ECG Flashcards
What is the SA node?
dominant pacemaker of the heart has an intrinsic rate of 60-100
What is the AV node?
AV node- back up pacemaker and has a rate of 40-60
What is the AV node?
AV node- back up pacemaker and has a rate of 40-60
What does a p-wave on an ECG represent?
Atrial depolarisation
What does the QRS complex on an ECG represent?
Ventricular depolarisation and atrial repolarisation
What does the T-wave on an ECG represent?
Ventricular repolarisation
What does the PR interval on an ECG represent?
Atrial depolarisation and the delay caused by the AV node to allow atria to contract
What do the boxes on ECG paper represent?
One large box= 0.2s
One small box= 0.04s
Where do the 6 chest leads go on a 12 lead ECG?
V1- 4th intercostal space right of the sternum
(septal view )
V2- 4th intercostal space left of the sternum
(septal view)
V3- 4th intercostal space below Vā (anterior view)
V4- in the 5th intercostal space mid-clavicular line (anterior view)
V5- goes in between V4 and V6 (lateral view)
V6- goes in the 5th intercostal space mid-axillary line (lateral view)
Where do leads I, II, and III (standard limb leads) go in an ECG?
Lead I- goes from the right arm to the left arm (lateral view)
Lead II- goes from the right arm to left leg (inferior view)
Lead III- goes from the left arm to left leg (inferior view)
Where do leads aVF, aVR and aVL (augmented limb leads) go in an ECG?
aVR- goes to right arm -150 degrees (none)
aVF -goes to right leg 90 degrees (inferior)
aVL- goes to left arm -30 degrees (lateral)
What is rule number one of a normal ECG?
PR interval should be between 0.12-0.2 seconds
What is rule 2?
QRS complex should not exceed 0.12 seconds
What is rule 3?
QRS should be upright in leads I and II
What is rule 4?
QRS and T-wave have the same direction in limb leads
What is rule 5?
All waves are negative in aVR
What is rule 6?
R wave must grow from V1 to V4 and S wave must grow from V1-V3
What is rule 7?
ST segment must be isoelectric apart from in V1 and V2 where it may be slightly elevated
What is rule 8?
P waves should be upright in I, II and V2-V6
What is rule 9?
There should be no Q waves in I II and V2-V6
What is rule 10?
T waves must be upright in I II and V2-V6
How do you calculate heart rate on an ECG?
300/number of squares between QRS complexes
What would tall pointed T waves on an ECG indicate?
Right atrial enlargement (hypertrophy)
What would bifid (m-shaped) P waves on an ECG suggest?
Left atrial enlargement (hypertrophy) implicated in mitral regurgitation and stenosis
What does the lack of P waves on an ECG suggest?
Atrial fibrillation
What do sawtooth p waves (fairly prominent but lots of) on an ECG suggest?
Atrial flutter
What do chaotic P waves suggest?
Atrial fibrillation
What does first degree heart block look like on an ECG?
A prolonged but consistent PR interval
What does a second degree Mobitz type 1 heart block look like on an ECG?
Gradually increasing PR interval until a beat stop. Then the process starts again
What does a second degree Mobitz type 2 heart block look like on an ECG?
Consistent p wave duration with loss of QRS every 3 or 4 waves
What does a 3rd degree heart block look like on an ECG?
P waves and QRS complexes that have no association with each other, Need a junctional or ventricular pacemaker fitted
What does a decreased PR interval suggest?
P waves that originate from somewhere else e.g., if someone has a small atria
Could also mean the atrial impulse is getting to the ventricle via a shortcut would show as delta waves
What do delta waves (slurred QRS complex) on an ECG indicate?
Wolf-Parkinson white syndrome
What does a QRS complex wider than 0.12s indicate on an ECG?
Could indicate a left or right bundle branch block. The impulse is getting to one ventricle faster than the other
What is normal height of a QRS complex in the chest and limb leads?
<5mm limb leads and <10mm chest leads
What do tall QRS complexes indicate?
A tall QTS complex can imply ventricular hypertrophy
When is a ST elevation significant and what does it signify?
When it is greater than 1mm in limb leads or 2mm in chest leads above the baseline.
Signifies myocardial infarction
When is a ST depression significant and what does it signify?
When it is more than 0.5mm below the baseline in 2 contagious leads.
Signifies myocardial ischaemia
What 2 events are tall T waves associated with?
Hypokalaemia and a hyperacute STEMI
When are inverted T-waves normal?
In leads V1 and III
What conditions can inverted T waves be implicated in?
Ischaemia
Bundle branch block V4-V6 indicates LBBB and V1 to V3 indicates RBBB
LVH (in lateral leads)
Hypertrophic cardiomyopathy (widespread)
What can a biphasic T wave indicate?
Hypokalaemia
What can a flattened T wave indicate?
Electrolyte imbalance
Ischaemia
