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JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY
VOL. 64, NO. 6, 2014
ª 2014 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION
ISSN 0735-1097/$36.00
PUBLISHED BY ELSEVIER INC.
http://dx.doi.org/10.1016/j.jacc.2014.05.029
EDITORIAL COMMENT
Sick Sinus Syndrome
Synopsis*
Gordon A. Ewy, MD
S
ick sinus syndrome (SSS) is a term used for a
is most common in the elderly, its symptoms may be
variety of cardiac arrhythmias, occurring pre-
attributed to the aging process rather than to a dis-
dominantly in the elderly, that result from a
ease. One of the hallmarks of aging is the progressive
senescent sinus node. Because the sinus node is the
loss of cells, and this loss of cells in the sinus node is
normal pacemaker of the heart, its dysfunction is a
a commonly reported pathological finding in patients
cause for concern. Although the major problem is
with SSS. The frequent lack of an effective escape
failure of the sinoatrial node, the symptoms would
rhythm emphasizes the diffuse nature of the con-
be uncommon were it not for the diffuse nature of
duction system disease. Because the sinus node gets
the dysfunction, accounting for the frequent failure
its blood supply from a branch of a coronary artery,
of escape or rescue rhythms. Accordingly, SSS is char-
SSS also can be caused by atherosclerosis and may
acterized, not only by sinus node malfunction, result-
be associated with angina. The syndrome can be
ing in intermittent sinus pauses and rare sinus arrest,
accompanied by a variety of other supraventricular
but also by inappropriate and often intermittent
arrhythmias. Although the rescue rhythms are usu-
bradycardia, tachycardia, and the frequent alterna-
ally atrial, the association of atrioventricular nodal
tion between the 2 conditions (tachycardia-brady-
disease is not uncommon.
cardia syndrome) (1,2).
Clinically significant SSS often requires pacemaker
When sinus node dysfunction is associated with
implantation. Ferrer (5) pointed out in 1982 that one-
symptoms, or prolonged periods of asystole, it is
half of the 60,000 pacemakers implanted were for
referred to as the sick sinus syndrome. Although Dr.
SSS. By 2006, SSS was one of the most common rea-
Short (3) had previously published on “The Syndrome
sons for the escalating number of pacemaker im-
of Alternating Bradycardia and Tachycardia,” Dr.
plants (6).
Ferrer (4) was evidently the first, in 1968, to use the
In describing the epidemiology of SSS, Jensen et
term sick sinus syndrome to describe the sluggish re-
al. (7) in this issue of the Journal confirmed that SSS
turn of sinoatrial nodal function in patients following
was associated with the increasing age of the popu-
electrical cardioversion.
lation, predicted to produce a steady increase in the
Sick sinus syndrome is generally a disease of aging.
incidence of SSS and, thus, in the need for permanent
It is uncommon in children. If present in children, it
pacemaker implantation, estimating that by 2060,
was usually acquired post-operatively as a result of
there will be more than 170,000 new cases of SSS
trauma to the atrium during cardiac surgery to correct
per year.
congenital heart defects.
SEE PAGE 531
A characteristic feature of SSS is that the heart does
not respond normally to stimuli that should produce
increased heart rates, such as exercise. Because SSS
The investigators of this study identified SSS
by the International Classification of Disease-revision
9-Clinical
*Editorials published in the Journal of the American College of Cardiology
reflect the views of the authors and do not necessarily represent the
views of JACC or the American College of Cardiology.
From the University of Arizona Sarver Heart Center, Tucson, Arizona.
Modification
(ICD-9-CM)
code
427.81,
which incorporates SSS, sinoatrial node dysfunction,
tachycardia-bradycardia syndrome, and persistent
sinus bradycardia. They considered SSS to be pre-
Dr. Ewy has reported that he has no relationships relevant to the
sent if the medical record included a diagnosis of
contents of this paper to disclose.
SSS and symptoms or signs consistent with SSS
540
Ewy
JACC VOL. 64, NO. 6, 2014
AUGUST 12, 2014:539–40
Sick Sinus Syndrome: Synopsis
(e.g., syncope, dizziness, bradycardia, sinus pauses),
An asystole response of 3 or more seconds to carotid
with no evidence of other conditions responsible for
sinus pressure is strongly suggestive of SSS and an
the episode, such as atrioventricular block or medi-
indication for a permanent pacemaker if the patient
cation use (7). These investigators confirmed that the
has a history of syncope (8).
incidence of SSS increased with age, but found that
The definitive diagnosis is often made by ambu-
blacks had a lower risk than whites. They reported
latory monitoring or by electrophysiological studies.
that the incidence of SSS was associated with greater
Modern ambulatory monitoring alternatives are often
body mass index, greater height, longer QRS interval,
essential to this diagnosis. The increasing sophisti-
lower heart rate, and prevalent hypertension, right
cation, diagnostic ability, and surgical skills of the
bundle branch block, and cardiovascular disease (7).
modern electrophysiologists make the diagnosis easy
The SSS may be difficult to diagnosis, because
and therapy of patients with SSS effective. Jensen
initially, the symptoms may be mild and very inter-
et al. (7) predict that with the aging of our population,
mittent. When the patient presents with symptoms
SSS will be a major factor in increasing the need for
consistent with SSS, a detailed history of medica-
permanent pacemakers. This fact will drive research
tions, including alternative medications, is essential.
into more effective approaches to the diagnosis of
In addition, it is rare, but the patient may be taking
the SSS and into decreasing the size and type of
the same medication prescribed by 2 different phy-
permanent pacemakers, as well as increasing the
sicians: one by a generic name and the other by a
sophistication of future permanent pacemakers.
trade name, such as metoprolol and Toprol-XL, or
digoxin and Lanoxin, where known side effects of
REPRINT REQUESTS AND CORRESPONDENCE: Dr.
overdose are arrhythmias consistent with SSS.
Gordon A. Ewy, Department of Medicine, University
The physical examination and the electrocardio-
of Arizona Sarver Heart Center, 932 West San Martin
gram are important, including performing carotid si-
Drive, Tucson, Arizona 85704. E-mail: gaewy1933@
nus pressure, while observing the electrocardiogram.
gmail.com.
REFERENCES
1. Ewy GA. Management of bradydysrhythmias
and conduction disturbances. In: Ewy GA,
Bressler R, editors. Cardiovascular Drugs and the
Management of Heart Disease. New York, NY:
Raven Press, 1982:441–62.
2. Gregoratos G. Sick sinus syndrome. Circulation
5. Ferrer MI. The etiology and natural history of
sinus node disorders. Arch Intern Med 1982;142:
371–2.
6. Birnie D, Williams K, Guo A, et al. Reasons for
escalating pacemaker implants. J Am Coll Cardiol
2006;98:93–7.
2003;108:e143–4.
7. Jensen PN, Gronroos NN, Chen LY, et al. Inci-
3. Short DS. The syndrome of alternating
bradycardia and tachycardia. Brit Heart J 1954;16:
208–14.
dence of and risk factors for sick sinus syndrome
in the general population. J Am Coll Cardiol 2014;
64:531–8.
4. Ferrer MI. The sick sinus syndrome in atrial
disease. JAMA 1967;206:625–46.
8. Epstein AE, DiMarco JP, Ellenbogen KA, 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). J Am Coll Cardiol 2008;
51:e1–62.
KEY WORDS cardiac arrest, passive
ventilation, prevention, ventricular fibrillation