ECG Flashcards
what does the P wave represent?
atrial depolarisation
what do Q waves represent?
depolarisation of the inter ventricular septum
what does the QRS complex represent?
Ventricular depolarisation
what does the S wave represent?
depolarisation of the base of the heart
what does the PR interval represent?
the time it takes for the electrical activity to travel from the SA node to the ventricles
what is the normal time for the PR interval?
0.12-0.2 seconds
how long should a normal QRS complex be?
less than 0.1 seconds
what does the T wave represent?
ventricular Repolarisation
what does the ST segment represent?
The time where ventricular contraction is occuring
what does the QT interval represent?
the time for ventricular depolarisation and repolarisation
what is the normal time for the QT interval
0.36-0.44 seconds
What are the positions of the electrodes for each of the limb leads?
lead 1 - LA +ve, RA -ve
lead 2 - RA -ve, LL +ve
lead 3- LA -ve, LL +ve
what are the positions of the electrodes for the augmented leads?
AVR - positive electrode on right arm
AVL- positive electrode on left arm
AVF - positive electrode on left foot
what areas of the heart are recorded by the different limb leads and augmented leads?
Inferior - AVF, leads II and III
lateral - AVL, lead I
right lateral - AVR
which of the limb/augmented leads have positive/negative deflections?
- AVR is negatively deflected
- The rest are all positively deflected
what are the positions of the precordial leads?
V1 - 4th intercostal space immediately right of the sternum
V2 - 4th intercostal space immediately to the left of the sternum
V3 - between leads V2 and V4
V4- 5th intercostal space mid clavicular line
V5 - anterior axillary line on the same Level as V4
V6 - mid axillary line on the same level as V4
what areas of the heart do the precordial leads record?
V1,V2 - anteroseptal
V3,V4 - anterior
V5,V6 - lateral
how do you calculate heart rate from an ECG for a regular rhythm
300/ number of large squares between two R waves
how do you calculate heart rate from an ECG with an irregular heart rhythm
Number of R waves within 30 large squares x10
