Pediatric Sinus Node Dysfunction 

  • Author: M Silvana Horenstein, MD; Chief Editor: Stuart Berger, MD   more...
 
Updated: Aug 13, 2010
 

Background

The sinus node (SN) is a subepicardial structure normally located in the right atrial wall near the superior vena cava entrance on the upper end of the sulcus terminalis. It is formed by a cluster of cells capable of spontaneous depolarization. Normally, these pacemaker cells depolarize at faster rates than any other latent cardiac pacemaker cell inside the heart. Therefore, a healthy SN directs the rate at which the heart beats. Electrical impulses generated in the SN must then be conducted outside the SN in order to depolarize the rest of the heart. SN activity is regulated by the autonomic nervous system. For example, parasympathetic stimulation causes sinus bradycardia, sinus pauses, or sinoatrial exit block. These actions decrease SN automaticity, thereby decreasing the heart rate.

Sympathetic stimulation on the other hand, increases the slope of phase 4 spontaneous depolarizations. This increases the automaticity of the SN, thereby increasing the heart rate. Blood supply to the SN is provided by the right coronary artery in most cases.

SN dysfunction (SND) constitutes an important cause of morbidity in patients who have undergone surgery for congenital heart disease (CHD). It is also commonly seen in elderly persons who have normal cardiac anatomy.

SND may manifest as abnormal SN impulse formation and/or propagation, which leads to rhythms that are slow (ie, bradyarrhythmias) or fast (ie, tachyarrhythmias) for the person's age. SND is referred to as "sick sinus syndrome" when the SND is accompanied by symptoms such as dizziness or syncope.

ECG criteria for SND apply to the presence of one or more of the following:

  • Sinus bradycardia below the heart rate expected for age (ie, < 100 beats per minute [bpm] in an infant, < 80 bpm in a preschool child, < 60 bpm in a school child, < 50 bpm in an adolescent)
  • Sinus pause or absence of an expected P wave for more than 3 seconds, which may be due to sinus arrest (failure of the SN pacemaker cells to depolarize) or due to sinoatrial exit block (depolarization of the SN but failure to conduct to the atria)
  • Slow escape rhythms that originate within the atria, His bundle, or ventricles
  • Marked sinus arrhythmia with constant variation in the P-P interval, which is likely to be accompanied by sinus bradycardia
  • Presence of both bradyarrhythmias and tachyarrhythmias (ie, SN reentry tachycardia, atrial tachycardias from an ectopic focus, atrial flutter, atrial fibrillation)

Classic electrophysiologic (EP) criteria for SND apply to the presence of one or more of the following:

  • Corrected SN recovery time (CSNRT) greater than 275 milliseconds
  • Sinoatrial conduction time greater than 200 milliseconds
  • Sinoatrial node arrest
  • Sinoatrial exit block
  • SN reentry tachycardia

However, the current recommendation is that the diagnosis should rely on noninvasive methods rather than measuring SN recovery time or sinoatrial conduction time in the EP laboratory because results can be normal despite the patient having symptoms of SND or vice versa. The most reliable noninvasive methods to diagnose SND are 24-hour Holter monitoring (which may show one or more of the ECG criteria already mentioned) and exercise testing (which may reveal chronotropic incompetence).

Next

Pathophysiology

The acquired form of SND may occur after damage to the SN artery during cardiac surgery or may be due to occlusion, such as after myocardial infarction. In the pediatric population SND and atrioventricular (AV) block have been found to occur more frequently in patients with Kawasaki disease with moderate to severe coronary artery disease than in the general population. This is believed to be secondary to myocarditis or abnormal microcirculation in the SN artery and the AV-node artery.[1]

The idiopathic form of SND is degenerative, with fibrosis and fatty infiltration of the SN and consequent decrease of functional nodal cells.

Previous
Proceed to Clinical Presentation
 
 
Contributor Information and Disclosures
Author

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, and American Medical Association

Disclosure: Nothing to disclose.

Coauthor(s)

Peter P Karpawich, MD  Professor of Pediatric Medicine, Department of Pediatrics (Cardiology), Wayne State University School of Medicine; Director, Cardiac Electrophysiology and Pacemaker Services, Children's Hospital of Michigan

Peter P Karpawich, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Heart Association, Heart Rhythm Society, Michigan State Medical Society, and Pediatric Electrophysiology Society

Disclosure: Nothing to disclose.

Specialty Editor Board

Paul M Seib, MD  Associate Professor of Pediatrics, University of Arkansas for Medical Sciences; Medical Director, Cardiac Catheterization Laboratory, Co-Medical Director, Cardiovascular Intensive Care Unit, Arkansas Children's Hospital

Paul M Seib, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Heart Association, Arkansas Medical Society, International Society for Heart and Lung Transplantation, and Society for Cardiac Angiography and Interventions

Disclosure: Nothing to disclose.

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.

John W Moore, MD, MPH  Professor of Clinical Pediatrics, Section of Pediatric Cardiology, Department of Pediatrics, University of California San Diego School of Medicine; Director of Cardiology, Rady Children's Hospital

John W Moore, MD, MPH is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, and Society for Cardiac Angiography and Interventions

Disclosure: Nothing to disclose.

Gilbert Z Herzberg, MD  Assistant Professor, Department of Pediatrics, Section of Pediatric Cardiology, New York Medical College; Consulting Staff, Department of Pediatrics, Sound Shore Medical Center

Gilbert Z Herzberg, MD is a member of the following medical societies: American Academy of Pediatrics

Disclosure: Nothing to disclose.

Chief Editor

Stuart Berger, MD  Professor of Pediatrics, Division of Cardiology, Medical College of Wisconsin; Chief of Pediatric Cardiology, Medical Director of Pediatric Heart Transplant Program, Medical Director of The Heart Center, Children's Hospital of Wisconsin

Stuart Berger, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American College of Chest Physicians, American Heart Association, and Society for Cardiac Angiography and Interventions

Disclosure: Nothing to disclose.

References

  1. Sumitomo N, Karasawa K, Taniguchi K, et al. Association of sinus node dysfunction, atrioventricular node conduction abnormality and ventricular arrhythmia in patients with Kawasaki disease and coronary involvement. Circ J. Feb 2008;72(2):274-80. [Medline].

  2. Fabritz L, Kirchhof P, Fortmuller L, et al. Gene dose-dependent atrial arrhythmias, heart block, and brady-cardiomyopathy in mice overexpressing A(3) adenosine receptors. Cardiovasc Res. Jun 1 2004;62(3):500-8. [Medline].

  3. Pasquali SK, Marino BS, Kaltman JR, et al. Rhythm and conduction disturbances at midterm follow-up after the ross procedure in infants, children, and young adults. Ann Thorac Surg. Jun 2008;85(6):2072-8. [Medline].

  4. Drago F, Silvetti MS, Grutter G, De Santis A. Long term management of atrial arrhythmias in young patients with sick sinus syndrome undergoing early operation to correct congenital heart disease. Europace. Jul 2006;8(7):488-94. [Medline].

  5. Silvetti MS, De Santis A, Marcora S, De Santo T, Grovale N, Drago F. Circadian pattern of atrial pacing threshold in the young. Europace. Feb 2008;10(2):147-50. [Medline].

  6. Shah MJ, Nehgme R, Carboni M, Murphy JD. Endocardial atrial pacing lead implantation and midterm follow-up in young patients with sinus node dysfunction after the fontan procedure. Pacing Clin Electrophysiol. Jul 2004;27(7):949-54. [Medline].

  7. Ben Ameur Y, Smiri Z, Malek S, et al. Sinus node dysfunction after complete correction of tetralogy of Fallot. Report of a case. Arch Mal Coeur Vaiss. Dec 1998;91(12):1519-23. [Medline].

  8. Brembilla-Perrot B, Beurrier D, Houriez P, et al. Utility of transesophageal atrial pacing in the diagnostic evaluation of patients with unexplained syncope associated or not with palpitations. Int J Cardiol. Sep 2004;96(3):347-53. [Medline].

  9. Fish FA, Benson W. Disorders of cardiac rhythm and conduction. In: Moss and Adam's Heart Disease in Infants, Children and Adolescents. Vol 1. Philadelphia, PA: Lippincott Williams and Wilkins; 2000:495-6.

  10. Gaynor JW. Management of sinus venosus defects. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2006;35-9. [Medline].

  11. Hasselman T, Schneider D, Madan N, Jacobs M. Reversal of fenestration flow during ventricular systole in Fontan patients in junctional or ventricular paced rhythm. Pediatr Cardiol. Sep-Oct 2005;26(5):638-41. [Medline].

  12. Hu K, Qu Y, Yue Y, Boutjdir M. Functional basis of sinus bradycardia in congenital heart block. Circ Res. Mar 5 2004;94(4):e32-8. [Medline]. [Full Text].

  13. Jose AD. Effect of combined sympathetic and parasympathetic blockade on heart rate and cardiac function in man. Am J Cardiol. Sep 1966;18(3):476-8. [Medline].

  14. Kugler JD. Sinoatrial node dysfunction. In: Gillette PC, Garson A Jr, eds. Pediatric Cardiac Dysrhythmias. New York, NY: Grune and Stratton; 1981:265-93.

  15. Kusumoto FM, Goldschlager N. Device therapy for cardiac arrhythmias. JAMA. Apr 10 2002;287(14):1848-52. [Medline].

  16. Morita H, Fukushima-Kusano K, Nagase S, et al. Sinus node function in patients with Brugada-type ECG. Circ J. May 2004;68(5):473-6. [Medline].

  17. Numata T, Abe H, Terao T, Nakashima Y. Possible involvement of hypothyroidism as a cause of lithium-induced sinus node dysfunction. Pacing Clin Electrophysiol. Jun 1999;22(6 Pt 1):954-7. [Medline].

  18. Sanders P, Morton JB, Kistler PM, et al. Electrophysiological and electroanatomic characterization of the atria in sinus node disease: evidence of diffuse atrial remodeling. Circulation. Mar 30 2004;109(12):1514-22. [Medline]. [Full Text].

  19. Smerup M, Hjertholm T, Johnsen SP, et al. Pacemaker implantation after congenital heart surgery: risk and prognosis in a population-based follow-up study. Eur J Cardiothorac Surg. Jul 2005;28(1):61-8. [Medline].

  20. Stieber J, Hofmann F, Ludwig A. Pacemaker channels and sinus node arrhythmia. Trends Cardiovasc Med. Jan 2004;14(1):23-8. [Medline].

  21. Takeshita K, Fujimori T, Kurotaki Y, et al. Sinoatrial node dysfunction and early unexpected death of mice with a defect of klotho gene expression. Circulation. Apr 13 2004;109(14):1776-82. [Medline]. [Full Text].

  22. Ueda K, Nakamura K, Hayashi T, et al. Functional characterization of a trafficking-defective HCN4 mutation, D553N, associated with cardiac arrhythmia. J Biol Chem. Jun 25 2004;279(26):27194-8. [Medline]. [Full Text].

  23. Vetter VL, Tanner CS, Horowitz LN. Electrophysiologic consequences of the Mustard repair of d-transposition of the great arteries. J Am Coll Cardiol. Dec 1987;10(6):1265-73. [Medline].

  24. Vytopil M, Vohanka S, Vlasinova J, et al. The screening for X-linked Emery-Dreifuss muscular dystrophy amongst young patients with idiopathic heart conduction system disease treated by a pacemaker implant. Eur J Neurol. Aug 2004;11(8):531-4. [Medline].

  25. Warner KG, Halpin DP, Berul CI, Payne DD. Placement of a permanent epicardial pacemaker in children using a subcostal approach. Ann Thorac Surg. Jul 1999;68(1):173-5. [Medline].

 
Previous
Next
 
This 12-lead ECG is from an asymptomatic 10 year-old girl, which was brought to our attention because of the irregularity of the P-P intervals. This ECG shows sinus arrhythmia at a rate of 65-75 beats per minute. The P waves all originate from the sinus node because they have a positive axis (upright) in leads I, II, and aVF. The PR interval is 104 milliseconds, and the QRS is narrow at 86 milliseconds, with a normal axis of 64°. The corrected QT (QTc) interval measures 402 milliseconds. Therefore, this is a normal ECG.
Below is an ECG of a 2-year-old girl who was referred to the clinic by the pediatrician for evaluation of a heart murmur. This ECG shows atrial rhythm originating most likely from the lower left atrium (P waves are inverted in lead I and are positive in II and aVF, with a frontal axis of 124°). The PR interval measures 113 milliseconds, and the QRS is narrow at 90 milliseconds. Right ventricular conduction delay is shown, which is best seen in the precordial leads V1 and V2. The QRS frontal axis shows right axis deviation (reference range for a 2-year-old child is 0-110°). The patient does not have right ventricular hypertrophy by voltage criteria. The inverted T waves in V1 are a normal finding at this age. An echocardiogram showed a moderately sized atrial septal defect. Nonsinus atrial rhythm is not a synonym of sinus node dysfunction.
This is a 12-lead ECG from a 12-year-old boy with history of syncope. This patient was healthy until 1 month earlier, when he started to experience episodes of lightheadedness. The ECG shows sinus arrhythmia (bradycardia) at a rate of 50-79 beats per minute with a PR interval of 136 milliseconds. Two junctional escape beats are present after a prolonged pause. The QRS is narrow at 85 milliseconds with a normal frontal axis of 70°. The corrected QT interval (QTc) is 411 milliseconds. A later electrophysiologic (EP) study showed prolonged sinus node recovery time (SNRT) and sinoatrial conduction time (SACT). Because of the patient's symptoms and his sinus node dysfunction, he received an atrial pacemaker. If this 12-lead ECG had been recorded from an asymptomatic patient, the findings would be considered within normal limits and no further workup would be indicated. In this case, the lightheadedness and, ultimately, the syncope define sick sinus syndrome, with the patient requiring pacemaker therapy.
 
 
 
All material on this website is protected by copyright, Copyright © 1994-2012 by WebMD LLC.
This website also contains material copyrighted by 3rd parties.

DISCLAIMER: The content of this Website is not influenced by sponsors. The site is designed primarily for use by qualified physicians and other medical professionals. The information contained herein should NOT be used as a substitute for the advice of an appropriately qualified and licensed physician or other health care provider. The information provided here is for educational and informational purposes only. In no way should it be considered as offering medical advice. Please check with a physician if you suspect you are ill.