Arrhythmias- 1 Flashcards
What are the two Rough anatomical types of arrhythmias?
- Supraventricular (anything above ventricles)
- Ventricular
What are Ectopic beats?
Beats originate from places other than the SA node.
Ectopic beat- may cause single beats, or take over the heart dictating overall beat.
Dangerous- if they affect the CO -vely.
What are three categories of arrhythmias?
- Supraventricular- AF, atrial flutter, SVT, Sinus bradycardia
- AV Node- AV block, AVN re-entry, accessory pathway
- Ventricular- VF, VT, Premature ventricular complex.
What are the clinical causes of arrhythmias?
- Anatomical- LVH, accessory pathways. congenital HD.
- Autonomic:
- Sympathetic stimulation: nervousness, exercise, CHF
- Increased vagal tone- bradycardia, heart block
3, Metabolic- hypoxic or ischaemic myocardium
- Inflammation- myocarditis
- Drugs
- Genetic mutations
What are the three physiological mechanisms of arrhythmias?
- Altered automaticity
- Triggered activity
- Re-entry
What type of changes occur in the AP graph in altered automaticity?
- Change in slope
- Change in threshold
- Change in RMP
- Decrease Phase 4 slope and hyper-polarise
What physiological factors can change the slope of nodal conductance? (Phase 4)
- Increases slope
- hyperthermia
- hypoxia, hypercapnia
- hypokalemia (more ectopic beats, prolonged repolarisation)
- Cardiac dilatation - Decreases slope
- Hypothermia
- Hyperkalaemia
What happens in triggered activity?
Terminal phase of AP (phase 3), a small depolrisation may occur.
If this reaches threshold, it may trigger sustained depolarisations= triggered activity
Causes= digoxin, long QT syndrome, hypokaleamia.
If after-depolarisation in phase 3= pause-dependent triggered activity
if in phase 4= catechol dependent.
What are the requirements for Re-entry?
- Available circuit
- Unidirectional block
- different conducting speeds of the limb circuits.
Conditions that depress conduction velocity or increase refractory period favour re-entry.
Eg- MI, AV nodal reentry, reciprocating tachycardia.
What happens in re-entry?
A transient block on one side of the conduction system
- Impulse travles down the other side
- Then travels through the block in a retrograde manner
- if the tissue is excitable, the impulse travels down non occluded branch.
- Result is a circus movement.
If in the AV node can cause echo beat, or nodal tachycardia.
What are the symptoms of arrhythmia?
- Palpitations
- Syncope
- SOB
- Dizzy
- sudden cardiac death
- worsen existing condition- angina, hf
What investigations would you do?
- ECG:
- Exercise ecg- asses for ischaemia
- 24hr ecg- detect paroxysmal arrhythmia - ECO gram- assess structural heart disease like LVH
- Electrophyisiological study
What is an atrial ectopic beat? Symptoms + treatment?
Abnormal (Not sinus) beat produced in the atria, causing an extra beat to be produced during sinus rhythm.
Symptoms- Asymptomatic. Palpitations
Treatment- B blocker may help. Avoid stimulants like coffee, cig
What is sinus bradycardia? What can cause it? Treatment?
Sinus (normal) rhythm is slower than 60bpm.
Seen in- anterior MI, Heart block, (b blocker) , athletes
Treatment- Atropine (if acute)
What is sinus tachycardia? Causes? Treatment?
Sinus rhythm faster than 100bpm.
Seen in- Drugs, physiological (tension, fever, hypotension, anaemia).
Treatment- B blocker.
What are some causes of SVT?
- AV nodal reentrant tachycardia
- Accessory pathway “ (eg Wolff parkinson white syndrome)
- Ectopic atrial tachycardia
What is the management (acute/ chronic) for SVT’s?
- Acute
- Vagal manoeuvres, carotid massage
- IV adenosine
- IV Verapamil - Chronic
- Avoid stimulants
- Radiofrequency ablation
- Anti arrhythmic (II, IV)
What is ablation?
Selective cautery (burn) of cardiac tissue= prevent tachycardia
Which cardiac conditions can cause AVN conduction disease?
- acute MI
- Drugs
- infiltrative disease
- myocarditis
- aortic valve disease
What are three types of AV block?
1st Degree- not proper block. Prolonged PR interval.
Treatment- not needed. Long term follow up needed tho.
2nd Degree- intermittent AVN block. (dropped beats)
Mobitz I- progressive PR interval increase. Eventual dropped beat.
Mobitz II- Pathological. Dropped beat every 2nd/3rd cycle. May progress to complete block.
3rd Degree- no AP gets from the SA node/atria to the AV node.
Treatment- ventricular pacing
What are the two delivery options for pacing?
- Transcutaneous (painful)
2. Transvenous (via IJV, subclavian or femoral veins)
What are the two types of pacemakers?
- Single chamber (used in defective SA, or as ventricular pacemakers)
- Dual chamber (used in AVN disease)
What are premature ventricular ectopics? what factors cause it?
Heartbeat initiated by purkinjee fibres in the ventricles instead of SA node. Felt as missed beat- as ventricles contract before SA node can initiate and fill the ventricles fully with blood.
Causes- ischaemic changes, hypertension, inherited cardiomyopathy.
Usually asymptomatic. Treat with B blockers
What happens in VT?
Ventricles beating abnormally fast. Cannot properly contract hence CO poor. Life threatening.
Most patients- significant disease like CAD, MI.
What Signs to check in VT?
Stable or unstable
Chest pain, hypotension, CHF, altered conscious level
What is VF?
Spasmic ventricular electric activity. Needs defibrillator
What is the acute/ chronic treatment for VT
Unstable- DC cardioversion
Stable- Anti arrhythmic drugs (B blockers, Ca, Na, K drugs)
Management- look for causes ie ischaemia, electrolytes, hypoxia
Long term- correct ischaemia if possible. AAD can be worse. Implantable defibs in worst cases.
