Electrocardiogram & rhythm disorders Flashcards
why is ECG used?
cheap
easy to undertake
reproducible
quick turnaround on results/reporting
what is ECG used to view/diagnose?
conduction abnormalities
structural abnormalities
perfusion abnormalities
what are ECG electrodes?
sticky pads placed on body
what are ECG cables/wires?
cables with coloured ends attached to machine and body
what are ECG leads?
heart perspectives based on where the electrodes are placed
what do the characteristics of deflections on the leads mean?
width of deflection - duration of event
steepness of line - velocity of action potential
downward deflection - towards -ve electrode
upward deflection - towards +ve electrode
what are the normal deflections on an ECG?
P wave - small upwards
QRS complex - tiny down large up tiny down
T wave - small but long upwards
what does the P wave of an ECG tell you?
conduction of sinoatrial node and atrial depolarisation
what does the pause between P and Q on an ECG represent?
atrioventricular node depolarisation
what is represented by the isoelectric line just before Q on an ECG?
rapid conduction down bundle of His
what is represented by the Q complex on an ECG?
bundle branches depolarisation/septal depolarisation
what is represented by the R wave of an ECG?
apex of heart purkinje fibre depolarisation
what is represented by the S wave of an ECG?
purkinje fibres depolarising up the side of the myocardium
what is represented by the isoelectric line between S and T waves on an ECG?
fully depolarised ventricles
what represents the T wave on an ECG?
ventricular repolarisation
what is the electrode placement for an ECG?
V1 - right sternal border of 4 IC space V2 - left sternal border of 4 IC space V3 - midway between V2/4 V4 - mid clavicular line of 5 IC space V5 - midway between V4/6 V6 - mid axillary line of 5 IC space electrodes on both limbs on both sides
what lead goes between right and left arm?
rule of Ls - lead I
what lead goes between right arm and left leg?
rule of Ls - lead II
what lead goes between left arm and left leg?
rule of Ls - lead III
how do you read ECG findings?
rate&rhythm P wave/P-R interval QRS duration QRS axis ST segment QT interval T wave
what is sinus rhythm on an ECG?
each P wave followed by QRS
normal and regular rate
otherwise unremarkable
what is sinus bradycardia on an ECG?
each P wave followed by QRS
rate is regular and slow
healthy, caused by medication or vagal stimulation
what is sinus tachycardia on an ECG?
each P wave followed by QRS
rate is regular and fast
often due to physiological response
what is sinus arrythmia?
each P wave followed by QRS
rate is irregular and normal
R-R varies with breathing cycle
what is atrial fibrillation on an ECG?
oscillating baseline - atria contracting asynchronously
rhythm may be irregular and rate slow
what is atrial flutter on an ECG?
regular saw tooth pattern in baseline (II,III,aVF) not always in all leads
atrial to ventricular beats at a 2:1 ratio, 3:1 ratio or higher
what is first degree heart block on an ECG?
prolonged P-R interval/segment
regular rhythm and rate
P waves followed by QRS complexes
what is second degree heart block mobitz I on an ECG?
gradual prolongation of PR interval until a beat skips
some P waves not followed by QRS
regularly irregular rhythm
what is second degree heart block mobitz II on an ECG?
regular P waves, only some are followed by QRS
no P-R prolongation
regularly irregular
what is third degree (complete) heart block on an ECG?
P waves regular, QRS regular but no relationship to each other
P waves can be hidden by other, larger vectors
non-sinus rhythm
what is ventricular tachycardia on an ECG?
P waves hidden
rate is regular and fast
no isoelectric line
but shockable rhythm
what is ventricular fibrillation on an ECG?
rate irregular and 250bpm+
shockable rhythm
what heart rhythms are shockable?
ventricular tachycardia
ventricular fibrillation
what is ST elevation on an ECG?
P waves visible followed by QRS
regular rate and rhythm
ST segment depressed >2mm below isoelectric line in leads related to obstructed vessel
myocardial infarction
what is ST depression on an ECG?
regular rate rhythm
ST segment depressed 2mm below isoelectric line
myocardial ischaemia - not infarction
what does a saw tooth pattern in II, III and aVF indicate?
atrial flutter
what does a gradual prolonging of PR interval until a beat dropped indicate?
2nd degree heart block Mobitz I
what does a prolonged PR interval with some dropped QRS indicate?
2nd degree heart block mobitz II
what does an ECG with no isoelectric baseline, no P waves indicate? massive waves with small wave on top
ventricular tachycardia
how to read cardiac axis
lead I and aVF
what is right axis deviation
lead I negative
lead aVF positive
+90°- +180°
right reaching
what is left axis deviation
lead I positive
lead aVF negative
−30° - −90°
left leaving
what is normal cardiac axis
lead I positive
aVF positive
when may left axis deviation be normal
tall thin people
due to lungs rotating heart straighter
when may right axis deviation be normal
short wide people
due to more space in the mediastinum
what may be a cause of left axis deviation
left ventricular hypertophy - more working cardiac muscle to have electrical activity
myocardial infarction in right side - muscle dies so less activity on that side, shifts left
what is a long PR interval
bigger than 1 big square
investigations for suspected blocked coronary artery
coronary angiogram
treatment for coronary artery blockage
CABG - coronary artery bypass graft (harvest another vessel and pop it on)
PCI - percutaneous coronary intervention (basically a stent)
what does a STEMI/NSTEMI in lead II, III and aVF indicate
inferior ischaemia/infarction
right coronary artery involvement
what does a STEMI/NSTEMI of lead I, aVL and V5,V6 indicate
lateral ischaemia/infarction
left circumflex artery
what does a STEMI/NSTEMI in V1 2 indicate
septal ischaemia/infarction
left anterior descending artery
what does a STEMI in V3, V4 indicate
damage to anterior heart
left anterior descending artery blockage
How to calculate rate if ecg is irregular rhythm
Rhythm strip QRS complexes x 6
