Flashcards in Cardiac Deck (54)
Describe the stages of de and repolarisation in the contraction of the heart
0: rapid depolarisation due to influx of Na+
1: Rapid early repolarisation, efflux K+ with inactivation of fast Na+ channels
2: Repolarisation slowed by Ca2+ influx
3. Rapid repolarisation, K+ efflux
4. Diastole with steady state resting transmembrane voltage
What is AF?
Most common arrhythmia (1-2% population)
Irregular baseline, ventricle contraction irregularly irregular
Increases risk of hospitalisation, stroke, cardiomyopathy
Treatment of AF
Electrical w/DC current
When should flecanide be avoided in AF?
Don’t use flecanide with underlying ischaemic heart disease or structural abnormalities
Do you anticoagulate AF patients?
Use CHA2DS2 VASc score and HAS-BLED can quantify stroke risk
WARFARIN, NOAC (DABIGATRAN, RIVAROXABAN)
If cardioversion for AF does not work, what do you do?
Rate control: Beta-blockers, VERAPAMIL, DIGITALIS
Rhythm control: SOTALOL, FLECANIDE, AMIODARONE
Catheter ablation (if ectopic foci and paroxysmal AF)
8 causes of pathological bradycardia
• Cardiac surgery
• Chronic degeneration of AV or SA nodes
• Cholestatic jaundice
• Ischaemia/infarction of SA node
• Raised ICP
• Drugs: amiodarone, beta-blockers, diltiazem/verapamil, lithium salts, morphine, clonidine, anticholinesterase inhibitors (donepezil, rivastigmine)
Treatment of pathologic/symptomatic bradycardia
Stop ß-blockers/other causative drugs
Treat underlying cause (levothyroxine)
Acutely Atropine (reduces vagal inhibition) IV 500micrograms, repeat every 3-5mins
What is a sinus pause?
Sa node fails to generate impulse
• Acute myocarditis
• Digoxin toxicity
• Fibrosis of SA node (ageing)
• SE of antiarrythmic drug
Breathlessness, lethargy, dizziness, collapse, falls
Treatment of sinus pause?
What is sick sinus syndrome?
Palpitations caused by sinus bradycardia, sinus pause, paroxysmal atrial/tachy arrhythmias
Treatment: pacemaker/ rate controlling drugs
8 causes of AV block
• Conduction system fibrosis
• Connective tissue disease
• Drug induced (beta-blockers, diltiazem, digoxin)
When are pacemakers indicated?
Pacemakers are indicated in:
• RBBB/LBBB with intermittent 3rd degree AV block
• Carotid sinus hypersensitivity
• Pauses of >3secs during the day
• Sustained VT with pauses
• Symptomatic bradycardia
• Symptomatic sinus node dysfunction/2nd degree heart block
How do you differentiate between tachyarrhythmias?
Is it regular? No
⇒ irregularly irregular AF
⇒ unconscious patient VF
Is the QRS broad?
⇒ Yes means ventricular origin
⇒ No means supraventricular origin
What does atrial flutter look like?
2:1 or 3:1 P:R ratio
Characteristic saw tooth baseline
Treatment of supraventricular tachycardia
Give adenosine to block AV node. If this terminates the tachycardia-> AVRT/AVNRT
If it is independent of AV node-> focal atrial tachycardia
AVRT: atrioventricular re-entry tachycardia
AVNRT: atrial node re-entrant tachycardia
How do you treat a patient with a tachyarrhythmia who is haemodynamically compromised?
Electrical cardioversion under anaesthesia and sedation
Then IV amiodarone/beta-blocker
How do you manage a haemodynamically stable pt with a tachyarrhythmia?
Continuous ECG monitoring
Vagontonic manoeuvres (carotid massage, valsalva)
Rate control with IV lidocaine
Treatment of supraventricular tachycardia
Rate control (ß-blocker, verapamil, digoxin)
Rhythm control (amiodarone, flecanide, sotalol, DC shock)
Prevention of supraventricular tachycardia
Causes of AF
• Atrial septal defect
• Diabetes mellitus
• Thyroid dysfunction
• Valvular heart disease
Define 1st degree heart block
Conduction across AV node is delayed
Prolonged PR interval
Doesn't need treatment
Define 2nd degree heart block
Mobitz 1: PR interval progressively lenthens until QRS in dropped
Mobitz 2: Fixed number of p waves conduct (eg 3P to every 1 QRS). Conduction block at bundle of His
Where is the conduction block with Mobitz 2 2nd degree AV block?
Bundle of His
Define 3rd degree heart block
Complete dissociation between atria and ventricle contraction (P waves and QRS)
Atrial signal fails to reach ventricles
Can lead to sudden cardiac death
Describe sinus arrhythmia
HR INcreases on INspiration
What is left axis deviation?
(I +ve, AVF –ve)
• Left bundle branch block (treat w/pacemaker)
• Left ventricular hypertrophy
• Inferior MI
• Wolff-Parkinson White Syndrome
Name 5 causes of right axis deviation
• Lateral MI
• Lung consolidation (COPD, PE)
• Right ventricular hypertrophy
• WPW syndrome
How do p-waves change in atrial enlargement?
Spiked in right atrial enlargement, mountains in left atrial enlargement.