eMedicine Specialties > Cardiology > Arrhythmias

Sinus Node Dysfunction

Author: Yingbo Yang, MD, PhD, Clinical Assistant Professor of Cardiovascular Medicine, Division of Cardiology, Lawrence J Ellison Ambulatory Care Center, University of California, Davis, Medical Center
Coauthor(s): Yasir Batres, MD, Fellow, Division of Cardiology, University of California, Davis, Medical Center
Contributor Information and Disclosures

Updated: Aug 31, 2009

Introduction

Background

Sinus node dysfunction (SND) first appeared in the literature as a clinical entity in 1968 under the name of sick sinus syndrome.1 Today SND refers to abnormalities in sinus node impulse formation and propagation, and includes sinus bradycardia, sinus pause/arrest, chronotropic incompetence, and sinoatrial exit block.2 SND is frequently associated with conduction system disease in the heart and various supraventricular tachyarrhythmias, such as atrial fibrillation and atrial flutter. When associated with supraventricular tachyarrhythmias, SND is often termed tachy-brady syndrome.2

Although SND may occur at any age, it is primarily a disease of the elderly and, presumably, related to the senescence of the sinus node, which is often accompanied with the senescence of the atrium and the conduction system in the heart. When SND occurs earlier in life, it is often secondary to other cardiac disease processes.3 The natural history of SND may be highly variable, although it tends to be progressive in nature. The only effective treatment for patients with chronic symptomatic SND is pacemaker therapy. Asymptomatic patients do not require therapy.

Pathophysiology

SND involves abnormalities in sinus node impulse formation and propagation, which are often accompanied with similar abnormalities in the atrium and the conduction system in the heart. Together, these abnormalities may result in inappropriately slow ventricular rates and long pauses at rest or during various stresses. When SND is mild, patients are usually asymptomatic. As SND becomes more severe, patients may develop symptoms due to organ hypoperfusion and pulse irregularity. Among these symptoms are fatigue, dizziness, confusion, fall, syncope, angina, heart failure symptoms and palpitations.

Frequency

United States

The exact incidence of sinus node dysfunction is unknown. The syndrome occurs in approximately one in 600 cardiac patients older than 65 years.4

International

Due to its relationship with advanced age, SND is more prevalent in countries where citizens have a longer life expectancy.

Mortality/Morbidity

Symptoms of sinus node dysfunction almost invariably progress over time. The most dramatic symptom in patients with SND is syncope. About 50% of patients with SND develop tachy-brady syndrome over a lifetime8 ; such patients have higher risk of stroke and death. The survival of patients with SND appears to depend primarily on the severity of underlying cardiac disease and is not significantly changed by pacemaker therapy.5,6,7 However, incidence of sudden death owing directly to SND is extremely low.5

Race

No racial preponderance exists.

Sex

Men and women are affected in equal numbers.

Age

Sinus node dysfunction may occur at any age but is primarily a disease of the elderly, with the average age being about 68 years-old9 . SND in young patients is often related to underlying heart diseases.

Clinical

History

With mild SND, patients are usually asymptomatic. As SND progresses, patients often develop symptoms due to pulse irregularity and organ hypoperfusion. The severity of organ hypoperfusion symptoms depends on the severity of SND and on the functional reserve state of an organ.

  • Cerebral symptoms - Irritability, labile mood swings, forgetfulness, dizziness, slurred speech, blanking periods, falls, and syncope
  • Cardiac symptoms - Palpitations, angina, congestive heart failure symptoms, and sudden cardiac death (rare)
  • Other symptoms
    • Vague gastrointestinal symptoms and oligurea
    • Tachy-brady syndrome may include palpitations due to tachycardia and stroke/transient ischemia attack (TIA) symptoms


Physical

  • Inappropriately slow heart rate.
  • Carotid sinus massage: may reveal sinus pause of more than 3 seconds ± hypotension in patients with carotid sinus hypersensitivity.

Causes

Although the exact etiology is usually not identified, most cases are believed to be attributable to a combination of various intrinsic and extrinsic factors. The most common intrinsic causes are cardiac age-related sinus node changes and coronary artery disease. The most common extrinsic causes are medications and autonomic hyperactivity.

Intrinsic SND

  • Age-related changes: the most common cause of SND is the replacement of sinus node tissue with fibrotic tissue. These fibrotic changes also occur in the atrium and the conduction system of the heart, and are believed to contribute to the association among SND, tachy-brady syndrome, conductive system disease and an inappropriately slow escape rhythm. Recently, age-related down-regulation of calcium channel expression in the sinus node has also been suggested as a potential cause of SND.10
  • Coronary artery disease: coronary artery disease is believed to be a common contributory cause of SND, probably through atherosclerotic changes in the sinus node artery.
  • Familial sick sinus syndromes and SND in children: Several molecular defects in human hearts (defects in the sodium channel, calcium channel and hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channel, ankyrin-B and connexin 40) have been associated with familial sick sinus syndromes.3 SND is seen in children with congenital and acquired heart disease, particularly after corrective surgery. The cause of SND in these children is likely related to the underlying structural heart disease and surgical trauma to the sinus node and/or sinus node artery.
  • Tachy-brady syndrome: tachycardia-mediated remodeling of the sinus node is present in patients with atrial fibrillation/flutter and it may contribute to SND in these patients. In patients with tachy-brady syndrome, atrial fibrillation ablation can reverse sinus node dysfunction as evidenced by a reduction in sinus node recovery time, increase in mean and maximal heart rates and lack of symptoms related to sinus bradycardia or pause.11
  • Other structural heart diseases are uncommon causes of SND. These include, but are not limited to various cardiomyopathies, myocarditis, pericarditis, infiltrative heart diseases (amyloidosis, hemochromatosis, neoplasm), collagen vascular diseases (systemic lupus, scleroderma), neuromuscular diseases (myotonic dystrophy, Friedreich ataxia).

Extrinsic SND

  • Medications: Beta-blockers, calcium channel blockers, digoxin, and various anti-arrhythmic drugs suppress sinus node function.
  • Autonomic dysfunction: SND can be secondary to autonomic nervous system dysfunction in patients with neurocardiogenic syncope, and carotid sinus hypersensitivity. Conditions associated with marked hypervagotonia, as in well-trained athletes, can also result in SND. Recent evidence, however, suggests that there may be some intrinsic factor as well in well-trained athletes who develop SND.12 .
  • Endocrine-metabolic diseases (hypothyroidism and hypothermia) and electrolyte imbalances (hypokalemia and hypocalcemia) can contribute to SND.

More on Sinus Node Dysfunction

Overview: Sinus Node Dysfunction
Differential Diagnoses & Workup: Sinus Node Dysfunction
Treatment & Medication: Sinus Node Dysfunction
Follow-up: Sinus Node Dysfunction
References
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References

  1. Ferrer MI. The sick sinus syndrome in atrial disease. JAMA. Oct 14 1968;206(3):645-6. [Medline].

  2. [Guideline] Epstein AE, DiMarco JP, Ellenbogen KA, Estes NA 3rd, Freedman RA, Gettes LS, et al. ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices) developed in collaboration with the American Association for Thoracic Surgery and Society of Thoracic Surgeons. J Am Coll Cardiol. May 27 2008;51(21):e1-62. [Medline].

  3. Dobrzynski H, Boyett MR, Anderson RH. New insights into pacemaker activity: promoting understanding of sick sinus syndrome. Circulation. Apr 10 2007;115(14):1921-32. [Medline].

  4. Rodriguez RD, Schocken DD. Update on sick sinus syndrome, a cardiac disorder of aging. Geriatrics. Jan 1990;45(1):26-30, 33-6. [Medline].

  5. Menozzi C, Brignole M, Alboni P, Boni L, Paparella N, Gaggioli G, et al. The natural course of untreated sick sinus syndrome and identification of the variables predictive of unfavorable outcome. Am J Cardiol. Nov 15 1998;82(10):1205-9. [Medline].

  6. Simon AB, Janz N. Symptomatic bradyarrhythmias in the adult: natural history following ventricular pacemaker implantation. Pacing Clin Electrophysiol. May 1982;5(3):372-83. [Medline].

  7. Alt E, Völker R, Wirtzfeld A, Ulm K. Survival and follow-up after pacemaker implantation: a comparison of patients with sick sinus syndrome, complete heart block, and atrial fibrillation. Pacing Clin Electrophysiol. Nov 1985;8(6):849-55. [Medline].

  8. Lamas GA, Lee KL, Sweeney MO, Silverman R, Leon A, Yee R, et al. Ventricular pacing or dual-chamber pacing for sinus-node dysfunction. N Engl J Med. Jun 13 2002;346(24):1854-62. [Medline].

  9. Adán V, Crown LA. Diagnosis and treatment of sick sinus syndrome. Am Fam Physician. Apr 15 2003;67(8):1725-32. [Medline].

  10. Jones SA, Boyett MR, Lancaster MK. Declining into failure: the age-dependent loss of the L-type calcium channel within the sinoatrial node. Circulation. Mar 13 2007;115(10):1183-90. [Medline].

  11. Hocini M, Sanders P, Deisenhofer I, Jaïs P, Hsu LF, Scavée C, et al. Reverse remodeling of sinus node function after catheter ablation of atrial fibrillation in patients with prolonged sinus pauses. Circulation. Sep 9 2003;108(10):1172-5. [Medline].

  12. Stein R, Medeiros CM, Rosito GA, Zimerman LI, Ribeiro JP. Intrinsic sinus and atrioventricular node electrophysiologic adaptations in endurance athletes. J Am Coll Cardiol. Mar 20 2002;39(6):1033-8. [Medline].

  13. Spodick DH. Normal sinus heart rate: sinus tachycardia and sinus bradycardia redefined. Am Heart J. Oct 1992;124(4):1119-21. [Medline].

  14. Hilgard J, Ezri MD, Denes P. Significance of ventricular pauses of three seconds or more detected on twenty-four-hour Holter recordings. Am J Cardiol. Apr 1 1985;55(8):1005-8. [Medline].

  15. Katritsis D, Camm AJ. Chronotropic incompetence: a proposal for definition and diagnosis. Br Heart J. Nov 1993;70(5):400-2. [Medline].

  16. Jose AD, Collison D. The normal range and determinants of the intrinsic heart rate in man. Cardiovasc Res. Apr 1970;4(2):160-7. [Medline].

  17. Jordan JL, Yamaguchi I, Mandel WJ. Studies on the mechanism of sinus node dysfunction in the sick sinus syndrome. Circulation. Feb 1978;57(2):217-23. [Medline].

  18. Josephson, ME. Clinical Cardiac Electrophysiology. 3rd edition. 2002.

  19. Alboni P, Menozzi C, Brignole M, Paparella N, Gaggioli G, Lolli G, et al. Effects of permanent pacemaker and oral theophylline in sick sinus syndrome the THEOPACE study: a randomized controlled trial. Circulation. Jul 1 1997;96(1):260-6. [Medline].

  20. Rosenqvist M, Obel IW. Atrial pacing and the risk for AV block: is there a time for change in attitude?. Pacing Clin Electrophysiol. Jan 1989;12(1 Pt 1):97-101. [Medline].

  21. Brandt J, Anderson H, Fåhraeus T, Schüller H. Natural history of sinus node disease treated with atrial pacing in 213 patients: implications for selection of stimulation mode. J Am Coll Cardiol. Sep 1992;20(3):633-9. [Medline].

  22. Andersen HR, Thuesen L, Bagger JP, Vesterlund T, Thomsen PE. Prospective randomised trial of atrial versus ventricular pacing in sick-sinus syndrome. Lancet. Dec 3 1994;344(8936):1523-8. [Medline].

  23. Lamas GA, Lee KL, Sweeney MO, Silverman R, Leon A, Yee R. Ventricular pacing or dual-chamber pacing for sinus-node dysfunction. N Engl J Med. Jun 13 2002;346(24):1854-62. [Medline].

  24. Sweeney MO, Bank AJ, Nsah E, Koullick M, Zeng QC, Hettrick D, et al. Minimizing ventricular pacing to reduce atrial fibrillation in sinus-node disease. N Engl J Med. Sep 6 2007;357(10):1000-8. [Medline].

  25. Lamas GA, Knight JD, Sweeney MO, Mianulli M, Jorapur V, Khalighi K, et al. Impact of rate-modulated pacing on quality of life and exercise capacity--evidence from the Advanced Elements of Pacing Randomized Controlled Trial (ADEPT). Heart Rhythm. Sep 2007;4(9):1125-32. [Medline].

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Further Reading

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Keywords

sick sinus syndrome, sinus node dysfunction, SND, sinoatrial disease, sinoatrial dysfunction, sluggish sinus syndrome, sinus nodal dysfunction, Valsalva maneuver, carotid sinus massage, idiopathic degenerative disease, coronary artery disease, autonomic hyperactivity, intrinsic sinus nodal dysfunction, infiltrative diseases, cardiomyopathy, hypertension, collagen vascular diseases, congenital heart disease, heart transplant, musculoskeletal disorders, myocarditis, pericarditis, beta-blockers, nondihydropyridine calcium channel blockers, cardiac glycosides, sympatholytic antihypertensives, membrane-active antiarrhythmics, autonomic dysfunction, vasovagal syncope, carotid sinus syndrome, extrinsic sinus nodal dysfunction, electrolyte imbalance, hypothyroidism, hyperthyroidism, hypothermia, sepsis

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Contributor Information and Disclosures

Author

Yingbo Yang, MD, PhD, Clinical Assistant Professor of Cardiovascular Medicine, Division of Cardiology, Lawrence J Ellison Ambulatory Care Center, University of California, Davis, Medical Center
Yingbo Yang, MD, PhD is a member of the following medical societies: American College of Cardiology and Heart Rhythm Society
Disclosure: Nothing to disclose.

Coauthor(s)

Yasir Batres, MD, Fellow, Division of Cardiology, University of California, Davis, Medical Center
Yasir Batres, MD is a member of the following medical societies: American College of Cardiology
Disclosure: Nothing to disclose.

Medical Editor

Justin D Pearlman, MD, PhD, ME, MA, Director of Advanced Cardiovascular Imaging, Professor of Medicine, Professor of Radiology, Adjunct Professor, Thayer Bioengineering and Computer Science, Dartmouth-Hitchcock Medical Center
Justin D Pearlman, MD, PhD, ME, MA is a member of the following medical societies: American College of Cardiology, American College of Physicians, American Federation for Medical Research, International Society for Magnetic Resonance in Medicine, and Radiological Society of North America
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Brian Olshansky, MD, Professor of Medicine, Department of Internal Medicine, University of Iowa College of Medicine
Brian Olshansky, MD is a member of the following medical societies: American Autonomic Society, American College of Cardiology, American College of Chest Physicians, American College of Physicians, American College of Sports Medicine, American Federation for Clinical Research, American Heart Association, Cardiac Electrophysiology Society, Heart Rhythm Society, and New York Academy of Sciences
Disclosure: Guidant/Boston Scientific Honoraria Speaking and teaching; Medtronic Honoraria Speaking and teaching; Guidant/Boston Scientific Consulting fee Consulting; Reliant Grant/research funds Other; Novartis Honoraria Speaking and teaching; Novartis Consulting fee Consulting

CME Editor

Amer Suleman, MD, Consultant in Electrophysiology and Cardiovascular Medicine, Department of Internal Medicine, Division of Cardiology, Medical City Dallas Hospital
Amer Suleman, MD is a member of the following medical societies: American College of Physicians, American Heart Association, American Institute of Stress, American Society of Hypertension, Federation of American Societies for Experimental Biology, Royal Society of Medicine, and Society of Cardiac Angiography and Interventions
Disclosure: Nothing to disclose.

Chief Editor

Michael E Zevitz, MD, Assistant Professor of Medicine, Finch University of the Health Sciences, The Chicago Medical School; Consulting Staff, Private Practice
Michael E Zevitz, MD is a member of the following medical societies: American College of Cardiology, American College of Physicians, American Medical Association, and Michigan State Medical Society
Disclosure: Nothing to disclose.

 
 
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