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Sick Sinus Syndrome

Sick sinus syndrome (sinus node dysfunction) is defined as a group of arrhythmias associated with sinus node dysfunction.


The following signs and symptoms are seen in sick sinus syndrome:

Coronary Artery Disease
  • Abstract A 62-year-old woman had acromegaly and developed congestive heart failure with cardiomyopathy, mitral regurgitation due to chordae rupture, coronary artery disease and sick sinus syndrome.[ncbi.nlm.nih.gov]
  • Coronary artery disease, high blood pressure, and aortic and mitral valve diseases may be associated with sick sinus syndrome, although this association may only be incidental. The mechanism is related to delayed escape.[en.wikipedia.org]
  • If a patient is on a class 1C antiarrhythmic drug and develops coronary artery disease, the drug should be discontinued.[thecardiologyadvisor.com]
  • This includes: Coronary artery disease Past heart attack Atrial fibrillation Heart failure or cardiomyopathy Taking certain medicines such as beta blockers, calcium channel blockers, and digoxin, and medicines to treat arrhythmias Severe hypothyroidism[cedars-sinai.edu]
  • Because the majority of patients with HB and SSS are elderly, coexisting hypertension and coronary artery disease are common.[tele.med.ru]
Developmental Delay
  • He developed severe apnea, epilepsy, and psychomotor developmental delay and died suddenly of sick sinus syndrome at 17 months of age. Severe bradycardia had been noticed since 16 months of age.[ncbi.nlm.nih.gov]
  • Postmortem needle aspiration revealed amyloidosis involving the heart, lung and skin. We conclude that cardiac amyloidosis should be considered in elderly patients with conduction disturbance and unexplained congestive heart failure.[ncbi.nlm.nih.gov]
  • (fast heart rate) such as atrial tachycardia (PAT) and atrial fibrillation.[en.wikipedia.org]
  • Abstract Exercise seldom provokes tachycardia in patients with paroxysmal supraventricular tachycardia (PSVT). This report presents a case of exercise-induced uncommon atrioventricular nodal reentrant tachycardia (AVNRT) with sick sinus syndrome.[ncbi.nlm.nih.gov]
  • A fast heart rate (tachycardia) may be treated with medicine. Sometimes, a procedure called radiofrequency ablation is used to cure tachycardia.[nlm.nih.gov]
  • METHODS: The study group consisted of three male patients with sick sinus syndrome, intraventricular conduction disease, and monomorphic sustained ventricular tachycardia.[ncbi.nlm.nih.gov]
  • Sick sinus syndrome has multiple manifestations on electrocardiogram, including sinus bradycardia, sinus arrest, sinoatrial block, and alternating patterns of bradycardia and tachycardia (bradycardia-tachycardia syndrome).[ncbi.nlm.nih.gov]
Heart Disease
  • Sustained bradycardia is infrequent in prenatal life and associated with maternal collagen vascular diseases, structural heart diseases or long QT syndrome.[ncbi.nlm.nih.gov]
  • After adjustment for confounders, SSS incidence was associated with increased mortality (hazard ratio [HR] 1.39, 95% confidence interval [CI] 1.14-1.70), coronary heart disease (HR 1.72, 95%CI 1.11-2.66), heart failure (HR 2.87, 95%CI 2.17-3.80), stroke[ncbi.nlm.nih.gov]
  • Abstract The most important manifestations of heart disease in hemochromatosis are congestive heart failure and cardiac arrhythmia.[ncbi.nlm.nih.gov]
  • Secondary causes such as antiarrhythmic drug consumption, organic heart disease, or electrolyte disturbance could be excluded. Standard 12-lead ECG showed a coved-type ST elevation in V1-V3, which increased after flecainide provocative test.[ncbi.nlm.nih.gov]
Irregular Heart Rhythm
  • Disruption of the node in SSS leaves patients at risk of a dangerous irregular heart rhythm often requiring a pacemaker to be fitted to correct the heart rhythm.[bhf.org.uk]
  • These signs include: a slower than normal pulse rate, irregular heart rhythm or pauses by auscultation, escape rhythms from alternate intracardiac pacemaker sites on a 12-lead EKG, a heart rhythm that alternates between slow and fast rates, and low blood[washingtonhra.com]
  • An irregular heart rhythm that can be heard with a stethoscope. Sinus "pauses," or gaps between signals from the SA node, that indicate the heart is not being paced at the normal, steady rate.[cvcde.com]
  • The type of pacemaker you need depends on the type of irregular heart rhythm you’re experiencing.[acls123.com]
Slow Pulse
  • Symptoms of SSS include: fainting or fainting sensations fatigue dizziness palpitations (abnormal heart beats) very slow pulse (bradycardia) difficulty breathing chest pain mental confusion memory problems disrupted sleep It’s important to see your doctor[healthline.com]
  • Diagnosis A slow pulse, especially one that is irregular, may be the first indication of sick sinus syndrome. Electrocardiography (ECGs) is a commonly used method of detecting sick sinus syndrome.[medical-dictionary.thefreedictionary.com]
Palpitations with Skipped Beats
  • Common symptoms include: Palpitations, or " skipped beats " Thumping or fluttering in the chest Sensation of the heart racing Other things that might happen: Feeling faint or tired Light-headedness or passing out Shortness of breath Chest pain or discomfort[webmd.com]
Tonic-Clonic Seizure
  • A 69-year-old man suffered two episodes of generalised tonic-clonic seizures. MRI and electroencephalogram failed to reveal the cause of seizures. In the emergency room, he experienced presyncope simultaneous to bradycardia and sinus pauses.[ncbi.nlm.nih.gov]


Patients may be initially examined physically when they present in the emergency room, they would most likely reveal irregular pulse rate and low blood pressure. Auscultation findings of slow rhythm and skip beats may be suggestive of a dysfunctional node. The succeeding tests for diagnosis may be implored in patients with high suspicion of sick sinus syndrome:

  • Electrocardiogram (ECG): Sick sinus syndrome may convey a characteristic pattern on ECG. Findings of bradyarrhythmias with heart rates less than 46-51 beats per minute may suggestive of a nodal pathology [8]. 
  • Holter monitor: This is a portable device that monitors the heart rhythm in a 24-48 hours period. It allows the cardiologist to detect heart rhythm abnormalities in an extended period of time. Sinus pauses of more than 3 seconds except in rare conditions like seizure disorders and sleep apnea syndrome is suggestive of a nodal pause or arrest [9].
  • Event recorder: This is also a portable device that may monitor the heart’s electrical activity at the time of an event with just a push of a button.
  • Implantable loop recorder: This small implantable device may is placed under the skin of the chest to monitor cardiac electrical activities from months to years. Rhythms may be recorded automatically when an event occurs or with a press of a button every time the patients feel some discomforts. 
Sinus Arrest
  • The diagnosis of SSS was based on electrocardiographic evidence of markedly prolonged sinus arrests associated with syncope attacks while in hospital.[ncbi.nlm.nih.gov]
  • A case of profound sinus bradycardia, sinus arrest with junctional escape, and pauses in a two-year-old infant with breath-holding and syncope episodes is presented.[ncbi.nlm.nih.gov]
  • SSS of all four cases was due to sinus arrest in association with paroxysmal atrial fibrillation (Rubenstein-III). Of special interest is that one patient showed a high prevalence of SSS and NIDDM among her close relatives.[ncbi.nlm.nih.gov]
  • Sick sinus syndrome has multiple manifestations on electrocardiogram, including sinus bradycardia, sinus arrest, sinoatrial block, and alternating patterns of bradycardia and tachycardia (bradycardia-tachycardia syndrome).[ncbi.nlm.nih.gov]
  • Electrocardiography identified sinus arrest, atrial flutter and right bundle-branch block in 2 cases and marked sinus bradycardia and first-degree atrioventricular block in 1 case.[ncbi.nlm.nih.gov]
Early Repolarization
  • The simultaneous occurrence of V596M and R16472H may increase the severity of early repolarization.[ncbi.nlm.nih.gov]
Left Ventricular Hypertrophy
  • Echocardiography revealed a normal-sized ventricular chamber, concentric left ventricular hypertrophy with a "granular sparkling" appearance of the myocardium, and impaired diastolic and systolic function of the left ventricle.[ncbi.nlm.nih.gov]


The main goal in the treatment of sick sinus syndrome focuses on the control of the patient’s discomfort. Nodal dysfunction may present mildly or asymptomatic, and may no longer require treatment. Patients on current hypertensive medications like beta-blockers and calcium channel blockers may need some revisions to control the symptoms.

Some patients with sick sinus syndrome may require a permanent pacing device called pacemakers which are implanted beneath the chest wall skin. Anti-arrhythmics may be given to patients with pacemaker whom rhythm remain abnormal. The regular intake of warfarin in face of arrhythmia in nodal dysfunction can prevent strokes in the future.

AV node ablation using radiofrequency probes to control irregularly fast rhythms can subdue tachyarrhythmia in sick sinus syndrome. However, nodal ablation may have a recurrence of abnormal pacing and may revert to atrial fibrillation as long term complication in a number of cases [10].


Sick sinus syndrome may rarely lead to sudden cardiac death [4]. Patients usually succumbs with their underlying cardiac disease rather than with the nodal dysfunction. The use of a cardiac pacemaker is primarily to alleviate symptoms and does not affect the overall mortality rating of the cardiac patients [5]. Patient with nodal dysfunction but with normal systemic ventricular function carry a very good prognosis. Among the sick sinus syndrome subtypes, the bradycardia-tachycardia syndrome has a guarded prognosis compared to the others.


The following sick sinus syndrome complications can lead to significant morbidity and mortality among cardiac patients:


The sinus node is the natural pacemaker of the heart that produces the electric impulses that initiates each heartbeat. These impulses traverse from the atria to the ventricles and contract the cardiac muscles to force out the blood. A sick sinus may insinuate a slow rhythm (bradycardia) or a very fast rhythm (tachycardia) that causes characteristic symptoms of the disease.

The following are the different types of sick sinus syndrome and their probable causes:

  • Sinus arrest: This is due to the halting of the sinus activity.
  • Sinoatrial block: Electrical impulses are described to move slowly through the sinus node causing a slow heart rate.
  • Bradycardia-Tachycardia syndrome: There is an alternate fast and slow pace rhythms with a long pause between heartbeats.


There are no available data on the exact incidence of sick sinus syndrome worldwide. The incidence of sick sinus syndrome is 1 out of 600 cardiac patients beyond 65 years of age [2]. Because sick sinus syndrome correlates well with old age, this syndrome is more prevalent in countries with high life expectancy. The age related occurrence of sick sinus syndrome has an average of 68 years old although it may occur in all ages [3]. The prevalence of sick sinus syndrome among the younger age group is usually associated with an underlying heart condition.

Sex distribution
Age distribution


The basic pathophysiology of sick sinus syndrome falls on the propagation of electrical impulses. Sometimes, the conduction path at the atrium is obscured by injury causing a delay in the conduction to the heart muscles. The ventricular contraction rate is consequently slowed down and may present with long pauses in between impulses, rest or stressful activities. Mild cases of sick sinus syndrome may be asymptomatic. Presentation of signs and symptoms occurs with concomitant organ hypoperfusion or irregular pulses.


By keeping one’s heart healthy by eating a balanced diet and by doing regular exercises, one may prevent the occurrence of sick sinus syndrome and other heart diseases. One must avoid taking unprescribed medications to avoid any adverse reactions that can cause arrhythmias in the future. These are good advices but majority of sick sinus cases are not preventable.


Sick sinus syndrome is a clinical disease characterized by the persistent dysfunction of the sinus node in the heart. Sick sinus syndrome is sometimes referred to as sinus node disease or sinus node dysfunction in medical literatures. The sinus node is defined as the specialized group of cells located in the right upper chamber of the cardiac musculature.

This node generates electrical impulses throughout the heart in a steady pace of regular electrical discharges. In sick sinus syndrome, these electrical impulses are abnormally paced whether too fast or too slow. Sick sinus syndrome is a relatively rare disease that occurs more often in older people that may eventually require a pacemaker to restore the heart’s normal rhythm [1].

Patient Information


Sick sinus syndrome refers to the persistent dysfunction of AV node in the heart causing abnormal heart rhythms.


Sinus arrest, Sino-atrial block and tachy-brady arrhythmias are possible causes of the condition.


Chest pain, confusion, fatigue, dypnea and abnormal pulses may occur.


Clinical examination, electrocardiogram (ECG) and Holter monitor may be needed to diagnose sick sinus syndrome.

Treatment and follow-up

Anti-arrhythmic drugs, anticoagulants, pacemaker insertion and AV node ablation using radio frequency are treatment options.



  1. Semelka M, Gera J, Usman S. Sick sinus syndrome: a review. Am Fam Physician. 2013; 87(10):691-6 (ISSN: 1532-0650)
  2. Rodriguez RD, Schocken DD. Update on sick sinus syndrome, a cardiac disorder of aging. Geriatrics. Jan 1990; 45(1):26-30, 33-6.
  3. Adán V, Crown LA. Diagnosis and treatment of sick sinus syndrome. Am Fam Physician. Apr 15 2003; 67(8):1725-32.
  4. 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.
  5. 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.
  6. Riahi S, Nielsen JC, Hjortshøj S, Thomsen PE, Højberg S. Heart failure in patients with sick sinus syndrome treated with single lead atrial or dual-chamber pacing: no association with pacing mode or right ventricular pacing site. Europace. 2012; 14(10):1475-82 (ISSN: 1532-2092)
  7. Lin YS, Guo GB, Chen YL, Tsai TH, Pan KL, Liu WH. Atrial size independently correlates with the development of paroxysmal atrial fibrillation in patients with sick sinus syndrome. Chang Gung Med J. 2010; 33(6):659-67 (ISSN: 2309-835X)
  8. Spodick DH. Normal sinus heart rate: sinus tachycardia and sinus bradycardia redefined. Am Heart J. Oct 1992; 124(4):1119-21.
  9. 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
  10. Masuda M, Inoue K, Iwakura K, Okamura A, Koyama Y. Preprocedural ventricular rate predicts subsequent sick sinus syndrome after ablation for long-standing persistent atrial fibrillation. Pacing Clin Electrophysiol. 2012; 35(9):1074-80 (ISSN: 1540-8159)

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Last updated: 2018-06-22 04:19