Arrythmias Flashcards
Heart blocks, AF and tachycardias
What is a heart block?
this is an arrythmia where the electrical signal is delayed or blocked, usually due to damage or fibrosis
What is an atrioventricular heart block?
this is where the electrical signal is delayed or completely blocked between the atria and the ventricles
Name some examples of damage that can lead to heart block
ischaemic heart disease
myocarditis
cardiomyopathies
What is Lev’s disease?
an idiopathic and progressive disease of the conduction system
most commonly, this is part of ageing but it can be hereditary and sometimes seen in younger patients
Describe the PR interval in 1st degree AV block
consistently >200ms
prolonged but regular
How does 1st degree AV block usually present?
usually asymptomatic, often an incidental finding
What is the management for 1st degree AV block?
typically doesn’t require treatment, other than addressing any underlying causes such as electrolyte imbalances or medications such as beta blockers or calcium channel blockers
Describe the PR interval in 2nd degree, type 1 AV block (Wenckebach)
PR interval progressively gets longer until conduction is blocked completely, leading to a ‘dropped beat’
How does 2nd degree, type 1 AV block usually present?
usually asymptomatic, but can occasionally present with light-headedness, dizziness and syncope
Describe the ECG seen in 2nd degree, type 2 AV block (Mobitz II)
there are intermittent dropped beats, but with no progressive lengthening of the PR interval
usually seen as a ratio of conducted: dropped beats
How does 2nd degree, type 2 AV block usually present?
fatigue
dyspnoea
chest pain
syncope
Describe the ECG seen in 3rd degree/complete heart block
signal is blocked completely, so there is no relationship between P waves and QRS complexes
atria and ventricles will be conducting at different rates
What are the symptoms of 3rd degree/complete heart block?
syncope
confusion
dyspnoea
severe chest pain
risk of VT/VF
What is the management for symptomatic AV heart blocks?
identify underlying causes e.g., medications or electrolyte imbalances
atropine to increase HR
transcutaneous pacing
permanent pacing
What are the L and R bundle branches?
these are the 2 branches of the bundle of His, before it separates into Purkinje fibres
What is a bundle branch block?
this is an arrythmia where the electrical signal gets blocked/delayed along one of the bundle branches
What can cause a bundle branch block?
acute fibrosis e.g., that seen in an MI or myocarditis
chronic fibrosis in conditions that cause cardiac remodelling e.g., HTN, cardiomyopathies
Why is a wide QRS complex seen in bundle branch blocks?
this is because there is delayed contraction of one of the ventricles
Which ventricle contracts first and second in a RBBB?
- LV contracts as conduction down the right bundle is blocked
- conduction travels across, allowing the RV to contract
Which ventricle contracts first and second in a LBBB?
- RV contracts as conduction down the left bundle is blocked
- conduction travels across, allowing the LV to contract
Describe the ECG changes seen in a RBBB
‘M’ seen in V1
‘W’ seen in V6
these show the delayed contraction of the RV
Describe the ECG changes seen in a LBBB
‘W’ seen in V1
‘M’ seen in V6
these show the delayed contraction of the LV
What is AF?
this is where the electrical activity of the atria becomes disorganised, leading to fibrillation/random muscle twitching of the atria
this causes a characteristic irregularly irregular pulse
Why are patient with AF at high risk of a stroke?
this is because the blood can ‘pool’ or stagnate in the atria, forming a thrombus that may travel to the brain, causing a stroke
List the most common causes of AF
SMITH pneumonic:
S - sepsis
M - mitral stenosis/regurgitation
I - ischaemia heart disease
T - thyrotoxicosis
H - hypertension
Name two lifestyle causes of AF
high alcohol intake
high caffeine intake
Describe the clinical presentation of AF
patients are often asymptomatic but may present with:
palpitations
SOB
dizziness or syncope
symptoms of associated conditions e.g., stroke
What ECG findings are seen in AF?
absent P waves
narrow QRS complex tachycardia
irregularly irregular ventricular rhythm
What is paroxysmal AF?
this refers to episodes of AF that reoccur and spontaneously return back to sinus rhythm
episodes can last between 30 seconds and 48 hours
What investigations can be carried out in suspected paroxysmal AF?
24-hour ambulatory ECG (Holter monitoring)
cardiac event recorder lasting 1-2 weeks
What are the two principles of treating AF?
rate/rhythm control - often bisoprolol
anticoagulation - often a DOAC
Name three pharmacological options for rate control
beta-blockers
calcium channel blockers
digoxin
