First degree AV block causes
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2]; Raviteja Guddeti, M.B.B.S. [3] Synonyms and keywords:
Overview
Causes
Life Threatening Causes
Life-threatening conditions can result in death or permanent disability within 24 hours if left untreated.
Common Causes
Enhanced vagal tone in athletes
electrolyte disturbances drugs; calcium channel blockers, beta-blockers, digitalis,cardiac glycosides, cholinesterase inhibitors.
- Normal variants of PR prolongation
- Vagal maneuvers
- Acute MI - esp [[inferior MI)
- Degenerative diseases
- Idiopathic bilateral bundle branch fibrosis and the heart block is called primary heart block
- Hypertension
- Chronic AV block in patients with HTN is thought to be due to CAD or sclerosis of the left side of the cardiac skeleton exacerbated by
- hypertension
- Acute rheumatic fever
- Dilated cardiomyopathy
- HCM: 3% of patients with HCM will develop heart block
- Myocarditis
- SLE
- Tumors, primary and secondary
- Valvular Heart Disease
- Calcific aortic stenosis may be accompanied by chronic partial or complete AV block
- There is an extension of the calcification to involve the main bundle or its bifurcation, resulting in degeneration and necrosis of the conduction tissue
- May also occur in rheumatic mitral valve disease, but is less common
- Occasionally, massive calcification of the mitral annulus as an aging process may cause AV block
- May also be seen in bacterial endocarditis, especially of the aortic valve
- Ebstein's anomaly may be associated with first-degree AV block.
- Drugs
- Digoxin is one of the most common causes of reversible AV block
- The ventricular response rate is more rapid than that due to organic lesions, and increased automaticity of the AV junctional pacemaker may be responsible.
- Quinidine and Procainamide may produce slight prolongation of the PR
- β blockers may cause AV block
- Diltiazem and verapamil may cause AV conduction delay and PR interval prolongation
- Digoxin is one of the most common causes of reversible AV block
First degree heart block is not an absolute contraindication for the use of these drugs but caution should be maintained while using these drugs in patients with first degree block, as exposure to these drugs increases the risk of developing a higher grade block.
- Congenital
- Occurs in the absence of other evidence of organic heart disease
- Site is usually proximal to the bifurcation of the His bundle, most often in the AV node
- Narrow QRS with a rate > 40 beats per minute
- Frequently seen in those with corrected transposition of the great vessels, and occasionally in ASDs and Ebstein's anomaly
- Trauma
- May be induced during open heart surgery in the area of AV conduction tissue
- Seen in patients operated on for the correction of VSD, tetralogy of Fallot, and endocardial cushion defect.
- May be due to edema, transient ischemia, or actual disruption of the conduction tissue. The block may therefore be permanent or transient.
- Also reported with both penetrating and non-penetrating trauma of the chest
Causes by Organ System
Cardiovascular | AV nodal disease, Myocarditis, Acute myocardial infarction (especially acute inferior MI), Hypertension, Acute rheumatic fever, Dilated cardiomyopathy, HCM, Myocarditis, Valvular heart disease, Transposition of the great vessels, ASDs, Ebstein's anomaly, VSD, Tetralogy of Fallot, Endocardial cushion defect, Lev's disease |
Chemical / poisoning | No underlying causes |
Dermatologic | No underlying causes |
Drug Side Effect | Calcium channel blockers, Beta-blockers, Digitalis, Cardiac glycosides, Cholinesterase inhibitors, Quinidine, Procainamide, Disopyramide, Flecainide, Encainide, Propafenone, Amiodarone, Sotalol, Dofetilide, Ibutilide, Magnesium |
Ear Nose Throat | No underlying causes |
Endocrine | No underlying causes |
Environmental | No underlying causes |
Gastroenterologic | Hemochromatosis |
Genetic | No underlying causes |
Hematologic | No underlying causes |
Iatrogenic | No underlying causes |
Infectious Disease | Acute rheumatic fever, Chagas disease, Diphtheria, Lyme disease, Myocarditis, Tuberculosis |
Musculoskeletal / Ortho | Ankylosing spondylitis, Muscular dystrophy |
Neurologic | No underlying causes |
Nutritional / Metabolic | No underlying causes |
Obstetric/Gynecologic | No underlying causes |
Oncologic | No underlying causes |
Opthalmologic | No underlying causes |
Overdose / Toxicity | No underlying causes |
Psychiatric | No underlying causes |
Pulmonary | Sarcoidosis |
Renal / Electrolyte | No underlying causes |
Rheum / Immune / Allergy | Ankylosing spondylitis, Dermatomyositis, Scleroderma, SLE, Rheumatoid arthritis |
Sexual | No underlying causes |
Trauma | No underlying causes |
Urologic | No underlying causes |
Dental | No underlying causes |
Miscellaneous | Amyloidosis, Enhanced vagal tone (for example in athletes), Normal variants |
Causes in Alphabetical Order
- Acute myocardial infarction (especially acute inferior MI)
- Acute rheumatic fever
- Amiodarone
- Amyloidosis
- Ankylosing spondylitis
- ASD
- AV nodal disease
- Beta-blockers
- Calcium channel blockers
- Cardiac glycosides
- Chagas disease
- Cholinesterase inhibitors
- Dermatomyositis
- Digitalis
- Dilated cardiomyopathy
- Diphtheria
- Disopyramide
- Dofetilide
- Ebstein's anomaly
- Encainide
- Endocardial cushion defect
- Enhanced vagal tone (for example in athletes)
- Flecainide
- HCM
- Hemochromatosis
- Hypertension
- Ibutilide
- Lev's disease
- Lenègre-Lev disease
- Lyme disease
- Magnesium
- Muscular dystrophy
- Myocarditis
- Normal variants
- Procainamide
- Propafenone
- Quinidine
- Rheumatoid arthritis
- Sarcoidosis
- Scleroderma
- SLE
- Sotalol
- Tetralogy of Fallot
- Transposition of the great vessels
- Tuberculosis
- Valvular heart disease
- VSD