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sinus bradycardia

Sinus bradycardia refers to a rhythm generated by a slowed pattern of initial depolarization in the sinus node. Etiology: 1) physiologic a) endurance-trained athletes b) during sleep (pulse may be as low as 30/min) [3] 2) pathologic a) increased vagal tone b) antiarrhythmic agents c) myocardial ischemia - acute inferior myocardial infarction d) sick sinus syndrome e) increased intracranial pressure f) hypothermia g) myxedema h) recovery from infection 1] typhoid 2] influenza Clinical manifestations: 1) patients may be asymptomatic 2) lightheadedness 3) breathlessness 4) angina 5) weakness 6) syncope & near-syncope 7) inability to increase heart rate with exercise [3] Special laboratory: - electrocardiogram 1) atrial rate <60/min 2) p waves with normal configuration & axis 3) normal or prolonged PR interval 4) normal QRS pattern - exercise stress test [3] Complications: - sinus bradycardia does not affect mortality [4,5] - endurance athletes with physiologic sinus bradycardia are healthier than others their age thus risk of mortality is more likely than not diminished Management: 1) asymptomatic patients require no therapy 2) treatment of symptomatic patient is directed towards specific etiology a) atropine 0.5-2.0 g IV b) transcutaneous pacemaker vs permanent pacemaker c) bradycardia refractory to atropine & transcutaneous pacemaker not available - dopamine 5-20 ug/kg/min - epinephrine 2-20 ug/min - isoproterenol 2-10 ug/min

Related

sick sinus syndrome; atrial fibrillation with bradyarrhythmia; tachycardia-bradycardia syndrome sinoatrial exit block

Specific

sinus arrest/pause

General

supraventricular arrhythmia bradyarrhythmia (bradycardia)

References

  1. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 139
  2. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 271
  3. Medical Knowledge Self Assessment Program (MKSAP) 18, 19 American College of Physicians, Philadelphia 2018, 2022
  4. Homound MK Sinus bradycardia UpToDate https://www.uptodate.com/contents/sinus-bradycardia#!
  5. Goldberger JJ, Johnson NP, Gidea C. Significance of asymptomatic bradycardia for subsequent pacemaker implantation and mortality in patients >60 years of age. Am J Cardiol. 2011 Sep 15;108(6):857-61. PMID: 21757182