Electrocardiography and rhythm disorders Flashcards
what is the clinical relevance of ecg
conduction abnormalities
structural abnormalities
perfusion abnormalities
what are some advantages of ecgs
relatively cheap and easy to undertake
reproducible between people and centres
quick and can give results over period of time
what are the sticky tabs called
electrodes
what are leads?
conceptual views - 12 leads
how many cables/wires are used in an ecg
10
what do downwards deflections show
going towards negative electrode
what do upwards deflections show
electrical activity is going towards positive electrode
what does a flat line on ecg show
electrical activity is 90 degrees/perpendicular to angle of lead = isoelectric
what does the steepness of the lines denote
velocity of action potential
= faster wave of excitation
what does width of deflection show
duration of the event
what does the p wave represent
electrical signal that stimulates contraction of the atria = atrial systole
what does qrs complex represent
electrical signal that stimulates contraction of the ventricles - ventricular systole
what does t wave represent
electrical signal signifies relaxation of ventricles
what does p wave on lead 2 do
shows action of sinoatrial node -
autorhythmic myocytes
atrial depolarisation
what does neg q wave on lead 2 show
septal depolarisation
negative - because some signals escape
what does r wave show on lead 2
ventricular depolarisation via purkinje fibres
what does neg s wave show
late ventricular depolarisation
heads in opposite direction
what does t wave on lead 2 show
ventricular repolarisation
where is placement of electrodes on lead 1
right arm to right leg
placement of electrodes on lead 2
right arm to left left
placement of electrodes on lead 3
left arm to left leg
how many chest electrodes are there?
6
where does v1 get placed
right sternal border in 4th intercostal space
where does v2 get placed
left sternal border in 4th intercostal space
where does v3 get placed
halfway between v2 and v4
where does v4 get placed
mid clavicular line in 5th intercostal space
where does v5 get placed
anterior axillary line at level of v4
where does v6 get placed
mid axillary line at level of v4
what information is given on ecgs
space for : name age dob where ecg taken rate of paper 12 leads
what is rate of paper always
25mm/s
amplitude/voltage
10mm/mv
how much is little and small square worth in time
big square = 0.2s
small square = 0.04s
which leads correlate with left circumflex artery
lead 1
aVL
which leads correlate with right coronary artery
lead 2
lead 3
aVf
which leads correlate to left anterior descending artery
v1,
v2
v3
v4
what is the ecg reporting procedure
rate and rhythm p wave and pr interval qrs duration qrs axis st segment (qt interval t wave)
what must you check before reading ecg
is it correct reading - matches patient?
review signal quality and leads
verify voltage and paper speed
review patient background if available
what is sinus rhythm
basic rhythm
each p wave is followed by qrs wave
rate is regular annd normal hr 60-100bpm
what is sinus bradycardia
each p wave followed by qrs complex
rate is regular but slow <60bom
can be healthy but caused by med/vgal stimulation
what is sinus tachycardia
each p wave is foloowed by qrs complex
rate is regular but fast >100
often due to physiological response
what is sinus arrythmia
each p wave followed by qrs complex
irregular rate
r-r interval varies with breathing cycle
what is atrial fibrillation
oscillating baseline
rhythm can be irregular and rate can be slow
turbulent flow pattern increases clot risk
what is atrial flutter
regular saw tooth pattern in baseline - 2,3 and avf
atria: ventricular beats is 2:1/3:1 ratio
* saw tooth not always visible
what is a first degree heart block
prolonged pr segment - caused by slower av conduction
regular rhythm
progressive disease of ageing
what is second degree heart block - mobitz 1
aka Wenckebach
gradual prolongation of pr interval until beat skipped
some p waves not followed by qrs
what is second degree mobitz 2
p waves are regular but only sum followed by qrs
no pr prolongation
regularly irregular
can rapidly deteriorate to 3rd degree block
what is a third degree heart block/complete block
p waves are regular, qrs are regular but no relationship dissociation of sa nodes to ventricles p waves hidden within bigger factors truly non sinus rhythm - pacemaker in action
what is ventricular tachycardia
p waves hidden - dissociated atrial rhythm
rate is regular and fast
high risk of deteriorating into fibrillation
shockable rhythm
what is ventricular fibrillation
heart rate is irregular 250bpm and above
heart is unable to generate output
shockable rhythm
what is st elevation
p waves are visible and always followed by qrs
rhythm is regular and rate is normal - 85bpm
st egment elevated - 2mm above isoelectric line
caused by infarction - tissue death caused by hypoperfusion
st depression
p waves are visible and always followed by qrs
rhythm is regular and rate is normal - 95bpm
st egment depressed - 2mm below isoelectric line
caused by myocardial ischaemia - coronary insufficiency
