Intro to ECG (complete)

Question 1

Discuss the anatomy and function of cardiac structures responsible for generation and spread of cardiac depolarization which produce a normal heart beat

Answer 1

• SA node = pacemaker => where electrical impulses begin
• Then go through internodal tracts =>activates depolarization in atrium
• Goes to AV node => then brief delay
• then sent to bundle of His => activates ventricles (via left and right bundles)
• Spread to Purkinje fibers => activate ventricular cell depolarization and contraction

Question 2

What is the significance of a P wave?

Answer 2

Atrial depolarization

Question 3

What is the significance of a PR interval

Answer 3

• Measure AV node conduction time

- Normal PR is 0.12 to 0.20 seconds

Question 4

What is the significance of the QRS complex?

Answer 4

Ventricular depolarization

Q = negative
R = positive
S = late negative deflection

Question 5

What is the significance of the QT interval?

Answer 5

Total duration of depolarization and repolarization

Question 6

What is the significance of a T wave?

Answer 6

Ventricular repolarization

Question 7

What is the significance of a U wave?

Answer 7

Not supposed to be there! Indicates bad things!

Question 8

Which leads monitor the RV?

Answer 8

V1, V2

Question 9

Which leads monitor the LV?

Answer 9

V5, V6

Question 10

Describe the EKG of ventricular hypertrophy

Answer 10

Remember: more muscle => more volts => greater amplitude in EKG

• Higher R wave
• T wave is negative

Question 11

Describe the EKG of left ventricular hypertrophy

Answer 11

• Large positive R waves in V5 and V6

- Large negative S waves in V1

Question 12

Describe the EKG of right ventricular hypertrophy

Answer 12

• Big R waves in right-sided leads (V1, V2)

Question 13

Describe the EKG of myocardial ischemia

Answer 13

Blood supply is insufficient to meet O2 demands

• ∆s ventricular repolarization => affects ST segment & T wave

Question 14

Describe the EKG of stress-induced myocardial ischemia in presence of fixed coronary obstruction

Answer 14

Depression of ST segment

• go look at ppt slide title “stressed-induced myocardial ischemia”

Question 15

Describe the EKG of myocardial ischemia due to acute coronary artery obstruction during low O2 demand

Answer 15

T wave inversion

• Go look at ppt slide titled “during acute coronary syndrome”

Question 16

Describe the EKG of myocardiac infarction

Answer 16

• Produces a Q wave (negative deflection in leads over myocardium)
• Needs to be present in multiple leads (must confirm it’s actually an infarct of a specific area)

Question 17

At what point does a Q wave indicate infarcted tissue?

Answer 17

1) ≥ 1/4 the amplitude of R wave
2) ≥ one small box wide (0.04seconds)
3) usually in at least 2 leads reflecting same region of left ventricle

Question 18

At what point would you expect to see a peaked T-wave in the progression of a transmural myocardial infarct?

Answer 18

• At the very moment when the artery is obstructed completely
• You rarely see this in an ER (no one is there right away)

Question 19

At what point would you expect to see a T-wave inversion in the progression of a transmural myocardial infarct?

Answer 19

• Happens very quickly

- You will usually see this in the ER (sometimes not though)

Question 20

At what point would you expect to see ST elevation in the progression of a transmural myocardial infarct?

Answer 20

• Happens when you get a massive MI

- Involves to the whole frickin muscle (all layers)

Question 21

At what point would you expect to see a Q-wave, ST-elevation, T-inversion in the progression of a transmural myocardial infarct?

Answer 21

• Means it’s late in the MI progression
• Q wave indicates dead tissue
• Can see this only 14 to 24 hours after initial peaked T-wave

Question 22

What’s the difference between transmural and subendocardial MIs?

Answer 22

Transmural:

• ST elevation w/ Q waves
• Involve all layers

Subendocardial

• ST depression, no Q wave
• inner layer

Question 23

Describe the EKG of hypercalcemia

Answer 23

Shortened QT

Question 24

Describe the EKG of hypocalcemia

Answer 24

Lengthened QT

• may be associated w/ life threatening ventricular arrhythmias

Question 25

Describe the EKG of hyperkalemia

Answer 25

• ^ T wave voltages (distinct peaked, symmetrical appearance)
• At higher levels => P waves flattened, QRS and T widened, a broad S wave
• At very high levels => sinusoidal pattern w/o P or R waves

A good time to go look at the ppt

Question 26

Describe the EKG of hypokalemia

Answer 26

• Prolonged QT
• Prominent U waves frequent
• T waves inverted