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.
