Basics: Leads, Normal ECG components Flashcards
Which frontal leads are the inferior leads? (3)
Lead II
Lead III
aVF
Which frontal leads are the left lateral leads?
Lead I
aVL
Which frontal lead is the right-sided lead?
aVR
Angle for lead II
+60 (5 o’clock position)
angle for lead III
+ 120 (7 o’clock position)
angle for aVF
+90 (6 o’clock position)
angle for lead I
0 (3 o’clock position)
angle for aVL
-30 (2 o’clock position)
angle for avR
-150 (10 o’clock position)
Which precordial lead?
4th ICS, right of sternum
V1
Which precordial lead?
4th ICS, left of sternum
V2
Which precordial lead?
5th ICS, MCL
V4
Where is V3 placed?
between V2 and V4
Which precordial lead?
5th ICS, MAL
V6
where is V5 placed?
between V4 and V6
Anterior group leads… (3)
V2, V3, V4
Left lateral group leads… (4)
I, aVL, V5, V6
inferior group leads (3)
II, III, aVF
Right ventricular group leads (2)
aVR, V1
small box = ___s
0.04s
large box = ___s
0.20s
small box = ____mV
0.10mV
what component of an ECG?
A deflection, either positive or negative, away from the baseline (isoelectric line) of the ECG tracing
wave
a complex is composed of…
several waves
what component of an ECG?
A straight line between waves or complexes
segment
what component of an ECG?
A segment and a wave
interval
3 components of a normal p wave
configuration:
amplitude:
precedes:
configuration: small, upright, round
amplitude: 0.05-0.25 mv (0.5-2.5 small boxes)
precedes each QRS
the P wave indicates ____ in the heart
atrial depolarization/contraction
the PR interval is the distance between beginning of ______ and beginning of _____
beginning of P wave to beginning of QRS
The PR interval represents the time it takes for an impulse to be conducted
from atria to AV node (depolarization)
normal PR interval:
time:
variability:
0.12-0.20s (3-5 small boxes)
constant
normal P wave duration…
0.06-0.10s (2.5 small squares)
A normal P wave is biphasic in which lead?
V1
A normal P wave is upright in which leads?
I, II, aVF, V2-V6
A normal P wave is inverted in which lead?
aVR
If normal P waves in lead II and preceding each QRS, it can be assumed that the impulse originated where?
SA node
P wave amplitude > 2.5 (tall) in lead II or > 1.5 mm in V1, what condition might be present?
Right atrial enlargement
A prolonged P wave > 0.12s on frontal plane (lead II) may indicate…
left atrial enlargement
If P wave becomes inverted after being normal/upright, consider…
retrograde/reverse conduction
Junctional Arrhythmia
varying P waves (3 or more different P waves) indicates
wandering pacemaker
The below conditions would have what effect on an ECG P wave?
junctional rhythm
atrial flutter
a fib
hyperkalemia
absent P wave
PR segment runs from…
end of p wave to start of QRS
this is the time from end of atrial depolarization to the beginning of ventricular depolarization.
PR segment
Q waves are best seen in which 4 leads?
left lateral leads: I, aVL, V5, V6
QRS complex represents what action taking place?
ventricular depolarization
Which lead has a deep negative normal S wave?
aVR
which leads show a large positive R wave in normal conditions?
left lateral and inferior leads
in precordial leads, R wave amplitude (increases/decreases) moving from right to left
increases ( V5>V1)
normal duration of QRS interval…
0.06-0.12s (1.5-3 small boxes)
roughly half of PR interval
This segment represents the time between end of ventricular depolarization to start of ventricular repolarization.
ST segment
This wave represents ventricular repolarization
T wave
T waves can have a very ____ appearance
variable (depends on hormonal, neuro, etc)
If there was a tall positive R wave, you can expect the T wave to be…
positive
normal amplitude (height) of a T wave is ___ - ____ of the corresponding R wave
1/3-2/3
This is the interval that represents the beginning of ventricular depolarization to the end of ventricular depolarization.
Therefore represents the electrical events of the ventricles
QT interval
duration of QT is proportional to…
HR
QT interval generally constitutes ___% of normal R-R interval
40%
normal QT interval duration…
0.36-0.44s (9-11 small boxes)
Prolonged QT can lead to what arrythmia?
torsade de pointes
This is a small, rounded, upright wave most easily seen w. slow HR.
it represents repolarization of purkinje fibers.
presence or absence isn’t abnormal
U wave
Prolonged PR interval can mean what? (3)
digoxin toxicity
heart block (AV block)
myocardial ischemia/infarction
Shortened PR interval can indicate…
junctional arrhythmia
pre-excitation syndromes
Deep, wide Q waves may indicate what condition? (Q wave amplitude 25% of r amplitude, or duration of Q wave 0.04s)
myocardial infarction
notched R waves can signify what condition?
bundle branch block
widened QRS (> 0.12s) may indicate
ventricular conduction delay
If QRS complexes are missing, what conditions (2) may be present?
AV block, ventricular standstill
Depressed ST segment (0.5mm < baseline) can indicate what two conditions? (downsloping)
digoxin toxicity
MI
ST elevation (1mm > than baseline) can indicate (upsloping)
MI
tall, peaked, tented T waves can indicate what 2 conditions?
MI
Hyperkalemia
Inverted T waves in leads I, II, V3-V6 may represent…
MI
Heavily knotched or pointed T waves may suggest…
pericarditis
