Sinus Node Dysfunction 

  • Author: Yingbo Yang, MD, PhD; Chief Editor: Jeffrey N Rottman, MD   more...
 
Updated: Apr 6, 2011
 

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.

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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.

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Epidemiology

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 lifetime; 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.[8]

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-old.[9] SND in young patients is often related to underlying heart diseases.

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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.

Specialty Editor Board

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.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

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; Novartis Honoraria Speaking and teaching; Novartis Consulting fee Consulting

Amer Suleman, MD  Private Practice

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

Jeffrey N Rottman, MD  Professor of Medicine and Pharmacology, Vanderbilt University School of Medicine; Chief, Department of Cardiology, Nashville Veterans Affairs Medical Center

Jeffrey N Rottman, MD is a member of the following medical societies: American Heart Association and North American Society of Pacing and Electrophysiology (NASPE)

Disclosure: Nothing to disclose.

Acknowledgments

We thank Dr. Adrian W Messerli, MD and professor Alan D Forker, MD for their important contributions to this article as the authors of its previous edition.

References

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