1. Chest pain- ECG basics and interpretation Flashcards
Basics:
What is the P wave
atrial depolarisation
Basics:
what is the PR interval
time taken for electrical activity to move between atria and ventricles
Basics:
what is the QRS complex
depolarisation of the ventricles
Basics:
what is the ST segment
the time taken between depolarisation and depolarisation of the ventricles
Basics:
what is the T wave
ventricular depolarisation
Which ECG leads represent the inferior view of the heart
II
III
aVF
which ECG leads represent the anterior aspect of the heart
V3
V4
which ECG leads represent the septal aspect of the heart
V1
V2
which ECG leads represent the lateral aspect of the heart
I aVL V5 V6 (aVR)
ECG interpretation:
If you are given an ECG what are the first things that you would check
Name on the ECG
date on the ECG
the settings are 25mm/sec, 10mm/mv
ECG interpretation:
How do you work out the rate
300/number of big squares between two R waves
or count the number of R waves in the 10 second strip and multiple by 6
ECG interpretation:
How do you know the ECG lead is in normal sinus rhythm
sinus rhythm means there will be a P wave between 3-5 squares
ECG interpretation:
how do you know if the axis are normal
leads I, II, III should all have positive deflections
ECG interpretation:
When looking at the QRS complex how do you know if it is broad or narrow
from beginning of Q wave (or R wave if there is no Q) should be less than 3 small squares
ECG interpretation:
What would be suggested if the QRS is broader than 3 small squares
either the rhythm is originating in the ventricles or there may be a conduction issue (ie a bundle branch block)
ECG interpretation:
how do you know if the cardiac axis is normal
If leads I and II are both positive then the axis is normal
(if lead I is positive and lead I is negative then probably LAD)
(if lead I is negative and lead II is positive then probably RAD)
ECG interpretation:
what are you looking at with the Q waves and what is pathological Q wave
- Q wave is the first downwad deflection before an R wave (R wave is first upward deflection)
- pathological if more than 1 square wide
- pathological if more than 2 squares deep (except in leads III & aVR)
- pathological if seen in chest leads V1-V3 as no Q waves are usually present in these leads
ECG interpretation:
how do you know if there is a LBBB
broad QRS complex ie greater than 3 small squares
deep S wave in V1
no Q wave in V5/6
ECG interpretation:
if LBBB is present then what is it not possible to do
make any further diagnosis of the ECG
ECG interpretation:
how do you know if there is a RBBB
broad QRS complex ie greater than 3 small squares
RSR (2 peaks) in V1
Slurred S wave in lateral leads I, V5, V6
ECG interpretation:
what do normal T waves look like
upward in all lead except aVR (where everything is weird), V1 and sometimes V2
ECG interpretation:
what should the ST segment look like
isoelectric with the rest of the ECG baseline and some deviation of more than 1mm above or below is abnormal
ECG interpretation:
what would ST depression mean
the heart muscle isn’t dying but it is hurting for oxygen (ischemic endocardium)
ECG interpretation:
what would ST elevation mean
the heart muscle is dying and this is a cardiac schema which needs to be treated immediately
Can see T wave inversion as well
What is atrial fibrillation (Afib)
there is no organised signal between the SAN and AV node which causes atrial spasming
what does atrial fibrillation look like on an ECG (Afib)
- there is an irregularly irregular rhythm (look at the distance between the R-R interval)
- no distinct P waves
What is supraventricular tachycardia (SVT)
the abnormal heat beat stats at or above the Av node
the heartbeat is above 100bpm at rest
may be asymptomatic but also may have paliptations and chest pain
what does supra ventricular tachycardia (SVT) look like on an ECG
- Regular rhythm with a very high rate
- No clear P waves
What is ventricular tachycardia (Vtach)
rapid heart heart beat that arises in the ventricles
caused by irritation by hormones, low O2, stretch
caused also by scars in myocardium
how is ventricular tachycardia diagnosed on an ECG
- broad QRS complex (more than 3 small squares)
- no clear P waves
- high rate above 100
what is ventricular fibrillation
ventricles loose the ability to contract and circulate blood to rest of the body therefore person will be unconscious
won’t be able to feel a pulse
will have course squiggly lines on ECG
name some risk factors for Vfib and Vtach
- Irritable ventricular cells (CAD and electrolyte abnormalities such as high K+ or low Ca2+
- Scar tissue (heart attack and cardiomyopathy which is disease of the heart tissue and can be caused by infection, genetic disorders and CAD)
- Electrocution
what would atrial flutter look like on an ECG
saw-tooth appearance of P waves
Complications post MI:
what are the 3 main problems with the hear post MI
decreased contractility
electrical instability
tissue necrosis
Complications post MI:
why is decreased contractility a problem
get pathological low blood pressure as LV can’t pump enough blood to the rest of the body leading to decreased coronary vessel perfusion
can lead to ischemia, cariogenic shock and a ventricular thrombus may form
Complications post MI:
why is electrical instability a problem
lead to arrhythmias
Complications post MI:
what happens is the papillary muscles becomes necroses
then the caudate tendinea can’t ensure the valves don’t invert
Complications post MI:
how does cardiac tamponade occur
necrosis of ventricle therefore it ruptures into the pericardium
