Normal ECG Flashcards
Which leads have an inferior view of the heart?
2, 3, aVF
Which leads have a lateral view of the heart?
1, aVL, aVR, V5, V6
Which leads have an anterior view of the heart?
V3, V4
Which leads have a septal view of the heart?
V1, V2
Why can we consider all atrial and all ventrical cells to contract as groups?
cardiac myocytes are connected by gap junctions which allow rapid transmission of electrical impulses from cell to cell
Which direction does current flow?
from negative to positive
What direction is the current going if there is an upward deflection?
current moving towards electrode
What direction is the current going if there is a downward deflection?
current moving away from electrode
What directions do the deflections of depolarisation and repolarisation point?
the same direction
What is the natural pacemaker of the heart?
sinoatrial (SA) node
pacemaker cells spontaneously depolarise and initiate the heartbeat
Is depolarisation or repolarisation slower? How does this show on an ECG?
repolarisation is a slower process
deflection is wider and has a smaller amplitude
What 2 types of waves can an ECG record?
depolarisation
repolarisation
What does the P wave represent? What does it look like?
atrial depolarisation
dome-shaped + symmetrical
What does the QRS complex represent?
ventricular depolarisation
What does the T wave represent? What does it look like?
ventricular repolarisation
longer than P wave + asymmetrical
usually points same direction as QRS complex
What does the PR interval represent?
the time for wave of depolarisation to spread from SA node –> across atria –> through AV node –> ventricular muscle
measure from beginning of P wave to beginning of QRS
Why is having adequate PR interval important physiologically?
physiologic delay gives ventricles enough time to fill up with blood before they depolarise
What is a Q wave?
if the first deflection is down in the QRS complex, this is a Q wave
What is an R wave?
the first upwards deflection of the QRS complex
What is an S wave?
the downward deflection after an R wave
What does the ST segment represent?
interval between ventricular depolarisation and repolarisation
flat, isoelectric portion of ECG between S wave and T wave
What does the QT interval represent?
time taken for ventricular depolarisation an repolarisation
beginning of QRS to end of T wave
What are the limb leads? How can these be further classified?
limb leads = 1, 2, 3, aVR, aVL, aVF
bipolar leads = 1, 2, 3
augmented leads = aVR, aVL, aVF
What are the chest leads?
V1, V2, V3, V4, V5, V6
