ECG Flashcards
(19 cards)
P wave
Atrial depolarisation <0.12s
QRS complex
Ventricular deoplarisation about 1 second
T wave
Ventricular repolarisation
PR Interval
Largely AV node delay 0.12-0.2
ST Segment
Ventricular systole, end of QRS to start of T wave
TP Interval
Diastole (ventricles relax)
what is the pacemaker potential?
slow depolarisation of membrane potential to a threshold
what is the pacemaker potential due to?3
- decrease in K efflux
- Na influx (funny current)
- Transient Ca influx through T type Ca channels
what causes a rising phase of action potential in pacemaker cells?
activation of L type Ca channels which causes a Ca influx
what causes repolarisation in pacemaker cells?
Inactivation of L type Ca channels and activation of K efflux
what is in the intercalated disc between cardiac myocytes?
desmosomes and gap junctions
what is the resting membrane potential of atrial and ventricular myocytes?
-90mV
what happens when depolarization moves away from the recording electrode?
upwards deflection on ECG
position of the standard limb lead?
I : RA to LA
II : RA TO LL
III : LA to LL
QT interval
start of QRS to end of T wave, 0.44-.46 seconds
what are the lateral leads?
I and aVL
what are the inferior leads?
II, III, aVF
which leads look at
- inter ventricular septum?
- anterior of the heart
- lateral aspect of the heart
V1 and V2
V3 and V4
V5 and V6
Khogali’s 6 step ECG analysis?
- Verify patient details: name and date of birth
- Check date and time ECG was taken
- Check the calibration of the ECG paper
- Determine the axis, if possible
- Workout the rate and rhythm – use the rhythm strip and ask yourself the following 7 questions:
1 Is electrical activity present?
2 Is the rhythm regular or irregular?
3 What is the heart rate?
.4 P-waves present?
5 What is the PR interval?
6 Is each P-Wave followed by a QRS complex?
7 Is the QRS duration normal? - Look at individual leads for voltage criteria changes OR any ST or T-wave changes
