First degree AV block causes

First degree AV block Microchapters
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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:; AV block, atrioventricular block, heart block

Overview

An atrioventricular block (or AV block) is a type of heart block involving an impairment of the conduction between the atria and ventricles of the heart. It usually involves the atrioventricular node, but it can involve other structures too. AV block is categorized by degree and site of conduction block. In first-degree AV block, all atrial impulses are conducted to the ventricle. However, there is a delay within the AV node, resulting in a prolonged PR interval on ECG (>200 msec or >5 small blocks). In other words, first degree block is a slowed conduction without loss of atrioventricular synchrony.

Causes

Life Threatening Causes

Life-threatening conditions can result in death or permanent disability within 24 hours if left untreated.

• Acute myocardial infarction
• Acute rheumatic fever
• Bacterial endocarditis
• Myocarditis

Common Causes

• Hyperkalemia
• Hyperthyroidism
• Increased vagal tone (e.g. sleep, athletes)
• Ischemic heart disease
• Medications ( e.g. adenosine, amiodarone, beta-blockers, diltiazem, procainamide, verapamil)

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, Donepezil, Cardiac glycosides, Cholinesterase inhibitors, [Dolasetron]], Eslicarbazepine acetate, Quinidine, Procainamide, Disopyramide, Flecainide, Encainide, Propafenone, Amiodarone, Sotalol, Dofetilide, Ibutilide, Magnesium, Fesoterodine, Fingolimod
Ear Nose Throat	No underlying causes
Endocrine	No underlying causes
Environmental	No underlying causes
Gastroenterologic	Hemochromatosis
Genetic	* Emery-Dreifuss muscular dystrophy, x-linked, Fabry disease, Glycogenosis type 2b, Hereditary neuromuscular heredodegenerative disease
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, Hereditary neuromuscular heredodegenerative disease
Neurologic	No underlying causes
Nutritional / Metabolic	Fabry disease, Glycogenosis type 2b
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, Degenerative diseases, Enhanced vagal tone (for example in athletes), Normal variants

Causes in Alphabetical Order

• Acute myocardial infarction

• Acute rheumatic fever

• Amyloidosis

• Ankylosing spondylitis

• ASD

• Bacterial endocarditis

• Beta-blockers

• Calcific aortic stenosis

• Calcium channel blockers

• Cardiac glycosides

• Cardiac tumors

• Chagas disease

• Cholinesterase inhibitors

• Clonidine

• Degenerative diseases

• Dermatomyositis

• Digitalis

• Digoxin

• Dilated cardiomyopathy

• Diltiazem

• Diphtheria

• Disopyramide

• Dolasetron

• Donepezil

• Drugs

• Ebstein anomaly

• Ebstein's anomaly

• Electrolyte disturbances

• Emery-Dreifuss muscular dystrophy, x-linked

• Endocarditis

• Enhanced vagal tone in athletes

• Eslicarbazepine acetate

• Fabry disease

• Fesoterodine

• Fingolimod

• Glycogenosis type 2b

• HCM

• Hereditary neuromuscular heredodegenerative disease

• Hodgkin lymphoma

• Hyperkalaemia

• Hypersensitive carotid sinus syndrome

• Hyperthyroidism

• Hypokalaemia

• Hypothermia

• Ibutilide

• Idiopathic bilateral bundle branch fibrosis

• Idiopathic progressive cardiac conduction disease

• Ischaemic heart disease

• Kearns-Sayre syndrome

• Labetalol

• Lacosamide

• Lanatoside C

• Lenegre's disease

• Lev's disease

• Lyme disease

• Mitochondrial genome inherited conditions

• Multiple myeloma

• Muscular dystrophy

• Myocardial bridging

• Myocarditis

• Myotonic dystrophy

• Myxedema

• Neonatal lupus syndrome

• Normal variants of PR prolongation

• Paget disease

• Pain

• Paliperidone

• Post aortic valve replacement

• Post catheter ablation for arrhythmias

• Post closure of a ventricular septal defect

• Post mitral valve replacement

• Procainamide

• Propoxyphene

• Propranolol

• Protozoal infection

• Quinidine

• Quinine

• Rheumatic mitral valve disease

• Sarcoidosis

• SLE

• Sleep

• Systemic sclerosis

• Terodiline

• Tetralogy of fallot

• Thyrotoxic periodic paralysis

• Tolterodine

• Transposition of the great vessels

• Trauma

• Vagal maneuvers

• Valsalva manouevre

• Valvular heart disease

• Verapamil

• VSD

• X-linked inherited conditions

References

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