EKGs Flashcards
The duration of any wave may be determined by measuring along the (blank)
Horizontal axis
Limb leads
I, II, III, aVR, aVL, aVF
Chest leads
V1- V6
Lead I is horizontal and its left arm electrode is ______ while its right arm electrode is _____
Positive
Negative
Lead III: the left arm electrode is _____, while the left leg electrode is ________
Negative
Positive
What is Einthoven’s Triangle?
The bipolar limb lead configuration
(Right arm, left arm, left leg)
Lead II: the right arm electrode is _____ while the left leg electrode is_____
Negative
Positive
The aVF lead uses the left foot as _______
positive
aVF is a cross between leads II and III
where is the electrode positive in the following leads?
aVR:
aVL:
avF:
aVR: Right arm positive
aVL: Left arm positive
aVF: Foot positive (left foot
The flat plane of the limb leads is called the _______
Frontal plane
What are the lateral leads?
I, aVL, V5, V6
What are the inferior leads?
II, III, aVF
What are the anteroseptal leads?
V1-V4
What are the right ventricular leads?
aVR, V1, V2
What leads show the right ventricle?
V1, V2, V3, aVR
What leads show the interventricular septum?
V1, V2
What leads show the anterior of the heart?
V2, V3, V4
What leads show the lateral wall of the left ventricle?
V5, V6, I, aVL
What leads are associated with the RCA?
II, III, aVF
What leads are associated with the LAD?
V1-V4
What leads are associated with the LCX?
V5, V6, I, aVL
Define Automaticity foci
Potential pacemakers that are capable of pacing in emergency situations. They have the potential to pace at their inherent rate. They are in the atria, ventricles and AV junction
The rate of the automaticity foci within the atria
60-80
The rate of the automaticity foci within the AV Junction
40-60
The rate of the automaticity foci in the ventricles
20-40
Define overdrive suppression
Any automaticity center will overdrive-suppress all others that have a slower inherent pacemaking rate.
Define axis
Refers to the direction of depolarization as it passes through the heart
What is the axis of the heart?
The mean QRS vector when located by degrees in the frontal plane.
Sinus Rhythm
Sinus Bradycardia
Sinus Arrhythmia
an irregular rhythm that varies w respiration
-All p-waves are identical
Wandering pacemaker
P-waves change shape
Pacemaker location varies
Rate under 100 bpm
Multifocal atrial tachycardia
Same as Wandering pacemaker but with a rate above 100bpm
Atrial fibrillation
Irregular ventricular rhythm
-No p-waves
-Erratic atrial spikes from multiple atrial automaticity foci
Fibrillation: rate 350-450
Atrial Flutter
Flutter rate: 250-350
-Saw-toothed atrial complexes from a single rapid firing atrial focus
-Many flutter waves needed to produce a ventricular response
Atrial Escape Rhythm
60-80 bpm
A sick sinus node may cease pacing (sinus arrest) causing an automaticity focus to escape to assume pacemaker status
Junctional Escape Rhythm
40-60 bpm- idiojunctional
Ventricular Escape Rhythm
20-40 bpm - idioventricular
Ventricular Escape Beat
Junctional Escape Beat
Escape rhythm vs beat
Premature Atrial beat
From an irritable automaticity focus
Premature Junctional beat
Premature ventricular contraction (PVC)
Ventricular focus produces a rapid (150-250 bpm) sequence of PVC-like wide ventricular complexes
Paroxysmal atrial tachycardia (SVT)
AV-junction focus produces rapid sequence of QRS-T cycles at 150-250bpm
-QRS may be slightly widened
Ventricular Tachycardia
Torsades de Pointes
Ventricular flutter
aka Torsades
Rapid, smooth waves from a single rapid-firing ventricular focus
-Usually short bursts leading to v.fib
Ventricular fibrillation
Multiple ventricular foci rapidly discharging produce an erratic ventricular rhythm without identifiable waves
-Needs immediate tx
Sinus Block
An unhealthy SA node misses one or more cycles
First degree AV Block
Consistently prolonged PR interval greater than .2 seconds (one big box)
2nd Degree Mobitz 1/Wenkebach
Some p-waves without QRS responses
-PR interval gradually lengthens with each cycle until the last P does not produce a QRS
2nd degree Mobitz 2 AV block
Some P-waves don’t produce a QRS response
Complete heart block (AV dissociation)
Right Bundle Branch Block
Look at V1 for a double R, V6 for a swooping S wave
Left Bundle Branch Block
Look at V1 for bunny ears
Look at V6 for inverted T-wave
Bundle branch blocks
What does an EKG record?
the electrical activity of the heart muscle (myocardium).
Information recorded represents the electrical activity of contraction of the myocardium
What is the dominant pacemaker of the heart normally?
SA node:
Initiated a wave of depolarization that spreads outwards, stimulating the atria to contract as the circular wave advances.
It’s pacing activity is known as sinus rhythm
What is Automaticity?
The generation of pacemaking stimuli.
The ability of the SA node to generate pacemaking stimuli
QRS
Ventricular depolarization
(<.12 seconds)
Q wave
Septal depolarization
P wave
The depolarization and contraction of both atria
T-wave
The final “rapid phase” of ventricular repolarization
K+ ions leaving the myocytes
PR interval
The impulse from the SA node to AV node and to the Bundle of His
Should sit on the isoelectric line
ST segment
Initial repolarization
“Plateau phase” of ventricular repolarization
The horizontal segment of baseline that follows the QRS complex
QT interval
Represents the duration of ventricular systole.
Measures from the beginning of QRS until the end of the T-wave
What is the QT interval a physiologic marker of?
A good indicator of repolarization.
Pts w hereditary long QT interval syndromes are vulnerable to dangerous rapid ventricular rhythms
J-point:
located at the end of the QRS where the T-wave begins
R-R interval
The entire cardiac cycle
Slowing of the wave of depolarization at the AV node allows what to happen?
When the wave of atrial depolarization enters the AV node, depolarization slows, producing a brief pause, thus allowing time for the blood in the atria to enter the ventricles.
Slow conduction through the AV node is carried by calcium ions
AV node is the only electrical conduction pathway between the atria and the ventricles
What are the Limb leads
I, II, III, aVL, aVR, aVF
What are the chest/precordial leads
V1-V6
What is Einthoven’s Triangle?
Electrodes are placed on the right arm, left arm, and left leg. A pair of electrodes are used to record a lead.
Einthoven used these 3 locations for limb electrodes. They remain the conventional standard for recording the EKG.
Two electrodes are used to record a lead. A different pair is used for each lead.
What information can we gain by looking at multiple leads of the electrical impulse of the heart?
It may be difficult to see a specific wave in a given lead, but with different lead positions, it is certain to show up better in other leads
What are the things that you should check on every EKG?
Rate, Rhythm, Axis, Hypertrophy, Infarction
Describe 2 different ways to measure the heart rate on the EKG
Find an R-wave that starts on the heavy black line. The following heavy black lines should be noted as 300, 150, 100, 75, 60, 50. Where the R-wave falls next determines the rate. Triplet method: 300, 150, 100 then 75, 60, 50
Box method: 300/ number of boxes between R waves
10 second rhythm strip: number of R-waves x 6
Describe a simple way to determine the axis of ventricular depolarization.
We can demonstrate the general direction of the movement of depolarization by using a vector (arrow).
The vector shows the direction in which depolarization is moving.
When interpreting EKG’s a vector shows the general direction of depolarization in the heart.
What things may cause axis deviation?
-Obesity (up and to the left)
-Tall, slender people may have a “vertical heart” (down and to the right)
-Hypertrophy (deviates towards the ventricle that is hypertrophied)
-MI (vector points away from the infarct bc dead tissue can’t depolarize)
The tail of the vector is the______
AV node
There is an increased depolarization in a ________
Hypertrophied ventricle
The mean QRS vector should point downward and to the patient’s ______
Left
In the 0-degree to +90-degree range.
Lead 1 is best for detecting______
right axis deviation
What lead would you look at to determine atrial hypertrophy?
V1
What would you see on the 12 lead EKG with Right Ventricular Hypertrophy?
The P-wave is usually diphasic (both positive and negative)
If the initial component of a diphasic P-wave in V1 is the larger then this is right atrial enlargement
If the height of the P-wave in any of the limb leads exceeds 2.5mm (even if it’s not diphasic) suspect right atrial enlargement)
What would you see on the 12 lead EKG with Left Ventricular Hypertrophy?
Large S in V1 and large R in V5, T-wave inversion w T-wave asymmetry
QRS complexes that are exaggerated amplitude, both in height and in depth, especially in the chest leads.
Even deeper S wave in V1.
(There is a left axis deviation, and often the vector is displaced in a leftward direction in the horizontal plane.)
What EKG changes could be seen with myocardial ischemia?
Characterized by symmetrically inverted T-waves
What EKG changes could be seen with myocardial infarction?
ST elevation must be at least 2 mm in V2 and V3 for it to be a true ST elevation
Must be seen in 2 contiguous leads
Can have ST depression (.5 mm in 2 contiguous leads)
Upsloping ST elevation
Hyperacute T-wave
Anterior myocardial infarction
Always check V1 and V2 for ST elevation and Q waves
Due to an occlusion of the LAD
Inferior myocardial infarction
Qs in II, III aVF
Due to an occlusion in the right or left coronary arteries
Lateral myocardial infarction
Qs in lateral leads 1, aVL
Caused by an occlusion of the circumflex (LCX) branch of the left coronary artery
Posterior myocardial infarction
Always check V1 and V2 for ST depression and large R waves
Usually caused by an occlusion of RCA or one of its branches
What unusual wave might be seen on the EKG with hypokalemia?
T-wave becomes flat (or inverted) and a U wave appears
What EKG changes would you expect with hyperkalemia?
P-wave flattens down, the QRS complex widens, T-waves become peaked
In what condition would you expect to see a Delta wave on the EKG?
When there is an extra pathway conducting electricity from atria to the ventricles - Seen in WPW syndrome
Define axis
Refers to the direction of depolarization as it passes through the heart
