Ectopic pacemaker

An ectopic pacemaker or ectopic focus is an excitable group of cells that causes a premature heart beat outside the normally functioning SA node of the human heart. Acute occurrence is usually non-life threatening, but chronic occurrence can progress into ventricular fibrillation.

Contents 1 Etiology 2 Physiology 3 Diagnosis 4 References 5 See Also

Etiology

Ectopic pacemakers can occur within healthy hearts in response to various stimulating events, such as:

• Elevated sympathetic nervous system output
• Overstimulation from drugs such as caffeine^[1].
• Cardiac Ischemia (particularly ventricular ischemia) - The membranes of apoptotic (dying) cells become "leaky" and cause surrounding tissue to become hyperkalemic or hypercalcemic (high concentration of potassium/calcium), causing random excitation.^[2]

Physiology

An ectopic pacemaker can reside within a part of the conduction system of the heart, or within the muscle cells of the atria or ventricles. When an ectopic pacemaker initiates a beat, premature contraction occurs. A premature contraction will not follow the normal signal transduction pathway, and can render the heart refractory or incapable of transmitting the normal signal from the SA node.

Diagnosis

On an ECG, the QRS complex will be abnormally shaped. It can be perceived as a skipped beat on both the ECG and through normal pulse-taking.

References

1. ^ Carol, Mattson, Port. Pathophysiology: Concepts of Altered Health States 7th Ed, Pg 588. Lippincott Williams & Wilkins, 2005. ISBN 0-7817-4988-3
2. ^ Keller-Wood, Maureen. "Electrical Activity in the Heart." Lecture at the University of Florida College of Pharmacy, 23-Oct-2007.

See Also

Cardiac ectopy

Clinical cardiac electrophysiology

Electrical conduction system of the heart

v • d • e Cardiovascular disease: heart disease - Circulatory system pathology (I00-I52, 390-429) Ischaemic/ Acute coronary CHD: CAD - Coronary thrombosis - Coronary vasospasm - Coronary artery aneurysm Angina pectoris (Prinzmetal's angina) - Myocardial infarction (heart attack) Myocardial rupture - Dressler's syndrome Layers Pericardium Pericarditis (Acute, Constrictive) - Pericardial effusion - Cardiac tamponade - Hemopericardium Myocardium Myocarditis Cardiomyopathy: Dilated (Alcoholic) - Hypertrophic - Restrictive (Loeffler endocarditis, Cardiac amyloidosis) Arrhythmogenic right ventricular dysplasia Endocardium/ valves Endocarditis (Subacute bacterial endocarditis, Libman-Sacks endocarditis, Nonbacterial thrombotic endocarditis) mitral (regurgitation, prolapse, stenosis) - aortic (stenosis, insufficiency) - tricuspid (stenosis, insufficiency) - pulmonary (stenosis, insufficiency) Conduction/ arrhythmia Heart block AV (1°, 2°, 3°) - Bundle branch (Left, Right) - Bifascicular/Trifascicular - Sinoatrial - Sick sinus syndrome - Adams-Stokes syndrome Pre-excitation syndrome Wolff-Parkinson-White - Lown-Ganong-Levine Tachycardia Paroxysmal - Supraventricular (AV nodal reentrant, Accelerated idioventricular rhythm, Sinus) - Ventricular (Torsades de pointes, Catecholaminergic polymorphic) Premature contraction Atrial - Ventricular Flutter/fibrillation Atrial flutter - Ventricular flutter - Atrial fibrillation (Familial) - Ventricular fibrillation Pacemaker Wandering pacemaker - Ectopic pacemaker - Parasystole - Multifocal atrial tachycardia Long QT syndrome Romano-Ward syndrome - Andersen-Tawil syndrome - Jervell and Lange-Nielsen syndrome Cardiac arrest Sudden cardiac death - Asystole - Pulseless electrical activity Other Cardiomegaly - Ventricular hypertrophy (Left, Right/Cor pulmonale) Heart failure (Cardiac asthma) - Rheumatic fever See also congenital, neoplasia

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