ECG Revisted Flashcards
What can ECGs helps see?
- Conduction abnormalities
- Structural abnormalities
- Perfusion abnormalities
Why are ECGs helpful?
- Relatively cheap and easy to undertake
- Reproducible between people and centres
- Quick turn around on results/report
- Leads are views of the heart
What is a vector?
A quantity that has both magnitude and direction
How is a vector usually shown?
by an arrow in the net direction of movement, whose size reflects the magnitude
What does an isoelectric line represent?
no net change in voltage I.e. vectors are perpendicular to the lead
What does the width of of the deflection show?
‘duration’ of the event
Which direction are upward deflection?
towards the cathode (+)
Which direction are downward deflection?
towards the anode (-)
What is each wave composed of?
both the up and downstrokes
What is the P wave?
electrical signal that signifies relaxation of the ventricles
What is the QRS complex?
electrical signal that stimulates contraction of the ventricles (ventricular systole)
What is the T wave?
electrical signal that stimulates contraction of the atria
What happens at the SAN? What does it look like on a ECG?
- Auto-rhythmic myocytes (sponateanously depolarising)
- Atrial depolarisation
- Wide as slow and not high as small and going more towards positive then negative vector
(P)
What happens at the AVN?
- AVN depolarisation
2, Isoelectric ECG - Slow signal transduction
- Protective
What happens at the bundle of his?
- Rapid conduction
- Insulated
What happens at the bundle branches?
Septal depolarisation (S)
What happens at the purkinje fibres (1)?
Ventricular depolarisation (R)
What happens at the purkinje fibres (2)?
Late ventricular depolarisation (S)