ECG Flashcards
How are ECGs generated
Depolarisation & repolarisation produce electrical current in opposite directions
Magnitude of reflection determined by:
Direction of depolarisation
Amount of muscle mass that is depolarising
Which lead you are using
What are the ECG leads
Lead I – RF & LF
Lead II – RF & LH
Lead III – LF & LH
Label the ECG
Explain origin of P QRS & T waves & PR & ST intervals
P wave – depolarisation of atria
QRS complex – ventricular depolarisation
Q = begins in septum, -ve
R = +ve
S = -ve
T wave – ventricular repolarisation
PR interval – time for electrical impulse to travel from atria to ventricles
ST interval – ventricles have depolarised but not yet begun to repolarise
What are some clues abnormal ECGs give us
Tall P wave = R atrial enlargement
Wide P wave = L atrial enlargement
Tall R wave = L ventricular enlargement
Deep S wave = R ventricular enlargement
What are wide and bizarre complexes
Ventricular premature complexes
Can happen if conducting system is damaged
P wave initiated but impulse not conducted normally
What causes this baseline interference
Muscle tremor (due to cat purring)
What is a long P wave suggestive of
Left atrial enlargement
takes longer for electrical activity to get from right atrium to left atrium as distance is longer. Not all animals with left atrial enlargement have long P wave & some large healthy breeds have long P wave
What is a tall P wave suggestive of
Right atrial enlargement
if you have more muscle you generate more electrical activity
What is a tall QRS complex suggestive of
Left ventricular enlargement
left ventricle is bigger than right so it dominates QRS complex, would need to be confirmed with imaging
What is a wide QRS complex suggestive of
Left ventricular enlargement
taking longer than normal for electrical activity to spread across left ventricle
