Cardiac Arrhythmias 1 Flashcards
What is a Cardiac Arrhythmia
Cardiac arrhythmias (dysrhythmias) are disturbances in cardiac rhythm, including abnormalities in the site of origin, rate, or conduction of the cardiac impulse, disrupting normal activation in the atria or ventricles.
What are the 2 mechanisms behind arrhythmias?
Arrhythmias result from either abnormal impulse generation/initiation, abnormal impulse conduction, or both.
How are arrhythmias classified based on the origin of the abnormal impulse?
Arrhythmias are classified as:
Supraventricular: Originating in the SA node, atria, or AV node.
Ventricular: Originating in the His-Purkinje system or ventricles.
What are tachyarrhythmias and bradyarrhythmias?
Tachyarrhythmias: Arrhythmias with an increased heart rate.
Bradyarrhythmias: Arrhythmias with a decreased heart rate.
What are the 3 subtypes of tachyarrhythmias?
Tachyarrhythmias include:
Tachycardia: Sustained run of regular premature beats.
Flutter: Very rapid, regular premature beats.
Fibrillation: Rapid, irregular, and chaotic depolarizations.
List specific types of arrhythmias
Common arrhythmias include:
Ventricular Premature Contractions (PVCs)
Ventricular Tachycardia (VT)
Ventricular Fibrillation (VF)
Atrial Flutter
Atrial Fibrillation (AF)
What are the primary causes of cardiac arrhythmias?
Causes include:
Ischemia, hypoxia, and acidosis
Electrolyte abnormalities: Mainly K+, Mg++, and Ca++ imbalances.
Heart tissue changes: Infarction, fibrosis, structural abnormalities.
Genetic mutations: e.g., Long QT Syndrome.
Drug toxicity: e.g., digoxin toxicity.
Enhanced autonomic influences: Sympathetic or parasympathetic.
3 Things commonly associated with Arrhythmias
- Drug Therapy - 25% of patients on digitalis
- Anaesthetic Use - 50% of patients
- Heart Disease - 80% of patents
What are possible clinical consequences of arrhythmias?
Consequences depend on arrhythmia frequency, duration, impact on cardiac/vital organ function, and underlying heart disease. They may range from being asymptomatic, symptomatic (dizziness, palpitations, syncope), to lethal (cardiac arrest, sudden death).
Describe abnormal impulse generation mechanisms in arrhythmias
Mechanisms include:
- Altered normal automaticity: Changes in the rate of firing of normal pacemaker cells.
Enhanced automaticity: Leads to tachyarrhythmias.
Depressed automaticity: Leads to bradyarrhythmias.
- Abnormal automaticity: Spontaneous firing of partially depolarized cells, often in atrial or ventricular muscle or Purkinje fibers. (MDP -50mV) Also involve generation of slow type cardiac action potentials
What is triggered activity in cardiac arrhythmias?
Triggered activity refers to abnormal impulses resulting from a previous normal impulse, occurring as either:
Early Afterdepolarizations (EADs): Depolarisations occur before full repolarization of the initiating impulse
Delayed Afterdepolarizations (DADs): Depolarisations occur after full repolarization of the initiating impulse
Describe the 2 types of abnormal impulse conduction in arrhythmias
Conduction block: Occurs between the sinus node and atria, or within the AV node/His-Purkinje system.
Reentrant mechanisms: A cardiac impulse repeatedly excites the same region due to:
-slow conduction
-unidirectional conduction block
(often causing continuous arrhythmic loops)
Diagram of reenterant mechanisms
What are the general principles of arrhythmia management and the 3 criteria for treatment?
Consideration of risks and benefits: Treatments may have adverse effects.
3 Criteria for treatment: Treatment is needed if the arrhythmia causes severe hemodynamic failure, predicts/instigates serious or lethal arrhythmias, or causes significant distress.
What are the 5 C’s for arrhythmia management?
Causes: Treat/remove underlying causes.
Coagulation: Anticoagulation to prevent stroke.
Cardioversion: Convert heart to a normal sinus rhythm.
Control: Managing ventricular rate to maintain adequate CO.
Cure: Permanently terminate the arrhythmia.
Diagram of Class 1a vs 1b vs 1c of Antiarrhythmic Agents
