Arrythmias Flashcards
Presentation of arrhythmias
Asymptomatic Palpitations Dyspnoea Chest pain Fatigue Embolism
Investigations for arrhythmias
12 lead ECG (24 hours)
Blood test (esp. thyroid function)
ECHO
Therapeutic options for arrhythmias
Rate control vs. Rhythm control
- Digoxin/Beta-blocker/Ca-antagonist PLUS warfarin (or aspirin if low risk)
- Electrical Approaches occasionally
- Pace and ablation of AV node
- Substrate modification e.g. pulmonary vein ostial ablation, maze procedures
Types of arrthymias
- Sinus arrhythmias
- Supraventricular Arrhythmias
- Atrial fibrillation
- Supraventricular tachycardia - Ventricular arrhythmia
- Ventricular tachycardia
- Ventricular fibrillation - Heart block
A normal sinus rhythm ECG
Rhythm: regular Rate: 60-99bpm QRS duration: normal P wave: visible before each QRS complex P-R interval: normal (<5 small squares)
1st degree heart block on ECG
Prolonged P-R interval
2nd degree heart block on ECG
Mobitz Type 1: - Progressive PR prolongation until a P wave (e.g. 6th) fails to conduct through the ventricle Mobitz Type 2: - P wave ratio 2:1, 3:1 - QRS duration prolonged
3rd degree heart block on ECG
Complete heart block
- Rate = slow
- P wave = constant but bear no relation to QRS complex or ventricular activity
- P-R interval = variation
Atrial Flutter Treatment
Control ventricular rate and thromboembolic risk
Usually cardiovert
Prevent with AA drugs or RFA of cavotricuspidsthmus
Atrial Flutter on an ECG
P waves replaced with multiple F (flutter waves) usually at a ratio at 2:1 (2F:1QRS) but sometimes 3:1
High heart rate
P-R interval not measurable
Atrial Fibrillation on an ECG
Rhythm: irregularly irregular
Rate usually high but slower if on medication
P wave not distinguishable
P-R interval not measurable
Supraventricular tachycardia types
AV-nodal re-entrant tachycardia
AV re-entrant tachycardia (due to accessory pathway - WPW if overt)
Supraventricular tachycardia on an ECG
High heart rate
P Wave often buried in preceding T wave
P-R interval depends on site of supraventricular pacemaker
Symptoms of Wolff-Parkinson White syndrome
Palpitations Syncope SOB Chest pain Sweating Anxious Finding physical activity exhausting Fainting
Ventricular fibrillation on an ECG
Rate over 300bpm, disorganised
Rhythm is irregular
P wave not seen
DEFIBRILLATE
Ventricular tachycardia on an ECG
Rate high
QRS duration prolonged
P wave not seen
Indications for ICD therapy
Secondary prevention
- Cardiac arrest due to VF/VT not due to transient or reversible cause e.g. early phase of acute MI
- Sustained VT causing syncope or significant compromise
- Sustained VT with poor LV function
Causes of sinus bradycardia
Healthy athletic person = may be normal
Drug abuse
Hypoglycaemia
Brain injury with increased intracranial pressure
Causes of sinus tachycardia
Stress
Fright
Illness
Exercise
Symptoms of AF
Palpitations Fatigue Poor exercise tolerance Presyncope or syncope Generalised weakness, dizziness, fatigue
Goals of treatment for AF
Maintain sinus rhythm
Avoid risks of complications e.g. stroke
Minimise symptoms
Treatment for AF
Warfarin for patients at high risk of complications e.g. stroke
Clopidogrel
Antiarrhythmic drugs
Unstable patients requiring immediate DC cardioversion in AF include…
Patients with decompensated congestive heart failure
Patients with hypotension
Patients with uncontrolled angina/ischaemia
Indications for a pacemaker
Temporary
- Intermittent or sustained symptomatic bradycardia, particularly syncope
- Prophylactic when patient high risk for development of severe bradycardia (e.g. 2nd/3rd degree heart block, post anterior MI, even when asymptomatic)
Permeant
- Symptomatic or profound 2nd/3rd degree heart block particularly when cause unlikely to disappear
- Probably Mobitz type II 2nd degree/3rd degree AV block even if asymptomatic
- AV block associated with neuromuscular diseases
- After (or in preparation for) an AV node ablation
- Alternating RBBB/LBBB
- Syncope when bifascular/trifascular block and no other explanation
- Sinus node disease associated with symptoms
- Carotid sinus hypertension/malignant vasovagal syncope
Vaughan-Williams Classification of drugs used to treat arrthymias
Class I (1a, 1b, 1c) Class II Class III Class IV Other
Class I antiarrhytmic drugs
Membrane stabilising agents
Fast Na Channel blockers
Class Ia drugs
Quinide
Increase action potential duration
Used for AF, Premature atrial contractions, premature ventricular contractions, ventricular tachycardia, WPW syndrome
Class Ib drugs
Lidocaine
Accelerate repolarisation and decrease action potential duration
Used for ventricular dysrhythmias only
Class Ic drugs
Propafenone
Block Na channels with a more pronounced effect
Little effects on AP or repolarisation
Use for severe ventricular dysrhythmias and possible AF/flutter
Class II
Beta blockers Atenolol e.g. Reduce/block sympathetic nervous system Supraventricular and ventricular dysrhythmias First line for AF (Bisoprolol)
Class III
Increase action potential duration
Block K channels
Amoidarone
Used for difficult to treat arrhythmias
Class IV
Verapamil
Calcium channel blockers
Used for paroxysmal SVT, rate control for AF and flutter
Digoxin
Cardiac glycoside
Inhibits Na/K ATPase pump
Improves strength of cardiac contraction (positive inotrope)
Adenosine
Slows conduction through AV node
Used to convert paroxysmal SVT to sinus rhythm
Only administered as fast IV push
Digoxin toxicity signs
Vision changes: yellow glow around objects
ECG: changes in T waves, reverse tick of ST segment in lateral leads
Nausea and vomiting
Brady/tachycardia
Arrythmias: VT or VF
Treatment for digoxin toxicity
Stop digoxin - but long half life
Digibind (digoxin immune antibody)
Amoidarone side effects (striking side effects)
Thyroid problems Pulmonary fibrosis Slate: grey pigmentation Coreal deposits LFT abnormalities
Indications for anticoagulation
AF - reduce risk of stroke by 80%
DVT/PE
After surgery
Immobilisation (prophylactic)
Anticoagulant drugs
Warfarin Dabigatran Rivaroxaban Apixaban (Edolaban)
Monitoring warfarin therapy
INR (international normalised ratio)
Actual thromboplastin time/standard thromboplastin time
Normal INR is 1
Therapeutic INR normally 2.5-4
Adverse effects of warfarin
Bleeding
Teratogenic (chondrosdyplasia)
Drug interactions of warfarin
Macrolide antibiotics
Antifungals
Anti-epileptics
Bleeding risk on warfarin - CHADS2
Congestive Heart failure - 1 Hypertension - 1 Age - >75 years - 1 Diabetes mellitus - 1 Stroke/TIA - 2
