Abnormal cardiac rhythms Flashcards
What is a first degree AV block?
ECG changes due to a delay at the AV node/bundle of His
What is a Mobitz type I/Wenkebach block?
ECG change due to block in AV node
What are the types of second degree AV blocks?
Mobitz type I / Wenkebach
Mobitz type II
What is a Mobitz type II block?
ECG change due to block of bundle of His
What is a third degree AV block?
Complete heart block due to atrioventricular dissociation, i.e. no impulses make it though to the ventricles
=> atria beat normally, ventricles beat escape rhythm
What is the ECG appearance of a third degree AV block?
Wide QRS complex (as slowly conducted)
What is the physiological cause of a third degree AV block?
Due to degenerative disease and requires a pacemaker as a medical emergency
What is the physiological cause of a Mobitz type II block?
Often signifies serious heart disease
What is the ECG appearance of a Mobitz type II block?
Random dropping of QRS complex but with normal PR interval
P:QRS ratio can be constant but normall varies
How does Mobitz type I / Wenkebach block appear on ECG?
Progressively longer PR interval until dropped QRS complex
Described as Wenkebach 4:3 if one QRS dropped every 4 p waves
What is usually the cause of a Wenkebach block?
Usually transient and benign
What is a right bundle branch block?
ECG change due to right ventricle not depolarising until left ventricle depolarisation has ended
How does a right bundle branch block appear on ECG?
Wide QRS complex
ST depression and T wave inversion seen in V1 and V2
What is the cause of right bundle branch block?
Often normal but may be due to conduction disease
What is a left bundle branch block?
ECG change due to slow rate of left ventricle and resulting lack of opposition from right ventricle
