Lec 2-3 EKG Flashcards
What is normal p-wave height/width?
height < 2.5 mm [< 2.5 small sq]
width < 0.11 sec [<3 small sq]
What is normal PR interval?
0.12-0.2 sec [3-5 small sq] = P wave + PR segment
What is normal QRS complex duration?
< 0.12 sec [3 small sq]
What is normal QTc interval duration?
< 460 ms [11 small sq]
What are the standard 12 leads of ECG?
6 precordial [chest] leads V1 to V6 right to left= cross-sectional view of heart
6 limb leads [I, II, III, aVR, aVL, aVF] = frontal view of heart
What are characteristics of normal sinus rhythm?
- p waves axis upright in I, II, inverted in AVR
- each p wave followed by a QRS
- p wave rate 60-100 bpm
In normal sinus rhythm, which leads have upright p wave and which inverted?
- p waves upright in I, II
- p waves inverted in AVR
What does the pr segment represent?
time from atria to AV node
What does the p wave represent?
depolarization of the atria
What does the pr interval represent?
p wave + pr segment = time from SA node to AV node
How many mV is one small square on EKG?
0.1 mV
How much time is one small square on EKG
0.4 seconds = 40 mS
What does the QRS complex represent?
duration of depolarization of the ventricles
What is the ST segment?
time from end QRS to T wave → duration of repolarization of ventricles
What is QT interval?
start of Q though end of T = everything depolarizing and repolarizing in ventricles
What are the 2 leads that are essentially negative normally?
AVR, V1
How does HR change in inspiration?
INspiration = Increase; variation from inspiration to expiration should be less than 10%
What does premature atrial contraction look like?
- early QRS complex originated/preceded by abnormal P wave
- QRS complex itself looks normal
What does premature ventricular contraction look like?
broad QRS wave, not preceded by P wave
What is cheat method for determining rate of HR from EKG?
distance between QRS waves: 300 = 1 big square; 150 = 2 big sq; 100 = 3 big sq; 75 = 4 big sq; 60 bpm = 5 big sq
Thus if 5 big squares between QRS waves = 60 bpm
3-6 big boxes = normal
What is non-cheat method for determining HR from EKG?
1500/n → n = number of small squares between R-R
What is sinus bradycardia?
rate < 60/min; normal P wave axis
What is sinus tachycardia?
rate > 100/min; normal P wave axis
What is lead II direction?
toward left foot [+60]