ECG interpretation Flashcards
What is the normal width of the P wave
<120 ms wide (3 small squares)
What is the normal height of the P wave
<1.3 mV (3 small sqaures)
What could cause a P wave to have low amplitude
Atrial fibrosis
Obesity (fat between SAN and ECG electrodes)
Hyperkalaemia (can inhibit sodium channels)
What could cause a tall P wave?
Right atrial enlargment
What could cause a bifid p wave?
Left atrial enlargement (delayed depolarisation of different parts of atrium)
What could cause focal atrial tachycardia?
Alternative pacemaker foci (ectopic pacemaker, excitable cells outside of SAN)
What is the normal time for PR interval?
120-200 ms
What could cause a longer PR interval?
Disorders of AV node
Disorders of specialised conducting tissue
What could cause a shorter PR interval?
Younger patients
Wolf-Parkinson-White syndrome
What is Wolf-Parkinson-White syndrome?
There is an abnormal accessory electrical pathway called the Bundle of Kent between the atria and ventricles. Signals travel more quickly than through AV node leading to premature activation of ventricles
Delta wave characteristic feature - initial part of ventricular contraction before main pathway contraction.
Rapid and irregular heartbeat, supraventricular tachycardia.
Symptoms of Wolf-Parkinson-White Syndrome
Palpitations, raid heartbeat, chest pain, dizziness, fainting.
Can be asymptomatic.
How fast is normal QRS complex?
<120ms
What is the normal frontal axis between
-30 and +90
What can cause QRS >120 ms?
ventricular conduction delay
Bundle branch block
Pre-excitation (delta wave in WPW syndrome)
What can cause small amplitude QRS complex
Obese patients (fat between ventricles and ECG electrode)
Pericardial effusion (fluid between ventricles and ECG electrode, may compress heart and hinder transmission through myocardium)
Infiltrative cardiac disease (disorders which deposit abnormal substances into heart eg amyloids. can cause fibrosis and impaired myocardial conduction)
What can cause tall QRS complexes?
Left ventricle hypertrophy
Thin patient (minimal fat between ventricles and ECG electrodes)