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==Overview==
==Overview==
Bradycardia is defined as a resting [[heart rate]] of under 60 beats per minute.


==Pathophysiology==
==Pathophysiology==

Revision as of 03:23, 27 August 2012

Bradycardia
ICD-10 R00.1
ICD-9 427.81, 659.7, 785.9, 779.81

Bradycardia Microchapters

Home

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Bradycardia from other Conditions

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Diagnosis

History and Symptoms

Physical Examination

Laboratory Findings

Electrocardiogram

Chest X Ray

CT

Echocardiography

MRI

Other Imaging Findings

Other Diagnostic Studies

Treatment

Medical Therapy

Surgery

Primary Prevention

Secondary Prevention

Cost-Effectiveness of Therapy

Future or Investigational Therapies

Case Studies

Case #1

Bradycardia On the Web

Most recent articles

Most cited articles

Review articles

CME Programs

Powerpoint slides

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American Roentgen Ray Society Images of Bradycardia

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X-rays
Echo & Ultrasound
CT Images
MRI

Ongoing Trials at Clinical Trials.gov

US National Guidelines Clearinghouse

NICE Guidance

FDA on Bradycardia

CDC on Bradycardia

Bradycardia in the news

Blogs on Bradycardia

Directions to Hospitals Treating Bradycardia

Risk calculators and risk factors for Bradycardia

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: M.Umer Tariq [2]

Overview

Pathophysiology

Pathologic bradycardias are caused by disorders of impulse generation (impaired automaticity at SA node), impulse conduction (heart block) or escape pacemakers and rhythms. Bradycardia can be underlain by several causes, which are best divided into cardiac and non-cardiac causes. Non-cardiac causes are usually secondary, and can involve recreational drug use, endocrine disorders (hypothyroid); electrolyte imbalance (hyperkalemia); autonomic reflexes; situational factors (prolonged bed rest); infections lyme disease, medications, and autoimmunity disorders. Cardiac causes include acute or chronic ischemic heart disease, vascular heart disease, valvular heart disease, or degenerative primary electrical disease (fibrosis and calcification of the sinus node and conduction system).

Natural History, Complications, Prognosis

Slower sinus rates are often very well tolerated. Asymptomatic resting bradycardias, particularly in trained athletes and young individuals are not pathological and doesn't not require treatment.

Causes

It is difficult and sometimes impossible to assign a mechanism to any particular bradycardia. However, the underlying mechanism is not clinically relevant to treatment, which is the same in both cases of sick sinus syndrome: a permanent pacemaker.

There are generally two types of problems that result in bradycardias:

Disorders of the sinus node

  • Impaired automaticity - Sinus node dysfunction/sick sinus syndrome)
  • Exit block - Impaired conduction of the impulse from the sinus node into the surrounding atrial tissue

Disorders of the atrioventricular node (AV node)

Causes of Bradycardia By Organ System

Cardiovascular

Atrioventricular Block, Cardiac arrhythmia, Cardiac Dysrhythmias, Cardiomegaly, Right Bundle Branch Block, Second Degree AV Block, ST Elevation Myocardial Infarction Complications, Sinoatrial Block, Pulseless ventricular tachycardia, Sick sinus syndrome, Cardiomyopathy, Distichiasis - heart and vasculature anomalies - sinus bradycardia


Chemical / poisoning Carbamate,

Opioid poisoning,

Dermatologic No underlying causes
Drug Side Effect

Aceclidine, Acepromazine, Acetylcholinesterase inhibitor, Adenosine, Amiodarone, Amodiaquine, Atenolol, Barbiturates, Beta-blockers, Bupivacaine, Calcium channel blocker, Clomipramine, Clonidine, Detomidine, Digitalis, Diltiazem, Diphenhydramine, Donepezil, Doxepin, Glyceryl trinitrate , Hydrocodone, Ibuprofen, Isosorbide dinitrate, Ivabradine, Levobetaxolol, Levobupivacaine, Lidocaine, Lithium, Medetomidine, Mefloquine, Mepivacaine, Methacholine, Methoxamine, Methyldopa, Morphine, Moxonidine, Nadolol, Nalbuphine, Nalmefene, Opioid, Oxymorphone, Phenobarbital, Phenylephrine, Phenytoin, Pilocarpine, Propafenone, Propranolol, Quinidine, Reserpine, Ropivacaine, Sulpiride, Suxamethonium chloride, Tacrine, Timolol, Trazodone, Uncaria tomentosa, Xylazine,

Ear Nose Throat No underlying causes
Endocrine Hypothyroidism,

Hashimoto's Thyroiditis,

Environmental

Grayanotoxin, Hellebore, Hypothermia, Heat exhaustion

Gastroenterologic Obstructive jaundice, Necrotizing enterocolitis , Typhoid fever
Genetic

Congenital Long QT Syndrome, Catecholaminergic polymorphic ventricular tachycardia, Emery-Dreifuss muscular dystrophy, Congenital Central Hypoventilation Syndrome, Distichiasis - heart and vasculature anomalies - sinus bradycardia

Hematologic No underlying causes
Iatrogenic

Enema, Gastric lavage, PCI Complications: Radiocontrast toxicity, Rapid sequence induction, Cardiac catheterization

Infectious Disease

Chagas' disease, Hantavirus pulmonary syndrome, Legionella pneumonia and Mycoplasma pneumonia, Tularaemia, Colorado tick fever, Brucellosis, Trypanosoma cruzi, Typhoid fever, Septic shock



Musculoskeletal / Ortho

Holt-Oram syndrome, Vertebral subluxation,


Neurologic

Vasovagal syncope, Vagal episode, Neurogenic shock, Subarachanoid hemorrhage, Raised Intracranial pressure, Autonomic neuropathy, Cerebral hemorrhage, Cerebral venous sinus thrombosis, Cushing triad, Cushing reaction, Cushing reflex, Neurocardiogenic Syncope, Increased intracranial pressure



Nutritional / Metabolic

Hypercalcemia, Hyperkalemia, Hypokalemia, Anorexia Nervosa, Malnutrition


Obstetric/Gynecologic

Fetal distress, Neonatal lupus erythematosus, Vasa previa,


Oncologic No underlying causes
Opthalmologic Oculocardiac reflex, Distichiasis - heart and vasculature anomalies - sinus bradycardia
Overdose / Toxicity

Gamma-Hydroxybutyric acid, Hydroxyethyl starch Speedball (drug), Theobromine poisoning, Sedatives Cyclic antidepressant poisoning

Psychiatric Anorexia Nervosa,
Pulmonary Apnea of prematurity, Asphyxia neonatorum , Pneumothorax
Renal / Electrolyte No underlying causes
Rheum / Immune / Allergy No underlying causes
Sexual No underlying causes
Trauma Skull fracture
Urologic No underlying causes
Miscellaneous

Drowning, Mammalian diving reflex,


Causes in Alphabetical Order

Epidemiology and Demographics

Bradycardia is more common in older patients.

Diagnosis

Evaluation of bradycardia includes assessment of the heart rhythm, symptoms, medications, and associated medical conditions (reversible and irreversible). Symptomatic bradycardias are treated by removal of the underlying causes, medications (atropine) or insertion of a temporary or permanent pacemaker. The term relative bradycardia is used to explain a heart rate that, while not technically below 60 beats per minute, is considered too slow for the individual's current medical condition.

Symptoms

Resting EKG

The heart rate is < 60 beats per minute.

24 Hour Ambulatory Electrocardiogram Monitoring

The diagnosis is usually made with the help of a 24-hour ambulatory electrocardiogram (ECG) or telemetry.

Treatment

Urgent Treatment

  • Check drug list and remove drugs predisposing to bradycardia like beta blockers, calcium channel blocker, anti-arrhythmic drug.
  • Drug treatment for bradycardia is typically not indicated for patients who are asymptomatic.
  • In symptomatic patients, underlying electrolyte or acid-base disorders or hypoxia should be corrected first.
  • IV atropine may provide temporary improvement in symptomatic patients, although its use should be balanced by an appreciation of the increase in myocardial oxygen demand this agent causes. Atropine 0.5-1 mg IV or ET q3-5min up to 3 mg total (0.04 mg/kg)

Indications For a Temporary Pacemaker

Advanced heart block such as complete heart block is an indication for a temporary pacemaker insertion.

Chronic Management

There are two main reasons for treating brandycardia:

  1. With bradycardia, the first is to address the associated symptoms, such as fatigue, limitations on how much an individual can physically exert, fainting (syncope), dizziness or lightheadedness, or other vague and non-specific symptoms.
  2. The other reason to treat bradycardia is if the person's ultimate outcome (prognosis) will be changed or impacted by the bradycardia.

Treatment in this vein depends on whether any symptoms are present, and what the underlying cause is. Primary or idiopathic bradycardia is treated symptomatically if it is significant, and the underlying cause is treated if the bradycardia is secondary.

See also

References

  1. Pagon RA, Bird TD, Dolan CR; et al. PMID 20301600. Missing or empty |title= (help)
  2. Goldstein S, Qazi QH, Fitzgerald J, Goldstein J, Friedman AP, Sawyer P (1985). "Distichiasis, congenital heart defects and mixed peripheral vascular anomalies". Am. J. Med. Genet. 20 (2): 283–94. doi:10.1002/ajmg.1320200212. PMID 3976722. Unknown parameter |month= ignored (help)

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