Pediatric Second-Degree Atrioventricular Block Medication: Beta-adrenergic agonists, Anticholinergic
Pediatric Second-Degree Atrioventricular Block Medication: Beta-adrenergic agonists, Anticholinergics
In general, patients with second-degree atrioventricular (AV) block with symptomatic bradycardia may be medicated with intravenous isoproterenol or atropine acutely. However, these agents must be administered in a hospital setting with cardiac monitoring available. Patients with Mobitz I (Wenckebach) AV block secondary to increased vagal tone may respond to theophylline, glycopyrrolate, or scopolamine. Pacemaker therapy is required when medications fail to control symptoms.
Isoproterenol has beta1-adrenergic and beta2-adrenergic receptor activity. It binds beta receptors of the heart, smooth muscle of bronchi, skeletal muscle, vasculature, and alimentary tract. Isoproterenol has positive inotropic and chronotropic actions.
Isoproterenol is usually given as a continuous intravenous infusion for rate support. It is usually administered as a temporizing measure, initiated during the organization of temporary or permanent pacing system placement for symptomatic patients with bradycardia from heart block or sinus node disease.
The goal of anticholinergic therapy is to improve AV node conduction by reducing vagal tone via the muscarinic receptor blockade. This is effective only if the site of a block is within the AV node. Anticholinergic therapy is ineffective for patients with infranodal block.
Atropine is administered to increase heart rate through vagolytic effects, causing an increase in cardiac output.
M Silvana Horenstein, MD Assistant Professor, Department of Pediatrics, University of Texas Medical School at Houston; Medical Doctor Consultant, Legacy Department, Best Doctors, Inc
M Silvana Horenstein, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Medical Association
Coauthor(s)
Robert Murray Hamilton, MD, MSc, FRCPC Electrophysiologist, Senior Associate Scientist, Physiology and Experimental Medicine, Labatt Family Heart Centre; Professor, Department of Pediatrics, University of Toronto Faculty of Medicine
Robert Murray Hamilton, MD, MSc, FRCPC is a member of the following medical societies: American Heart Association, Canadian Medical Association, Ontario Medical Association, Royal College of Physicians and Surgeons of Canada, Canadian Medical Protective Association, Heart Rhythm Society, Canadian Cardiovascular Society, Cardiac Electrophysiology Society, Pediatric and Congenital Electrophysiology Society, Society for Pediatric Research
Chief Editor
Steven R Neish, MD, SM Director of Pediatric Cardiology Fellowship Program, Associate Professor, Department of Pediatrics, Baylor College of Medicine
Steven R Neish, MD, SM is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Heart Association
Acknowledgements
Charles I Berul, MD Professor of Pediatrics and Integrative Systems Biology, George Washington University School of Medicine; Chief, Division of Cardiology, Children's National Medical Center
Charles I Berul, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Heart Association, Cardiac Electrophysiology Society, Heart Rhythm Society, Pediatric and Congenital Electrophysiology Society, and Society for Pediatric Research
Disclosure: Johnson & Johnson Consulting fee Consulting
Alvin J Chin, MD Professor of Pediatrics, University of Pennsylvania School of Medicine; Attending Physician, Cardiology Division, Children's Hospital of Philadelphia
Alvin J Chin, MD, is a member of the following medical societies: American Association for the Advancement of Science, American Heart Association, and Society for Developmental Biology
Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Nothing to disclose.
References
A common pattern of second-degree atrioventricular (AV) block consists of gradual prolongation of the PR interval leading up to a nonconducted P wave; this pattern is known as Wenckebach AV block, or Mobitz I AV block. This rhythm strip is an example of classic Mobitz I, or Wenckebach, AV block, in which the PR interval prolongs by sequentially smaller increments, with consequent shortening of the RR intervals until the blocked beat occurs. However, classic Wenckebach block is present in only a minority of cases. Wenckebach block is most easily diagnosed by comparing the PR interval following the blocked beat with the PR interval preceding the blocked beat; if the PR interval shortens following the blocked beat, the block is most likely of the Wenckebach type.
If the PR interval fails to shorten following a blocked beat, non-Wenckebach AV block (or Mobitz II AV block) is said to be present. This block is usually located more distally in the His bundle or the His bundle branches, or both, and the escape rates are usually slower and less stable.
Medication Summary
In general, patients with second-degree atrioventricular (AV) block with symptomatic bradycardia may be medicated with intravenous isoproterenol or atropine acutely. However, these agents must be administered in a hospital setting with cardiac monitoring available. Patients with Mobitz I (Wenckebach) AV block secondary to increased vagal tone may respond to theophylline, glycopyrrolate, or scopolamine. Pacemaker therapy is required when medications fail to control symptoms.
Beta-adrenergic agonists
Class Summary
Isoproterenol has beta1-adrenergic and beta2-adrenergic receptor activity. It binds beta receptors of the heart, smooth muscle of bronchi, skeletal muscle, vasculature, and alimentary tract. Isoproterenol has positive inotropic and chronotropic actions.
Isoproterenol (Isuprel)
Isoproterenol is usually given as a continuous intravenous infusion for rate support. It is usually administered as a temporizing measure, initiated during the organization of temporary or permanent pacing system placement for symptomatic patients with bradycardia from heart block or sinus node disease.
Anticholinergics
Class Summary
The goal of anticholinergic therapy is to improve AV node conduction by reducing vagal tone via the muscarinic receptor blockade. This is effective only if the site of a block is within the AV node. Anticholinergic therapy is ineffective for patients with infranodal block.
Atropine
Atropine is administered to increase heart rate through vagolytic effects, causing an increase in cardiac output.
M Silvana Horenstein, MD Assistant Professor, Department of Pediatrics, University of Texas Medical School at Houston; Medical Doctor Consultant, Legacy Department, Best Doctors, Inc
M Silvana Horenstein, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Medical Association
Coauthor(s)
Robert Murray Hamilton, MD, MSc, FRCPC Electrophysiologist, Senior Associate Scientist, Physiology and Experimental Medicine, Labatt Family Heart Centre; Professor, Department of Pediatrics, University of Toronto Faculty of Medicine
Robert Murray Hamilton, MD, MSc, FRCPC is a member of the following medical societies: American Heart Association, Canadian Medical Association, Ontario Medical Association, Royal College of Physicians and Surgeons of Canada, Canadian Medical Protective Association, Heart Rhythm Society, Canadian Cardiovascular Society, Cardiac Electrophysiology Society, Pediatric and Congenital Electrophysiology Society, Society for Pediatric Research
Chief Editor
Steven R Neish, MD, SM Director of Pediatric Cardiology Fellowship Program, Associate Professor, Department of Pediatrics, Baylor College of Medicine
Steven R Neish, MD, SM is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Heart Association
Acknowledgements
Charles I Berul, MD Professor of Pediatrics and Integrative Systems Biology, George Washington University School of Medicine; Chief, Division of Cardiology, Children's National Medical Center
Charles I Berul, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Heart Association, Cardiac Electrophysiology Society, Heart Rhythm Society, Pediatric and Congenital Electrophysiology Society, and Society for Pediatric Research
Disclosure: Johnson & Johnson Consulting fee Consulting
Alvin J Chin, MD Professor of Pediatrics, University of Pennsylvania School of Medicine; Attending Physician, Cardiology Division, Children's Hospital of Philadelphia
Alvin J Chin, MD, is a member of the following medical societies: American Association for the Advancement of Science, American Heart Association, and Society for Developmental Biology
Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Nothing to disclose.
References
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A common pattern of second-degree atrioventricular (AV) block consists of gradual prolongation of the PR interval leading up to a nonconducted P wave; this pattern is known as Wenckebach AV block, or Mobitz I AV block. This rhythm strip is an example of classic Mobitz I, or Wenckebach, AV block, in which the PR interval prolongs by sequentially smaller increments, with consequent shortening of the RR intervals until the blocked beat occurs. However, classic Wenckebach block is present in only a minority of cases. Wenckebach block is most easily diagnosed by comparing the PR interval following the blocked beat with the PR interval preceding the blocked beat; if the PR interval shortens following the blocked beat, the block is most likely of the Wenckebach type.
If the PR interval fails to shorten following a blocked beat, non-Wenckebach AV block (or Mobitz II AV block) is said to be present. This block is usually located more distally in the His bundle or the His bundle branches, or both, and the escape rates are usually slower and less stable.
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