ECG Flashcards
What does the P wave and PR segment and QRS represent on a ECG?
P wave = Depolarization of Artia and AV Node
PR segment = Delay at AV node & depolarization of the bundle of HIS, bundle branches and Purkinje fibers
QRS - depolarization of cardiac myocytes (ventricles)
What is the difference in Segments & intervals
Intervals: The time between 2 waves and included an isoelectric segment
Segment: The time from the end of a wave and the start of the next
What is Einthovens Triangle
This is the make up of the views of the 3 lead ECG
Lead 1 = Right and left arm
Lead 2 = Right arm and left leg
Lead 3 = Left arm and left leg
What does Bi polar leads mean?
This is the leads reading the opposite side.
What are the 4 rules of current
A impulse travelling towards the positive lead will show a Positive (upright) deflection.
An impulse that travels towards the Negative lead will cause a negative (downward) deflection
An impulse that travels parallel to the lead will produce the greatest deflection.
impulses perpendicular to the lead will be small
Why is lead 2 used for general monitoring in the ECG
The bulk of the direction of depolarization in the heart is towards the +ve end of lead 2
We should see
Upright p wave
Upright QRS
Large complexes
What does the ECG paper represent
The vertical axis represents voltage in mV 10mm = 1 mV (10 tiny squares)
The Horizontal axis represents time in seconds
The TINY squares are 1mm by 1 mm and represent 0.04 seconds
A medium square is 5mm by 5mm and this represents 0.20 seconds
What leads are correlate where
Inferior leads receive blood by right coronary artery
Leads 2
Leads 3
Leads AVF
Lateral leads receive blood from left circumflex artery
Leads 1
Lead AVL
Leads V5 & V6
Both anterior and septal areas are supplied by left anterior descending artery
V1 & V2 are septal leads.
V3 & V4 are anterior leads
What is the 5 step systematic approach for analyzing a rythum
- Regularity
- Rate
- P waves
- PR intervals
- QRS complexes
What are the 3 types of irregularity in rhythms
Basically regular - A regular rhythm interrupted by a beat or two
Regularly irregular - has a pattern of irregularity (grouped beats)
Totally irregular - there is no pattern to the RRI’s
What is the easiest way of getting an irregular rhythm rate
The 6-second method
Print off a 6-second piece of paper and count the amount of QRS complexes in it and x that num by 10 e.g. 7x10=70
How long is a PR interval meant to be
0.12 & 0.20 seconds (3-5 small squares)
What are the normal for QRS complex
What is a normal PR Interval and a normal QRS
Nomral PR interval is 0.12 0.20 seconds
Nomral QRS is between 0.06 - 0.11 seconds
What are the 5 steps for normal sinus rhythm
What is the difference with sinus arrhythmia
The only different between sinus rhythm and sinus arrhythmia is that the R-R internal is irregular.
Most commonly caused by a change in vagal tone associated with breathing.
What are the 4 rhythms that originate from the atria
Wandering Pace maker
Atrial Tachycardia
Atrial Fibrillation
Atrial Flutter
(PAC , pre mature artial contraction)
What causes a wandering pacemaker
This is where is impluses fire from other areas other than the SA node.
The shape of the P wave can change as the site of origin changes
Causes could be from.
Increased vagal tone
Digoxin toxcitity
Heart disease
What are the rules for identifying wandering pacemaker
Irregular RRI’s may be slightly different
Rate: 60-100 per min
P wave: changes as pace maker site changes
PR interval: <0.20 secs (may vary)
QRS: <0.12 secs (uniform and constant)
What is artial tachycardia
This is one of the supraventricular tachycardias
Pacemaker site is not the SA node so the P waves are not smooth. the ventricles are able to keep up
HR: 150-250
This causes decreased cardiac output
What is Paroxysmal Atrial Tachycardia (PAT)
PAT is when there are brief periods of atrial tachycardia followed by periods of sinus rhythm
What are the 5 steps for Atrial tachycardia
Regular
Rate: 150-250 atrial and ventricular rates are equal
P wave: may be difficult to see if hidden in the T wave
PR interval: between 0.12-0.20 PRI is constant
QRS: less that 0.12 secs with uniform shape
What causes AF (Atrial Fibrillation)
This is where there is multiple pacemaker sites and is defined as chaotic electrical activity of the atrial tissue.
The impulses fire at such speeds that they cannot contract but quiver instead.
This causes decreased cardiac output
MI
and possibly formation of emboli
When does AF be considered controlled or uncontrolled
This is determined to the ventricular rate
<100/min = controlled A fib
>100/min = uncontrolled A fib
Uncontrolled A fib is associated with
heart failure
cardiac chest pain
Syncope
Cardiogenic shock
What are the 5 steps for AF
Irregularly irregular
Rate: artial rate is chaotic >350 per/min the ventricular rate is variable
P wave: no P wave
PR interval: Not measurable
QRS: <0.12 secs, constant, uniform QRS shape
What is Artial Flutter
This is another supraventricular tachycardia
It has characteristic flutter waves
Rate is between 250-350
AV node blocks all the flutter waves and allows time for ventricles to fill
Ratio of conduction is usually even - 2:1, 4:1, 8:1
What are the 5 steos for artial flutter
Atrial rhythm is regular, the ventricular rhythm will be regular is conduction is consistent
Rate: atrial rate 250-350, Ventricular rate depends on the ratio of impulses
P wave: Sawtooth Flutter waves
PRI: Not measurable
QRS: >0.12 secs
PAC is a ectopic beat
This is where there is a premature contraction of the P wave
What are the 3 rythums that originate at the AV junction
Junctional escape
Accelerated junctional
Junctional Tachycardia
What is a Junctional rythm
This happens when the SA node or pacemaker cells in the atria fail. The AV node then serves as the pacemaker sending the impulse upwards and downwards
What happens to the P wave in a junctional rythum
Since it is starting in the AV node it travels up and towards the negative electrode in lead 2 showing a inverted P wave
the impulse is travelling parallel and therefore shows a large P wave (<3mm)
What is Junctional escape
This is the fail safe rythum when the SA node and atria fail to fire
The rate can be 40-60 BPM
The P waves can be inverted in lead 2 occuring after before or be lost in the QRS
What is accelerated junctional rythum
This is where the pacemaker in the AV node becomes irritable and fire more rapidly
Rate can be 60-100 BPM
P waves will be inverted
What is junctional tachycardia
This is a type of supra ventricular tachycardia where the AV junction has over ridden the SA node
The rate can be 100-200 BPM
The P waves again are inverted
What is a PJC
A Premature Junctional Contraction occurs before a normal beat and are followed by a pause
The P wave will be inverted and may occur before after or hidden in the QRS
What is SVT
Supraventricular tachycardia is used to describe fast rhythms that have a pacemaker site above the ventricles
The QRS is narrow and the P wave is not identifiable due to the fast rate
These are regular rythms
How many different types of heart block are there
4
First degree is a delay od the impluse at the AV node rather than a block
second degree 1 & 2 allow some impulses to go through the AV node
Third degree is the most serious and has a complete block at the AV node
What does the ECG show in a first degree heart block
There is a prolonged PRI >0.20 (5 small squares) secs but is consistent
All P waves are eventually conducted to the ventricles
How do you identify a 1st degree heart block
how do you identify a 2nd degree type 1 hear block
how do you identify a 2nd degree type II hart block
Why is 3rd degree heart block so serious
This is because there is no impulses making it from the SA node down into the ventricles.
This causes the ventricular pacemakers to fire independently usually at a much slower rate dropping cardiac output
How do you Identify a 3rd degree heart block
What are the 3 ventricular rhythms
VT - Ventricular tachycardia
VF - Ventricular Fibrillation
Idioventricular Rhythm
What is a PVC
These are premature ventricular contractions and present with a wide QRS complex (3 small squares wide)
What is Bigeminy
This is a grouped beating of PVC’s (every other beat is a ectopic beat)
Can PVC’s cause VT
Yes when a PVC falls on a T wave it can cause the rthhm to go into a VT
What are the rules for VT
what are the rules for VF
What is a Idioventricular Rhythm
this is a last ditch escape effort when all the other pacemaker sites fail the pacemakers in the ventricles are take over.
The rate of this is usually 20-40 BPM
The QRS complexes are wide and bizzare with no P waves
what are the rules for Idoiventricular rhythm
