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Ectopic pacemaker

February 06, 2023

An ectopic pacemaker, also known as ectopic focus or ectopic foci, is an excitable group of cells that causes a premature heart beat outside the normally functioning SA node of the heart. It is thus a cardiac pacemaker that is ectopic, producing an ectopic beat. Acute occurrence is usually non-life-threatening, but chronic occurrence can progress into tachycardia,[1] bradycardia or ventricular fibrillation.[2] In a normal heart beat rhythm, the SA node usually suppresses the ectopic pacemaker activity due to the higher impulse rate of the SA node. However, in the instance of either a malfunctioning SA node or an ectopic focus bearing an intrinsic rate superior to SA node rate, ectopic pacemaker activity may take over the natural heart rhythm.[3] This phenomenon (an intrinsically slower pacemaker activity being unmasked by failure of faster pacemaker tissue 'upstream') is called an escape rhythm, the lower rhythm having escaped from the dominance of the upper rhythm. As a rule, premature ectopic beats (i.e. with a shorter than the prevailing preceding R-R' interval) indicate increased myocyte or conducting tissue excitability, whereas late ectopic beats (i.e. with a prolonged preceding R-R' interval) indicate proximal pacemaker or conduction failure with an escape 'ectopic' beat.

Ectopic pacemaker
Other namesEctopic focus, ectopic foci
An illustration of ectopic foci near papillary muscles in the left ventricle
SpecialtyElectrophysiology, Cardiology
Symptoms
  • Isolated ectopic beats
  • Feeling faint
  • Palpitations

Signs and symptoms

  • Isolated ectopic beats frequently cause no symptoms, although the most common symptom is the perception of a 'missed beat'. This occurs because the person notices the prolonged gap between the early (ectopic) beat and the next normal beat.
  • Palpitations
  • Feeling faint[4]

Cause

Ectopic pacemakers can occur within healthy hearts in response to various stimulating events, they can be caused by automaticity or triggered activity, such as:

They can also occur within unhealthy hearts, caused by:

  • Infection
  • Disease, such as sinus venosus and atrial defects[8][9]
  • SA node dysfunction (1st degree block) which can cause the rate of impulse to slow[1]
  • SA node blockage so that impulses never leave the atria[1]
  • AV node blockage (3rd degree block) prevents normal conduction across ventricles[1]

Physiology

An ectopic pacemaker can reside within a part of the electrical 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. Location of the pacemaker can also change its effect on the SA node and its rhythm. An ectopic pacemaker located in the atria is known as an atrial pacemaker and can cause the atrial contraction to be faster.[10] An ectopic pacemaker situated near the AV node and the septum is known as a junctional pacemaker.[11] The pacemaker that is operating in the ventricles is known as the ventricular.[12] Other such ectopic pacemakers can even lie within the pulmonary vein and thoracic vein walls.[13][14]

Diagnosis

On an ECG, the QRS complex will be abnormally shaped when looking at ventricular ectopic activity, often it occurs earlier with an absent P wave. It can be perceived as a skipped beat on both the ECG and through normal pulse-taking.[12] During atrial ectopic activity where the P wave is normally rounded can be inverted or peaked. However the QRS complex and T waves appear relatively normal.[10] Conversely, during junctional ectopic activity the P wave is frequently absent or can be hidden in the QRS complex.[11]

See also

References

  1. ^ a b c d Phibbs, B. (1963). "Paroxysmal Atrial Tachycardia with Block Around the Ectopic Pacemaker: Report of a Case". Circulation. 28 (5): 949–50. doi:10.1161/01.CIR.28.5.949. PMID 14079200.
  2. ^ Tveito, Aslak; Lines, Glenn T. (2008). "A condition for setting off ectopic waves in computational models of excitable cells". Mathematical Biosciences. 213 (2): 141–50. doi:10.1016/j.mbs.2008.04.001. PMID 18539188.
  3. ^ a b c Rozanski, GJ (1991). "Atrial ectopic pacemaker escape mediated by phasic vagal nerve activity". The American Journal of Physiology. 260 (5 Pt 2): H1507–14. doi:10.1152/ajpheart.1991.260.5.H1507. PMID 2035673.
  4. ^ Abbott, Louise (December 2012). "Atrial Fibrillation – information, symptoms and treatment". Bupa.
  5. ^ Port, Carol Mattson (2005). Pathophysiology: Concepts of Altered Health States (7th ed.). Lippincott Williams & Wilkins. p. 588. ISBN 978-0-7817-4988-6.
  6. ^ Maupoil, V; Bronquard, C; Freslon, J-L; Cosnay, P; Findlay, I (2007). "Ectopic activity in the rat pulmonary vein can arise from simultaneous activation ofα1- andβ1-adrenoceptors". British Journal of Pharmacology. 150 (7): 899–905. doi:10.1038/sj.bjp.0707177. PMC 2013875. PMID 17325650.
  7. ^ Keller-Wood, Maureen. "Electrical Activity in the Heart." Lecture at the University of Florida College of Pharmacy, 23-Oct-2007.[verification needed]
  8. ^ Hamilton, S. D.; Bartley, T. D.; Miller, R. H.; Schiebler, G. L.; Marriott, H. J. L. (1968). "Disturbances in Atrial Rhythm and Conduction Following the Surgical Creation of an Atrial Septal Defect by the Blalock-Hanlon Technique". Circulation. 38 (1): 73–81. doi:10.1161/01.CIR.38.1.73. PMID 11712295.
  9. ^ Hoogaars, Willem M.H.; Engel, Angela; Brons, Janynke F.; Verkerk, Arie O.; de Lange, Frederik J.; Wong, L.Y. Elaine; Bakker, Martijn L.; Clout, Danielle E.; et al. (2007). "Tbx3 controls the sinoatrial node gene program and imposes pacemaker function on the atria". Genes & Development. 21 (9): 1098–112. doi:10.1101/gad.416007. PMC 1855235. PMID 17473172.
  10. ^ a b "Wandering pacemaker". ECG Interpretation: An Incredibly Easy! Pocket Guide (4th ed.). Lippincott Williams & Wilkins. 2007. pp. 116–18. ISBN 978-1-58255-701-4.
  11. ^ a b "Junctional escape rhythm". ECG Interpretation: An Incredibly Easy! Pocket Guide (4th ed.). Lippincott Williams & Wilkins. 2007. pp. 125–28. ISBN 978-1-58255-701-4.
  12. ^ a b "Atrial tachycardia". ECG Interpretation: An Incredibly Easy! Pocket Guide (4th ed.). Lippincott Williams & Wilkins. 2007. pp. 96–98. ISBN 978-1-58255-701-4.
  13. ^ Haghjoo, Majid (2007). "Efficacy, safety, and role of segmental superior vena cava isolation in the treatment of atrial fibrillation". Journal of Electrocardiology. 40 (4): 327.e1. doi:10.1016/j.jelectrocard.2007.04.003. PMID 17599474.
  14. ^ Tan, Alex Y.; Zhou, Shengmei; Jung, Byung Chun; Ogawa, Masahiro; Chen, Lan S.; Fishbein, Michael C.; Chen, Peng-Sheng (2008). "Ectopic atrial arrhythmias arising from canine thoracic veins during in vivo stellate ganglia stimulation". AJP: Heart and Circulatory Physiology. 295 (2): H691–98. doi:10.1152/ajpheart.01321.2007. PMC 2519231. PMID 18539751.

February 06, 2023
ectopic, pacemaker, ectopic, pacemaker, also, known, ectopic, focus, ectopic, foci, excitable, group, cells, that, causes, premature, heart, beat, outside, normally, functioning, node, heart, thus, cardiac, pacemaker, that, ectopic, producing, ectopic, beat, a. An ectopic pacemaker also known as ectopic focus or ectopic foci is an excitable group of cells that causes a premature heart beat outside the normally functioning SA node of the heart It is thus a cardiac pacemaker that is ectopic producing an ectopic beat Acute occurrence is usually non life threatening but chronic occurrence can progress into tachycardia 1 bradycardia or ventricular fibrillation 2 In a normal heart beat rhythm the SA node usually suppresses the ectopic pacemaker activity due to the higher impulse rate of the SA node However in the instance of either a malfunctioning SA node or an ectopic focus bearing an intrinsic rate superior to SA node rate ectopic pacemaker activity may take over the natural heart rhythm 3 This phenomenon an intrinsically slower pacemaker activity being unmasked by failure of faster pacemaker tissue upstream is called an escape rhythm the lower rhythm having escaped from the dominance of the upper rhythm As a rule premature ectopic beats i e with a shorter than the prevailing preceding R R interval indicate increased myocyte or conducting tissue excitability whereas late ectopic beats i e with a prolonged preceding R R interval indicate proximal pacemaker or conduction failure with an escape ectopic beat Ectopic pacemakerOther namesEctopic focus ectopic fociAn illustration of ectopic foci near papillary muscles in the left ventricleSpecialtyElectrophysiology CardiologySymptomsIsolated ectopic beats Feeling faint Palpitations Contents 1 Signs and symptoms 2 Cause 3 Physiology 4 Diagnosis 5 See also 6 ReferencesSigns and symptoms EditIsolated ectopic beats frequently cause no symptoms although the most common symptom is the perception of a missed beat This occurs because the person notices the prolonged gap between the early ectopic beat and the next normal beat Palpitations Feeling faint 4 Cause EditEctopic pacemakers can occur within healthy hearts in response to various stimulating events they can be caused by automaticity or triggered activity such as Increased local parasympathetic nervous system activity 3 Elevated sympathetic nervous system output 3 Overstimulation from drugs such as caffeine 5 digitalis and catecholamines 6 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 7 They can also occur within unhealthy hearts caused by Infection Disease such as sinus venosus and atrial defects 8 9 SA node dysfunction 1st degree block which can cause the rate of impulse to slow 1 SA node blockage so that impulses never leave the atria 1 AV node blockage 3rd degree block prevents normal conduction across ventricles 1 Physiology EditAn ectopic pacemaker can reside within a part of the electrical 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 Location of the pacemaker can also change its effect on the SA node and its rhythm An ectopic pacemaker located in the atria is known as an atrial pacemaker and can cause the atrial contraction to be faster 10 An ectopic pacemaker situated near the AV node and the septum is known as a junctional pacemaker 11 The pacemaker that is operating in the ventricles is known as the ventricular 12 Other such ectopic pacemakers can even lie within the pulmonary vein and thoracic vein walls 13 14 Diagnosis EditOn an ECG the QRS complex will be abnormally shaped when looking at ventricular ectopic activity often it occurs earlier with an absent P wave It can be perceived as a skipped beat on both the ECG and through normal pulse taking 12 During atrial ectopic activity where the P wave is normally rounded can be inverted or peaked However the QRS complex and T waves appear relatively normal 10 Conversely during junctional ectopic activity the P wave is frequently absent or can be hidden in the QRS complex 11 See also EditCardiac ectopy Clinical cardiac electrophysiology Electrical conduction system of the heartReferences Edit a b c d Phibbs B 1963 Paroxysmal Atrial Tachycardia with Block Around the Ectopic Pacemaker Report of a Case Circulation 28 5 949 50 doi 10 1161 01 CIR 28 5 949 PMID 14079200 Tveito Aslak Lines Glenn T 2008 A condition for setting off ectopic waves in computational models of excitable cells Mathematical Biosciences 213 2 141 50 doi 10 1016 j mbs 2008 04 001 PMID 18539188 a b c Rozanski GJ 1991 Atrial ectopic pacemaker escape mediated by phasic vagal nerve activity The American Journal of Physiology 260 5 Pt 2 H1507 14 doi 10 1152 ajpheart 1991 260 5 H1507 PMID 2035673 Abbott Louise December 2012 Atrial Fibrillation information symptoms and treatment Bupa Port Carol Mattson 2005 Pathophysiology Concepts of Altered Health States 7th ed Lippincott Williams amp Wilkins p 588 ISBN 978 0 7817 4988 6 Maupoil V Bronquard C Freslon J L Cosnay P Findlay I 2007 Ectopic activity in the rat pulmonary vein can arise from simultaneous activation ofa1 andb1 adrenoceptors British Journal of Pharmacology 150 7 899 905 doi 10 1038 sj bjp 0707177 PMC 2013875 PMID 17325650 Keller Wood Maureen Electrical Activity in the Heart Lecture at the University of Florida College of Pharmacy 23 Oct 2007 verification needed Hamilton S D Bartley T D Miller R H Schiebler G L Marriott H J L 1968 Disturbances in Atrial Rhythm and Conduction Following the Surgical Creation of an Atrial Septal Defect by the Blalock Hanlon Technique Circulation 38 1 73 81 doi 10 1161 01 CIR 38 1 73 PMID 11712295 Hoogaars Willem M H Engel Angela Brons Janynke F Verkerk Arie O de Lange Frederik J Wong L Y Elaine Bakker Martijn L Clout Danielle E et al 2007 Tbx3 controls the sinoatrial node gene program and imposes pacemaker function on the atria Genes amp Development 21 9 1098 112 doi 10 1101 gad 416007 PMC 1855235 PMID 17473172 a b Wandering pacemaker ECG Interpretation An Incredibly Easy Pocket Guide 4th ed Lippincott Williams amp Wilkins 2007 pp 116 18 ISBN 978 1 58255 701 4 a b Junctional escape rhythm ECG Interpretation An Incredibly Easy Pocket Guide 4th ed Lippincott Williams amp Wilkins 2007 pp 125 28 ISBN 978 1 58255 701 4 a b Atrial tachycardia ECG Interpretation An Incredibly Easy Pocket Guide 4th ed Lippincott Williams amp Wilkins 2007 pp 96 98 ISBN 978 1 58255 701 4 Haghjoo Majid 2007 Efficacy safety and role of segmental superior vena cava isolation in the treatment of atrial fibrillation Journal of Electrocardiology 40 4 327 e1 doi 10 1016 j jelectrocard 2007 04 003 PMID 17599474 Tan Alex Y Zhou Shengmei Jung Byung Chun Ogawa Masahiro Chen Lan S Fishbein Michael C Chen Peng Sheng 2008 Ectopic atrial arrhythmias arising from canine thoracic veins during in vivo stellate ganglia stimulation AJP Heart and Circulatory Physiology 295 2 H691 98 doi 10 1152 ajpheart 01321 2007 PMC 2519231 PMID 18539751 Retrieved from https en wikipedia org w index php title Ectopic pacemaker amp oldid 1112159386, wikipedia, wiki, book, books, library,

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