Sinus Node Dysfunction

Sinus Node Dysfunction

• Refers to problems with sinus node impulse formation and propagation
• May include sinus bradycarda, sinus pauses or arrest, chronotropic incompetence, and sino-atrial exit block
• When accompanied by symptoms it is referred to as Sick Sinus Syndrome
• When associated with periods of paroxysmal supraventricular tachycardia it is referred to as Tachycardia-Bradycardia Syndrome or “Tachy-Brady Syndrome”

Causes of Sick Sinus Syndrome

• Idiopathic
• Ischemic heart disease
• Primary non-ischemic cardiomyopathy
• Hypertensive heart disease
• Secondary cardiomyopathy
  • Connective tissue disease
  • Syphilis
  • Metastatic tumor
  • Amyloidosis
  • Myxedema
  • Hemochromatosis
  • Friedreich’s ataxia
  • Muscular dystrophy
  • Scleroderma
• Mitral valve prolapse
• Rheumatic heart disease
• Acute myocarditis
• Congenital heart disease
• Familial sinus node disease
• Surgical injury to the SA node (especially following repair of transposition of the great vessels)
• Following the Cox-Maze III procedure for management of atrial fibrillation

Tachycardia-Bradycardia Syndrome

• Observed in 54 to 76% of patients with Sick Sinus Syndrome
• Not a pure clinical or ECG entity but rather a constellation of cardiac rhythm disturbances and their clinical manifestations
• Occurs in all age groups but most common in the elderly

Indications for Permanent Pacing

• Sinus pauses of 3 seconds or greater
• Sustained symptomatic sinus rates of 40 BPM or less in the awake patient

See also: The basics of paced rhythms.

Example

A Sign of the Times?

Here’s an interesting example of new medicine relayed by a cardiologist colleague pic.twitter.com/uqKWeC1s9N

— Eric Topol (@EricTopol) July 15, 2015

Further Reading

Sinus Node Dysfunction at Life in the Fast Lane.

Sick Sinus Syndrome at the Heart Rhythm Society

Click here for a great case from Dr. Smith’s ECG Blog.

References

Epstein A, DiMarco J, Ellenbogen K et al. ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities. Journal of the American College of Cardiology. 2008;51(21):e1-e62. doi:10.1016/j.jacc.2008.02.032.

Hayes D, Lloyd M, Friedman P. Cardiac Pacing And Defibrillation. Armonk, NY: Futura Pub. Co.; 2000.

Surawicz B, Knilans T, Chou T. Chou’s Electrocardiography In Clinical Practice. Philadelphia: Saunders; 2001.

Content Reviewer

Kelly A. Bouthillet, APRN, MSN, CCNS, ACNP-BC (@BarefootNurse24)