Flashcards in Intro to ECG (complete) Deck (26)
Discuss the anatomy and function of cardiac structures responsible for generation and spread of cardiac depolarization which produce a normal heart beat
- 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
What is the significance of a P wave?
What is the significance of a PR interval
- Measure AV node conduction time
- Normal PR is 0.12 to 0.20 seconds
What is the significance of the QRS complex?
Q = negative
R = positive
S = late negative deflection
What is the significance of the QT interval?
Total duration of depolarization and repolarization
What is the significance of a T wave?
What is the significance of a U wave?
Not supposed to be there! Indicates bad things!
Which leads monitor the RV?
Which leads monitor the LV?
Describe the EKG of ventricular hypertrophy
Remember: more muscle => more volts => greater amplitude in EKG
- Higher R wave
- T wave is negative
Describe the EKG of left ventricular hypertrophy
- Large positive R waves in V5 and V6
- Large negative S waves in V1
Describe the EKG of right ventricular hypertrophy
- Big R waves in right-sided leads (V1, V2)
Describe the EKG of myocardial ischemia
Blood supply is insufficient to meet O2 demands
- ∆s ventricular repolarization => affects ST segment & T wave
Describe the EKG of stress-induced myocardial ischemia in presence of fixed coronary obstruction
Depression of ST segment
- go look at ppt slide title "stressed-induced myocardial ischemia"
Describe the EKG of myocardial ischemia due to acute coronary artery obstruction during low O2 demand
T wave inversion
- Go look at ppt slide titled "during acute coronary syndrome"
Describe the EKG of myocardiac infarction
- 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)
At what point does a Q wave indicate infarcted tissue?
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
At what point would you expect to see a peaked T-wave in the progression of a transmural myocardial infarct?
- At the very moment when the artery is obstructed completely
- You rarely see this in an ER (no one is there right away)
At what point would you expect to see a T-wave inversion in the progression of a transmural myocardial infarct?
- Happens very quickly
- You will usually see this in the ER (sometimes not though)
At what point would you expect to see ST elevation in the progression of a transmural myocardial infarct?
- Happens when you get a massive MI
- Involves to the whole frickin muscle (all layers)
At what point would you expect to see a Q-wave, ST-elevation, T-inversion in the progression of a transmural myocardial infarct?
- 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
What's the difference between transmural and subendocardial MIs?
- ST elevation w/ Q waves
- Involve all layers
- ST depression, no Q wave
- inner layer
Describe the EKG of hypercalcemia
Describe the EKG of hypocalcemia
- may be associated w/ life threatening ventricular arrhythmias
Describe the EKG of hyperkalemia
- ^ 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