QRS?

A

Ventricular muscle depolarization spreading toward electrode

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11
Q

What is the S of the QRS?

A

Ventricular muscle depolarization spreading away from the electrode

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12
Q

What is the ST segment?

A

Plateau phase of the ventricular myocyte

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13
Q

What is the T-wave?

A

Ventricular myocyte repolarization

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14
Q

Is atrial repolarization viewed?

A

NO, it is buried in the QRS

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15
Q

What is the chart speed of an ECG tracing?

A

25 mm/sec

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16
Q

How much time passes between 5mm?

A

0.2 sec (1 large box)

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17
Q

How much time passes between 1mm?

A

0.04 sec (1 small box)

18
Q

What corresponds to 1.0 mV?

A

10mm (2x large boxes vertically)

19
Q

Where is lead I?

A

+ left arm to - right arm

20
Q

Where is lead II?

A

+ left foot to - right arm

21
Q

Where is lead III?

A

+ left foot to - left arm

22
Q

Where the standard limb leads bipolar or unipolar? What about the augmented limb leads?

A 
Standard= bipolar
Augmented= unipolar
23
Q

Where is aVR?

A

+ right arm

24
Q

Where is aVL?

A

+ left arm

25
Q

Where is aVF?

A

+ left foot

26
Q

Draw the hexaxial lead system.

27
Q

List the placement of the precordial leads.

A 
V1= R. sternal border 4th intercostal space 
V2= L. sternal border, 4th intercostal space
V4= Midclavicular, left 5th intercostal space 
V3= between V2 & V4 
V5= anterior axillary line, in line with V4 
V6= in line with V4 & V5, midclavicular
28
Q

List the R-R rate as determined by counting “large boxes.”

A 
1= 300
2= 150
3= 100
4= 75
5= 60
6= 50
7= 42
29
Q

What causes left axis deviation?

A 
End of deep expiration
Supine 
Obesity 
Hypertrophy (systemic, valvular disease, congenital) 
LBBB (occurs with wide QRS)
30
Q

What causes right axis deviation?

A 
End of deep inspiration
Moving to standing 
Tall 
Hypertrophy (pulmonary valve stenosis, pulmonary HTN, congenital) 
RBBB (with wide QRS)
31
Q

What is the normal PR-interval?

A

0.12-0.2 seconds

3-5 small boxes

32
Q

What is the normal QRS duration?

A

0.03-0.12 seconds

<1-3 small boxes

33
Q

What is the normal QT interval?

34
Q

What causes increased voltage of QRS?

A

Hypertrophy

Thin chest

35
Q

What causes decreased voltage of QRS?

A

Previous MI
Fluid in pericardium or pleural space
Large chest

36
Q

What are the clinical manifestations of hyperkalemia on ECG?

A

Tall, peaked T-waves

37
Q

What are the clinical manifestations of hypokalemia on ECG?

A

Decreased T-wave amplitude
Inverted T-wave
U-waves

38
Q

What is the pathophysiology underlying a PR interval that is longer than normal?

A

1st degree AV block

39
Q

What is the pathophysiology underlying a PR interval that is shorter than normal?

A

Junctional rhythm or accessory pathway between the atria & ventricles

40
Q

What is the pathophysiology underlying a few very large & wide QRS complexes appearing in a lead with mostly normal QRS complexes?

41
Q

What is the pathophysiology underlying all very large & wide QRS complexes?

A

Ventricular rhythm

Extreme hyperkalemia

42
Q

What is the pathophysiology underlying a p-wave that occurs without a subsequent QRS complex?

Medical Physiology (74 decks)

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