Bradyarrhythmia’s Flashcards
Define Bradyarrhythmia’s
Bradyarrhythmia refers to an abnormally slow heart rate (<60 bpm)
What is the cut off bpm for bradycardia
< 60 bpm
Bradyarrhythmia’s can be divided into two major categories.
Names these categories
Those affecting the Sino-atrial node (SAN)
Those affecting the atrioventricular node (AVN)
Name 4 examples of bradycardia that is a result of sino-atrial node involvement
- Sinus bradycardia
- Sinus pause/arrest
- Sinus node dysfunction
- Sinus node exit block
Name an example of bradycardia that is a result of atroventricular node involvement
Heart block (1st degree, 2nd degree (Mobitz type I and II) and 3rd degree or complete heart block)
Name the hallmark ECG features of sinus bradycardia
Sinus rhythm with a heart rate < 60 bpm
What is the aetiology associated with sinus bradycardia
- May be normal in young, fit, and healthy individuals
- May be suggestive of underlying SAN disease
This ECG strip shows what kind of bradycardia
Sinus bradycardia
Define the term “heart block”
Refers to the partial or complete interference of the normal conduction through the AV node, affecting the impulse transmission from the atrial to the ventricles
Heart block interference of the normal conduction through which node?
Aterioventricular node (AVN)
Heart block can be subdivided into 3 categories.
Name them?
- First degree block
- Second degree block
- Mobitz type I (Wenckebach)
- Mobitz type II
- Third degree block
Describe what is going on in the heart to cause first degree heart block
Caused by a delay in conduction from the SA node to the ventricle
What are the hallmark ECG features of first degree heart block
Prolonged PR interval (> 200ms)
This ECG strip shows what kind of bradycardia
1st degree heart block
Describe what is going on in the heart to cause second degree heart block
Caused by the intermittent failure of the AV node to conduct between atria and ventricles
What are the hallmark ECG features of second degree heart block
“Dropped beat” i.e. not every P wave has a QRS complex following it
This ECG strip shows what kind of bradycardia
2nd degree heart block
If I said the second heart block is 2:1 block what am I commenting on in the ECG
Two P waves occur for every QRS complex
Second degree heart block can be subdivided into two types.
Name these two types
Mobitz type I (Wenckebach)
Mobitz type II
Wenckebach second degree heart block is also known as:
a) Mobitz type I
b) Mobitz type II
a) Mobitz type I
What are the hallmark ECG features of Mobitz type I?
Characterised by the gradual prolongation of PR intervals before a block, so called ‘dropped beat’, occurs.
What are the hallmark ECG features of Mobitz type II?
The block appears random – no pattern
There will constant PR intervals and then randomly a block occurs.
No prolong progressive PR interval.
This ECG strip shows what kind of bradycardia
Mobitz type I, a second degree heart block
This ECG strip shows what kind of bradycardia
Mobitz type II, a type of second degree heart block
complete AV block refers to what kind of heart block:
a) 1st degree
b) 2nd degree
c) 3rd degree
c) 3rd degree
Describe what is going on in the heart to cause 3rd degree heart block
Caused by a complete failure to conduct atrial impulses to the ventricles
What are the hallmark ECG features of 3rd degree heart block
- Complete dissociation between P waves and QRS complexes
- QRS complex are broad (>120 ms) as the ventricles are being conducted by a slow ventricular rhythm
- P waves are normal because the atria are conducting normally
This ECG strip shows what kind of bradycardia
3rd degree heart block
Name some of the clinical features of bradyarrhythmia
- Fatigue, lethargy
- Pre-syncope: dizziness
- Syncope: transient loss of consciousness
- Dyspnoea: may suggest pulmonary oedema
- Chest pain: may suggest myocardial ischaemia
- Shock: low BP (< 90 mmHg), pallor, sweating, cold
- Impaired consciousness
Name some of the clinical features suggestive of unstable bradycardia
- Syncope
- Myocardial ischaemia (chest pain)
- Heart failure (breathlessness)
- Shock (BP < 90 mmHg
Presentation of bradycardia ranges from asymptomatic to shock.
What is the nature of the clinical features?
Features may be permanent or occur intermittently due to the paroxysmal nature of the arrhythmia
Name the first line pharmacological therapy for the acute management of bradycardia’s?
IV bolus of Atropine 500mcg
If patient has not improved after the admission of IV Atropine 500mcg, what should be given?
Atropine 500mcg IV repeated (up to 6 doses for a total to 3mg)
Other inotropes (such as noradrenalin)
Transcutaneous cardiac pacing (using a defibrillator)
How many doses of atropine could be given to manage bradycardia’s?
Up to 6 doses can be given
Total: 3mg
Atropine is what kind of drug
Antimuscarinic medication
Describe the mechanism of action of atropine
- Reversible antagonist of muscarinic acetylcholine receptors blocking the action of the vagus nerve on the SAN and AVN (i.e. inhibits the parasympathetic nervous system)
- The effect is to increase the SAN electrical activity and increased conduction through the AVN
Name some of the adverse effects of atropine
Pupil dilatation
Urinary retention
Dry eyes
Constipation
What is the definitive management for bradycardia’s
- Medications usually act as a bridge to more definitive pacing or while the underlying cause of bradycardia is treated
- Pacing (temporary or permanent) delivers electrical stimuli to the heart via pacing leads
- Permanent pacing via pacemaker
