Arrythmias Flashcards
What are the 2 types of arrhythmia based on where they occur?
Ventricular- within the ventricles
Supraventricular- above the AV node (Atrial), at av junction, within av node
What is bradychardia?
Slow heart rate <60bpm
What is tachycardia?
Fast heart rate >100bpm
What are the symptoms of an arrhythmia?
May be asymptomatic
- dizzy, light-headed
- palpitations
- chest pain
- fatigue
- loss of consciousness
- can result in cardiac arrest
What is the management of arryhmias?
-identify any underlying cause e.g thyroid disease- hyper or hypo, Electrolyte imbalances- K+, CA2+, MG2+
treatment:
- Drug therapy e.g. beta blockers, sodium channel blockers, CCBs
- Electrical cardio version, radio frequency ablation, pacemakers, defibrillation
What are they types of bradychardic arrythmias?
- sinus bradychardia- sinoatrial node fires slowly
- Sinus node disease- sa node fails ro generate an electrical impulse. Mainly idiopathic cause e.g. fibrosis of conductive tissue, secondary to MI or cardiomyopathy
- Atrioventricular node disease ‘Heart block’- (most common!)- failure of the av node to conduct the electrical impulse to the ventricles. Often secondary to MI, congenial defects, infection, surgery
What are the treatment options for a bradychardic arrhythmia?
ACUTE= Atropine (increases heart rate)
May require stat dose if HR too low
- look fo underlying cause e.g. if drug-induced- stop drug. Treat disease if causing it e.g. hypothyroidism
- Permanent pacemaker- inserted into the ‘skin pocket’ below the collar bone
- leads sense the electrical activity of the heart and then it delivers small electrical impulses to the myocardial tissue if it detects inappropriate rhythm.
What are the divisions of tachycardia arrythmias?
- Supraventricular (atria originating) e.g. Sinus tachycardia, AF, atria, atrial flutter
(AV junction originating) e.g. wolff-parkinson white syndrome, av functional tachycardia - ventricular tachycardias - MOST PROBLEMATIC
e.g. ventricular ectopics, torsades de pointes, ventricular fibrillation (most serious- is a cardiac arrest)
What is atrial flutter?
Atria ‘flutter’
Caused by re-entry circuit with the right atrium - rapid atrial rhythm (300bpm)
- Ventricles usually beat once for every 2-4 atrial flutter waves = cause stasis of blood in atria = need anticoagulation
What is Wolff-Parkinson white syndrome?
Where there is extra pathways that conduct an electrical pulse direct from atria to ventricles BUT bypasses the AV node- this is what slows the HR normally
- can cause up to 600 bpm
What is Torsades de pointes?
A ventricular tachycardia where the QRS complex twists due to prolongation of QT
What is ventricular fibrillation?
= cardiac arrest!
Rapid, uncoordinated contraction of ventricles= severely decreases cardiac output
- will lose consciousness within 10-20 seconds
- most common cause of death
- urgently requires a defibrillator
What are the non-pharmacological management options for arrythmias?
Direct current cardio version:
Application of a controlled electric current shock across the chest wall- – - This overrides the disordered conduction
- The SA node can regain control of HR
This is unpleasant- so patient is anaesthetised
Has increased risk of thromboembolism- need anti-coagulation 3 weeks before and 4 weeks after
Radiofreuency/cyoablation:
- Have to find the exact location of the point responsible for generating the arrhythmia via electrophysiological studies
- Then guide a catheter with an electrode at the tip to this location
- This then freezes or uses RF energy to freeze the point and destroy the tissue and disrupts the faulty conduction pathway
Defibrillation
- Electric shock delivery to myocardium via the chest wall
- needed asap in cardiac arrest
- used in combination with CPR
Internal cardio version defibrillator (ICDs)
- Is implanted into patients into a pocket beneath the collar bone
- Used in patients who are high risk e.g. those who had suffered a cardiac arrest and are at risk of another
- They monitor the rate and rhythm of the heart - if they detect ventricular tachycardias- it delivers a rapid rate impulse that is faster than the arrythmia
- This allows it to try and regain control of the HR and then it slowly brings it down
- If the above fails, t delivers an internal electric shock to the heart- this is unpleasant and would likely knock the patient to the ground
What medication needs to be given alongside a direct current cardio version?
Has increased risk of thromboembolism- need anti-coagulation 3 weeks before and 4 weeks after
How do internal cardioversion defibrillators work?
Internal cardio version defibrillator (ICDs)
- Is implanted into patients into a pocket beneath the collar bone
- Used in patients who are high risk e.g. those who had suffered a cardiac arrest and are at risk of another
- They monitor the rate and rhythm of the heart - if they detect ventricular tachycardias- it delivers a rapid rate impulse that is faster than the arrythmia
- This allows it to try and regain control of the HR and then it slowly brings it down
- If the above fails, t delivers an internal electric shock to the heart- this is unpleasant and would likely knock the patient to the ground
What should be given during the insertion of a permanent pacemaker?
Swish in some Gentamicin into the atrial pocket- prevents infection
What is the difference between first, second and third degree heart block?
In heart block there is always a p-wave but not always a qrs complex
First:
- 1:1 ratio of p wave to QRS complex
but the PR interval is long
conduction through av node is delayed
Second:
Not very p wave results in a QRS complex- not all atrial contraction are followed by ventricular contractions
Third:
= complete heart block
No conduction through av node
Atrial conduction continues due to sa nose = always p-wave
- There is a slight ventricular contraction due to automatic rhythm of AV node= this produces an ‘Escape rhythm’ - this is weak, slow but prevents immediate death- nor forever so medical emergency
What drugs need to be stopped and restarted in admission of a heartblock patient?
On admission:
Stop any rate controlling drugs e.g. CCBs, beta-blockers
Stop anti-coagulants
Review eye drops- e.g timolol containing drops- beta blocker and can have systemic effects
Prior to discharge:
Restart anticoagulant and eye drops
Consider restart rate control depending on indication/consider aternative
Why dose Amiodarone need a loading dose (+ what is it)?
because it has a long half-life- 40-50 days so takes a while to work
200mg TDS fir 1 week
200mg BD for 1 week
200mg OD maintenance
As half life is so long- may have an add on therapy:
Digoxin - 500mcg x2 STAT dose (6 hours apart)
Then 125mcg OD maintenance
What base line functions are needed before starting amiodarone+side effects?
Liver function- as can cause dysfunction
Report SOB etc as can cause pulmonary toxicity
Thyroid function- as can cause dysfunction- contains iodine and can lead to hypo or hyper thyroidism
other side effects
- bradychardia
- phototoxicity- need high spf, sit in shade, cover skin
- gray skin
- metallic taste
- corneal microdeposits- glow/halo in eyes
What is the important interaction between amiodarone and another drug?
Amiodarone increases levels of digoxin by up to 50%
Digoxin has a narrow therapeutic index- so reduce digoxin dose by 50% if continued use with amiodarone
- often digoxin is only used short term- until ventricular rate decreases
