|
|
| Line 3: |
Line 3: |
| {{SI}} | | {{SI}} |
| {{CMG}}; '''Associate Editor-In-Chief:''' {{CZ}} | | {{CMG}}; '''Associate Editor-In-Chief:''' {{CZ}} |
| | |
| {{SK}} | | {{SK}} |
|
| |
|
| ==Overview== | | ==[[Sinus bradycardia overview|Overview]]== |
| Sinus bradycardia is a heart rhythm that originates from the [[sinus node]] and has a rate of under 60 beats per minute. Common causes include [[sick sinus syndrome]] and pharmacotherapy such as [[beta-blockers]]. Sinus bradycardia is fairly common in highly trained athletes. It only requires treatment if the patient is symptomatic. | |
|
| |
|
| ==Pathophysiology== | | ==[[Sinus bradycardia pathophysiology|Pathophysiology]]== |
| This rhythm may be caused by one of the following:
| |
| * Increased [[vagal]] tone
| |
| * Intrinsic disease of the [[SA node]]
| |
| * An effect of [[drugs]], such as the use of [[digitalis]] or [[beta-blockers]]
| |
| * [[Sleep]]
| |
| * Sinus bradycardia is a normal finding in a healthy, well-conditioned athlete
| |
|
| |
|
| ===Genetics=== | | ==[[Sinus bradycardia causes|Causes]]== |
| The [[HCN4]] genetic variant is associated with sinus bradycardia. Certain sodium [[channelopathies]] are associated with sinus bradycardia<ref name="pmid16407510">{{cite journal | author = Milanesi R, Baruscotti M, Gnecchi-Ruscone T, DiFrancesco D | title = Familial sinus bradycardia associated with a mutation in the cardiac pacemaker channel | journal = [[The New England Journal of Medicine]] | volume = 354 | issue = 2 | pages = 151–7 | year = 2006 | month = January | pmid = 16407510 | doi = 10.1056/NEJMoa052475 | url = http://dx.doi.org/10.1056/NEJMoa052475 | issn = | accessdate = 2011-02-23}}</ref>.
| |
|
| |
|
| ==Epidemiology and Demographics== | | ==[[Sinus bradycardia differential diagnosis|Differentiating Sinus bradycardia from other Diseases]]== |
| Among people under 25 years of age, approximately 30% have sinus bradycardia<ref name="pmid13855921">{{cite journal | author = HISS RG, LAMB LE, ALLEN MF | title = Electrocardiographic findings in 67,375 asymptomatic subjects. X. Normal values | journal = [[The American Journal of Cardiology]] | volume = 6 | issue = | pages = 200–31 | year = 1960 | month = July | pmid = 13855921 | doi = | url = | issn = | accessdate = 2011-02-23}}</ref>. During sleep, heart rates may decline by 25 beats per minute in young patients, and 15 beats per minutes in the elderly. Heart rates of 30 beats/minute and pauses of up to 2 seconds are not uncommon in healthy people <ref name="pmid3984858">{{cite journal | author = Hilgard J, Ezri MD, Denes P | title = Significance of ventricular pauses of three seconds or more detected on twenty-four-hour Holter recordings | journal = [[The American Journal of Cardiology]] | volume = 55 | issue = 8 | pages = 1005–8 | year = 1985 | month = April | pmid = 3984858 | doi = | url = http://linkinghub.elsevier.com/retrieve/pii/0002-9149(85)90735-0 | issn = | accessdate = 2011-02-23}}</ref><ref name="pmid65912">{{cite journal | author = Brodsky M, Wu D, Denes P, Kanakis C, Rosen KM | title = Arrhythmias documented by 24 hour continuous electrocardiographic monitoring in 50 male medical students without apparent heart disease | journal = [[The American Journal of Cardiology]] | volume = 39 | issue = 3 | pages = 390–5 | year = 1977 | month = March | pmid = 65912 | doi = | url = | issn = | accessdate = 2011-02-23}}</ref><ref name="pmid6339245">{{cite journal | author = Bjerregaard P | title = Mean 24 hour heart rate, minimal heart rate and pauses in healthy subjects 40-79 years of age | journal = [[European Heart Journal]] | volume = 4 | issue = 1 | pages = 44–51 | year = 1983 | month = January | pmid = 6339245 | doi = | url = http://eurheartj.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=6339245 | issn = | accessdate = 2011-02-23}}</ref>
| |
|
| |
|
| ==Diagnosis== | | ==[[Sinus bradycardia epidemiology and demographics|Epidemiology and Demographics]]== |
| ===Symptoms===
| |
| The decreased heart rate can cause a decreased [[cardiac output]] resulting in symptoms such as:
| |
|
| |
|
| *[[Dizziness]]
| | ==[[Sinus bradycardia risk factors|Risk Factors]]== |
| *[[Lightheadedness]]
| |
| *[[Presyncope]]
| |
| *[[Syncope]]
| |
| *[[Vertigo]]
| |
|
| |
|
| Sinus bradycardia may be associated with no symptoms in a young athlete. | | ==[[Sinus bradycardia natural history, complications and prognosis|Natural History, Complications and Prognosis]]== |
|
| |
|
| ===Physical Examination=== | | ==Diagnosis== |
| ====Vitals====
| | [[Sinus bradycardia history and symptoms| History and Symptoms]] | [[Sinus bradycardia physical examination | Physical Examination]] | [[Sinus bradycardia laboratory findings|Laboratory Findings]] | [[Sinus bradycardia electrocardiogram|Electrocardiogram]] |
| *There may be a [[wide pulse pressure]]
| |
| | |
| ====Skin====
| |
| If [[cardiac output]] is reduced, there may be signs of end organ hypoperfusion such as cold [[clammy skin]]
| |
| | |
| ===Laboratory Studies===
| |
| Based upon the patient's history and demographics, the following laboratory studies should be considered:
| |
| *[[Serum electrolytes]] including Ca, Mg
| |
| *[[TFT]]s should be checked
| |
| *[[Hypoglycemia]] should be excluded
| |
| *Consider a [[toxicologic screen]]
| |
| | |
| ===Electrocardiogram===
| |
| *Rate: Less than 60
| |
| *Rhythm: Regular
| |
| *[[P wave]]s: Upright, consistent, and normal in morphology and duration
| |
| *[[PR Interval]]: Between 0.12-0.21 seconds in duration
| |
| *[[QRS complex]]: Less than 0.12 seconds in width, and consistent in morphology
| |
| *[[Early repolarization]] is accentuated in the setting of sinus bradycardia
| |
| *[[Sinus arrhythmia]] often accompanies sinus brdycardia
| |
| | |
| ===EKG Examples===
| |
| ----
| |
| Shown below is an EKG depicting sinus bradycardia. The heart rate is around 40 bpm. It also shows [[PR prolongation]] and decrease in [[QRS complex]].
| |
| [[Image:Sinusbradycardia2.png|center|800px]]
| |
| Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:Rhythm_sinusbradycardia.png
| |
| ----
| |
| Shown below is an EKG example of sinus bradycardia. The heart rate is around 45 bpm. It also shows [[PR prolongation]] and a shortening of the [[QRS complex]]es.
| |
| [[Image:Sinusbradycardia.png|center|800px]]
| |
| Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:Sinusbradycardia.png
| |
| ----
| |
| Shown below is an EKG example of sinus bradycardia. The heart rate is around 45 bpm.
| |
| [[Image:Sinusbrady.PNG|center|800px]]
| |
| Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/Main_Page
| |
| ----
| |
|
| |
|
| ==Treatment== | | ==Treatment== |
| ===Acute Management===
| | [[Sinus bradycardia medical therapy|Medical Therapy]] | [[Sinus bradycardia primary prevention|Primary Prevention]] |
| *If a patient is symptomatic, intravenous access should be established.
| |
| *[[Atropine]] can be administered down an [[endotracheal tube]] or can be administered intravenously. The dose is 0.5-1 mg IV or ET q 3-5 min up to 3 mg total (0.04 mg/kg). The pediatric dosing is 0.02 mg/kg/dose IV, minimum of 0.1 mg. [[Isoproteronol]] ([[Isoprel]]) has been used in the past, but carries risks.
| |
| *Transcutaneous pacing can be undertaken while a temporary wire is being placed.
| |
| *Offending or exacerbating agents such as [[beta-blockers]], [[calcium channel blockers]] or [[digitalis]] should be discontinued and underlying causes treated.
| |
| *[[Sleep apnea]] is a common cause and should be treated with weight loss and [[BiPAP]].
| |
| *Continuous monitoring in the hospital is recommended.
| |
| | |
| ===Chronic Management===
| |
| Asymptomatic sinus bradycardia requires no treatment. Patients with [[sick sinus syndrome]] generally require a pacemaker.
| |
| | |
| ==ACC/AHA/HRS Guideline Recommendations for Pacemaker Implantation (DO NOT EDIT)<ref name="pmid18534360">{{cite journal | author = Epstein AE, Dimarco JP, Ellenbogen KA, Estes NA, Freedman RA, Gettes LS, Gillinov AM, Gregoratos G, Hammill SC, Hayes DL, Hlatky MA, Newby LK, Page RL, Schoenfeld MH, Silka MJ, Stevenson LW, Sweeney MO | title = ACC/AHA/HRS 2008 Guidelines for device-based therapy of cardiac rhythm abnormalities | journal = [[Heart Rhythm : the Official Journal of the Heart Rhythm Society]] | volume = 5 | issue = 6 | pages = e1–62 | year = 2008 | month = June | pmid = 18534360 | doi = 10.1016/j.hrthm.2008.04.014 | url = http://linkinghub.elsevier.com/retrieve/pii/S1547-5271(08)00462-1 | issn = | accessdate = 2011-02-23}}</ref>==
| |
| | |
| Recommendations for Permanent Pacing in Sinus Node Dysfunction (SND)
| |
| | |
| {{cquote|
| |
| | |
| '''Class I'''
| |
| | |
| 1. Permanent pacemaker implantation is indicated for SND with documented symptomatic bradycardia, including
| |
| frequent sinus pauses that produce symptoms.(Level of Evidence: C)
| |
| | |
| 2. Permanent pacemaker implantation is indicated for symptomatic chronotropic incompetence. (Level of
| |
| Evidence: C)
| |
| | |
| 3. Permanent pacemaker implantation is indicated for symptomatic sinus bradycardia that results from required
| |
| drug therapy for medical conditions. (Level of Evidence: C)
| |
| | |
| '''Class IIa'''
| |
| | |
| 1. Permanent pacemaker implantation is reasonable for SND with heart rate less than 40 bpm when a clear
| |
| association between significant symptoms consistent with bradycardia and the actual presence of bradycardia
| |
| has not been documented. (Level of Evidence:C)
| |
| | |
| 2. Permanent pacemaker implantation is reasonable for syncope of unexplained origin when clinically significant
| |
| abnormalities of sinus node function are discovered or provoked in electrophysiological studies. (Level of Evidence: C)
| |
| | |
| '''Class IIb'''
| |
| | |
| 1. Permanent pacemaker implantation may be considered in minimally symptomatic patients with chronic heart rate less than 40 bpm while awake. (Level of Evidence: C)
| |
| | |
| '''Class III'''
| |
| | |
| 1. Permanent pacemaker implantation is not indicated for SND in asymptomatic patients. (Level of Evidence:C)
| |
| | |
| 2. Permanent pacemaker implantation is not indicated for SND in patients for whom the symptoms suggestive of bradycardia have been clearly documented to occur in the absence of bradycardia. (Level of Evidence:C)
| |
| | |
| 3. Permanent pacemaker implantation is not indicated for SND with symptomatic bradycardia due to nonessential drug therapy. (Level of Evidence: C)}}
| |
|
| |
|
| | ==Case Studies== |
| | [[Sinus bradycardia case study one|Case#1]] |
| ==References== | | ==References== |
| {{Reflist|2}} | | {{Reflist|2}} |