Week 02 - ECG (heart block) Flashcards
First degree heart block is the delay between …?
atrial and ventricular depolarisation (longer PR interval)
- 1:1 ratio of P wave to QRS
Second degree heart block occurs when …?
excitation intermittently fails to pass through the AV node or bundle of His
Mobitz type 2 is when one __ wave not….?
P wave is not followed by a QRS complex
Wenckebach type 2:
- progressive lengthening of PR interval
- timing issue
- One non conducted P wave
- Next conducted beat has a shorter PR interval than the preceding conducted beat
2:1 type 2:
- Two P waves per QRS complex
- Normal, constant, PR interval in conducted beats
- P wave in the T wave can be identified because of its regularity
Third degree heart block is also known as ___ heart block
complete
Third degree heart block
- Atrial contraction normal but no conduction through to the ventricles
- Ventricle depolarisation occurs within the ventricles
- Called ‘escape rhythm’, results in wide QRS
- PR interval will be variable, and no relationship between P waves and QRS complexes
- May be chronic and due to fibrosis around bundle of His
- Can also be caused by block of both bundle branches
Right Bundle Branch Blocks
- No conduction through R bundle branch
- L ventricle depolarised before R
- Takes longer than normal to depolarise the R ventricle
- Causes a second R wave in V1 and a wide / deep S wave in V6 (aka RSR pattern)
- Best vied : V1
- Reaches back to baseline
Left Bundle Branch Blocks
- No conduction down L bundle branch
- R ventricle depolarised before L ventricle
- LBBB is best seen in lead V6: shape of M (doesn’t reach back to baseline)
What is this??
- Often seen in normal people
- Acute myocardial infarction and acute rheumatic fever can be possible causes
- No specific action needed
First degree heart block
What is this??
- Usually indicates heart disease; often seen in acute MI
Second degree heart block
Mobitz type 2 and Wenckebach block treatment?
Do not need specific treatment
2:1, 3:1 and 4:1 block treatment and indications?
May indicate a need for temporary or permanent pacing, especially if the ventricular contraction is slow
Third degree block treatment and indicaition?
- Always indicates conducting tissue disease – more often fibrosis than ischemia
- Consider a permanent or temporary pacemaker
Finding Heart Rhythm: __ lead ECG is better than rhythm strip (V2) for detecting arrhythmias
12
Finding Heart Rhythm: Locate …?
lead showing best P waves
Finding Heart Rhythm: Relationship between P waves and QRS complex should be ____
1:1
Finding Heart Rhythm: QRS width?
Width of QRS complex <120ms
Sinus Arrhythmia (HRV) is…
- Good arrhythmia
- Non pathological; high HRV (not continuous beats, pattern, not even, heart rate variability high) = better health
- RR interval different distance each beat
Abnormal Rhythms can begin in….
- atrial muscle
- region around the AV node
- Ventricular muscle
Abnormal Rhythms are divided into….(2)?
- Supraventricular arrhythmias
- Normal QRS complexes (<120ms)
- Ventricular arrhythmias
- wide QRS complexes
Bradycardias
Aka escape rhythm/beat:
- Occur as fail safe mechanism when SA fails to depolarise
- Can occur at the atria, AV node or in the ventricles
- Takes time to kick in
Extrasystoles
- Premature contraction, early
- Any part of the heart can occur early
- Can occur at the atria, AV node or in the ventricles
Types of Tachycardias…
- Atrial tachycardia
- Atrial flutter
- Ventricular tachycardia
