EKG Interpretation 1 and 2 Flashcards
What are the 6 goals of EKG evaluation?
- diagnose arrhythmia
- diagnose conduction blocks
- evaluate chamber enlargement
- ischemia
- electrolyte disturbance
- non-cardiac disease manifestations
Where is the SA node located and what is its inherent conduction rate?
What does it initiate?
What wave on the EKG is associated with it?
It is in the upper-posterior RA.
It depolarizes at 60-100 bpm.
It initiates atrial systole (squeezing blood into the ventricles)
It corresponds to the P wave on the EKG (SA to AV node)
Where is the AV node located and what is its inherent conduction rate?
What does it initiate?
What does it correspond to on the EKG?
Located near the inferior interatrial septum.
It has inherent conduction of 40-60bpm.
In sinus conduction, it serves as a delay to allow time for blood to enter ventricles before initiating ventricular systole.
AV node correlates to PR segment on the EKG
What are the conduction fibers of the ventricle called?
What does their depolarization correspond to on the EKG?
His bundles and Purkinje system (LBB and RBB)
Left bundle divides into left anterior and left posterior and is supplied by LAD artery.
Corresponds to QRS complex on the EKG
What is occurring in the heart during:
- P wave
- PR segment
- QRS wave
- T wave
- U wave
- atrial depolarization (SA to AV) or P’ if its an ectopic atrial site to AV
- Delay at AV node (due to Ca not Na)
- ventricular depolarization- LBB and RBB
- ventricular repolarization
- delayed repolarization (seen in hypokalemia)
What is the paper speed for EKG?
What is each “little box”?
What is each “large box”?
What are the axis of the paper?
25mm/s
Each little box is 1mm and 40 msec and each large box is 5mm and 200 msec
Horizontal : time
Vertical : voltage (each 10mm is 1 mV)
What are the limb leads? What plane do they look at the heart from?
I, II, III, AVF, AVL, AVR and they look at the heart from the frontal plane
What are the precordial leads and what plane do they look at the heart from?
V1-V6 and they look at the heart from the vertical plane (front to back)
If an impulse is traveling toward a lead, what will be the direction of the deflection on the EKG?
+
What are the 8 steps for reading an EKG?
- Name
- Rate
- Rhythm
- Axis
- Intervals
- hypertrophy
- infarctions
- important patterns
How do you calculate rate?
Find a QRS on a dark black line from a large box.
300, 150, 100, 75, 60, 50
If below 50, use the 3 second marks to figure out how many peaks were in 6 seconds and multiply by 10.
OR count the number of peaks on the rhythm strip of the sheet (10 seconds) and multiply by 6
What is the inherent conduction rate of:
- ventricle
- junctional rhythm
- normal sinus rhythm
- sinus tachycardia
- supraventricular/ventricular tachycardia
- Flutter
- Fibrillation
- 20-40 bpm
- 40-60 bpm
- 60-100 bpm
- 100-150 bpm
- 150-250 bpm
- 300 integers (300, 150, 100)
- 350+
What is “normal sinus rhythm?
regular rate of 60-100 bpm.
P wave with the same morphology preceding each QRS complex
Describe bradycardia with idioventricular rhythm.
It goes at a rate of 20-40 bpm with no P waves and wide QRS. This is because there is no SA node, AV node stimulation or His/bundle branch. Instead of depolarizing at the same time, the ventricle will depolarize more slowly.
What is junctional rhythm?
The “pacemaker” is the AV junction instead of the SA node so the rate will be 40-60 bpm.
There will be no P waves because there is simultaneous depolarization of atria and ventricle
Low in junction: P wave inverted/ after QRS
High in junction: P wave inverted before QRS
What are 5 common causes for the heart switching to junctional rhythm?
- hypoxia
- ischemia
- digitalis toxicity (Digoxin OD)
- electrolyte abnormality (hypokalemia)
- chronic lung disease
What is the difference between sinus bradycardia and wandering atrial pacemaker?
Who are these conditions usually seen in?
Sinus bradycardia is still conducting from the SA node, just slower. All the P waves will look the same and be followed by QRS.
Wandering atrial pacemaker- different ectopic pacemakers in the atrium are firing to the AV node so the P waves will look different. They will still all be followed by QRS
Both can be normal and seen in young healthy athletes
What is multifocal atrial tachycardia?
What 3 pathological states might you see MAT in?
Three different P wave morphologies followed by a QRS complex at a rate greater than 100 bpm (below 100 it is wandering atrial pacemaker).
- chronic lung disease
- coronary artery disease
- congestive heart failure
Describe the waveform of sinus tachycardia.
It has a rate between 100 and 150 bpm due to conduction from the SA node. It has the same morphology P followed by QRS I can be due to: 1. exercise 2. infection 3. MI 4. PE 5. sepsis 6. obesity 7. hyperthyroidism
Describe the rate of paroxysmal supraventricular tachycardia.
What are the 2 major types?
What is the rhythm?
PSVT has a regular rhythm between 150-250bpm originating in the atria.
- AVNRT- av node reentry tachycardia
- AVRT- AV reciprocating tachycardia (associated with WPW)
PSVT usually involves a reentry pathway that has been triggered by a premature atrial contraction.
This results in delayed conduction to ventricles and wide QRS
What is atrial tachycardia?
- HR
- Rhythm
- P wave
- PR interval
- QRS
Regular rhythm that is fast because of a reentry pathway in the atria at a focus other than the SA node.
P wave is different from SA node P wave, but is regular and conducts 1:1 with the ventricle.
- 150-250
- regular
- abnormal P before each QRS
- <.12
What is the cause of atrial flutter?
What is the rate?
What determines ventricular contraction?
What can cure atrial flutter?
- Reentry pathway in the atrium that causes the atria to have a rate that is an integer of 300.
- 300, 150, 100, 75
- The AV node determines the ventricular contraction and fires in a 2:1 or 4:1 blocking some of the atrial conduction
- cured by ablation (cryo or radiofreq)
If the HR is 150, what should one view as the prime reason?
Atrial flutter with a 2:1 block rather than a sinus tachycardia
What is the rhythm of atrial fibrillation due to?
What is the rate of atrial contraction?
What is the ventricular rate?
What does the waveform look like?
It is due to multiple reentry pathways in the atria that cause irregular rate over 350.
AV node blocks most impulses and leads to a ventricular contraction rate of 60-140.
It looks irregularly irregular because there is no coordination between atrial and ventricular contraction.
No P waves, bc the chaos in the atrium can’t sustain contraction
What is the regular rate of a ventricular tachycardia?
What is characteristic about the waveform?
What is the cause?
120-220 bpm and the QRS waves are really wide because the ventricle has to depolarize itself by reentry instead of using conduction pathways.
It is caused by hypoxia, hypokalemia, ischemia
What is ventricular fibrillation?
What does the waveform look like?
What is the treatment?
V fib is pulseless, chaotic contraction of the ventricle caused by ischemia or hypoxia.
It looks like a “bag of works”
The patient needs to be shocked out of it.
What is a premature beat?
What are the 2 kinds?
Irregular beats that occur when another focus takes over as the pacemaker for a beat and then returns to SA conduction.
PAC - premature atrial contraction
PVC or VPB- premature ventricular contraction (ventricular premature beat)
What is bigeminy?
When a premature beat occurs at a fixed rhythm.
Normal beat, premature beat, normal beat, premature beat
What is sinus arrhythmia?
variation in rhythm with respiration but it is really small and not clinically significant
What is meant by axis?
What is the normal axis?
What is LAD (left axis deviation)?
What is RAD (right axis deviation)?
The estimate of the angle of the hearts primary electrical vector.
Normal = -30 to 90
LAD = 90 ( more positive)
What gives you the correct axis?
the isoelectric lead (QRS height with equal positive and negative deflection)
Lead I protects the _____ axis. If QRS is negative in lead I then there is a _____________.
Right, right axis deviation
Lead II protects the _____ axis. If QRS is negative in lead II, then there is a ___________________.
left, left axis deviation
If lead I and lead II both have negative deflections, the patient has __________________________.
Extreme right or left deviation
If I and AVF are both positive, the axis is _________.
Normal
What leads tell you the axis is normal?
+ deflection of lead I and AVF
What are 9 causes of right axis deviation?
- infants/ tall thin adults
- RV hypertrophy
- chronic lung disease
- anterolateral myocardial infarct
- left posterior hemiblock
- PE
- WPW syndrome with left sided accessory
- atrial septal defect
- ventricular septal defect
What are 6 causes of left axis deviation?
- left anterior hemiblock
- emphysema
- hyperkalemia
- WPW with a right sided accessory
- tricuspid atresia
- ostium primum ASD
After you identify a right or left axis deviation, what do you do?
Find the most isoelectric lead. 90 degrees to that will be the direction of the impulse (perpendicular to the isoelectric lead)
What is the normal PR interval?
What is the PR interval?
Where does it begin? end?
The PR interval is the time between atrial and ventricular depolarization (slow conduction through the AV node).
It starts at the BEGINNING of the P wave to the beginning of the QRS complex.
It is 0.12-0.2 seconds (3-5 small blocks on the EKG)
What does a PR interval less than 0.12sec suggest?
What are the 3 major symptoms the patient will present with?
a pre-excitation syndrome where there is an accessory pathway conducting to the ventricles faster than the normal SA-AV node pathway.
Patients present with shortness of breath, palpitations and chest pain
What are the two major syndromes associated with short PR interval (below 0.12)?
- Wolf-Parkinson-White (WPW) where the bundle of Kent creates a delta wave indicating pre-excitation of the ventricle.
- Lown-Ganong-Levine which has an accessory pathway NOT associated with a delta wave due to the fact that it merges with the his-purkinje bundle below the AV node.