Flashcards in Arrhythmias Deck (59):
What are the cardiac causes of arrhythmia?
Coronary artery disease
Mitral valve disease
Abberant conduction pathwayds
What are non-cardiac causes of arrhythmia?
Drugs- Beta2-antagonists, digoxin, L-dopa, tricyclics)
Metabolic imbalance (potassium, calcium, magnesium, hypoxia, hypercapania, metabolic acidosis, thyroid disease)
How is bradycardia treated?
If asymptomatic and rate is >40bpm, no treatment is required
Stop any drugs that may be contributing
If rate is <40bpm or patient is symptomatic, give atropine
If no response insert a temporary pacing wire
If necessary, start an isoprenaline infusion or use external cardiac pacing
What drugs may cause bradycardia?
What may cause bradycardia?
Sick sinus syndrome
What is sick sinus syndrome? How does it present? How is it treated?
1. Arrythmia caused by caused by a malfunction of the sinus node
2. Bradycardia +/- arrest, sinoatrial block or SVT alternating with bradycardia (tachy-brady syndrome)
3. Pacing if symptomatic
Describe the acute management of SVT
1. Vagal manoeuvres: e.g. valsalva manoeuvre, immersion of face in cold water or carotid sinus massage (all designed to stimulate the vagus nerve)
2. IV adenosine (Verapamil if adenosine is contraindicated UNLESS patient is on beta-blocker)
3. If vagal manoeuvres and medication fail to slow heart rate, and adverse signs are present, defibrilator conversion (DC) shock is done
What drugs are taken for long term management of SVT?
Beta blockers; verapamil
What treatment is recommended for recurrent SVT?
What are the DD's for a narrow complex tachycardia?
1. Sinus tachycardiac
2. Supraventricular tachycardia
3. Atrial fibrillation/flutter
4. Atrial tachycardia
5. Junctional tachycardia
What adverse signs seen in a SVT might indicate need for DC?
1. Hypotension BP 200bpm
If adverse signs are not present and DC is deemed unnecessary, how is SVT treated following vagal manoeuvres and adenosine administration?
1. Beta blockers
4. Pacing (not AF)
If an SVT has an irregular rhythm, what is the likely diagnosis? How should this be treated?
AF. Control rate with either beta-blocker or digoxin. If onset <48h consider cardioversion with either amiodarone IVI or DC shock. Consider anticoagulation with heparin and/or warfarin to reduce risk of stroke
What are the relative contraindications of adenosine?
2nd/3rd degree AV block
What are the interactions of adenosine?
Potentiated by dipyridamole
Antagonized by theophylline
In what condition is multi-focal atrial tachycardia most likely to occur? How should it be treated?
2. Correct hypoxia and hypercapnia. Consider verapamil if rate remains >110bpm
What drugs are used in treatment of WPW?
What is flecaininde?
A class 1C anti-dysrrhythmic
Works as a sodium channel blocker, slowing the upstroke of the cardiac action potential. This thereby slows conduction of the electrical impulse within the heart, i.e. it "reduces excitability".
What is amiodarone?
A class III antiarrhythmic agent, which prolongs phase 3 of the cardiac action potential, the repolarization phase where there is normally decreased calcium permeability and increased potassium permeability
What is sotalol?
A non-selective competitive β-adrenergic receptor blocker that also exhibits Class III antiarrhythmic properties by its inhibition of potassium channels
What are major side effects of amioderone?
1. Interstitial lung disease
3. Minor visual impairment
4. Abnormal liver enzyme levels (hepatitis and jaundice occur rarely)
5. Blue-grey tinge to the skin
What are the three types of junctional tachycardia?
1. AV nodal re-entry tachycardia (AVNRT)
2. AV re-entry tachycardia (AVRT)
3. HIS bundle tachycardia
What is holiday heart syndrome?
Acute cardiac rhythm or conduction disturbances caused by binge drinking. Most commonly causes SVT, esp. AF. Diagnosis should be considered in patients with new onset AF without structural heart disease
What is the commonest cause of broad complex tachycardia?
What is a fusion beat in VT?
A normal beat which fuses with a VT complex to create an unusual complex?
What is a capture beat in VT?
A normal QRS between abnormal beats
Management of broad complex tachycardia
1. Is there a pulse: No- use arrest protocol. Yes...
2. ...Give oxygen if sats sedate; DC shock; amioderone IVI
No--> Correct electrolyte problems (esp. low K+). Assess rhythm- if regular assume VT and give amioderone IVI; if irregular diagnosis is probably AF with BBB- (treat for AF)
If no response- DC
What other drugs might be considered in refractory cases of VT? (i.e. other than amiodarone)
What is lidocaine?
A class 1b anti-dissrhythmic
Works by blocking sodium channels to prolong upstroke of the action potention
What are the important electrolyte abnormalities to check and correct in VT?
Low potassium and low magnesium
What is procainamide?
A class 1a anti-disrhythmic
Works by blocking sodium channels to prolong upstroke of the action potention
If VT occurs after MI, how should it be treated?
Amioderone IVI +/- oral anti-arrhythmic sotalol (if good AV function); amiodarone (if poor AV function)
What is Torsade de pointes?
A form of VT with a constantly varying axis, often in the setting of long QT syndromes
What causes Torsade de pointes?
Drugs: some anti-arrhythmics, tricyclics, anti-malarials, antipsychotics
How is Torsade de pointes treated?
Stop all contributing drugs
Give magnesium sulphate
What is the main risk for atrial fibrillation?
How is risk of atrial fibrillation reduced in patients who have had an embolic stroke?
Describe the ventricular rhythm in patients with atrial fibrillation
Irregular as AV conducts depolarization intermittently
What causes atrial fibrillation?
Mitral valve disease
How does the pulse feel in a patient with atrial fibrillation?
What are the two major signs of atrial fibrillation seen on the ECG?
1. Absent P waves
2. Irregular QRS complexes
Describe the management of acute AF
2. Check U&E
3. Emergency cardioversion- DC or IVI amiodarone
4. Treat associated illness e.g. MI, pneumonia
5. Control ventricular rate:
- first line verapamil or bisoprolol
-second line- digoxin or amiodarone
6. Start anticoagulation with LMWH
N.B. if the 48 hour window has elapsed, cardioversion is OK it a trans-oesophageal echo is thrombus free
When is atrial fibrillation described as "acute"? Why is this important?
Onset less than 48 hours previously. This is important as this is the window for cardioversion
Which arrhythmias respond to defibrillation/cardioversion?
1. Ventricular tachycardia
2. Ventricular fibrillation
3. Atrial fibrillation
How is cardiversion/defibrillation carried out in atrial fibrillation?
1. Give patient oxygen
2. Unless critically unwell. patients require general anesthetic or monitored heavy sedation
3. If elective cardioversion of AF, ensure adequate anticoagulation beforehand
3. Using a biphasic defibrillator, discharge the machine to 120-200J. Three shocks are normal for AF
How is drug cardioversion carried out?
Amiodarone IVI (5mg over 1 hour then 900mg over 24 hours) OR amiodarone PO (200mg/8hr for 1 week; 200mg/12 hours for 1 week; 100- 200mg/24 hours maintenance.
Alternatively, if patient is stable and has no known IHD or WPW, flecainide may be used.
What are the main goals in managing chronic AF?
1. Rate control
What 2 drug classes are first line for rate control in AF? What additional treatments may be used?
Beta-blocker or rate limiting calcium channel blocker are first line
If this fails, add digoxin then consider amiodarone
How is rhythm control carried out when treating AF?
If cardioversion is chosen, first do an echo, then pretreat with sotalol for >4 weeks. If there is increased risk of cardioversion failure (previous failure or recurrence), pre-treat with amiodarone for >4 weeks.
Flecainide is the first line treatment for pharmacological cardioversion if there is no structural heart disease. If there is structural heart disease, IV amiodarone is used
How is anticoagulation carried out in acute AF?
1. Use heparin until a full risk assessment for emboli is made
2. Use warfarin if risk of emboli is high
3. Use no anticoagulation if stable sinus rhythm is restored and no risk factors for emboli and AF recurrence unlikely
How is risk of stroke calculated? Why is this useful?
Risk is calculated using the CHA2DS2VASc score.
C= Congestive heart failure= 1
H= Hypertension= 1
A= Age >75= 2
D= Diabetes= 1
S= Stroke/TIA= 2
V= Vascular disease= 1
Age= 64-75= 1
S= female= 1
A score of 1 or more (or 2 or more in older patients) indicates that oral anticoagulation should be considered
This is useful in deciding whether to use warfarin in AF patients who are also at risk of bleeding.
Anticoagulation in chronic AF
1. Use warfarin unless contraindicated
2. If warfarin is contraindicated can use aspirin although less effective.
What contraindications are there for warfarin use in AF?
1. Bleeding diathesis (bleeding tendency)
2. Low platelet count
3. High BP
4. Compliance issues around dosing or INR monitoring
5. Issues such as >75-80 years old, frequent falls, NSAID use, polypharmacy, low Hb and past intracranial bleeds may also be considered but have less evidence base
What is dabigatran?
A thrombin inhibitor which does not need regular lab monitoring and dose adjustment. Expensive but may be used as an alternative to warfarin e.g. if warfarin is declined or has CI/SE
How are atrial flutter waves 'unmasked'?
Carotid sinus massage or IV adenosine as both transiently block the AV node
What is the characteristic sign of atrial flutter on an ECG?
How is atrial flutter treated?
1. Cardioversion may be indicated (anticoagulate before)
2. Anti-AF drugs may not work but consider amiodarone to restore sinus rhythm and amiodarone or sotalol to maintain it
When is temporary pacing required?
1. Symptomatic bradycardia unresponsive to atropine
2. After acute anterior MI, prophylactic pacing is required in complete AV block, Mobitz type I and II AV block and bi-/tri-fascicular block
3. Supression of drug reisistant arrhythmias
4. Special situations: during GA, during cardiac surgery, drug overdose (e.g. digoxin, verapamil, beta-blockers)