CARDIO: Arrythmias Flashcards
What is absolute bradycardia?
HR is <40bpm
What is relative bradycardia?
Where HR is inappropriately slow for the haemodynamic state of the patient.
Oxford clinical handbook definition of bradycardia = <60bpm
Signs that may indicate haemodynamic instability?
Systolic BP < 90mmHg HR <40 Poor perfusion Poor urine output Ventricular arrhythmias that need suppression Heart failure
How can bradycardia be classified?
Based on the pacemaker that is faulty:
- sinus node e.g. sinus bradycardia
- AV node
List some causes of bradycardia
Physiological:
- athletes
Cardiac:
- degenerative changes/fibrosis of conduction pathways in elderly
- post-MI (especially inferior MI (leads II, III, aVF)
- sick sinus syndrome
- iatrogenic —> ablation, surgery
- aortic valve disease e.g. infective endocarditis (rheumatic fever)
- myocarditis, cardiomyopathy, sarcoidosis, SLE
Non-cardiac origin:
- vasovagal
- endocrine = hypothyroidism, adrenal insufficiency
- metabolic = hyperkalaemia, hypoxia
- other = hypothermia, raised ICP (Cushing’s triad - bradycardia, hypertension and irregular breathing), pericarditis, haemochromatosis,
Drug induced:
- Beta blockers
- amiodarone
- verapamil
- diltiazem
- digoxin
Main management for pt with symptomatic sinus node disease (e.g. a sinus bradycardia)?
Pacemaker is indicated
What are categories of sinus node dysfunction?
Sinus bradycardia
Sick sinus syndrome
Sinus arrest
Part of vasovagal syncope
How are AV node bradycardias classified?
According to the degree of nodal dysfunction:
- First degree AV block
- Second degree AV block Mobitz Type I aka Wenckebach
- Second degree AV block Mobitz Type II
- Complete/Third degree AV block
How is First degree AV block characterised?
PR interval >0.2s
Pt has bradycardia. What rate limiting drug should you check pt is on and why?
Digoxin. Why? Digoxin toxicity - can worsen conduction abnormalities and worsen heart block
How is Second degree AV block: Wenckebach/Mobitz Type I characterised?
Lengthening of PR interval. Followed by failure of atrial impulse to conduct to the ventricles.
i.e. QRS is dropped after progressive lengthening of PR interval.
Who is more likely to have Second degree AV block: Wenckebach/Mobitz Type I?
- Young fit patients with a high vagal tone
- Patients after inferior MI
How is Second degree AV block: Mobitz Type II characterised?
Constant PR interval followed by sudden failure of a p wave to be conducted to the ventricles.
i.e. PR length constant, then drop of QRS. 2 p waves for every QRS
How is complete heart block/ Third degree AV block characterised?
No conduction from atria to the ventricles. No relationship between p waves and QRS complexes
What does complete/ third degree heart block look like on ECG?
Rate is slow. Broad complex QRS escape rhythm seen, with no linkage of p waves and QRS - they are both independent.
Sometimes can look intermittent - see trifascicular or bifascicular block (RBBB, with or without prolonged PR interval) and alternating LBBB and RBBB.
Where can complete/third degree block occur?
Either:
- above AV node at the HIS region
- beneath AV node
Causes of complete/third degree AV block?
Anti-arrhythmic drugs - especially digoxin toxicity!!
Post- inferior STEMI (will resolve in hrs-days)
Anterior MI
Severe hyperkalaemia
How to treat severe hyperkalaemia causing. complete/third degree AV heart block?
- IV calcium gluconate/calcium chloride 30ml of 10% solution over 3-5 mins: to stabilise the myocardium
- insulin/dextrose infusion: short-term shift in potassium from ECF to ICF
- other treatments such as nebulised salbutamol may be given to temporarily lower the serum potassium
How to treat a haemodynamically unstable patient with complete/third degree AV heart block?
Atropine - 500micrograme to 3 mg.
Isoprenaline - at rate of 5micrograms/minute
Main management for complete/ third degree AV heart block?
Urgent permanent pacemaker. Within 24hrs unless they are likely to have a recovery of conduction (e.g post inferior STEMI)
Types of tachycardic arrhythmias?
Atrial fibrillation
Supraventricular tachycardia = in atria
Ventricular tachycardia
Presentation of AFib?
Asymptomatic Breathlessness Palpatations Syncope/dizziness Chest discomfort Stroke or TIA
Complications of AFib?
Cardioembolic stroke
Cardiac instability
Death
Increase in healthcare costs
How to diagnose A fib?
Presence of symptoms - palpitations, dizziness/syncope, breathlessness, chest discomfort, stroke, TIA
ECG used to confirm if an irregular pulse is due to A fib.
What to do before treating suspected AFib just from clinical picture?
Do an ECG to confirm.
Why? Irregular pulse may be due to other reasons
Pt has intermittent AFib. What is next step in investigation?
Short term cardiac monitoring with 24hr cardiac monitor
Disadvantage of 24hr cardiac monitor to identify arrhythmia?
Symptoms need to be very frequent to diagnose an arrhythmia - this is a short time period - delivers low yield results.
What are the different types of prolonged cardiac monitors?
Prolonged Holter monitor
Implantable loop recorder
When/ In what circumstances is an echocardiogram carried out for AFib ?
- Suspected structural heart disease - from symptoms, murmer or signs of HF
- When considering cardioversion to control rhythm
- When a baseline is needed to inform long term management
How to manage AFib?
- Anticoagulation to prevent stroke
- Rate control
- Rhythm control
Scoring tool to assess whether pt with AFib needs anticoagulation? State and explain
CHA2DS2-VASc Congestive heart failure Hypertension Age >75 = 2, 65-74 = 1 Diabetes Stroke or Tia = 2 Vascular disease Sex category (female)
Higher score = higher risk of stroke or embolism.
- Score of 2+ = significant risk. Offer anticoagulant.
- Score of 1 in men = intermediate risk, consider anticoagulant
- Score of 0 = low risk, not offered anticoagulant
Scoring tool to assess risk of major bleeding when on anticoagulation?
ORBIT is now used.
HAS-BLED Hypertension Abnormal renal and liver function - 1 point for each Stroke Bleeding Labile INRs (poor INR control while on warfarin) Elderly (65 + ) Drugs or alcohol - 1 point each
Anticoagulant options for AFib?
DOACs - apixaban, rivaroxaban, edoxaban, dabigatran
How does the mechanism of action of dabigatran differ to other DOACs?
Apixaban, rivaroxaban, edoxaban = inhibit factor Xa directly so prevent conversion of prothrombin —> thrombin.
Dabigatraan = direct thrombin inhibitor so prevents conversation of fibrinogen —> fibrin
Benefit of DOAC compared to warfarin?
Less monitoring (INR monitoring)
No restrictions on food or alcohol
Lower rates of bleeding to warfarin
Better reduction in stroke
How are DOACs excreted and why is this important?
Via kidney. Need to monitor renal function yearly
Other management options available for AFib, other than anticoagulants?
Rate control
Electrical cardioversion
Drug therapy
Pathophysiology of supraventricular tachycardia (SVT)?
AV nodal re-entry tachycardia (a re-entry within the AV node)
OR
Atrio-ventricular re-entry tachycardia (an anatomical re-entry)
Both of these depend on AV nodal conduction
First line treatment of supra ventricular tachycardia in haemodynamically stable patients?
Vagal manoeuvres
e. g. breath holding, valsalva manoeuvre
e. g. carotid massage (younger patients)
These slow down conduction in AV node so can interrupt re-entrant circuit
What should you do before attempting carotid massage for treating supra ventricular tachycardia?
Auscultate for bruits before carotid massage manoeuvre
Why? Risk of stroke from emboli
Short term management options for SVT if vagal manoeuvres do not help?
IV adenosine
CCBs
Route of administration and dose of adenosine for SVT?
IV - rapid bolus Followed by saline flush immediately.
Administered via three way stopcock.
Give 6mg stat followed by 12mg if unsuccessful. Repeat 12mg if unsuccessful after first 12mg dose.
In antecubital fossa
Describe half life of adenosine?
Very short half life
Why is it important that dose of adenosine is given IV and in antecubital fossa via large bore cannula?
Needs to reach heart quickly to minimise cellular uptake en route - so need large bore cannula and entry to be as proximal as possible.
ADRs of adenosine given for SVT?
Chest discomfort
Transient hypotension
Flushing
Contraindication for adenosine use in SVT management?
Pts with significant reversible airway disease e.g asthma or COPD - as can cause bronchospasm
Safety precautions to have in place before administering adenosine to a pt?
Crash trolley next to pt - as possibility of bradyarrhythmia or tachyarrhythmia
ECG findings of SVT?
A narrow-complex tachycardias with a QRS interval of 100 ms or less
When is verapamil contraindicated for SVT control?
Pts on B-blockers
Pts with LV dysfunction
If adenosine and verapamil are ineffective/contraindicated for SVT, what can be done for SVT?
Electrical cardioversion under GA or sedation
Second line drugs for SVT?
IV flecainide can be used if they don’t have PMH of MI
Sotalol
Amiodarone
ECG findings of VT?
Regular broad QRS
Management for sustained VT in haemodynamically compromised pts?
- oxygen
- IV access
- exclude reversible factors - e.g. PA catheter in RV, hypokalaemia, hypomagnesia
- synchronised DC shock - up to 3 attempts
- if unsuccessful = Amiodarone 300 mg IV over 10–20 min. Repeat synchronised DC shock
Pharmacological options for VT?
B-blockers
Amiodarone
Lidocaine
Maximum dose of lidocaine that can be given in 1hr?
200-300mg
Reversal agent for Apixaban?
Adanexanet alfa
Reversal agent for Dabigatran?
Idarucizumab
Reversal agent for Rivoraxban?
Adanexanet alfa
