Sinus Node Dysfunction

 

Am Fam Physician. 2021 Aug ;104(2):179-185.

  Patient information: A handout on this topic is available at https://familydoctor.org/condition/sick-sinus-syndrome.

Author disclosure: No relevant financial affiliations.

Sinus node dysfunction, previously known as sick sinus syndrome, describes disorders related to abnormal conduction and propagation of electrical impulses at the sinoatrial node. An abnormal atrial rate may result in the inability to meet physiologic demands, especially during periods of stress or physical activity. Sinus node dysfunction may occur at any age, but is usually more common in older persons. The causes of sinus node dysfunction are intrinsic (e.g., degenerative idiopathic fibrosis, cardiac remodeling) or extrinsic (e.g., medications, metabolic abnormalities) to the sinoatrial node. Many extrinsic causes are reversible. Electrocardiography findings include sinus bradycardia, sinus pauses or arrest, sinoatrial exit block, chronotropic incompetence, or alternating bradycardia and tachycardia (i.e., bradycardia-tachycardia syndrome). Clinical symptoms result from the hypoperfusion of end organs. About 50% of patients present with cerebral hypoperfusion (e.g., syncope, presyncope, lightheadedness, cerebrovascular accident). Other symptoms include palpitations, decreased physical activity tolerance, angina, muscular fatigue, or oliguria. A diagnosis is made by directly correlating symptoms with a bradyarrhythmia and eliminating potentially reversible extrinsic causes. Heart rate monitoring using electrocardiography or ambulatory cardiac event monitoring is performed based on the frequency of symptoms. An exercise stress test should be performed when symptoms are associated with exertion. The patient's inability to reach a heart rate of at least 80% of their predicted maximum (220 beats per minute – age) may indicate chronotropic incompetence, which is present in 50% of patients with sinus node dysfunction. First-line treatment for patients with confirmed sinus node dysfunction is permanent pacemaker placement with atrial-based pacing and limited ventricular pacing when necessary.

Sinus node dysfunction, previously known as sick sinus syndrome, is characterized by abnormal initiation and propagation of electrical impulses from the sinoatrial node (SAN). The resulting abnormalities include bradycardia (less than 50 beats per minute [bpm]), sinus pause (more than three seconds), sinus arrest, and sinoatrial exit blocks, which are sometimes associated with supraventricular tachyarrhythmias in bradycardia-tachycardia syndrome14  (Table 1511). Bradycardia-tachycardia syndrome occurs in approximately 50% of patients with sinus node dysfunction and increases the risk of stroke and death.5,12 Symptoms manifest as end-organ hypoperfusion, including palpitations, decreased physical activity tolerance, easy fatigability, dizziness, and syncope.2,5,6,13 To diagnose sinus node dysfunction, a combination of symptoms and documented electrical abnormalities must be present.5,7

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SORT: KEY RECOMMENDATIONS FOR PRACTICE

Clinical recommendationEvidence ratingComments

A diagnosis of sinus node dysfunction requires direct correlation of observed bradyarrhythmia with symptoms of end-organ hypoperfusion.2,5

C

Expert opinion and consensus guideline

Permanent pacemaker placement with atrial-based pacing is the first-line therapy for symptomatic treatment of sinus node dysfunction.2,5,37,38

B

Expert opinion, consensus guidelines, and randomized controlled trial with three-year follow-up analysis

In patients who decline permanent pacemaker placement, a trial of phosphodiesterase inhibitors may be effective for controlling symptoms associated with sinus node dysfunction.2,35

C

Consensus guideline and retrospective case-control study


A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to https://www.aafp.org/afpsort.

SORT: KEY RECOMMENDATIONS FOR PRACTICE

Clinical recommendationEvidence ratingComments

A diagnosis of sinus node dysfunction requires direct correlation of observed bradyarrhythmia with symptoms of end-organ hypoperfusion.2,5

C

Expert opinion and consensus guideline

Permanent pacemaker placement with atrial-based pacing is the first-line therapy for symptomatic treatment of sinus node dysfunction.2,5,37,38

B

Expert opinion, consensus guidelines, and randomized controlled trial with three-year follow-up analysis

In patients who decline permanent pacemaker placement, a trial of phosphodiesterase inhibitors may be effective for controlling symptoms associated with sinus node dysfunction.2,35

C

Consensus guideline and retrospective case-control study


A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to https://www

The Authors

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MATTHEW KENDALL HAWKS, MD, FAAFP, is an assistant professor in the Department of Family Medicine at the Uniformed Services University of the Health Sciences, Bethesda, Md....

MADISON L.B. PAUL, MD, is a resident in the Department of Family Medicine at Fort Belvoir (Va.) Community Hospital.

OMOJO ODIHI MALU, MD, MSc, is a staff physician at the DiLorenzo Health Clinic, Washington, DC.

Address correspondence to Matthew Kendall Hawks, MD, FAAFP, 4301 Jones Bridge Rd., Bethesda, MD 20814 (email: matthewkhawks@gmail.com). Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.

References

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