Basic Intervals and Measurements Flashcards
What is meant by the term ‘wave’?
deflection from baseline which determines a cardiac event
height of wave = amplitude mV (millivolts)
What is meant by the term interval?
distance occurring between two cardiac events
measured in time
What is meant by the term segment?
specific portion of the complex
How do you measure heart rate?
1500 / number of small squares between R-R (each complex)
How to convert R - R interval into HR (BPM)?
60000 / R - R interval ms
What does the P wave represent?
time taken for depolarisation to spread across the atria
What does the PR interval tell us?
time taken for depolarisation to spread from SA node, across atria, through the AV node and then the bundle of his
QRS marks the start of ventricular depolarisation
Where is QRS duration best measures?
lead with a Q wave (first negative deflect)
Where must the PR interval be measured?
Lead II
What does the QRS complex tell us?
time taken for ventricular depolarisation
Purkinje fibres adapted to rapidly depolarise ventricles
What does the QT interval tell us?
time for depolarisation to spread across ventricles, period where no electrical forces are produced, time for repolarisation
How to measure amplitude such as P wave?
number of small squares / 10
