Arrhythmia and anti-arrhythmics Flashcards
How do you tell if an ECG has a sinus rhythm?
Regular
Every P is followed by a QRS complex
How do you tell is an ECG shows bradycardia or tachycardia?
RR interval
HR= 300/no. big squares in RR interval
>5 big squares → bradycardia
<3 big squares → tachycardia
Bradycardia is <____bpm, Tachycardia is >_______bpm.
Bradycardia <60/min
Tachycardia >100/min
What do you do for a px with asystole?
CPR or certify death
What are 5 causes of sinus bradycardia?
1) High vagal tone (eg. young, athletes)
2) Sick sinus syndrome (elderly)
3) Drugs (eg. ß-blockers, Non-DHP Ca blockers)
4) SA node injury (Ischaemia, Infection eg. myocarditis)
5) Hypothyroidism
How do you tell if an ECG has a sinus arrhythmia?
Irregular RR intervals
but every P is followed by a QRS complex
Why does sinus arrhythmia occur?
Effect of varying vagal tone on HR due to respiration
How do you tell if an ECG has a 1st degree AV block?
Prolonged PR interval
but every P is followed by a QRS complex
(if every P not coupled with QRS → 2nd degree or higher)
What are 3 causes of 1st degree AV block?
1) High vagal tone
2) Drugs (eg. ß-blockers, Non-DHP Ca blockers)
3) Aging (fibrosis of AV node)
1st degree AV block are often (symptomatic/asymptomatic)
Asymptomatic
How do you tell if an ECG has a 2nd degree AV block?
Regularly irregular RR intervals
not every P has QRS but P:QRS ratio is fixed
What are 2 causes for 2nd degree AV block?
1) Aging
2) AV node injury (eg. MI for RCA, Myocarditis, Infiltrative disorder)
How do you tell if an ECG has a 3rd degree AV block?
No relationship between P and QRS
but regular PP and RR intervals
What are 2 causes for 3rd degree AV block?
1) Aging
2) injury to AV node/bundle of his (eg. MI for RCA, Myocarditis, Infiltrative disorder)
What are 4 symptoms of bradycardia?
1) Lethargy
2) Giddiness
3) Syncope
4) Exertional dyspnoea (due to chronotropic incompetence)
What are 5 causes of sinus tachycardia?
Physiological:
1) Exercise
2) Pain/psychological stress
Pathological:
3) Sepsis/pyrexia
4) Hypovolemia
5) Thyrotoxicosis (excess thyroid hormone)
What are 4 causes of abnormal automaticity (AA) or triggered activity (TA) (eg. EAD, DAD) in tachycardic px?
1) Electrolyte abnormalities
2) Channelopathies (eg long QT, brugada)
3) Myocyte injury (eg. ischemia, infection, stretch, infiltration)
4) Anti-arrhythmics
How do you tell if an ECG has an atrial ectopic?
Ectopic beat (PQRST complex) disrupting sinus rhythm (occurring earlier than expected)
Differing P wave morphology (inverted P wave on lead II)
narrow QRS
How do you tell if an ECG has an ventricular ectopic?
Broad QRS interrupting normal sinus rhythm
- inverted T wave
- R wave»_space;» S wave
How do you tell if an ECG has an ventricular tachycardia?
HR>100, sustained ectopics
QRS broad and bizzare
How do you tell if an ECG has an atrial flutter?
no p waves
F waves (sawtooth baseline)
regular RR intervals (can be irregular is AV block)
What are some possible causes of atrial flutter?
Scarring sets-up closed loop circuits
1) Cardiac failure
2) Atrial surgery
3) Mitral valve disorders
True or false: Ventricular re-entry and ventricular tachycardia have similar ECGs.
True
- cannot be differentiated by ECG alone
How does supraventricular tachycardia occur?
1) Dual AV node pathways
2) Accessory pathways
How do you tell if an ECG has an atrial fibrillation?
Irregularly irregular RR
no p waves
fibrillatory baseline (f waves)
What are some possible causes of atrial fibrillation?
1) Thyrotoxicosis
2) Mitral valve disease
3) Cardiac failure
4) IHD
5) HTN
6) Chronic lung disease
7) Aging
8) ↑risk of stroke
What are some possible causes of ventricular fibrillation?
Irregularly irregular RR (no discernable rs btwn P and QRS/QRS all the time)
1) structural aetiologies (eg. AMI, HF, Hypertrophic cardiomyopathy)
2) Inherited channelopathies (long QT, brugada)
3) Hyperkalaemia
What are 4 symptoms of tachycardia?
1) Cardiac arrest
2) Palpitations
3) Syncope
4) Giddiness
How does defibrillation help with ventricular tachycardia?
Passes current through thorax to completely depolarise cardiac myocardium
Describe the cation flow in excitable cells.
K+/Na+ maintains RMP
K+ efflux → polarise
Na+ influx → depolarise
Ca2+ influx → depolarise
CL- influx → polarise
Where is the effective refractory period on an ECG?
QT interval
What is excitability of cells?
Cells’ ability to change its internal electrical balance to reach trashold
What is automaticity of cells?
Cells able to generate an electrical impulse wtihout being stimulated
What is conductivity of cells?
Cells’ ability to transfer an electrical impulse to the next cell
What anti-arrhythmic is used in emergencies?
Adenosine
What is the T1/2 of adenosine?
<10s
When is adenosine clinically indicated?
Supraventricular tachycardia
What is the moa of adenosine?
Suppress AV nodal conduction and ↑ AV nodal refractory period
- stimulates K+ channel
- inhibits Ca2+ channel
What are 4 AEs of adenosine?
1) Flushing
2) SOB, chest burning
3) Induction of AV block or Afib
4) Headache, hypotension
What class of anti-arrhythmic is procainamide?
Class 1A (Na+ channel blocker)
What is the effect of procainamide?
1) slows phase 0 depolarisation
2) ↓ conductivity
3) ↓ automaticity
4) ↑ ERP and APD
What class of anti-arrhythmic is lidocaine?
Class 1B (Na+ channel blocker)
What is the effect of lidocaine on the heart?
1) slows phase 0 depolarisation
2) shortens phase 3 repolarisation
3) ↓ automaticity
4) ↓ APD
What class of anti-arrhythmic is flecainide?
Class 1C (Na+ channel blocker)
What is the effect of flecainide?
1) slows phase 0 depolarisation
2) shortens phase 3 repolarisation
3) ↓ automaticity and conductivity
What is the clinical use of flecainide/class 1C Na+ channel blockers?
Refractory ventricular tachycardias that send to progress to Vfib
What are 2 examples of ß-blockers used as anti-arrhythmics?
1) Bisoprolol
2) Metoprolol succinate
What is the anti-arrhythmic effect of ß-blockers?
1) ↓ HR and contractility
2) reduces phase 4 depolarisation
3) ↓ autopmaticity
4) prolonged AV conduction
What are 4 clinical uses for ß-blockers?
1) Tachycardia by sympathetic activation
2) Afib
3) AV nodal reentrant tachycardia
4) post MI (reduces sudden arrhythmic death)
What class of anti-arrhythmic is amiodarone?
Class 3 (K+ channel blockers)
What is the anti-arrhythmic effect of amiodarone?
1) Prolongs phase 3
2) ↑ ERP and APD
A px was prescribed an anti-arrhythmic and has been experiencing bradycardia for the past 2 months after stopping the medication, what medication could it have been?
Amiodarone
Amiodarone undergoes ______ metabolism to form a (inactive/bioactive) metabolite.
Hepatic metabolism to bioactive metabolite
(effected maintained for 1-3months after discontinuation)
What are 2 AEs of amiodarone?
1) Bradycardia
2) Heart block
What are 2 clinical uses for amiodarone?
1) Afib to maintain normal sinus rhythm
2) Prevention of reentrant ventricular tachycardia
What are Class 4 anti-arrhythmics (give 2 examples)?
Non-DHP Ca2+ channel blockers
1) Verapamil
2) Diltiazem
What is the anti-arrhythmic effect of non-DHP calcium channel blockers?
1) prolongs phase 4 depolarisation
2) ↓ conductivity of AV node
3) ↑ ERP and APD
What are 3 clinical uses for verapamil?
1) Supraventricular tachycardia
2) HTN
3) Angina
What is the main AE for verapamil?
Hypotension
When is Verapamil contraindicated?
In px with pre-existing depressed cardiac function
