11 - ECG Flashcards
What stops the wave of depolarisation from passing straight from the AV node to the ventricles?
Dense connective tissue
Label this diagram of the conducting system of the heart.
Describe how the path of depolarisation and repolarisation occurs in the heart.
How do repolarisation and depolarisations appear on an ECG?
Describe what the following electrical waves of activity would look like on an ECG?
How does SAN depolarisation appear on an ECG?
No trace, not sufficient enough to surface
How long does atrial depolarisation last?
80-100ms
How long should it be between atrial depolarisation and ventricular muscle depolarisation?
120-200ms
Draw and ECG wave in lead II and explain why each section is the shape it is?
What does bundle of His depolarisation look like on an ECG?
Isoelectric segment
What is this ECG demonstrating?
AV/Heart block
What does the P wave and the QRS complex represent?
P = depolarisation of atria
QRS: Ventricular depolarisation
Describe how to put the leads on a person in an ECG and the colours of each lead.
Draw on this diagram the different limb leads and their views of the heart.
Vertical plane
Draw on this diagram the different views of the chest leads?
- Horizontal plane
- V1 and V2 face RV and septum
- V3 and V4 face apex and anterior wall of RV and LV
- V5 and V6 face LV
What order are each of the leads shown on the ECG paper?
What would the waves look like at each of the chest leads?
What are the time scales on the ECG graph paper?
How do you calculate the heart rate of a regular rhythm?
- Count how many large boxes between R to R peak
- Divide 300 by the number of boxes
How do you calculate the heart rate if the rhythm is irregular?
How long should should each interval that you look at on the ecg (e.g P-R interval) be?
QT upper limit
What does a wider QRS complex indicate?
Ventricular depolarisations that are not normal, e.g depolarisation is originating in the ventricle and not spreading via normal system, e.g Purkinje, so takes longer
What does a long P-R interval indicate?
Slow conduction from atria to ventricle, first degree heart block
What should the ST segment look like and what does it indicate if not normal?
Should be isoelectric, if raised or depressed indicates MI or ischemia
What does a prolonged QT interval mean?
- Suggest prolonged repolarisation of ventricles
- Can lead to arrhythmias as occur in long QT syndrome
- Long QT can be corrected by an increase in heart rate, common cause of sudden cardiac death in young people
What is normal sinus rhythm?
When depolarisation is initiated by sinus node
What will an ECG of atrial fibrillation look like?
- No P wave
- Irregular fast heart beat as more A.P’s
What is the difference between atrial flutter and atrial fibrillation?
See ECG’s
