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