Second 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] Mahmoud Sakr, M.D. [3]
Synonyms and keywords:; AV block, atrioventricular block, heart block, Mobitz type I AV block, Mobitz type II AV block, Advanced second degree AV block, (Wenckebach) AV block

Overview

Atrioventricular (AV) block is defined as an interruption in the transmission of an impulse, either transient or permanent, from the atria to the ventricles due to an anatomic or functional impairment in the conduction system. In second degree AV block, some atrial impulses fail to reach the ventricles. Wenckebach described progressive delay between atrial and ventricular contraction and the eventual failure of an atrial beat to reach the ventricles. Mobitz subsequently divided second degree AV block into two subtypes, as determined by the findings on the electrocardiogram. In Mobitz type I AV block, progressive PR interval prolongation precedes a non-conducted P wave. While in Mobitz type II AV block, the PR interval remains unchanged prior to a P wave that suddenly fails to conduct to the ventricles.

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

• Acute rheumatic fever
• AV nodal disease
• Bacterial endocarditis, especially of the aortic valve
• β blockers may cause AV block
• Calcific aortic stenosis
• Degenerative diseases
• Digoxin
• Dilated cardiomyopathy
• Diltiazem
• Enhanced vagal tone
• HCM
• Hypertension
• Iatrogenic after correction of VSD, tetralogy of Fallot, and endocardial cushion defect.
• Inferior ST elevation MI
• Massive calcification of the mitral annulus
• myocarditis
• Normal variants
• Penetrating and non-penetrating trauma of the chest
• Rheumatic mitral valve disease
• Sclerodegenerative disease of the bundle branches first described by Lenegre
• Transposition of the great vessels
• Valvular Heart Disease
• 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
Chemical / poisoning	No underlying causes
Dermatologic	No underlying causes
Drug Side Effect	Calcium channel blockers, Beta-blockers, Digitalis, Cardiac glycosides, Cholinesterase inhibitors, Quinidine,Procainamide
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
Musculoskeletal / Ortho	Ankylosing spondylitis, Muscular dystrophy
Neurologic	No underlying causes
Nutritional / Metabolic	No underlying causes
Obstetric/Gynecologic	No underlying causes
Oncologic	No underlying causes
Ophthalmologic	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
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
• Amyloidosis
• Ankylosing spondylitis
• ASD
• AV nodal disease
• Beta-blockers
• Calcium channel blockers
• Cardiac glycosides
• Chagas disease
• Cholinesterase inhibitors
• Dermatomyositis
• Digitalis
• Dilated cardiomyopathy
• Diphtheria
• Ebstein's anomaly
• Endocardial cushion defect
• Enhanced vagal tone (for example in athletes)
• HCM
• Hemochromatosis
• Hypertension
• Lyme disease
• Muscular dystrophy
• Myocarditis
• Normal variants
• Procainamide
• Quinidine
• Sarcoidosis
• Scleroderma
• SLE
• Tetralogy of Fallot
• Transposition of the great vessels
• Valvular heart disease
• VSD

References

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