Afterdepolarization

Afterdepolarization

Illustration of mechanisms of arrhythmia, including afterdepolarization.

Afterdepolarization refers to a phenomenon in cardiac electrophysiology where an abnormal depolarization occurs during or after the repolarization phase of the cardiac action potential. These afterdepolarizations can lead to cardiac arrhythmias if they reach the threshold potential and trigger additional action potentials.

Types of Afterdepolarization

Afterdepolarizations are classified into two main types based on their timing relative to the cardiac action potential:

Early Afterdepolarization (EAD)

Early afterdepolarizations occur during the repolarization phase of the action potential, specifically during phases 2 or 3. They are often associated with conditions that prolong the action potential duration, such as long QT syndrome. EADs can lead to torsades de pointes, a type of polymorphic ventricular tachycardia.

Delayed Afterdepolarization (DAD)

Delayed afterdepolarizations occur after the completion of repolarization, during phase 4 of the action potential. They are typically associated with increased intracellular calcium levels and can be triggered by conditions such as digitalis toxicity or catecholaminergic polymorphic ventricular tachycardia.

Mechanisms

The mechanisms underlying afterdepolarizations involve complex interactions between ionic currents and intracellular calcium handling. Key factors include:

• Calcium Overload: Excessive intracellular calcium can lead to spontaneous calcium release from the sarcoplasmic reticulum, triggering DADs.
• Ion Channel Dysfunction: Abnormalities in ion channels, such as sodium channels or potassium channels, can contribute to EADs by prolonging the action potential.
• Electrophysiological Remodeling: Changes in the expression or function of ion channels and transporters can predispose cardiac cells to afterdepolarizations.

Clinical Significance

Afterdepolarizations are significant because they can initiate arrhythmias that may lead to sudden cardiac death. Understanding the mechanisms of afterdepolarizations is crucial for developing therapeutic strategies to prevent and treat arrhythmias.

Related Pages

• Cardiac action potential
• Arrhythmia
• Long QT syndrome
• Torsades de pointes
• Digitalis

Cardiovascular disease A-Z

Most common cardiac diseases

• Cardiac arrhythmia‎
• Cardiogenetic disorders‎
• Cardiomegaly‎
• Cardiomyopathy‎
• Cardiopulmonary resuscitation‎
• Chronic rheumatic heart diseases‎
• Congenital heart defects‎
• Heart neoplasia‎
• Ischemic heart diseases‎
• Pericardial disorders
• Syndromes affecting the heart‎
• Valvular heart disease‎

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

• Accelerated idioventricular rhythm
• Acute decompensated heart failure
• Arteriosclerotic heart disease
• Athletic heart syndrome
• Atrial flutter
• Atrioventricular fistula
• Cardiovascular disease in Australia
• Autoimmune heart disease

B

• Brown atrophy of the heart

C

• Ebb Cade
• Cardiac allograft vasculopathy
• Cardiac amyloidosis
• Cardiac asthma
• Cardiac tamponade
• Cardiogenic shock
• Cardiogeriatrics
• Cardiorenal syndrome
• Cardiotoxicity
• Carditis
• Coronary artery aneurysm
• Coronary artery anomaly
• Coronary artery disease
• Spontaneous coronary artery dissection
• Coronary artery ectasia
• Coronary occlusion
• Coronary steal
• Coronary thrombosis
• Coronary vasospasm
• Cœur en sabot
• Coxsackievirus-induced cardiomyopathy

D

• Duke Treadmill Score
• Duroziez's disease

E

• Eisenmenger's syndrome
• Embryocardia
• Endocardial fibroelastosis
• Eosinophilic myocarditis

H

• Heart attack
• Heart failure
• Heart failure with preserved ejection fraction
• Heart to Heart (1949 film)
• High-output heart failure
• Hyperdynamic precordium

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

I

• Idiopathic giant-cell myocarditis
• Interventricular dyssynchrony
• Intraventricular dyssynchrony
• Isolated atrial amyloidosis

K

• Keshan disease

L

• Loeffler endocarditis

M

• Mydicar
• Myocardial bridge
• Myocardial disarray
• Myocardial rupture
• Myocardial scarring
• Myocardial stunning
• Myocarditis

N

• Nonbacterial thrombotic endocarditis

O

• OLR1
• Ostial disease

P

• Papillary fibroelastoma
• Pathophysiology of heart failure
• Postpericardiotomy syndrome
• Pulmonary vein stenosis

R

• Right axis deviation
• Roemheld syndrome

S

• Saturated fat and cardiovascular disease
• SCAR-Fc
• Shone's syndrome
• Strain pattern
• Subacute bacterial endocarditis
• Sudden cardiac death of athletes

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

T

• Traumatic cardiac arrest

V

• Ventricular aneurysm
• Vibroacoustic disease
• Viral cardiomyopathy

W

• Waon therapy