Diseases of the conduction system and bradyarrhythmias
You don't need to be Editor-In-Chief to add or edit content to WikiDoc. You can begin to add to or edit text on this WikiDoc page by clicking on the edit button at the top of this page. Next enter or edit the information that you would like to appear here. Once you are done editing, scroll down and click the Save page button at the bottom of the page.
| Cardiology Network |
 Discuss Diseases of the conduction system and bradyarrhythmias further in the WikiDoc Cardiology Network |
| Adult Congenital |
|---|
| Biomarkers |
| Cardiac Rehabilitation |
| Congestive Heart Failure |
| CT Angiography |
| Echocardiography |
| Electrophysiology |
| Cardiology General |
| Genetics |
| Health Economics |
| Hypertension |
| Interventional Cardiology |
| MRI |
| Nuclear Cardiology |
| Peripheral Arterial Disease |
| Prevention |
| Public Policy |
| Pulmonary Embolism |
| Stable Angina |
| Valvular Heart Disease |
| Vascular Medicine |
Editor-in-Chief: Alena Goldman, MD
Please Take Over This Page and Apply to be Editor-In-Chief for this topic: There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [1] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
Bradyarrhythmias can be broadly divided into two categories: those at the atrial level that are caused by sinus node dysfunction, and those at the subatrial level resulting in AV conduction disturbances.
1. Sinus Node Dysfunction
- Sick Sinus Syndrome (SSS)
- refers to an abnormal impulse formation in the sinus node, and/or abnormal impulse conduction. It is frequently associated with AV nodal conduction disturbances, where alternating tachycardia (more commonly atrial fibrillation (AF) or atrial flutter, although can be seen with other supraventricular tachycardias) and bradycardia can be seen in up to 50% of patients.
SSS is defined by the electrocardiographic criteria,as clinical symptoms are often vague.
- Here is the list of findings that can be seen with SSS:
- unexplained persistent bradycardia without warning
- sinus arrest or sinus exit block
- paroxysmal atrial fibrillation (PAF) followed by sinus arrest
- SA block/arrest or severe sinus bradycardia following a cardioversion of atrial fibrillation
- Alternating bradycardia and atrial tachyarrhythmias
- Slow ventricular response in atrial fibrillation in patients off any nodal agents reflects AV nodal disease that often co-insides with a significant SA nodal dysfunction and an unstable sinus rhythm upon conversion
- Inadequate sinus acceleration with exercise
Etiology
SA node dysfunction may be a result of intrinsic or extrinsic factors.
- Intrinsic Factors
- Idiopathic degenerative disease (fibrosis) associated with aging: most common cause overall
- SA Nodal Artery Involvement
- Atherosclerosis
- Vasculitis
- Embolus
- Infiltrative diseases
- Amyloidosis
- Hemochromatosis
- Malignancies
- Inflammatory conditions
- Myotonic Dystrophy
- Freidrech’s Ataxia
- Collagen Vascular Diseases
- After cardiac surgery:
- Corrective Cardiac Surgery for Congenital Heart Disease yabekref1 hayesref2
- Transplant
- Congenital/genetic SA node dysfunction
- Familial SSS is rare, but some familial cases have been reported:
- SCN5a mutations
- HCN4 mutations
- Extrinsic Factors
- Drugs
- Antiarrhythmics: classes Ia, Ic, III.
- Antihypertensives:
- Beta-blockers
- Calcium Channel Blockers
- Digitalis
- Lithium: SA nodal abnormalities seen in up to 50% of patients
- Dilantin
- Cimetidine
- Electrolyte Disturbances
- Endocrine abnormalities
- Inferior Myocardial Infarction (Bezold-Jarish phenomenon)
- Autonomic Nervous System Influence
- CSP
- Vasovagal response
- Miscellaneous
- High Intracranial Pressure
- Obstructive Sleep Apnea
Natural History
SA Block
SA Block can be classified as the following:
- First degree SA Block: due to a prolonged Conduction
- Second degree SA Block: due to intermittent Conduction
- Type 1: Progressive prolongation
- Type 2: Sudden failure of conduction
- Third Degree SA Block: No conduction
References
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
