6.5 - Arythmia

Front 1

Heart beat. What are the following
- P
- QRS
- T
- PR
- QT

Back 1

- P: atrial depolarisation
- QRS: ventricular depolarisation
- T: ventricular repolarisation
- PR: atrial activation to the start of ventricular activation
- QT: to the end of T: ventricular depolarisation

Front 2

What are the steps involved in the depolarisation of a heart cell?

Back 2

There are voltage gated sodium and calcium channels. The calcium channels are also time dependent (slow depolarising)
Late repolarisation makes resistant to depolarisation (absolute refractory period)

Front 3

Persistent bradycardia (eg. "sick sinus syndrome")
- What causes it?
- What is the treatment?

Back 3

Caused by damage to impulse formation or conduction (either pacemaker cells: AV node or SA node or Bundle of His or Purkinje system)

Treat by:
1. prefer a pace maker
2. atropine (short acting)
3. isoprenaline (infusion)

Front 4

What is Torsades des pointes?

Back 4

Type of VT
Has a long QT interval
Almost always due to medications

Front 5

What drugs prolong QT interval?
What else prolongs QT interval?

Back 5

- genetics, electrolyte disurbances, heart disease
- amiodarone, sotalol
- antipsychotics: amisulpride, droperidol, haloperidol and pimozide
- TCAs
- anti-infectives: clarithromycin, erythromycin, moxifloxacin, quinine, chloroquine, fluconazole, voriconazole, pentamidine
- cisapride, dolasetron, methadone, tacrolimus, vardenafil

Front 6

Sinus tachycardia - cause and treatment?

Back 6

Usually a physiological response to precipitants such as pain, hypovolaemia, pyrexia, anxiety, but may be due to sympathomimetic drugs or thyrotoxicosis. If there is no obvious cause, drug treatment is not necessary unless symptoms are troublesome, in which case beta-blockers or controlled release verapamil can be used.

Front 7

AF
(a) complications
(b) symptoms
(c) cause
(d) result
(e) epidemiology
(f) diagnosis

Back 7

(a) stroke, HF
(b) often asymptomatic, may have palpitations, fainting, dyspnoea
(c) generally a re-entry problem, where there is circular impulse propagation in the atria
(d) the atria do not contract in a coordinated or useful fashion; the ventricles beat irregularly
(e) 10% of people over 80 y/o have AF
(f) ECG, echocardiogram, TFTs

Front 8

Rate versus Rhythm contol: when to use which?

Rate control of AF
- what goal?
- which drugs?
- what goal?

Back 8

Both are first line. Rhythm might be attempted for a once-off AF, or where there is symptomatic AF. However, if there is persistent or permanent AF, use rate control first because its just as effective with less side effects.

Rate control: Aim: <90bpm at rest, <180 at exercise to prevent HF and control symptoms.
Use:
1. BB
2. Verapamil/diltiazem
3. Digoxin (less effective, may be used if there is also HF)
4. Combinations (not BB and verapamil)
5. Amiodarone - specialist territory

Front 9

How do you do rythm converstion?

Back 9

1. Anticoagulate
2. Short term control of ventricular rate is usually done with a beta-blocker or verapamil (rather than digoxin) to avoid post-conversion digoxin arrhythmias.
3. It's called DC Cardioversion rather than DC defibrillation (because they are not in VF) - use IV analgesia and sedation because painful and frightening

Front 10

DC cardioversion doesn't work or is CI, use chemical cardioversion. Which drugs are used?

Back 10

Flecainide, disopyramide, sotalol and amiodarone can be used. Amiodarone is considered to be the safest agent in heart failure.

Front 11

Atrial flutter
(A) what is it
(b) management

Back 11

Different from AF in that there IS a regular heart beat. It's just very fast. It's different from sinus tacchycardia, in that the beat arises from an ectopic source in the atrial muscle. Rythm can be 250-450bpm.

DDX: AF, but does not respond well to digoxin

Tm: Adenosine, verapamil or a beta-blocker may be effective. Also, treat the cause.

Front 12

Cardiac arrest: VF
- treatment?

Back 12

CPR, intubate with CPAP at 100% oxygen
Defibrillate @ 200J and increase; attempt 3x at maximum Joules
Give adrenaline 1mg IV - give intratracheal if no venous access
Then give amiodarone, sotalol or lignocaine with adrenaline (alternate) & DC CARDIOVERSION
Stabilise with amiodarone/sotalol or (second line) atenolol/metoprolol - The dosage is ?? symptom relief may not = VF relief

Front 13

Cardiac arrest: Asystole
- treatment?

Back 13

Very poor prognosis
CPR, CPAP, adrenaline

Front 14

When do you use
- pacemakers
- Implantable cardioverter defibrillators

Back 14

- bradycardia, some tachyarrhythmias (overdrive pacing)
- VTs, VF episode, HF

Front 15

Anti-arrythmics
- drugs not in classes
- class 1 drugs
- class 2 drugs
- class 3 drugs
- class 4 drugs

Back 15

- digoxin and adenoside

Class 1: blocks Na channels (membrane stabilising)
1a: intermediate & also blocker K channels, prolongs QT interval (quinidine, procainamide, disopyramide)

1b: fast (only at fast heart rate - less potent) (phenyoin, lignocaine, mexiletine)
1c: slow (very potent) (Flecainide, propafenone)
**1a,c for SVTs
**1b for SVTs and VTs

Class 2: Beta blockers
*SVTs and VTs

Class 3: K channel blockers (prevent depolarisation)
*Sotalol, Amiodarone, Bretylium
*Increase repolarisation, prolongs QT interval and refractory period
* SVTs and VTs

Class 4: Ca channel blockers
*Useful for SVTs

Front 16

How does digoxin work?
How does potassium interact with digoxin?
How do you treat digoxin OD?

Back 16

Digoxin
1. Inhibitos Na-K-ATPase: increases Ca2+ release from SR: positive chronotropic effect; also increases extracellular K+ (worrisom in OD)
2. Increases vagal tone (negative chronotropic effect) - at high concentrations increases SNS --> arrythmia

- Potassium decreases binding of digoxin to Na-K-ATPase
- Low K+ can lead to toxicity in therapeutic range
- High digoxin increases extracellular K

Give IV atropine and/or Magnesium. Monitor vitals. Give Digoxin antibodies in severe cases.
Adenosine - temporarily blocks AV nodal conduction

Front 17

Digoxin
- Indications
- Precautions (remember its MOA and when it might not work)
- Preg/BF

Back 17

Digoxin
Indications: SVT, AF, atrial flutter, HF & fetal arrythmias
Precautions:
- heart block, - VF/VT/cor pulmonale/constrictive pericarditis, HOCM
- When there is increased SNS: hyperthyroidism, fever (~ineffective)
- Hypothyroidism: only small doses needed
- Increased risk of digoxin toxicity with: low Mg, low K, high Ca, acdiosis, hypoxia
- Renal impairment: 70% renally cleared
- Elderly
- Cat A but unpredictable dose requirement
- BF: safe to use

Front 18

Digoxin
- products

Back 18

62.5mcg - Lanoxin PG, Sigmaxin PG,
250mcg tab - Lanoxin, Sigmaxin
Oral liquid: 50mcg/ml.60ml
Injection: 25 & 250mcy/ml.2ml

Front 19

Digoxin
- half life & time to SS
- loading dose (when do you need this)
- normal dose
- TG algorith for calculating initial maintenance dose?

Back 19

- 24-36 hours & ss in ~5 days
- 250-500mcg q4-6h, max 1.5mg d (not needed for HF)
- 125-250mcg d. elderly/mod RI: 62.5-125, severe RI: 62.5mcg
- CrCl x2 +50 (then round up if >70kg or down if <70kg to nearest 62.5mcg)

Front 20

Digoxin concentration monitoring:
1. dose range in HF
2. dose range in AF
3. signs of toxicity
4. when do you take bloods?

Back 20

1. 0.6-1nmol/L (0.5-0.8 micromol/L) - higher levels may increase mortality
2. 0.6-2.6 nmol or 0.5-2 micromol per Litre
3. anorexia --> nausea --> vomiting (3 microgram)
4. Trough levels: before next dose or at least 6hr after last dose

Front 21

Digoxin SEs
(common and infrequent)

Back 21

Common
- anorexia, n/v, diarrhoea
- blurred vision, visual disturbance
- confusion, drowsiness, dizziness, nightmares, depression

infrequent:
- psychosis
- VT, VF, heart block

Front 22

Digoxin
- what monitoring?
- what if patient reverts to sinus rhythm?
- what if another antiarrythmic is used with digoxin?

Back 22

- check RF and electrolytes, signs of toxicity
- stop digoxin - it has no preventative role
- once stable, try to reduce and stop digoxin

Front 23

Counselling points - digoxin

Back 23

LABEL FIVE

Front 24

Digoxin DIs

Back 24

1. pro-arythmic
2. bradycardia, heart block
3. Electrolyte disturbance (low K, low Mg, high Ca), especially potassium loss, increase risk of arrythmia and QT prolongation

4. Decreases absorption
- acarbose, bile acid binding resins (give dig 2 hr before), sucralfate, sulfasalazine, cytotoxics (damage gut can reduce BA OF TABLETS ONLY by almost 50%), St John's Wort, rifampicin (no effect on IV digoxin)

5. Increase absorption
- macrolides: clarithro and erythro (rare, monitor conc) & tetracycline (use decimates metabolising bacteria, significant in ~10% of patients)

6. Increases concentration (unknown mechanism: probably excretion inhibition)
- amiodarone (starts within 4/52), verapamil (up to 80%, within 2/52), diltiazem, nifedipine, quinine, itraconazole

Drugs decreasing renal excretion: trimethoprim, cyclosporin, NSAIDs, ACEIs (only a problem if it decreases RF), spirinolactone (decreases excretion & may also affect some digoxin assays)

Front 25

Amiodarone
- MOA
- Indications

Back 25

MOA
1. Class III antiarrythmic (inhibits K channel, decreasing repolarisation): slows nodes, conduction, muscle contraction
2. weak BB
3. structural analogue of thyroid hormone

Serious arrythmias, resistant to other treatments

Front 26

AMIODARONE precautions

Back 26

- CI in iodine allergy
- CI in heart block
- OK in HF (least inotropic antiarrythmic)
- caution in lung disease, thyroid disease, liver disease and electrolyte disturbance

- Preg Cat C. avoid for 3/12 before and during preg (fetal thyroid problems and bradycardia)
- DO NOT BREASTFEED

Front 27

Amiodarone products

Back 27

100mg.30, 200mg.30 tabs - Aratac, Cordarone X, Amiodarone, Cardinorm, Rithmik

Injectable - Cordarone X

Front 28

Amiodarone
- Adverse Effects

Back 28

Common
- N/v (especially at loading doses), constipation, anorexia, taste disturbance
- hyper/hypo thyroidism
- photosensitivity
- blue-grey skin tone
- transient elevation in LFTs
- fever, headache, dizziness, fatigue, neurotoxicity (tremor, paresthesia), vivid dreams, nightmares
- pulmonary toxicity (acute potentially reversible toxicity @ any time & chronic fibrotic, irreversible)

Infrequent
- bradycardia
- arrythmias

Rare
- hepatotoxicity
- torsades des pointes
- heart failure

Front 29

Amiodarone
- dose
- serum levels
- why is concentration monitoring rarely done?
- half life?

Back 29

maintenance: 100-400mg d
loading: 200-400mg tds for 7/7, then 200-400mg bd for 7/7
Also given IV for acute tachycardias

1.6-4 micromol or 1-2.5mg/L

Toxicity can occur within therapeutic range. Effects of dose changes take 1-3/12+

Half life: 30-100 days

Front 30

Advice for administration of amiodarone IV?

Back 30

Incompatible with NaCl
Use glucose
Use non-PVC giving set

Front 31

What moniroring of amiodarone requried?

Back 31

Baseline:
LFTs
ECG
Chest X-ray
TFTs
U&E, Cr
** Repeat 6/12

Annual eye exam (stop if eye problems develop)

Thyroid probs may develop up to 3/12 after stopping
Liver problems up to 1 year after stopping.

Front 32

Amiodarone - patient counselling.

Back 32

SEs
- report SOB/dry cough
- report toxicity signs: worsening heart problems, n,v, problems with vision
- Label 8: sunscreen, sun protection

Also
- Label 5 & 18

Front 33

Amiodarone DIs

Back 33

1. bradycardia/heart block
2. pro-arrythmic & prolongs QT interval
3. drugs affecting electrolytes (--> pro-arrythmic)

4. inhibits CYP1A2, 2C9, 2D6, 3A4 (all except 2C19!!!)
- increases metoprolol, digoxin, phenytoin (also decreased by phenytoin), warfarin (reduce by about 25%), simavastatin, cyclosporin

Absorption inhibited by cholestyramine

Front 34

Mexiletine - how does it work?

What is it for?

Back 34

It is an orally active lignocaine analogue. Lignocaine is a class 1b antiarrythmic (inhibits sodium channels, only at high heart rates)

1. Prevention of serious VAs
2. neuropathic pain - specialists

Front 35

Isoprenaline
- how does it work?
- what is it for?

Back 35

- Beta agonist
- heart block, shock, bradycardia with haemodynamic compromise

Front 36

Sotalol
- MOA
- Indications

Back 36

- Beta blocker & a Class III anti-arrythmic (inhibits K channels, prolonging refractory period)
- atrial and ventricular arrythmias

Front 37

Sotalol
- A/Es

Back 37

- palpitations, hypotension, bradycardia, dyspnoea, fatigue, dizziness, headache
- n/v/d, dyspepsia
- impotence

Infrequent: prolong QT, Torsades, heart block

Front 38

Sotalol
- products
- dose

Back 38

- 80mg, 160mg.60 tabs (Solavert, Sotacor, Cardol)
- injectable (Sotacor)

Dose: 40-160mg bd (max 320mg bd)

Front 39

Sotalol drug interactions

Back 39

1. QT intervals, pro-arrythmics, drugs disturbing electrolyte concentratiosn
2. DIs as for BBs:
(a) hypotension, decreased HR
(b) ergot alkaloids - increased risk of peripheral vasoconstriction
(c) isoprenaline, beta agonist
(d) clonidine - enhanced bradycardia and hypotension of paradoxical effect; withdraw over 7 days before withdrawing clonidine to prevent rebound hypertension