EKG lecture 2 (4.3.25) Flashcards
1) Waves of depolarization moving toward a positive electrode cause a ______________deflection on the EKG
2) Waves of depolarization moving away from a positive electrode cause a ______________ deflection on EKG
1) positive (upward)
2) negative (downward)
1) A wave of repolarization moving toward + electrode = __________ deflection
2) A wave of repole moving away + electrode = __________ deflection
1) downward
2) upward
Repolarization has a similar but ___________ effect on an EKG
opposite
Describe 3 electrodes looking at heart from different perspective:
A) wave of depole moving toward electrode
-Amplitude of R wave is bigger bc it’s more directly in line with main vector
-looking from left side (i think)
B) Wave of depole moving away from electrode
-No R wave
C) Wave moving perpendicular to electrode
-(looking from middle)
________ electrodes combined to form 12 leads looking at heart from specific “observation points”
10
Describe typical lead placement
1) 2 electrodes on arms and 2 electrodes on legs = provide basis for the 6 limb leads
3 standard limb leads
3 augmented limb leads
2) 6 electrodes across chest = 6 precordial (chest) leads
6 Limb leads:
1) Where should you observe these?
2) How are these 6 leads generated? Explain
1) Observe from Frontal plane
2) EKG machine designates + & - electrodes creating 6 leads
-3 limb leads + 3 augmented limb leads
List the locations and degrees of the main limb leads
1) Lead 1: left arm +, right arm, -0 degrees
2) Lead 2: legs +, right arm, +60 degrees
3) Lead 3: legs +, left arm, + 120 degrees
List the locations and degrees of the augmented limb leads
1) Lead aVL: Left arm +, others -30 degrees
2) Lead avr: right arm +, others -150 degrees
3) Lead avf: legs +, others + 90 degrees
How can you remember AVF?
AVF = AV foot
List the positions of all the EKG leads around the heart
Pre-cordial (chest) leads:
1) How many?
2) Where are they?
3) Describe their positivity or negativity
1) 6 leads
2) Transverse/axial or horizontal plane across the chest – view electrical activity anterior to posterior
3) Each lead made positive in turn
Entire body is negative
List the locations of the 6 precordial (chest) leads
V1 4th ICS right of sternum
V2 4th ICS left of sternum
V3 placed between V2 and V4
V4 is placed 5th ICS in MCL
V5 is placed between V4 and V6
V6 is placed 5th ICS in mid axillary line
What are some notes for getting a good/ readable EKG?
1) Lead placement very important….must be accurate, especially chest leads
2) Shave hair for lead placement PRN
3) Patient should be lying flat….elevate bed only if needed (HF, pain)
4) Always check leads if unexpected tracing
EKG leads record the average current flow or VECTOR
1) Define vector
2) Define length
1) Direction of average current flow
2) Voltage magnitude or amplitude
P wave:
1) What does it represent?
2) Where does this start?
3) Where does the vector of this point?
1) Atrial depolarization
2) SA node in upper right atrium
Right atrium depolarizes 1st, then left atrium
3) VECTOR of atrial depole points right to left & slightly inferior
Describe what a normal P wave looks like
1) Amplitude small; normally does not exceed 2.5 mm (2.5 small boxes) or 0.25 mV
2) Usually most positive in lead 2 and most negative in lead aVR
-Individual patients vary so “typical” may not apply
3) Normal range of P vector = 0 – 70 degrees
Would you expect aVR lead P waves to be positive or negative?
Negative
Would you expect lead 2 P waves to be positive or negative?
Positive
1) Define PR interval
2) What does it include? Define this
3) How long does it usually last?
1) Start of atrial depole until start of ventricular depole
2) PR segment = end of atrial depole to start of ventricular depole
3) PR interval usually lasts 0.12 to 0.2 seconds or 3-5 small boxes
QRS complex
1) What occurs here?
2) How does it enter the ventricles?
1) Wave of depole is now leaving the AV node, where it hesitated for a fraction of a second, and now ready to enter the ventricles via the conduction system
2) Bundle of His, right and left bundle branches
Septal q waves: What is first to depolarize?
IV septum
Septal Q waves
Describe the depolarization of the IV septum (first to depolarize)
1) Septal fascicle of the LBB; left to right
2) Not always visible on EKG but may cause a small negative deflection in one or several of the lateral leads (1, aVL, V5-6)
3) Normal septal Q waves have amplitude of not greater than 0.1 mV (1 small box)
Explain the remainder of ventricular depolarization beyond the septum
Left ventricle dominates QRS complex
Average Vector is toward LEFT, between 0 to +90 degrees
Frontal plane – large R wave in lateral and inferior leads, lead aVR will have deep S wave
Explain the locations of V1, V5-6, and V3-4
V1 overlies RV – deep S
V5-6 overlies LV – tall R
V3-4 transition – biphasic
predominantly negative
to positive
R wave progression
