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Sinus bradycardia

Munther K Homoud, MD
Section Editor
Alan Cheng, MD
Deputy Editor
Brian C Downey, MD, FACC


Sinus bradycardia is a rhythm in which the rate of impulses arising from the sinoatrial (SA) node is lower than expected.

The normal adult heart rate, arising from the SA node, has been considered historically to range from 60 to 100 beats per minute, with sinus bradycardia being defined as a sinus rhythm with a rate below 60 beats per minute. However, the "normal" heart rate is, in part, the result of the complex interplay between the sympathetic and parasympathetic nervous systems. It is affected by numerous factors and varies in part with age and physical conditioning (table 1) [1,2]. Sinus arrhythmia, changes in the sinus rate as a result of respiration cycles, often accompanies sinus bradycardia. (See "Normal sinus rhythm and sinus arrhythmia".)

The etiology, clinical presentation, evaluation, and management of sinus bradycardia will be reviewed here. Primary sinus node dysfunction (ie, sick sinus syndrome) is discussed in detail separately. (See "Sick sinus syndrome: Epidemiology, etiology, and natural history" and "Sick sinus syndrome: Clinical manifestations, diagnosis, and evaluation" and "Treatment of the sick sinus syndrome".)


Normal sinus rhythm (NSR) is the characteristic rhythm of the healthy human heart. NSR is considered to be present in adults if the heart rate is between 60 and 100 beats per minute, the P waves on the electrocardiogram (ECG) are normal (unless there is concurrent atrial disease), and the rate does not vary significantly (waveform 1). The normal sinus P wave demonstrates right followed by left atrial depolarization giving rise to an upright P wave in leads I, II and aVL, and a negative P wave in lead aVR. The duration generally ranges between 80 and 110 milliseconds, and the amplitude is <0.25 millivolts. (See "ECG tutorial: Basic principles of ECG analysis", section on 'P wave'.)

By conventional definition, a bradycardia requires the heart rate to be less than 60 beats per minute with normal-appearing P waves on surface ECG. As such, sinus bradycardia is typically thought of as sinus rhythm occurring at a rate of less than 60 beats per minute, although one professional society has advocated a rate of less than 50 beats per minute (waveform 2) [3].


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Literature review current through: Oct 2015. | This topic last updated: Oct 8, 2015.
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  1. Spodick DH. Normal sinus heart rate: sinus tachycardia and sinus bradycardia redefined. Am Heart J 1992; 124:1119.
  2. Spodick DH, Raju P, Bishop RL, Rifkin RD. Operational definition of normal sinus heart rate. Am J Cardiol 1992; 69:1245.
  3. Kadish AH, Buxton AE, Kennedy HL, et al. ACC/AHA clinical competence statement on electrocardiography and ambulatory electrocardiography. A report of the ACC/AHA/ACP-ASIM Task Force on Clinical Competence (ACC/AHA Committee to Develop a Clinical Competence Statement on Electrocardiography and Ambulatory Electrocardiography). J Am Coll Cardiol 2001; 38:2091.
  4. Scott O, Williams GJ, Fiddler GI. Results of 24 hour ambulatory monitoring of electrocardiogram in 131 healthy boys aged 10 to 13 years. Br Heart J 1980; 44:304.
  5. Brodsky M, Wu D, Denes P, et al. Arrhythmias documented by 24 hour continuous electrocardiographic monitoring in 50 male medical students without apparent heart disease. Am J Cardiol 1977; 39:390.
  6. Bjerregaard P. Mean 24 hour heart rate, minimal heart rate and pauses in healthy subjects 40-79 years of age. Eur Heart J 1983; 4:44.
  7. 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 1985; 55:1005.
  8. Talan DA, Bauernfeind RA, Ashley WW, et al. Twenty-four hour continuous ECG recordings in long-distance runners. Chest 1982; 82:19.
  9. Abdon NJ, Landin K, Johansson BW. Athlete's bradycardia as an embolising disorder? Symptomatic arrhythmias in patients aged less than 50 years. Br Heart J 1984; 52:660.
  10. Agruss NS, Rosin EY, Adolph RJ, Fowler NO. Significance of chronic sinus bradycardia in elderly people. Circulation 1972; 46:924.
  11. Milanesi R, Baruscotti M, Gnecchi-Ruscone T, DiFrancesco D. Familial sinus bradycardia associated with a mutation in the cardiac pacemaker channel. N Engl J Med 2006; 354:151.
  12. Milanesi R, Bucchi A, Baruscotti M. The genetic basis for inherited forms of sinoatrial dysfunction and atrioventricular node dysfunction. J Interv Card Electrophysiol 2015; 43:121.
  13. Alpert MA, Flaker GC. Arrhythmias associated with sinus node dysfunction. Pathogenesis, recognition, and management. JAMA 1983; 250:2160.
  14. Eraut D, Shaw DB. Sinus bradycardia. Br Heart J 1971; 33:742.
  15. Ludomirsky A, Klein HO, Sarelli P, et al. Q-T prolongation and polymorphous ("torsade de pointes") ventricular arrhythmias associated with organophosphorus insecticide poisoning. Am J Cardiol 1982; 49:1654.
  16. Gilson GJ, Miller AC, Clevenger FW, Curet LB. Acute spinal cord injury and neurogenic shock in pregnancy. Obstet Gynecol Surv 1995; 50:556.
  17. Cunha BA. The diagnostic significance of relative bradycardia in infectious disease. Clin Microbiol Infect 2000; 6:633.
  18. Puljiz I, Beus A, Kuzman I, Seiwerth S. Electrocardiographic changes and myocarditis in trichinellosis: a retrospective study of 154 patients. Ann Trop Med Parasitol 2005; 99:403.
  19. Dobrzynski H, Boyett MR, Anderson RH. New insights into pacemaker activity: promoting understanding of sick sinus syndrome. Circulation 2007; 115:1921.
  20. Sanders P, Kistler PM, Morton JB, et al. Remodeling of sinus node function in patients with congestive heart failure: reduction in sinus node reserve. Circulation 2004; 110:897.
  21. Ruan Y, Liu N, Priori SG. Sodium channel mutations and arrhythmias. Nat Rev Cardiol 2009; 6:337.
  22. Neumar RW, Otto CW, Link MS, et al. Part 8: adult advanced cardiovascular life support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010; 122:S729.
  23. Epstein AE, DiMarco JP, Ellenbogen KA, et al. 2012 ACCF/AHA/HRS focused update incorporated into the ACCF/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2013; 61:e6.
  24. Tresch DD, Fleg JL. Unexplained sinus bradycardia: clinical significance and long-term prognosis in apparently healthy persons older than 40 years. Am J Cardiol 1986; 58:1009.