Arrythmias Flashcards
(42 cards)
What is the definiton of an arrythmia?
(AKA, dysrhythmia) is a disturbance of the normal rhythmic beating of the heart;
- Usually due to an ectopic pacemaker.
Symptoms depend on the nature of an arrythmia, but what are the common symptoms?
-
palpitations;
- (conscious sensation of pounding heart),
- breathlessness,
- dizziness, faintness,
-
syncope;
- (unconsciousness).
What are the four main types of arrythmias?
(there are more)
- Complete heart block,
- Atrial fibrillation,
- Ventricular fibrillation,
- Ventricular tachycardia.
What are the components of the heart’s conducting system?
- SA node initiates the impulse to the…
- AV node…
- Then through the bundle branches to the…
- Ventricles…
- Then Purkinje fibres to the…
- Myocardium.
What current is the Phase 4 depolarisation casued by?
The funny current (If)
Where are If channels found in the heart?
What does this allow the area to do?
Found everywhere in the conduction system but are found at a higher concentration in the SA node.
This allows the whole of the conducting system to potentially be a pacemaker.
What are the three ways to classify an arrythmia?
(and sub classifiactions below them?)
By rate:
- Inappropriate bradyarrhythmia (<60 bpm),
- Inappropriate tachyarrhythmia (>100 bpm).
By location:
- Supraventricular (atrial or AV nodal origin),
- Ventricular (ventricular origin).
By cause:
- Disorders of impulse generation,
- Disorders of impulse conduction.
What causes brady/tachycardias?
Bradycardias (<60);
- SA node (SAN) slows down,
or
- Impulse from SA node is blocked, slower distal pacemaker takes over.
Tachycardias (>100);
- Disorders of impulse generation,
- Disorders of impulse conduction;
What is Complete (3rd degree) Heart Block?
And how can it be caused?
The blocked electrical connection between atria and ventricles.
Causes:
-
Idiopathic bundle branch fibrosis,
- BBs become fibroses and cannot conduct.
-
Atherosclerotic coronary heart disease,
- Causes ischemia to the conduction system.
- Dilated cardiomyopathy.
How does complete heart block affect HR?
Heartbeat slows, degree of slowing depends on location of block.
- Further along the conduction system, slower the beat.
Heart rhythm driven by ‘escape beats’ originating from distal pacemaker just below the block.
What are symptoms of a complete heart block?
Temporary syncope (stop), followed by recovery.
Breathlessness, fatigue and possible chest pain (especially with effort).
When is a complete heart block more likely to result in death?
Risk depends on the location of block;
More distal block → slower rhythm → greater risk of asystole (heart stopping).
Complete heart block treatment?
Pacemaker.
What does a complete heart block ECG look like?
QRS complex becomes dissociated from the P wave as the atria and ventricles beat independently.
Called atrioventricular dissociation.
What is tachyarrythmia majorly casued by?
Re-entry.
What is Re-entry?
(how can it present?)
- When the impulse is delayed or ‘trapped’ in one region of the heart.
- Meanwhile, the adjacent tissue finishes depolarising and is no longer refractory.
The delayed impulse then re-enters the adjacent tissue and then spreads throughout the heart.
- So, two beats for every beat.
Presents:
- once, creating a premature beat,
- indefinitely, generating a sustained tachycardia.
How can you stop re-entry?
- Convert unidirectoinal block to bidirectional block by supressing conduction.
- Prolong the refractory period so the retrograde impulse cannot re-enter the conducting myocardium.
Whats the difference between anatomical and functional re-entry?
Anatomical re-entry:
- When the process of re-entry occurs along a conducting pathway with a non-excitable core.
- Around which the impulse can cycle.
- Has zones of differential conductivity.
Functional re-entry:
- No defined anatomical pathway.
- Typically occurs during or after an MI,
- When cardiac conduction is slowed in some regions of the heart and therefore becomes spatially heterogeneous.
What is atrial fibrillation?
Chaotic atrial rhythm with rapid and ‘irregularly irregular’ ventricular rhythm.
What causes atrial fibrillation?
(and some associated risk factors)
Cause:
- Most often an ectopic focus (pacemaker) located in the cardiac muscle layer.
Risk Factors:
- Atrial dilatation during heart failure, hypertension, excessive alcohol intake, old age.
Typical progression of Afib?
Paroxysmal (occasional) → persistent → permanent.
- This is associated with progressive electrical and structural remodelling of the atria.
- Creates more rotors and fibrillation until eventually it becomes permanent.
Afib is a major risk factor for another cardiovascular issue. What is it?
Stroke.
Increases chance of a stroke by x5!
- Lack of atrial beat causes stasis of blood, and thrombi can form and then embolise to the cerebral circulation.
What does the Afib ECG look like?
Lack of P waves due to chaotic atrial electrical activity.
- The small bumps you see are actually t-waves.
Baseline shows small fibrillatory (‘f’) waves of varying amplitude.
- These are not large enough to cause full depolarisation.
- Occasionally, an f wave is large enough to trigger the QRS complex.
Eventually over time, ‘f’ waves become smaller and QRS complexes occur less frequently, so HR slows down.
There are four classes of antiarrythmic drugs - Class 1-4.
What is Class 1?
Na+ channel blockers;
-
suppress conduction.
e. g. Flecainide.
