What causes the P wave?
Atrial Depolarization
What is the difference between a sevment and and interval?
Segments are the distance between waves, and do not include other waves,
Intervals include other waves
What should a normal PR interval be?
less than 0.2 seconds (one big or five little boxes)
How long should the QRS interval be?
Less than 0.12 seconds
How long a time interval are the big and small boxes?
Big = 0.2 seconds
Little = 0.04 seconds
If determining rate from the box method, what does each additional box count bring the heart rate to?
300
150
100
75
60
50
If using a six second strip, multiply by?
10
What are the six steps for analyzing an ECG?
- –Rate
- –Rhythm
- –Axis
- –Hypertrophy
- –Infarction
- –Wave interval and segment abnormalities
Rate and Rhythm?
~75
Normal sinus rythym
Unipolar chest leads are in what plane?
Horizontal plane
Describe the sequence of ventricular depolarization!
- Depolarization starts at the ventricular septum (Q wave) and the endocardial surfaces.
-
Average current flows from the base of the heart to the apex (R wave).
-
At the end of depolarization, the current reverses, flows toward the outer walls of the ventricles near the base (S wave).
Average current flows from the base of the heart to the apex (R wave).
At the end of depolarization, the current reverses, flows toward the outer walls of the ventricles near the base (S wave).
Describe the P waves and QRS complex in an atrial rythm.
Upright P waves
Narrow QRS
Describe the P waves and QRS complexes in Junctional rythms.
P waves will be absent or inverted
Narrow QRS complex
describe the P waves and QRS complexes in ventricular rythms
No P waves
QRS complexes are wide
What are the QRS complexes like for supraventricular rhythms?
Narrow QRS complexes
What is the characteristic description of the Atrial flutter rhythm?
What does it tend to deteriorate into?
"saw tooth"
Deteriorates into Atrial fibrillation
A-Fib is classically described as?
Irregularly irregular
(Wait, I though Steve and Michael described this as "a fuck"? TIL.)
What causes a WPW rhythm, and what does it look like?
D/t accessory conduction pathway - Bundle of Kent
Presence of delta waves - P waves merge into the QRS
Shortened PR interval
What is shown here?
What do you see here?
Wandering pacemaker
Rhythm?
Atrial Flutter
What does this patient have?
Atrial Fibrillation
Note lack of P waves, and QRS complexes occuring without pattern
Rhythm?
Junctional
No P waves before QRS, so not atrial origin
Rhythm?
Junctional Tachycardia
note the inverted P waves
Rhythm?
WPW
Rhythm?
WPW
What defines a first degree AV block?
a prolonged PR interval greater than 0.2 seconds
Second degree AV blocks have variable penetration of AV conductions, with lone P waves without QRS following.
What are the types?
Type I - Wenckebach: progressively prolonged PR intervals with a subsequent dropped beat and lone P wave. Usually in a fixed ratio/pattern
Type II - Mobitz: Failure of AV conduction in a fixed ratio/pattern, the PR inverval is not gradually increasing in length. Presents with a widened QRS.
What goes on in a third degree heart block?
–Complete Atrial and Ventricular dissociation – both are being independently paced
Rhythm?
First Degree AV Block
Rhythm?
Wenckebach (type I second degree heart block)
Rhythm?
Wenckebach
PR interval becomes progressively longer until it can no longer conduct.
Described as regularly irregular
Rhythm?
Mobitz type II
3 P waves per depolarization
Rhythm?
Second Degree AV block
Mobitz type II
Two P waves per depolarization
Rhythm?
Third degree AV block
Note how the P waves are disconnected from the QRS complex.
The P waves and QRS complexes have their own independent periodicities.
What is a typical cause of ventricular tachycardia?
–Irritable focus of a ventricular origin – usually reentry mechanism
The term "twisted ribbon" would likely refer to what?
Torsades de pointes
If you hear "multiple irritable automatic foci depolarization" you should think?
Ventricular fibrillation
What is shown here?
Ventricular Bigeminy
What is shown here?
Ventricular Tachycardia
Rhythm
Torsades de Pointes
Rhythm?
Prolonged QT syndrome
Rhythm?
Prolonged QT syndrome (hypomagnesemia)
Rhythm?
Ventricular Fibrillation
Bundle branch blocks are d/t lack of synchronization of the bundle branches. If the left bundle conducts first then?
Where would this be best viewed (what leads)?
Right bundle branch block
View in V1 and V2
If the right bundle branch conducts first then?
Best viewed in what leads?
Left bundle branch block
Best viewed in V5 and V6
Identify the indicated structures!
What do you see here?
Right bundle Branch Block
Rhythm?
Right bundle branch block
Rhythm?
Left bundle branch block
What is the normal cardiac axis?
–0-90 degrees is normal (actually -30 to 110)
Where would you find the cardiac isoelectric point?
Right angle from the axis plane
The limb leades determine what?
Since in the frontal plane, they determine the axis
The chest leads determine what?
In the horizontal plane, so they determine rotation
What is the axis?
+30
Axis?
-90
What is the axis?
-60
What is the axis?
0
Axis?
+100
