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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 2.1 Diagnosis 3 References 4 See Also

[edit] 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]

[edit] 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.

[edit] 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.

[edit] 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.

[edit] 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 heart disease CHD: CAD - Coronary thrombosis - Coronary vasospasm - Coronary artery aneurysm Angina pectoris (Prinzmetal's angina) - Myocardial infarction (heart attack) Acute coronary syndrome - Myocardial rupture - Dressler's syndrome Pericardium Pericarditis (Acute pericarditis, Constrictive pericarditis) - Pericardial effusion - Cardiac tamponade Endocardium/ heart valves Endocarditis (Subacute bacterial endocarditis) mitral (regurgitation, prolapse, stenosis) - aortic (stenosis, insufficiency) - pulmonary (stenosis, insufficiency) - tricuspid (stenosis, insufficiency) Myocardium Myocarditis - Cardiomyopathy (Dilated cardiomyopathy, Hypertrophic cardiomyopathy, Loeffler endocarditis, Restrictive cardiomyopathy, Alcoholic cardiomyopathy) - Arrhythmogenic right ventricular dysplasia Electrical 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) premature contraction: Atrial - Ventricular flutter/fibrillation: Atrial flutter - Ventricular flutter - Atrial fibrillation (Familial) - Ventricular fibrillation pacemaker: Wandering pacemaker - Ectopic pacemaker - Parasystole long QT syndrome: Romano-Ward syndrome - Andersen-Tawil syndrome - Jervell and Lange-Nielsen syndrome cardiac arrest: Sudden cardiac death Other Cardiomegaly - Ventricular hypertrophy (Left, Right) Cor pulmonale Heart failure - Rheumatic fever See also congenital (Q20-Q28, 745-747)