Lecture 2 - ECGs Flashcards
what is the rate of the SA node, AV junction, and ventrcles (purkinje fibres)?
AV junction = another pace-maker – can fire on its own if SA node isnt working
Purkinje fibres also fire on their own at 20-40
Muscle or nodes can still working individually, but heart still works
SA node is the fastest and that’s why it prevails
If you are doing exercise and HR is 40, something is wrong – between the AV and SA – the SA trying to pick up the slack from the AV
SA and AV use purkinje system – if using these fibres not using the system well enough
note: Muscle depolarizes slower than nerve fibres, (impulse sent is within a millisecond) – this is why it contracts slowly
describe the normal ECG wave
P = atrial depolarization
PR = lag between atria and ventrical - electrical mechanical coupling
QRS = ventrical depolarization
ST = lag period before repolarization
T = repolarization of ventrical
Where is repolarization of atrium? It is hidden in the QRS
The Q, R, and S waves occur in rapid succession, do not all appear in all leads, and reflect a single event, and thus are usually considered together. A Q wave is any downward deflection after the P wave. An R wave follows as an upward deflection, and the S wave is any downward deflection after the R wave. The T wave follows the S wave and, in some cases, an additional U wave follows the T wave.
Q first negative wave, R first positive wave, S second negative wave – if the first thing that happens is a positive wave, you dont name it a q anymore, it is an s after – the q does not exist anymore – it is based on the first thing you see – first thing you see is a Q or R, next you see is an S or prime of an R
what is the standard 12 lead vs rhythm strip?
A single lead tracing (rhythm strip) is assessed for heart rate, rhythm, and presence of arrhythmias. if hypertrophy, ischemia, or infarction is suspected a 12-lead ECG should be obtained (or if you want to compare previous ECGs for an individual).
what are the 5 steps to rhythm interpretation?
note: for rate - make sure the rate is also regular! from top of R to next top of R etc
What are the normal values of:
heart rate, QRS wave height and time, PR interval
HR: 60-100 bpm
QRS: 0.06-0.10s (7-8mm high)
PR interval: 0.12-0.20s
how to calculate ECG HR
define normal sinus rhythm, bradycardia, tachycardia
describe AV blocks
AV blocks
Total 3rd degree AV block
– dissociates the atrium and ventrical – on ecg would look like normal P, regular QRS but not really at the right time – your P functions independently of QRS, they are both regular just not clearly linked – P’s are marching through the QRS – will be wide bc not coming from sinus node
1st degree “block” = always have a P and QRS, but is it way longer – more than 200 ms – doesn’t really mean anything in terms of health
2nd degree block = type 1 and 2
1 – less severe - imperfect function of av node, once in a while drops a beat – progressively gets weaker and eventually can’t conduct - can live with this normally (no pacemaker) – type 1 is a sign that the system is getting weaker, but it can be fine for a few years – monitor them every few years
2 – no prolongation, suddenly it just drops an av beat – this becomes a 3rd degree block – dangerous – for this and 3rd degree block put in a pacemaker
*page 322-324
atrial tachycardia (rate, rhythm, P waves, PR interval, QRS complex, notes, causes)
atrial flutter (rate, rhythm, P waves, PR interval, QRS complex, notes, causes)
atrial fibrilation (rate, rhythm, P waves, PR interval, QRS complex, notes, causes)
ventrical tachycardia (rate, rhythm, P waves, PR interval, QRS complex, notes, causes)
ventricle fibrilation (rate, rhythm, P waves, PR interval, QRS complex, notes, causes)
atrial premature contraction - PAC (rate, rhythm, P waves, PR interval, QRS complex, notes, causes)
premature ventricular complexes - PVC (rate, rhythm, P waves, PR interval, QRS complex, notes, causes)
heart assessment points
Where you hear the sounds
Will hear valves closing best at these areas
Bone doesn’t transmit sound very well so go just left
1 (near aorta) – hear s2 louder than s1
2 will hear s1 and s2, but s2 louder
If right over tricuspid might hear them, etc
notes:
You have the sounds when the valve closes
S1 = the mitral intercuspid closing
S2 = …
S3 = blood flowing into a floppy ventrical – if your ventrical is normal, wont hear this sound
S4 = if tou have a-fiba nd don’t have an atrial contraction, you don’t get this sound – it is the sound of forcing more blood in when it is already full
