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ECG Made Easy - Chapter 2 - Conduction and its problems

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benryan95's version from 2015-09-10 15:00

Section 1

Question Answer
Which wave is best looked at to determine the rhythm of the heart?The P wave
Which leads often show the P wave most clearly?lead II or V1
What is first degree heart block?A delay in conduction from the SA node to the ventricle - lengthened PR interval
What can first degree heart block be a sign of?Coronary artery disease, acute rheumatic carditis, digoxin toxicity or electrolyte disturbances
What is second degree heart block?When excitation intermittently doesn't pass to the AV node or bundle of His
What is meant by Mobitz type 2 phenomenonA type of second degree heart block with a constant PR interval but occasionally there is atrial contraction without ventricular contraction
What is meant by Wenckebach phenomenon?A type of second degree heart block with progressive lengthening of the PR interval and then failure of conduction of an atrial beat to the ventricles
What is meant by 2:1 conduction?A type of second degree heart block where every other atrial depolarisation will lead to ventricular depolarisation
Why might you not be able to clearly see a P wave in 2:1 conduction?The P wave can become a distortion of the T wave
What is meant by third degree heart block?When atrial contraction is normal but no beats are conducted to the ventricles
Do the ventricles beat in third degree heart block?Yes, they are excited by a slow escape mecahnism from a depolarising focus within the ventricles
What is the association between P waves and QRS complexes in third degree heart block?There isn't an association
What can cause third degree heart block?MI (acute) or fibrosis around bundle of His/branches (chronic)
How long should the PR interval be?120-200ms (3-5 small squares)
What is the normal route for depolarisation in the heart?SA node --> AV node --> Bundle of His --> Bundle Branches
What can cause second degree heart block?Heart disease, such as acute MI
What more commonly causes 3rd degree heart block, ischemia or fibrosis?Fibrosis
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Section 2

Question Answer
What happens to the QRS complex is there is abnormal conduction through either the left or right bundle branches?widening of the QRS complex
How long should the QRS complex be?120ms (3 small squares) or less
What happens to the QRS complex if depolarisation occurs within the ventricular muscle itself?widening of the QRS complex
Which direction is the septum depolarised?The depolariastion of the septum moves from left to right
Which ventricle exerts more influence on the ECG?Left ventricle
What happens to the QRS complex in RBBB?widening of the QRS complex
What happens to the QRS complex in lead V1 in RBBB?An RSR1 pattern
What happens to the QRS complex in V6 in RBBB?Deep S wave
What happens to the QRS complex in LBBB?widening of the QRS complex
Which direction is the septum depolarised in LBBB?From right to left
What often happens in T waves in the lateral leads (I, V2, V5 and V6) in LBBB?T wave inversion
What happens to the QRS complex in lead V1 in LBBB?LBBB has a W shape in V1
What happens to the QRS complex in lead V6 in LBBB?LBBB has an M shape in V6
What should be thought about in LBBB?Presence of aortic stenosis and ischaemic disease
What should be thought about in RBBB?Presence of an atrial septal defect
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Section 3

Question Answer
How many divisions does the right bundle branch have?1
How many divisions does the left bundle branch have?2
What are the divisions of the left bundle branch?An anterior and a posterior fascicle
What happens when the anterior fascicle of left bundle branch is blocked?Cardiac axis rotates upwards --> left axis deviation
What happens when the posterior fascicle of the left bundle branch is blocked?right axis deviation
Which fascicle of the left bundle branch is more commonly blocked?The anterior fascicle
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