EKG Basics Flashcards
Normal orientation for P waves in all leads
I - positive II - positive III - biphasic (negative ok) aVR - negative aVL - positive aVF - positive V1 - biphasic
In which leads are the P waves normally most positive and most negative?
most positive in II
most negative in aVR
Normal amplitude of a P wave
not exceeding 0.25mV (2.5 small squares)
Anterior leads
V2, V3, V4
Left Lateral Leads
I, aVL, V5, V6
Inferior leads
II, III, aVF
Right Ventricular leads
aVR, V1
What does the PR interval represent?
start of atrial depolarization to the start of ventricular depolarization
Length of normal PR interval
0.12 to ).20 sec (3 to 5 small squares)
What does the PR segment represent?
time from the end of atrial depolarization to the beginning of ventricular depolarization
See Q wave in which leads?
I, aVL, V5, V6, (ie left lateral leads) sometimes inferior leads and V3 and V4
What does a Q wave represent?
septal depolarization
Normal Q wave amplitude?
not greater than 0.1mV (1 small square)
In what leads are R waves (positive deflections) seen in the QRS complex?
I, II, III, aVL, aVF, V5, V6
In what leads are S waves (negative deflections) seen in the QRS complex?
aVR, V1
In what leads is the QRS complex usually biphasic?
V3, V4 (usually one or the other)
Normal duration of QRS complex?
0.06 to 0.1 sec (1.5-2.5 small squares)
What does ST segment represent?
time from the end of ventricular depolarization to the start of ventricular repolarization
What does the QRS interval represent?
QRS complex
What does the T wave represent
ventricular repolarization
Amplitude of a normal T wave
1/3 to 2/3 the amplitude of the accompanying R wave
How do you know if a T wave should be positive or negative?
T waves follow the direction of an R wave (ie if R wave present, T should be positive) or S wave (if no R, then S wave will be negative deflection in QRS, so negative T)
What does the QT interval represent?
time from the beginning of ventricular depolarization to the end of ventricular repolarization
Should the T wave be longer or narrower than the QRS complex?
longer
Progression of current
SA -> AV -> (slight delay) -> Bundle of His -> RBB/LBB -> Prukinje fibers
small squares
0.04 sec or 0.1 mV
large squares
0.2 sec or 0.5 mV
