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CVPR Exam 1 > ECG as diagnostic tool > Flashcards

Flashcards in ECG as diagnostic tool Deck (43):
1

Is the Q wave positive or negative?

• Negative

2

What does the QT interval represent?

• The sum total duration of depolarization and repolarization

3

What's the normal PR interval?

• 0.12 - 0.2 seconds

4

The thick lines, forming large boxes, represent how many seconds?

• 0.2 seconds per every large box
• 0.5mV per every large box on the y-axis

5

Each tiny box is 1mm wide and that represents what?

• Time = x-axis, represents 0.04 seconds every mm
• Every 5 large boxes is one second or 1000 miliseconds

6

What is the paper speed in the ECG?

• 25mm/second

7

What is the normal duration of the QRS complex?

• 0.06 - 0.10 seconds

8

Is the S wave negative or positive?

• Negative

9

Is the R wave positive or negative?

• Positive

10

Using the lines on the ECG paper, how do you determine heart rate?

• HR = 300/(# of heavy lines btw QRS's
○ Should be 3-5 heavy lines btw QRS's
○ Less than 3, that's tachycardia
○ More than 5, bradycardia
• HR = 1500/(# of mm between QRS's

11

In what leads will the QRS complex be upright (positive deflection)?


• Left and lateral leads

12

In what leads will the QRS complex be downward (negative deflection)?

• Right sided leads

13

What do ischemic changes in the heart do to the ECG?




• Alter ventricular repoloarizatoin
• Affect the ST segment and the T wave

14

What does ST elevation suggest?

• Sign of transmural injury in an acute coronary syndrome
• Usually a clot due to platelet aggregation obstructing a coronary artery
• Injury often associated with an acute myocardial infarction
• If clot is busted fast enough, ST elevation can regress

15

A T wave inversion should make you think…?

• Acute coronary artery obstruction (when you see it during low oxygen demand)

16

What other wave, besides an ST depression, can you look at to see an acute coronary artery obstruction?

• During low oxygen demand, acute coronary artery obstruction leads to T wave inversion

17

What causes an ST depression?

• Ischemia due to sudden high oxygen demand in the presence of a fixed coronary obstruction
• Thus, if you see ST depression in an emergent situation, very likely a fixed coronary obstruction

18

What leads monitor the Right ventricle?


• V1 and V2 monitor the RV

19

What leads monitor the Left ventricle?

• V5 and V6 monitor LV

20

What, on the ECG is indicative of hypertrophy in the ventricle?

• A super large/tall R wave, in particular in V5 and V6, which are monitoring the left ventricle

21

What leads would you expect to show large/tall R waves in left ventricular hypertrophy?


• Left-sided leads
• I, aVL, V5, V6

22

What leads would you expect to show large/tall R waves in RIGHT ventricular hypertrophy?

• Right sided leads
• V1, V2

23

What do you think when you see a large Q wave?

• This is normally indicative of a transmural blockage/infarct

24

What are you likely to see on the ECG with a transmural infarct?


• Q waves
• ST elevation

25

What are you likely to see on the ECG with a subendocardial infarct?

• ST depression
• NO Q wave

26

When you are trying to find an anterior vs. inferior infarct, what leads will you need to look at?

• V1, V2 are anteroseptal wall
• V3, V4 are anterior wall
• V5, V6 are anterolateral wall
• II, III, Avf are inferior wall
• I, aVL are high lateral wall

27

What is considered a prolonged QT interval?


• QT interval more than 1/2 the R-R interval is considered prolonged
• Could be caused by:
○ Hypocalcemia, hypokalemia, hypomagnesemia
○ Class1A or 3 anti-arrhytmic drugs
○ Hypothermia
○ Congenital long QT syndrome

28

What might cause a prolonged QT interval?

• QT interval more than 1/2 the R-R interval is considered prolonged
• Could be caused by:
○ Hypocalcemia, hypokalemia, hypomagnesemia
○ Class1A or 3 anti-arrhytmic drugs
○ Hypothermia
○ Congenital long QT syndrome

29

If you have hyper or hypo calcemia, what would that look like on the ECG?

• Hypercalcemia = shortened QT interval
• Hypocalcemia = prolonged QT interval

30

If you have hypokalemia, what would you expect to see on the ECG?

• T-wave elevation, and merging with U-wave
• Plus, it's kinda rare to have a U-wave anyway

31

In hyperkalemia, what is the ECG finding?

• Depends on severity
• Mild - tall T waves, peaked and symmetrical
○ 5.5 -7.5 mmol/L
• Moderate - P and R waves flatten, QRS and T broaden and big S waves develop
○ 7.5 - 9 mmol/L
• Severe - P and R waves gone, S and T waves broaden, looks like a Sine wave
○ Over 9 mmol/L

32

What is the normal P-R interval? What does it mean if that interval is prolonged?

The period of time from the onset of the P wave to the beginning of the QRS complex is termed the P-R interval, which normally ranges from 0.12 to 0.20 seconds in duration.
*If the P-R interval is >0.20 sec, there is an AV conduction block
* first-degree heart block if each impulse from the atria is still able to be conducted into the ventricles.

33

What is the normal QRS duration and what might it mean if that is prolonged?

The duration of the QRS complex is normally 0.06 to 0.10 seconds.
* If the QRS complex is prolonged (> 0.10 sec), conduction is impaired within the ventricles.
* This can occur with bundle branch blocks or whenever a ventricular foci (abnormal pacemaker site) becomes the pacemaker driving the ventricle.
* ectopic foci nearly always results in impulses being conducted over slower pathways within the heart, thereby increasing the time for depolarization and the duration of the QRS complex.

34

Leads V1 and V2 cover what ventricular region?

Anteroseptal - right ventrical

35

Leads V3 and V4 cover what ventricular region?

Anteroapical - both ventricals

36

Leads V5 and V6 cover what ventricular region?

Anterolateral - left ventricle

37

What might ST elevation mean in Leads II, III, and aVF?

ST elevation in leads II, III and aVF indicate inferior wall ischemia

38

What might ST elevation mean in Leads V5 and V6?

ST elevation in leads V5 and V6 indicate left ventricular anterolateral ischemia.

39

What does the ST segment represent?

The isoelectric period (ST segment) following the QRS and ending at the beginning of the Twave is the time at which both ventricles are completely depolarized. This segment roughly corresponds to the plateau phase of the ventricular action potentials.

40

Why is the ST segment so important in using he ECG as a diagnostic tool?

The ST segment is very important in the diagnosis of ventricular ischemia or hypoxia because under those conditions, the ST segment can become either depressed or elevated.

41

What does the QT interval represent?

The Q-T interval represents the time for both ventricular depolarization and repolarization to occur, and therefore roughly estimates the duration of an average ventricular action potential. This interval can range from 0.20 to 0.40 seconds depending upon heart rate.

42

What can decrease the QT interval?

This interval can range from 0.20 to 0.40 seconds depending upon heart rate. At high heart rates, ventricular action potentials shorten in duration, which decreases the Q-T interval.

43

Why is the QT interval important for using the ECG as a diagnostic tool?

Because prolonged Q-T intervals can be diagnostic for susceptibility to certain types of tachyarrhythmias, it is important to determine if a given Q-T interval is excessively long.