FInal- ECG Flashcards
Normal impulse conduction in heart
Sinoatrial node AV node Buundle of His Bundle branches Purkinje fibres
What is P wave, QRS and T wave
P- Atrial depolarization
QRS- Ventricular depolarization
T- Ventricular repolarization
What happens in the PR interval
Atrial depolarization + delay in AV junction (delay allows time for atria to contract before the ventricals)
3 pacemakers of the heart
SA node- dominant pacemaker with rate of 60-100 BPM
AV node- Back up pacemaker with rate of 40-60BPM
Ventricular calls- Back up with rate of 20-45bpm
ECG paper- horizontaly how long is a small and large box
Vertically one large box is how many mV
small- 0.04s
large- 0.20
vertically- 0.5mV
15 boxes is how long
3 seconds
5 steps in rythm analysis
- calculate rate
- determne regularity
- Assess the P waves
- Determine PR interval
- determine QRS duration
How to calulate rate
find r wave that lands on bold line and count number of large boxes it is away ( one box away = 300 then 2=150, 100, 75, 60, 50)
How to calculate regularity
look at r-r distances (regular, occasionaly irregular, regularly irregular, irregularly irregular)
How to assess the p waves
- are there p waves
- do the p waves occur at a regular rate
- is there one p wave before each QRS
How to determine PR interval
usually 0.12-.20 sec (3-5 boxes)
How to dtermine QRS duration
usually 0.04-0.12 sec
1-3 boxes
What are some SA node problems
fire to slow- bradycardia
fire to fast- tachycardia
What are some atrial cell problems
fire occasionally premature
fire continuosly due to a looping re-entrant circuit (atrial fibrilation)
AV junctional problems
- fire continously due to looping re-entrant curcuit (paroxysmal supraventricular tachycardia)
- block impulses coming from the SA node
Ventricular cell problems
- fire occasionally from 1 or more foci (premature contraction)
- Fire continously from multiple foci ( ventricular fibrilation)
- FIre continously due to looping re-entrant circuit ( ventricular tachycardia)
2nd degree av block, type 1
PR interval progressively lengthens then the impulse is completely blocked (p wave not followed by qrs)
2nd degree av block, type II
Occasional p waves are completely blocked
3rd degree av block
P waves are completely blocked in the AV junction, QRS complexes originate independently from below the junction
sinus bradycardia
<60 bpm (SA node depolarizing slower than normal)
sinus tachycardia
> 100bpm
Premature atrial contractions
Originate in the atria therefore contour of the P wave, Pr interval and timing are different
PVCs
One or more ventricular cells are depolarizing and impulses are abnormally conducting through the ventricals (looks like massive spike downswards)
Atrial fibrilation
No atrial depolarization so no normal P waves
atrial activity is chaotic resulting in irregular irregular HR
Atrial flutter
No p waves, instead flutter waves (sawtooth pattern)
caused by reentrant pathway in r. atrium
PSVT
the heart rate suddenly speeds up, p waves are lost
Ventrical tachycardia
impulse is originating in ventricals ( no p waves, wide QRS), looks like massive hills
Ventrical fibrilation
completely abnormal just random small waves
what leads look at lateral wall, anterior wall, septum, inferior wall
lateral- 1, aVl, V5, V6
anterior- V1-V4
Septum- V1, V2
Inferior wall- 11, 111, aVF
ST elevation or depression
in two leads is consistent with a myocardial infarction
