Arrhythmias Flashcards
Where does a Supraventricular Arrhythmia originate?
above the ventricle, i.e., SAN, atrial muscle, AV node or HIS origin
Where does a Ventricular Arrhythmia originate?
origin is in ventriclar muscle (common)
or fascicles of the conducting system (uncommon)
Name some types of SVT?
Supraventricular tachycardia Atrial Fibrillation Atrial Flutter Ectopic atrial tachycardia Bradycardia Sinus bradycardia Sinus pauses
Name some types of VT?
Ventricular ectopics or Premature Ventricular Complexes (PVC)
Ventricular Tachycardia
Ventricular Fibrillation
Asystole
Name some AV node arrhythmias?
AVN re-entry tachycardia
AV reciprocating or AV re-entrant tachycardia
AV block - 1st, 2nd or 3rd
Outline the clinical causes of Arrhythmias?
Abnormal anatomy Autonomic nervous system (ANS) hyperthyroidism Metabolic Inflammation Drugs Genetic
What abnormal anatomy may cause arrhythmias?
left ventricular hypertrophy
accessory pathways
congenital heart defect
What Autonomic nervous system changes may cause arrhythmias?
Sympathetic stimulation: stress, exercise, hyperthyroidism
Increased vagal tone causing bradycardia
What metabolic changes may cause arrhythmias?
Hypoxia: chronic pulmonary disease, pulmonary embolus
Ischaemic myocardium: acute MI, angina
Electrolyte imbalances: K+, Ca 2+, Mg2+
What inflammation may cause arrhythmias?
viral myocarditis
What drug effects may cause arrhythmias?
direct electrophysiologic effects or via ANS
What genetic defects may cause arrythmias?
mutations of genes encoding cardiac ion channels e.g. the congenital long QT syndrome
What are Ectopic Beats?
Beats or rhythms that originate in places other than the SA node
What may cause ectopic beats?
Altered automaticity e.g. ischaemia, catecholamines
Triggered activity, e.g. digoxin, long QT syndrome
What is re-entry?
requires more than one conduction pathway, with different speed of conduction (depolarization) and recovery of excitability (refractoriness)
What may cause re-entry?
accessory pathway tachycardia (Wolf Parkinson White syndrome)
scar from previous myocardial infarction or congenital heart disease
Conditions that depress conduction velocity or shorten refractory period promote functional block, e.g. ischaemia, drugs
Describe the mechanism of tachycardia?
The ectopic focus may cause single beats or a sustained run of beats, that if faster than sinus rhythm, take over the intrinsic rhythm.
Re-entry: triggered by an ectopic beat, resulting in a self perpetuating circuit.
What are the symptoms of Arrhythmias?
Palpitations, “pounding heart” Shortness of breath Dizziness Loss of consciousness; “Syncope” Faintness: “presyncope” Sudden cardiac death Angina, heart failure
What is Wolf Parkinson White Syndrome?
pre-excitation on an ECG (wide QRS and short PR)
What are the investigations of Arrhythmias and why?
12 lead ECG (in tachycardia, during SR)
CXR
Echocardiogram – assess structural heart disease
Stress ECG
- Look for myocardial ischaemia, exercise related arrhythmias
24 hour ECG Holter monitoring – assess paroxysmal arrhythmias
Event recorder: (capture the arrhythmia)
Electrophysiological (EP) study
- Induce clinical arrhythmia to study mechanism and map arrhythmia
What can cause sinus bradycardia?
Physiological i.e., athlete
Drugs (B-Blocker)
Ischaemia: common in inferior STEMIs
How do you treat sinus bradycardia?
Atropine (if acute, e.g. acute MI)
If haemodynamic compromise: hypotension, CHF, angina, collapse
What can cause sinus tachycardia?
Physiological - Anxiety, fever, hypotension, anaemia
Inappropriate - drugs, etc
What is the treatment of sinus tachycardia?
Treat underlying cause
B-adrenergic blockers
What is the signs and treatment for atrial ectopic beats?
Asymptomatic or palpitations
B-adrenergic blockers may help
Avoid stimulants (caffeine, cigarettes)
What is Regular Supraventricular Tachycardia due to?
AV nodal re-entrant tachycardia (AVNRT)
AV reciprocating tachycardia / AV re-entrant tachycaria (via an accessory pathway) (AVRT)
Ectopic atrial tachycardia (EAT)
What is the Acute management of SVT?
SVT: Supraventricular Tachycardia
- Increase vagal tone: valsalva, carotid massage
- Slow conduction in the AVN
- IV Adenosine
- IVVerapamil
What is the chronic management of SVT?
- Avoid stimulants
- Electrophysiologic study and Radiofrequency ablation (first line in young, symptomatic patients)
- Beta blockers
- Antiarrhythmic drugs
What is Radiofrequency Catheter Ablation?
Selective cautery of cardiac tissue to prevent tachycardia, targeting either an automatic focus orpart of a re-entry circuit
What are the causes of heart block/AV conducting disease?
Ageing process Acute myocardial infarction Myocarditis Infiltrative disease Amyloid Drugs - B-adrenergic blockers - Calcium channel blockers Calcific aortic valve disease Post-aortic valve surgery Genetic: Lenegre’s disease, myotonic dystrophy
What are the ECG characteristics of 1st Degree AV block?
Conduction following each P wave but takes longer.
P-R interval longer than normal (> 0.2 sec)
What causes 2nd Degree AV block?
Intermittent block at the AVN (dropped beats)
Describe type 1 2nd Degree AV block?
Mobitz 1: -progressive lengthening of the PR interval, eventually resulting in a dropped beat.
Usually vagal in origin
Describe type 2 2nd Degree AV block?
Mobitz 2:
Pathological, may progress to complete heart block (3rd degree HB)
Some AP fails to get through the AV node
Usually 2:1, or 3:1, but may be variable
Permanent pacemaker indicated
Describe type 3 AV block?
Complete block
No action potentials from the SA node/atria get through the A-V node
Describe the two types of Pacemakers?
Single chamber: paces the right atria or right ventricle only
Dual chamber: paces the RA and RV
What causes Ventricular Ectopics?
- Structural causes: LVH, heart failure, myocarditis
- Metabolic: Ischaemic heart disease, electrolytes
- Beta-blockers, Ablation of focus
What are the causes of Ventricular Tachycardia?
Significant heart disease - Coronary artery disease - A previous myocardial infarction OR Rare causes: - Cardiomyopathy - Inherited/ Familial arrhythmia syndromes - Long QT, Brugada syndrome
What is the Acute treatment of VT?
Direct current cardioversion (DCCV) if unstable.
If stable: consider pharmacologic cardioversion with AAD
What is the chronic treatment of VT?
Correct ischemia if possible (revascularisation)
Optimise CHF therapies.
Implantable cardiovertor defbrillators (ICD) if life threatening.
VT catheter ablation.
What are the ECG characteristics of VT?
o The QRS complexes are rapid, wide, and distorted.
o The T waves are large with deflections opposite the QRS complexes.
o The ventricular rhythm is usually regular.
o P waves are usually not visible.
o The PR interval is not measurable.
o A-V dissociation may be present.
o V-A conduction may or may not be present.
Describe Ventricular Fibrillation
Chaotic ventricular electrical activity which causes the heart to lose the ability to function as a pump
What are the 2 treatments of Ventricular Fibrillation?
Defibrillation
Cardiopulmonary resuscitation
What does a wide QRS tachycardia with history of CAD/HF indicate?
Ventricular Tachycardia
What is the treatments in the ventricles AND atrium and ventricle by ICDs? (Implantable cardioverter defibrillator)
VENTRICLE:
VT prevention
antitachycardia pacing (ATP)
low-energy cardioversion
defibrillation for ventricular tachyarrhythmias (VT/VF).
ATRIUM AND VENTRICLE
brady sensing and pacing for bradyarrhythmias.
What is Atrial Fibrillation?
the disorganized electrical activity of the atria resulting in an irregular heartbeat
What is the mechanism of AF?
Initiated by rapid electrical activity arising from arrhythmogenic foci located in the muscular sleeves of pulmonary veins
The arrhythmia is maintained by multiple re-entrant wavelets.
Reduced refractoriness and conduction slowing facilitate re-entry
What are the three types of AF?
Paroxysmal
Persistent
Permanent
Describe Paroxysmal AF?
Paroxysmal and lasting less than 48 hours
Often recurrent
Describe Persistant AF?
An episode of AF lasting greater than 48 hours, which can still be cardioverted to normal sinus rhythm
Unlikely to spontaneously revert to normal sinus rhythm
Describe Permanent AF?
Inability of pharmacologic or non-pharmacologic methods to restore normal sinus rhythm
How can AF be stopped?
Pharmacologic cardioversion with anti-arrhythmic drugs (30% effective)
Electrical Cardioversion (90% effective)
Spontaneous reversion to sinus rhythm
What are the symptoms of AF?
Palpitations Pre-syncope (dizziness) Syncope Chest pain Dyspnea Sweatiness Fatigue
What does AF look like on an ECG?
Atrial Rate:> 300 bpm Rhythm: Irregularly irregular Ventricular Rate: Variable Absence of P waves Presence of ‘f’ waves
What is an F wave in an ECG?
irregular undulations of the base line in an electrocardiogram
What is the Management of AF?
Rhythm control to Maintain SR
Rate control - accept AF but control ventricular rate
Anti-coagulation for both approaches if high risk for thromboembolism
What is the pharmacological treatment of AF?
Rate control during AF- to slow down AVN conduction - Digoxin - Betablockers - Verapamil, diltiazem Rhythm Control during AF- Restoration of NSR - Pharmacologic cardioversion (anti-arrhythmic drugs e.g. amiodarone) - Direct Current Cardioversion (DCCV) Maintenance of NSR - Anti-arrhythmic drugs - Catheter ablation of atrial focus/ pulmonary veins - Surgery (Maze procedure)
What is Direct Current Cardioversion?
terminate the arrhythmia by the delivery of a dose of electrical current to the heart at a specific moment in the cardiac cycle
Name drugs from Class 1 - 4 of Anti-arrhythmic drugs?
Class 1: reducing Na channel current - Lignocaine, quinidine, flecainide, propafenone Class II: B-Adrenergic antagonists - Propranalol Class III: action potential prolongation - Amiodarone, sotalol - DRONEDARONE Class IV - Ca channel antagonists - Verapamil
Describe Atrial Flutter
Rapid and regular form of re-entrant atrial tachycardia.
It is usually paroxysmal, and it is sustained by a macro-reentry circuit located in the right atrial myocardium
What do patients with chronic atrial flutter have?
underlying heart disease?
What is the treatment for atrial flutter?
RF ablation (80-90% long term success) Pharmacologic therapy - Slow the ventricular rate - Restore sinus rhythm - Maintain sinus rhythm once converted Cardioversion Warfarin for prevention of thromboembolism
