Arrhythmias and Conduction Disorders
Arrhythmias and conduction disorders are disturbances in the rate, regularity, or sequence of the heart's electrical activation. They range from benign extra beats to life-threatening ventricular tachyarrhythmias and complete heart block, and they arise when the normal generation or propagation of the cardiac impulse is disrupted. This area orients the reader to how rhythm disorders are classified, the electrophysiological mechanisms behind them, and the major clinical syndromes they produce.
Definition
Cardiac arrhythmias are abnormalities in the rate, rhythm, or conduction of the heartbeat that result from disordered impulse formation, disordered impulse conduction, or a combination of the two within the heart's electrical system.
Scope
The area covers the spectrum of cardiac rhythm and conduction abnormalities organized by anatomical origin and rate: atrial fibrillation, other supraventricular arrhythmias, ventricular arrhythmias, bradyarrhythmias and atrioventricular conduction disease, and the syndromes of syncope and sudden cardiac death. It frames these as reference topics in clinical electrophysiology and does not provide individualized diagnostic or therapeutic guidance.
Sub-topics
Key concepts
- Automaticity and impulse formation
- Re-entry
- Triggered activity
- Conduction block
- Tachyarrhythmia versus bradyarrhythmia
- Supraventricular versus ventricular origin
- The cardiac conduction system (SA node, AV node, His-Purkinje)
Mechanisms
Arrhythmias arise through three broad electrophysiological mechanisms. Disordered impulse formation includes enhanced or abnormal automaticity (inappropriate spontaneous depolarization) and triggered activity from early or delayed afterdepolarizations. Disordered impulse conduction includes conduction block and re-entry, in which an impulse circulates around a region of unidirectional block and re-excites tissue that has recovered. The clinical phenotype depends on where in the conduction system — sinoatrial node, atria, atrioventricular node and His-Purkinje system, or ventricular myocardium — the abnormality occurs, and whether the result is too fast (tachyarrhythmia), too slow (bradyarrhythmia), or disorganized.
Clinical relevance
Rhythm and conduction disorders account for a large share of cardiology presentations, from palpitations and syncope to cardiac arrest, and they are central to the prevention of stroke (in atrial fibrillation) and sudden cardiac death (in ventricular arrhythmias). This area describes how these disorders are recognized and categorized for educational reference; it is not a basis for individual diagnosis or treatment.
Epidemiology
Atrial fibrillation is the most common sustained arrhythmia and its prevalence rises steeply with age; ventricular arrhythmias are the principal mechanism of sudden cardiac death, which remains a major cause of cardiovascular mortality. Bradyarrhythmias and conduction disease likewise increase with age and underlie a substantial proportion of pacemaker implantations.
Evidence & guidelines
Contemporary practice in this area is organized around major society guidelines, including the ESC guidelines on atrial fibrillation (Hindricks et al., 2021), supraventricular tachycardia, ventricular arrhythmias and sudden cardiac death prevention (Zeppenfeld et al., 2022), syncope (Brignole et al., 2018), and cardiac pacing (Glikson et al., 2021). These documents synthesize trial and observational evidence into graded recommendations and are the reference points for the topics in this area.
History
The understanding of arrhythmias developed alongside the electrocardiogram, introduced by Willem Einthoven in the early twentieth century, which made disordered rhythms directly observable. The mid-twentieth century established the re-entry concept and clinical electrophysiology, and later decades brought catheter ablation, implantable cardioverter-defibrillators, and pacing therapy, transforming rhythm disorders from descriptive entities into treatable conditions.
Related topics
Seminal works
- hindricks-2021
- zeppenfeld-2022
- glikson-2021
Frequently asked questions
- What is the difference between an arrhythmia and a conduction disorder?
- An arrhythmia is any abnormality of heart rate or rhythm, while a conduction disorder specifically refers to impaired propagation of the electrical impulse (for example, heart block). Conduction disorders are one cause of arrhythmias, particularly bradyarrhythmias.
- How are arrhythmias broadly classified?
- They are usually grouped by rate (tachyarrhythmias versus bradyarrhythmias) and by site of origin (supraventricular versus ventricular), which together frame the major clinical categories covered in this area.