Arrhythmia Mechanisms
Learning the mechanism behind an arrhythmia is more powerful than memorizing its name. Three broad mechanisms recur throughout electrophysiology: automaticity, triggered activity and reentry.
Three foundational mechanisms
Automaticity
Spontaneous impulse formation from cells acting as a focus. Abnormal automaticity can create ectopic rhythms.
Triggered activity
Impulse formation related to afterdepolarizations that occur during or after repolarization under particular physiologic conditions.
Reentry
Continuous propagation around a pathway when conduction and refractory properties allow activation to re-enter tissue that has recovered excitability.
Where this leads
Mechanism-based thinking helps organize AVNRT, AVRT, atrial tachycardia, atrial flutter, atrial fibrillation, PVCs and ventricular tachycardia. Each rhythm can eventually be studied using the same sequence:
Advanced Arrhythmia Library
Take each rhythm through the same EP reasoning pathway: ECG → intracardiac signals → pacing clues → mapping → ablation concept.
AV Nodal Reentrant Tachycardia
Reentry involving tissue in/around the AV nodal region.
Open lesson →Atrioventricular Reentrant Tachycardia
Macroreentry using the AV node/His-Purkinje system and an accessory atrioventricular pathway as limbs of the circuit.
Open lesson →Focal Atrial Tachycardia
Atrial tachycardia can arise from a focal atrial source; mechanisms may include automaticity, triggered activity, or microreentry depending on the tachycardia.
Open lesson →Atrial Flutter
Typical atrial flutter is a macroreentrant atrial tachycardia, classically involving the cavotricuspid isthmus; atypical flutters use other circuits.
Open lesson →Atrial Fibrillation
AF is characterized by disorganized atrial electrical activation and complex sustaining mechanisms. Pulmonary veins are important triggers in many patients.
Open lesson →Premature Ventricular Contractions
PVCs are premature ventricular activations arising from ventricular myocardium or the specialized conduction system; mechanisms vary by substrate.
Open lesson →Ventricular Tachycardia
VT encompasses multiple mechanisms and substrates. Monomorphic VT in structural heart disease is often related to reentry through or around scar, while idiopathic VTs may have focal mechanisms.
Open lesson →Trusted resources
Laboratory processes, protocols, equipment, personnel, safety and quality.
Open HRS resource →
Recommended reading and competency topics for invasive electrophysiology.
Open ESC resource →
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