Electrocardiography Revisited Flashcards
What is the clinical relevance of the ECG?
can identify conduction abnormalities, structural abnormalities and perfusion abnormalities
Advantages to the ECG
relatively cheap
reproducible between people and centres
quick turnaround on results/report
Downward deflections are towards which electrode?
anode (-)
Upward deflections are towards which electrode?
cathode (+)
An isoelectric line represents what?
no net change in voltage (i.e. vectors are perpendicular to the lead)
Steepness of line denotes the (?) of an action potential.
velocity
Width of the deflection denotes the (?) of the event.
duration
What does the P wave represent?
electrical signal that stimulates the contraction of the atria (systole)
What does the QRS complex represent?
electrical contraction that stimulates the contraction of the ventricles (systole)
What does the T wave represent?
signifies relaxation of the ventricles
SAN is made up of what type of cells?
autorhythmic myocytes
SAN stimulates what?
atrial systole
The PQ segment signifies?
AVN depolarisation
Q wave represents?
septal depolarisation
R and S wave represent?
R - ventricular depolarisation
S - late ventricular depolarisation
ST segment represents?
fully depolarised
T wave represents?
ventricular depolarisation
Lead I includes what limbs?
left arm to right arm
Lead II includes what limbs?
left leg to right arm
Lead III includes what limbs?
left leg to left arm
What is the rule of electrode reading?
left to right, top to bottom, first electrode of each pair is the anode (-ve)
V1 is placed where?
right sternal border
4th intercostal space
V2 is placed where?
left sternal border
4th intercostal space
V3 is placed where?
halfway between V1 and V2
V4 is placed where?
mid clavicular space
5th intercostal space
V5 is placed where?
anterior axillary line
at the level of V4
V6 is placed where?
mid axillary line
at the level of V4
What view of the heart?
ECG REVISITED LECTURE 1 TIMESTAMP 14.04
Most commonly used lead is?
II
How to calculate heart rate from ECG?
60/R-R interval = bpm
List the augmented limb leads.
aVF
aVL
aVR
The augmented limb leads use which electrodes?
fixed cathodes
virtual anodes
What is the angle between an augmented lead and the limb lead that has it’s virtual anode?
90 degrees
Which limb leads and augmented leads are perpendicular to each other?
aVR - Lead III
aVL - Lead II
aVF - Lead I
How to calculate axis with aVL and lead II?
find net deflection in both leads on ECG opposite side is Lead II adjacent side is aVL 90 degree angle use tan (x) find x report axis relative to zero zero to lead II is 60 0-x gives us axis
Reference for zero is?
looking at the heart from the same viewpoint as lead I
What other things to check when doing ECG?
Is it correct recording?
Review signal quality and leads
Verify voltage and paper speed
Review patient background if available
ECG reporting procedure
rate and rhythm P wave and PR interval QRS duration QRS axis (-30 to +90) ST segment QT interval T wave
QRS axis can be varied (within normal -30 to +90) for what reasons?
tall, thinner person tilts more +ve
shorter, stockier person tilts more -ve
