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
