Introduction to the ECG Flashcards
What is normal cardiac axis value?
Between -30 and +90
What do P waves represent?
Atrial depolarisation
What does the PR interval represent?
The time between atrial and ventricular depolarisation (conduction through the AV node)
What does the QRS complex represent?
Ventricular depolarisation
What does the ST segment represent?
The time between ventricular depolarisation and repolarisation
What does the T wave represent?
Ventricular repolarisation
What does a large T wave suggest?
Hyperkalaemia
What does a small T wave suggest?
Hypokalaemia
What does an inverted T wave suggest?
MI or ischaemia
Which section of an ECG is inversely proportional to heart rate?
QT interval
What is the method for calculating regular heart rhythms on an ECG?
300 / number of large squares between R-R intervals
What is the method for calculating irregular heart rhythms on an ECG?
Number of QRS complexes x 6
Why is there a small negative deflection at the start of the QRS complex?
The left bundle branch depolarises the right bundle branch, so initially depolarisation spreads from left to right, away from lead II
Which ventricle normally has a larger vector and why?
Left ventricle - thicker muscle
A negative aVF suggests which change in cardiac axis?
Left axis deviation
A negative lead I suggests which change in cardiac axis?
Right axis deviation
A left axis deviation would primarily show up in which lead?
aVF (negative QRS)
A right axis deviation would primarily show up in which lead?
Lead I (negative QRS)
Pulmonary hypertension could cause which axis change?
Why?
Right axis deviation
Pulmonary hypertension leads to right ventricular hypertrophy (cor pulmonale)
Which view of the heart do leads I and aVL show?
Left lateral surface
Which view of the heart do leads II, III, and aVF show?
Inferior surface
Which view of the heart does lead aVR show?
Right atrium
Which view of the heart do leads V1 + V2 show?
Septum
Which view of the heart do leads V3 + V4 show?
Anterior
Which view of the heart do leads V5 + V6 show?
Lateral
QRS complexes should be less than how many milliseconds?
< 120 ms
What pathology does no P wave suggest?
Atrial fibrillation
What pathology does a prolonged PR interval suggest?
AV block
What pathology does ST elevation or depression suggest?
MI or ischaemia
Prolonged QTc increases the risk of which pathology?
Torsades de pointes
