EKG Flashcards
Describe the conduction state of cardiac cells during Resting Membrane Potential, Depolarization and Repolarization?
RMP: Polarized
- *Depolarization:**
- Stimulus - Action Potential - Cell to Cell
- Polarity Reverses due to ionic fluxes (Ca++, Na+, K+)
- *Repolarization**:
- Cells return to resting state
What are the five phases of the Cardiac Action Potential?
4 - 0 - 1 - 2 - 3
Phase 4: Resting State
Phase 0: Rapid Depolarization
Phase 1: Initial Repolarization
Phase 2: Plateau phase of Repolarization
Phase 3: Final Repolarization
What is the resting membrane potential of the cardiac muscle?
-90 mV
Action Potential is due to fluxes in which ions?
Sodium, Potassium and Calcium
What is the normal electrical pathway of the heart ?
- Sinoatrial Node (SA)
- Atrioventricular Node (AV)
- Common Bundle (His)
- Bundle Branches:
- Left Anterior Fasicle
- Left Posterior Fasicle
- Right Bundle Branch - Purkinje Fibers
What is the polarization rate of the Sinoatrial Node?
60-100/min
What is the polarization rate of the AV Node?
40-60/min
What is the polarization rate of the Ventricle?
20-40/min
What are the seven steps of the cardiac depolarization sequence?
- Sinoatrial Node (SA)
- R & L Atrium
- Atrioventricular Node (AV)
- Common Bundle (His)
- Bundle Branches:
- Left Anterior Fasicle
- Left Posterior Fasicle
- Right Bundle Branch - Purkinje Fibers
- Myocardium
How does the septum depolarize?
From Left to Right
What is a Monophasic Waveform?
A complex all positive or all negative waveform
What is a Biphasic Waveform?
A complex waveform with both positive and negative deflections
What is a Triphasic Waveform?
Three deflections. e.g. rsR’
What is an Isoelectric or “equiphasic” Waveform?
A waveform where positive and negative (or vice versa) follow one another and are of equal deflection.
What makes a waveform a positive complex?
If the electrical current is traveling towards an EKG lead
What makes a waveform a negative complex?
If the electrical current is traveling away from an EKG lead
What makes a waveform a Biphasic complex?
If the electrical current is traveling perpendicular to an EKG lead
What is R’ called?
R Prime
What does the QRS Complex represent with respect to what is happening in the heart?
Ventricular Depolarization
What does the P wave represent?
1st deflection of a complex; atrial depolarization and contraction.
What is the intrventricular septum?
The wall that separates the right and left ventricles
What is a segment?
A segment is a straight line connecting two waves.
- PR Segment
- ST Segment
What is an interval?
An interval encompasses at least one wave plus, in most cases, the connecting straight line.
- PR Interval
- QRS Interval
- ST Interval
- QT Interval
What does the T Wave on an EKG represent?
Deflection after QRS wave showing Ventricular Repolarization
What is the Q Wave?
1st negative deflection after the P wave
What is the R Wave?
1st Positive Deflection after the P Wave
What is the S Wave?
1st Negative Deflection after the R wave.
What is the U Wave?
Deflection after the T wave, but it is rarely present
What is the “J” or Junction Point?
Where the QRS complex ends and the ST segment begins. Used to measure ST-segment deviation in relation to baseline.
What is the R-R Interval?
Interval from one R deflection to the next R deflection, which represents one complete cycle.
What is the TP Segment?
The TP Segment represents electrical baseline and is the segment from the end of ventricular repolarization to the beginning of atrial depolarization.
What are the three inferior leads and their angles?
Limb Leads:
Lead II +60
Lead III +120
Lead aVF +90
aVF - Augmented Vector Foot
What are the four Lateral Leads and their angles?
Lead aVL -30 (aVL = Augmented Vector Left )
Lead I 0 degrees
Precordial: V5 & V6
What Leads are found on the right side and their angles?
aVR -150
aVR = Augmented Vector Right
What does a large R Wave represent
Depolarization of the main mass of the venrticles as they pump blood out of the heart
What are the two Anterior Leads?
(Precordial)
Precordial: V3 & V4
What are the six Precordial Leads?
V1 - V2 - V3 - V4 - V5 - V6
What is the standard calibration of EKG paper?
- 25mm per sec
- 1-mV standardization mark is 10mm tall
What does one large 5mm x 5mm box on an EKG represent?
0.2 seconds (200 ms) and 0.5 mV amplitude
What does one small 1mm x 1mm block on an EKG represent?
0.04 seconds (40 ms) and 0.1 mV amplitude
What do the X and Y axis represent?
X Axis = Time
Y Axis = Amplitude
On EKG paper, what do the following represent?
1 small box:
2 small boxes:
3 small boxes:
4 small boxes:
5 small boxes:
1 small box: 0.04 seconds (40 ms)
2 small boxes: 0.08 seconds (80 ms)
3 small boxes: 0.12 seconds (120 ms)
4 small boxes: 0.16 seconds (160 ms)
5 small boxes: 0.2 seconds (200 ms)
What do the single tic marks at the top of the EKG graph represent?
Each tic mark represents 3 seconds of time
(HR Measurement Method 1)
What is the HR in the below example?
3 tic marks = 6 seconds
6 x 10 = 60 sec or 1 min
There are 8 QRS complexes in 6 seconds, so multiply 8 x 10 = 80 to get a HR of 80 bpm
(HR Measurement Method 2)
Using method 2, how do you calculate HR?
REMEMBER: 300 - 150 - 100 - 75 - 60 - 50 - 43 - 37
Count the number of large boxes between QRS Waves.
Remember, do not start on the actual QRS wave, 300 is the next box.
(HR Measurement Method 3)
Using method 3, how do you calculate HR?
Small boxes - divide by 1500
Large boxes - divide by 300
Count the number of small (1500) or large (300) boxes in between QRS waves and divide appropriately.
What does the PR Interval Represent?
The PR Interval shows the Atrioventricular (AV) conduction time.
Normally 0.12 to 0.2 seconds (120 - 200ms)
What is the normal time for a QRS Interval?
Less than or equal to 0.10 seconds (100ms)
What is the QT interval and what does it represent?
The QT interval is measured from the beginning of the QRS complex to the end of the T wave. It represents the time it takes for the ventricles to depolarize and repolarize, or to contract and relax.
What is Bazetts Formula for measuring HR?
QTc = QT / the quare root of RR
With a normal HR, normal QTc is 0.35 - 0.44 seconds (350 - 440 ms)
What are the polarity characteristics of EKG Leads?
Bipolar: Compares the electrical signal from one electrode to another.
Unipolar: Compares the electrical signal from one physical electrode (e.g. V1) and a “virtual lead”
What is Einthoven’s Triangle?
Leads placed on the Right Arm (RA), Left Arm (LA), Right Leg (RL - Neutral Lead) and Left Leg (LL).
What are the Bipolar Limb Leads?
Lead I is Right Arm (RA) to Left Arm (LA)
Lead II is Right Arm (RA) to Left Leg (LL)
Lead III is Left Leg to Left Arm (LL to LA)
What are the Unipolar Limb Leads?
aVF to Left Leg (LL)
aVL to Left Arm (LA)
aVR to Right Arm (RA)
What leads are on the Frontal Plane?
By using 4 limb electrodes, you get 6 frontal leads that provide information about the heart’s Frontal plane:
Lead I (0) - Lead II ( +60) - Lead III (+120)
Augmented Vector Right (aVR -150)
Augmented Vector Left (aVL -30)
Augmented vector foot (aVF +90)
Leads I, II, and III require a negative and positive electrode (bipolarity) for monitoring. On the other hand, the augmented leads-aVR, aVL, and aVF-are unipolar and requires only a positive electrode for monitoring.
What approach should be used when reading/assessing an EKG?
- Rate
- Rhythm / Conduction
- Axis (angle in degrees)
- Hypertrophy
- Infarct / Ischemia
What are the 12 Territories of the EKG Graph and their associated Leads?
Where should the six Precordial Leads be placed?
In what range is a deflection considered normal?
Between -30 degrees (aVL) and +90 degrees (aVF)
Articulate Axis Deviation Nomenclature
Northeast (-90 to 0) - LAD - Left Axis Deviated
Southeast (0 to +90) - Normal
Southwest (+90 to +180) - RAD - Right Axis Deviated
Northwest (+180 to -90) - EAD - Extreme Access Deviated
Axis Determination - Quadrant Method:
Describe how you would inspect the quadrants to determine axis deviation.
Normal Axis: QRS complex will be positive in both aVF and Lead I
Left Axis Deviated (LAD): QRS will be negative in aVF and positive in Lead I
Right Axis Deviated (RAD): QRS will be positive in aVF and negative in Lead I
Axis Determination - Isoelectric Method
Describe how you would inspect the quadrants to determine Isoelectric axis deviation.
If the QRS complex is isoelectric, find the perpendicular line based on the location of the isoelectric lead.
Inspect the two ends of the perpendicular line and identify which side had a POSITIVE QRS Complex.
Whichever Lead has a positive QRS will determine the HEART axis, which may not align with a specific lead.
Generally define cardiac hypertrophy
An increase in myocyte size in one of the four chambers of the heart.
- Atrial Hypertrophy is called Atrial Enlargement (not hypertrophy)*
- Ventricular Hypertrophy is called Hyoertrophy*
What does a larger spike in a particular wave represent?
Increased amplitutde in that section of the heart
What can cause chronic Left Ventricle overload?
- Systemic hypertension
- Mitral valve disease
- Aortic valve disease
- Obstructive hypertrophic cardiomyopathy
If there is Left Ventricular Hypertrophy, how will the electrical current of the heart represent this on an EKG?
There will be increased electrical forces to the left.
What are the three ways to confirm Left Ventricular Hypertrophy by examining the EKG?
Confirm the EKG Calibration
- If the sum of the S wave in V1 or V2, along with the R wave in V5 or V6 is greater than 35 - POSITIVE
- If the R wave in aVL is greater than 11- POSITIVE
- If the sum of the R wave in I and the S wave in III is greater than 25 - POSITIVE
What are the possible Left Ventricular Hypertrophy Repolarization Abnormalities?
Known as “Strain”
- Downsloping STD
- Asymmetric T-Inversion
What are some of the consequences of Right Ventricular Overload?
- Pulmonary Valve Stenosis
- Tricuspid Insufficiency
- Pulmonary Hypertension
- Congenital Abnormalities
If there is Right Ventricular Hypertrophy, how will the electrical current of the heart represent this on an EKG?
There will be increased electrical forces to the Right.
What are the 3 EKG findings required to diagnose Right Ventricular Hypertrophy?
- Right Axis Deviation greater than 100 degrees
- An R wave taller than 7mm in V1 - V2
- A deep S wave in V5 - V6
What wave changes on the EKG articulating Atrial Enlargement (AE) and what two leads provide the best view?
The P wave Changes.
V1 is positioned mostly over the Right Atrium
Lead II is normally aligned with the Atrial Axis
Since atrial activation starts in the Right Atrium (RA) and Left Atrium (LA) activation starts after, how should the P wave appear on Lead V1?
Biphasic
The Right Atrium fires towards V1 (positive wave) and the Left Atrium fires away from V1 (negative wave).
How would the P wave appear if there was Right Atrial Enlagrement (RAE)? and Left?
Since the P wave would be biphasic in Atrial Enlargement, RAE would present with greater amplitude in the positive portion of the wave. If there were LAE, the first portion would be normal and the negative portion would have greater amplitude.
How would the polarity of the P wave present between Lead II and Lead V1?
The polarity in Lead II would appear the same due to both signals traveling in the direction of the lead.
In V1, the wave would be Biphasic; the RA wave would be positive traveling towards V1 and the LA would be negative traveling away from V1
What are some consequences of Left Atrial Enlargement (Hypertrophy)?
- Mitral valve disease (stenosis or insufficiency)
- Aortic valve disease
- Hypertension
How would Left Atrial Enlargement (LAE) appear on an EKG?
Lead II would present with a wide, notched P wave, known as “P-Mitrale”
V1 would show a Biphasic wave with the Terminal Deflection being greater than or equal to 40ms with a depth greater than or equal to 1mm.
What are the criteria for Left Atrial Enlargement (LAE)?
- A wide, notched P wave in Lead II - “P-mitrale”
- A Biphasic wave in V1 with the terminal portion being greater than or equal to 40ms with a depth greater than or equal to 1mm.
What are some complications of Right Atrial Enlargement (RAE)?
- Tricuspid stenosis or insufficiency
- Pulmonary valve disease
- Pulmonary hypertension
How do you identify Right Atrial Enlargement (RAE) on an EKG?
“P-pilmonale”
- The P wave in Lead II will be taller than 2.5mm
- The positive deflection of the biphasic wave in V1 will be greater than 1.5mm
How do you identify Biatrial Enlargement on an EKG?
- In V1 there will be a deep terminal segment of the P wave.
- In II there will be a tall P wave.
