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. The Sinoatrial node (abbreviated SA node or SAN, also called the sinus node) is the impulse generating (pacemaker tissue located in the Right atrium The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic 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

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]. The Sympathetic Nervous System ( SNS) is a branch of the Autonomic nervous system along with the Enteric nervous system and Parasympathetic nervous Caffeine is a bitter white crystalline Xanthine Alkaloid that acts as a Psychoactive Stimulant Drug and a mild Diuretic
• 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. In Medicine, ischemia ( Greek ισχαιμία, isch- is restriction hema or haema is Blood) is a restriction Hyperkalemia ( AE) or Hyperkalaemia ( BE) is an elevated blood level of the Electrolyte Potassium. Hypercalcaemia (in American English '''Hypercalcemia''' is an elevated calcium level in the Blood. ^[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

Cardiac ectopy or "ventricular extra beats" is a disturbance of the Electrical conduction system of the heart in which beats arise from the wrong part of the heart Cardiac Electrophysiology (also referred to as clinical cardiac electrophysiology, Arrhythmia Services, or electrophysiology) is a branch of the medical The normal electrical conduction in the heart allows the impulse that is generated by the Sinoatrial node (SA node of the Heart to be propagated to (and stimulate the

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