Intro to ECG Flashcards
Direction of QRS
Q = negative
R = positive
S = late negative deflection
normal duration of QRS
0.06-0.10 sec
U waves are ____
inconsistent
___ wave is inconsistent
U wave
paper speed of ECG
25 mm/sec
thin lines are ___ long and ___ sec
thick lines are ___ long and ___ sec
thin = 1 mm, 0.04 sec
thick = 5 mm, 0.20 sec
PR interval means?
normal PR interval
PR interval = conduction time across AV node
normal PR interval = 0.12-0.20 sec
Equation for HR
HR = 300/ # heavy lines between 2 QRS
HR = 1500/ # mm between 2 QRS
Leads are electrodes that measure difference in electrical potential between ____
1)
2)
Leads measure difference in potential between
1) 2 diff points on body (bipolar lead)
2) 1 point on body and virtual reference point with 0 electrical potential (center of heart) = unipolar lead
what is a unipolar lead
lead locate in center of heart (0 electrical potentail)
Depolarization toward a positive electrode produces _____
positive deflection
Direction of QRS based on left and lateral lead
vs. right sided leads
QRS in left/lateral lead = UPRIGHT (+)
QRS in right side lead = DOWNWARD (-)
LOCATION OF bipolar Limb LEAD
1
2
3
1) BETWEEN BOTH HANDS (L = +, R = -)
2) BETWEEN R HAND AND L FOOT (HAND = -, FOOT = +)
3) BETWEEN L HAND AND L FOOT
what are the bipolar limb leads
leads 1, 2,3 (standard limb leads)
what are the bipolar precordial leads
NONE
what are the unipolar limb leads
aVR, aVL, aVR (augmented limb leads)
what are the unipolar precordial leads
V1- V6
Direction of Augmented unipolar leads
aVL
aVF
aVR
aVL (L hand diagonally to right side) Hand = +
aVF (vertical down body)
aVR (R hand diagonally to left side) Hand = -
which are the lateral leads
aVL and lead I
which are the inferior leads
II, III, aVF
which leads monitor the RV
V1 and V2
which leads monitor the LV
V5 and V6
signs of ventricular hypertrophy
more muscle = more volts = greater amplitude
ECG changes in LVH
big R waves in L-sided leads
1, aVL, V5, V6
ECG changes in RVH
big R waves in R-sided leads
V1, V2
What does depression of ST segment indicate?
ischemia due to sudden high O2 demand with fixed coronary obstruction
what does ischemia due to high O2 demand due to coronary obstruction appear on ecg?
depression of ST segment
what does T wave inversion indicate?
ischemia due to acute coronary artery obstruction and LOW OXYGEN DEMAND
what does ischemia due to acute coronary artery obstruction and low O2 demand appear on ecg?
T wave inversion
how does stress-induced myocardial ischemia appear?
normal at rest
ST depression with exercise (inability to incr coronary flow appropriately and incr O2 consumption)
how does acute coronary syndrome appear?
inverted T wave due to decr coronary flow without incr O2 consumption
how does transmural current of injury appear?
ST elevation
clot due to platelet clot
what happens if you open up obstructed artery on ecg?
ST elevation can be partially or reversed
what do Q waves mean?
transmural infarct (no transmural vector–> negative deflection)
what is a significant Q wave
1) > 1/4 amplitude of R wave
2) > 1 small box (0.04 sec) wide
3) in @ least 2 leads (same area of LV)
evolution of transmural MI
1) peak T wave (few min)
2) T wave inversion (ischemia)
3) ST elevation (current injury)
4) Q wave, ST elev, T inversion
Transmural infarcts usually involve how much damage?
full thickness of LV wall = large
transmural vs. subendocardial MI on ecg
transmural = ST elev with Q wave
subendocardial = ST depression NO Q WAVE
V1-V2
anteroseptal wall infarct
V3-V4
anterior wall infarct
V5-V6
anterolateral wall infarct
II, III, aVF
inferior wall infarct
I, aVL
high lateral wall infarct
when is QT interval prolonged?
> 1/2 RR interval
what are causes of prolonged QT
1) hypocalcemia, hypokalemia, hypomagnesium
2) class 1A or 3 anti-arrhythmic drugs
3) hypothermia
if T wave merges with U wave what does that mean?
hypokalemia
how does hypercalcemia appear on ecg?
shortened QT
what is the most common cause of shorten QT interval
hyperparathyroidism –> hypercalcemia
signs of hypokalemia
1) QT prolong
2) T wave inverted
changes in hyperkalemia
K+ 5.5-7.5 mmol/L
tall T waves- peaked and symmetrical
changes in hyperkalemia
K+ 7.5-9.0 mmol/L
P & R waves flatten
QRS & T broaden
Big S wave
changes in hyperkalemia
K+ ? 9.0 mmol/L
P& R waves gone
S and T broaden
“sine wave”
ABNORMALITIES IN THE QT INTERVAL AND T WAVE DUE TO DRUGS, ABNORMAL ELECTROLYTES, OR OTHER CAUSES
PREDISPOSE TO ARRHYTHMIAS USUALLY THROUGH ___
alterations in repolarization
