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]
What is lead III direction?
down and right [+120]
What is einthoven’s triangle?
leads 1, 2, and 3 together
What is aVR direction?
-150
What does it mean” normal people stand upright”?
normal = both lead I and AVF are upright
What does it mean “right people always meet”?
right axis deviation = lead 1 down, AVF up
What does it mean “leftists don’t see eye to eye”?
left axis deviation = lead I upright, AVF down
What is normal heart axis?
range: 0 to +90
What axis degree if right axis deviation?
+90 though + 180
What axis degree if left axis deviation
0 though -90
What axis if lead 1 upright and AVF negative?
left axis deviation
What axis if both lead 1 and AVF negative?
indeterminate
What axis if lead 1 negative and AVF upright?
right axis deviation
How do you get lead I?
right arm –> left arm [1 L]
How do you get lead II?
right arm –> left leg [2 Ls]
How do you get lead III?
left arm –> left leg [3 Ls]
What is meant by S1Q3 pattern of right axis deviation?
- lead 1 has a deep S wave
- lead 3 has a deep Q wave
What is moderate vs marked right axis deviation?
moderate = 90 to 120 marked = 120 to 180
What should you look out for when you are diagnosing left axis deviation?
make sure it is an S wave causing the big negative wave in AVF –> do this by looking to make sure theres a tiny little blip of a R wave right before the down wave
if its a Q wave –> might be an infarct
What is most important cause of left axis deviation?
left anterior fascicular block
How do you determine if left anterior fascicular block?
- extreme left axis devation [-45 to -90
2. negative lead II
What should you think if broad > 120 ms QRS looking down in V1 but normal p and pr?
think left bundle branch block
What produces rabbit ears of QRS?
two ventricles are depolarized separately = two R waves
due to bundle branch block in one side
What do you see in right bundle branch block?
- prolonged QRS > 0.12 sec
- secondary R wave [R’] with R’ greater than initial R
- wide S wave
- positive V1 QRS
Where do you see QRS rabbit ears in RBBB? LBBB?
RBBB = in V1 [+ V2 right precordial leads]
LBBB = in V4 and V5 [left precordial leads]
What do you see in left bundle branch block?
- prolonged QRS > 0.12 sec
- negative V1 QRS
Normal QRS in V1 is pos or neg?
negative
What 4 common conditions can cause big positive V1 QRS wave?
- RBBB
- posterior wall MI
- WPW syndrome [wolf-parkinson-white]
- RVH [right ventricle hypertrophy
What are sokolow criteria for LVH?
S in V1 + R in V5 or V6 > 35 mV
add the two together
What are cornell criteria for LVH?
S in V3 + R in AVL > 28 mV in men
S in V3 + R in AVL > 20 mV in women
What are framingham criteria for LVH?
R in AVL > 11 mV or R in I > 13 mV
What should you see in LVH?
- large QRS in left precordial [V4, V5, V6]
- repolarization abnormalities [ST depression, T wave inversion]
What are criteria for RVH?
- right axis deviation > + 100
- positive V1
plus one or more of the following:
- R in V1 + S in V5 or V6 > 10
- right atrium enlarged
- R wave in V1 > 7
- S wave in V1 < 2
- etc
What should you think if positive V1 QRS and deviation?
RVH
What are criteria for Wolf-parkinson-white?
- short PR interval less than 3 squares (< 120 ms)
- delta wave on upstroke QRS [pre-excitation]
- broad QRS
- secondary ST and T wave changes [inverted T, ST depression]
What are 3 types of rhythms with ST/T wave changes from which you can’t interpret ischemia/infarction?
- LBBB
- LVH
- WPW
What does direction of V1 tell you about WPW?
V1 negative –> accessory path on right side
V1 positive [upright] –> accessory path on left side
