Arrhythmias Flashcards
Class 1 (Na+ blockers)
Membrane stabilising drugs E.g. 1. Disopyramide 2. Lidocaine 3. Flecainide / Propafenone (contraindicated in asthma/severe COPD. Avoid in structural/ischemic heart disease)
Class 2 (Beta-blockers)
- Propranolol
2. Esomeprazole
Class 3 (K+ channel blockers)
- Amiodarone (4 weeks before and 12 months after electrical cardioversion to increase success)
- Sotalol
- Dronedarone (hepatotoxicity and HF side effects)
Class 4 (Calcium Channel Blockers, rate limiting)
- Verapamil
2. Diltiazem (unlicensed)
Other
- Adenosine
2. DIGOXIN (effective in sedentary patients with non-paroxysmal AF an in patients with associative congestive HF)
Atrial Fibrillation
Abnormal, disorganized electrical signals fired cause atria to fibrillate = rapid and irregular heartbeat
Symptoms of AF
Heart palpitations = pounding/fluttering
Dizziness, SOB, tiredness
AF complications
- Stroke
2. HF
Types of AF
- Paroxysmal AF = episodes stop within 48hrs without treatment
- Persis tend AF = episode lasts >7dys
- Permanent AF = present all the time
Rate Control
FIRST LINE Control ventricular rate 1. Verapamil (rate-limiting CCB) 2. Beta-blocker (NOT SOTALOL) 3. Digoxin monotherapy, dual therapy then rhythm control
Rhythm control
SECOND LINE
Restore and maintain sinus rhythm
1. Beta-blocker e.g. sotalol
2. OR oral anti-arrhythmic e.g. amiodarone/flecainide
CARDIOVERSION
- Electrical - direct current
- Pharmacological - anti-arrhythmic e.g. amiodarone/flecainide
- cant give if symptoms >48hrs due to increased rik of stroke
- electrical preferred if >48hrs
- wait until full anticoagulated for 3 weeks before cardioversion and continue 4 week after
- if hemodynamically unstable = electrical cardioversion, give parental anticoagulant and rule out left atrial thrombus immediately before procedure
Paroxysmal and symptomatic AF treatment
Rhythm control
- Standard beta-blocker
- Oral anti-arrhythmic
Infrequent episodes - “pill in pocket” self treatment
- Flecainide
- Propafenone
Atrial Flutter
Similar to AF but CATHETER ABLATION more suitable
Anticoagulation
CHA2DS2VASc tool - give if score 2 or more C - chronic HF or LV dysfunction H - hypertension A - age >75 D - diabetes S - stroke/transient ischemic attack/VTE hx V - vascular disease A - age 65-74 years S - sex e.g. female
Ventricular Tachycardia
Torsade de pointes (prolonged QT interval)
Causes
- Sotalol and other QT prolongation drugs
- HypOKalaemia
- Bradycardia
Treatment
1. Mg sulphate
Paroxysmal Supraventricular Tachycardia
Short circuit rhythm develops in the upper chamber of the heart
results in a regular but rapid heartbeat that starts and stops abruptly
can be recurrent - requires catheter ablation or drugs (verapamil, diltiazem, beta-blockers, flecainide or propaferone)
terminates spontaneously or with reflex vagal nerve stimulation e.g. Valsalva manoeuvre (breathing technique), carotid sinus massage or immersing face in cold water
Treatment
- IV adenosine
* contraindicated in COPD/asthma - IV verapamil
If haemodynamically unstable = direct current cardioversion
AMIODARONE (Class 3 anti-arrhythmic)
LOADING DOSES
- 200mg TDS for 7 days
- 200mg BD for 7 days
- 200mg OD as maintenance
AMIODARONE SIDE EFFECTS
- Eyes - corneal micro-deposits (night-time glares when driving) and optic neuropathy/neuritis (blindness) STOP
- Skin - phototoxic, slate-grey skin on light exposed areas, shield skin from light, use high SPF suncream for months after therapy
- Nerves - peripheral neuropathy, numbness, tingling in hand and feet
- Lungs - pneumonitis, pulmonary fibrosis, SOB, dry cough
- Liver - hepatotoxic, jaudice, n+v, itching, burning, bruising, abdo pain, 3x raised liver transaminases
- Thyroid - CONTAINS IODINE
- Hyperthyroidism (weight loss, heat intolerant, tachycardia). Withdraw amiodarone. Give carbimazole if necessary
- Hypothyroidism (weight gain, cold intolerance, bradycardia). Start levothyroxine without withdrawing amiodarone
AMIODARONE MONITORING
- Annual eye tests
- Chest X-ray before treatment
- LFTs every 6 months
- Monitor TSH, T3, T4 before and every 6 months
- BP and ECG - causes hypotension and bradycardia
- Serum K+ - causes HYPOkalaemia, enhances arrhythmic effects
AMIODARONE INTERACTIONS
EXTREMELY LONG 1/2 LIFE (50 days) = interactions several months after stopping
- Increased plasma amiodarone conc with enzyme inhibitors
e. g. SICKFACES.COM GAVID - Amiodarone is an enzyme inhibitor = reduce dose of warfarin, phenytoin, digoxin (half-dose)
- Increased risk of myopathy with statins
- Bradycardia, AV block and myocardial depression with beta-blockers, rate limiting CCB e.g. Verapamil and Diltiazem
- QT prolongation = increased risk of ventricular arrhythmias with quinolones, macrolides, TCAs, SSRIs, lithium, quinine, hydroxychloroquine, anti-malarial (chloroquine, mefloquine) and antipsychotics (esp sulpiride, pimozide, amisulpride)
DIGOXIN (Cardiac glycoside)
Action
Increases force of myocardial contraction (positive inotrope)
Reduces conductivity in the AV node (negative chronotrope)
Digoxin concentration
1-2mcg/L (6hrs after dose)
Regular monitoring is NOT required during maintenance treatment unless toxicity suspected or renal impairment (renally cleared)
Digoxin doses
Loading (long 1/2 life)
Maintenance OD
- Atrial flutter and non-paroxysmal AF in sedentary pts = 125-250mcg
- Worsening or severe HF (in sinus rhythm) = 62.5-125mcg
Different dosage forms have different bio.a
e.g. Elixir = 75% Tablet = 90% IV = 100%
Digoxin toxicity
SLOW AND SICK
- HYPO Mg2+
- HYPER Ca2+
- Hypoxia
- Renal impairment
- Bradycardia / heart block
- N+V, diarrhoea, abdo pain
- BLURRED YELLOW VISION (DY)
- Confusion, delirium
- Rash
Digoxin Interaction Effects
- HYPOKALAEMIA with diuretics (loop/thiazide) B2 agonist, steroids, theophylline. If K+ <4.5mmol/L give K+ supplements or K+ sparing diuretic
- Toxicity with amiodarone (half digoxin dose), rate limiting CCB, macrolides, ciclosporin
* ENZYME INHIBITORS - Sub-therapeutic (decrease plasma conc) with St John Wort, Rifampicin
* ENZYME INDUCERS - Reduce renal excretion = TOXICITY with NSAIDs, ACEi/ARBS
