First degree AV block causes: Difference between revisions

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{{First degree AV block}}
{{First degree AV block}}
{{CMG}}; {{AE}} {{CZ}}
{{CMG}}; {{AE}} {{CZ}}; {{RT}}
 
==Overview==
Common causes of [[first-degree AV block]] include [[ischemic heart disease]], [[congenital heart disease]], [[electrolyte]]  abnormalities (particularly [[hypokalemia]] and [[hypomagnesemia]]), [[inflammation]], [[infections]] ([[endocarditis]], [[rheumatic fever]], [[Chagas disease]], [[Lyme disease]], [[diphtheria]]), [[drugs]] ([[antiarrhythmic ]] Ia, Ic, II, III, IV and [[digoxin]], [[β-blockers]], [[calcium channel blockers]] ), [[infiltrative diseases]] ([[sarcoidosis]]), [[collagen vascular diseases]] ([[SLE]], [[rheumatoid arthritis]], [[scleroderma]]), idiopathic degenerative diseases ([[Lenegre]] and [[Lev diseases]]) and [[neuromuscular disorders]]  and increased [[vagal tone]] in younger [[patients]].


==Causes==
==Causes==
===Life Threatening Causes===
Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.
*[[Acute myocardial infarction]]
*[[Acute rheumatic fever]]
*[[Bacterial endocarditis]]
*[[Myocarditis]]
===Common Causes===
===Common Causes===
The most common causes of first degree heart block are an AV nodal disease, enhanced vagal tone (for example in athletes), [[myocarditis]], acute [[myocardial infarction]] (especially acute inferior MI), electrolyte disturbances and [[drugs]].  The drugs that most commonly cause first degree heart block are those that increase the refractory time of the [[AV node]], thereby slowing AV conduction. These include [[calcium channel blockers]], [[beta-blockers]], [[digitalis]],[[cardiac glycosides]] and anything that increases [[cholinergic]] activity such as [[cholinesterase inhibitor]]s.
*[[Hyperkalemia]]
====Normal Variants====
*[[Hyperthyroidism]]
* [[PR prolongation]] can be found in 0.5% of healthy patients.
*[[Hypothyroidism]]
* [[Second degree block type I]] may be seen in healthy patients during sleep.
*[[vagus nerve|Increased vagal tone]] (e.g. [[sleep]], athletes)
* Transient AV block can occur with [[vagal maneuvers]].
*[[Ischemic heart disease]]
*Medications ( e.g. [[adenosine]], [[amiodarone]], [[beta-blockers]], [[diltiazem]], [[procainamide]], [[verapamil]])


====ST Elevation MI====
===Causes by Organ System===
In acute ST elevation [[MI]]:
{|style="width:80%; height:100px" border="1"
* [[First degree block]] occurs in 8% to 13% of patients.
|style="height:100px"; style="width:25%" border="1" bgcolor="LightSteelBlue" | '''Cardiovascular'''
* [[Second degree block]] occurs in 3.5% to 10% of patients.
|style="height:100px"; style="width:75%" border="1" bgcolor="Beige" | [[Acute myocardial infarction]], [[acute rheumatic fever]], [[ASD]], [[dilated cardiomyopathy]],  [[Ebstein's anomaly]], [[Carotid sinus hypersensitivity|hypersensitive carotid sinus syndrome]], [[hypertension]], [[hypertrophic cardiomyopathy]], [[Lev's disease]], [[myocardial bridging]], [[myocarditis]], [[Aortic valve  replacement|post aortic valve  replacement]], [[catheter ablation|post catheter ablation for arrhythmias]], [[ventricular septal defect surgery|post closure of a ventricular septal defect]], [[mitral valve replacement|post mitral valve replacement]], [[tetralogy of Fallot]], [[endocardial cushion defect]], [[transposition of the great vessels]],  [[valvular heart disease]], [[VSD]]
* [[Complete heart block]] occurs in 2.5% to 8% of patients.
|-
|-bgcolor="LightSteelBlue"
| '''Chemical / poisoning'''
|bgcolor="Beige"| No underlying causes
|-
|-bgcolor="LightSteelBlue"
| '''Dermatologic'''
|bgcolor="Beige"| No underlying causes
|-
|-bgcolor="LightSteelBlue"
| '''Drug Side Effect'''
|bgcolor="Beige"| [[Amiodarone]], [[beta-blockers]], [[digitalis]], [[calcium channel blockers]], [[cholinesterase inhibitor|cholinesterase inhibitors]], [[disopyramide]], [[dofetilide]], [[dolasetron]], [[donepezil]], [[eslicarbazepine acetate]], [[fesoterodine]], [[fingolimod]], [[flecainide]], [[ibutilide]], [[lacosamide]], [[magnesium]], [[paliperidone]], [[pramipexole]], [[procainamide]], [[propafenone]], [[propoxyphene]], [[quinidine]], [[sotalol]], [[terodiline]]
|-
|-bgcolor="LightSteelBlue"
| '''Ear Nose Throat'''
|bgcolor="Beige"| No underlying causes
|-
|-bgcolor="LightSteelBlue"
| '''Endocrine'''
|bgcolor="Beige"| [[Hyperthyroidism]], [[myxedema]], [[periodic  paralysis|thyrotoxic periodic paralysis]], [[hypothyroidism]]
|-
|-bgcolor="LightSteelBlue"
| '''Environmental'''
|bgcolor="Beige"| [[Hypothermia]]
|-
|-bgcolor="LightSteelBlue"
| '''Gastroenterologic'''
|bgcolor="Beige"| [[Hemochromatosis]]
|-
|-bgcolor="LightSteelBlue"
| '''Genetic'''
|bgcolor="Beige"| [[Emery-Dreifuss muscular dystrophy]], [[Fabry disease]], [[glycogenosis type 2b]], [[Neuromuscular disease|hereditary neuromuscular disease]], [[Kearns-Sayre syndrome]]
|-
|-bgcolor="LightSteelBlue"
| '''Hematologic'''
|bgcolor="Beige"| [[Multiple myeloma]]
|-
|-bgcolor="LightSteelBlue"
| '''Iatrogenic'''
|bgcolor="Beige"| [[aortic valve  replacement|Post aortic valve  replacement]], [[catheter ablation|post catheter ablation for  arrhythmias]], [[ventricular septal defect surgery|post closure of a  ventricular septal defect]], [[mitral valve  replacement|post mitral valve  replacement]]
|-
|-bgcolor="LightSteelBlue"
| '''Infectious Disease'''
|bgcolor="Beige"| [[Acute rheumatic fever]], [[Chagas disease]], [[diphtheria]], [[Lyme disease]], [[myocarditis]], [[neonatal lupus erythematosus]], [[protozoa|protozoal infection]], [[sarcoidosis]], [[SLE]], [[tuberculosis]]
|-
|-bgcolor="LightSteelBlue"
| '''Musculoskeletal / Ortho'''
|bgcolor="Beige"| [[Ankylosing spondylitis]], [[Neuromuscular disease|hereditary neuromuscular disease]], [[Kearns-Sayre syndrome]], [[mitochondrial disease|mitochondrial genome inherited conditions]],  [[muscular dystrophy]]
|-
|-bgcolor="LightSteelBlue"
| '''Neurologic'''
|bgcolor="Beige"| No underlying causes
|-
|-bgcolor="LightSteelBlue"
| '''Nutritional / Metabolic'''
|bgcolor="Beige"| [[Fabry disease]], [[glycogenosis type 2b]]
|-
|-bgcolor="LightSteelBlue"
| '''Obstetric/Gynecologic'''
|bgcolor="Beige"| No underlying causes
|-
|-bgcolor="LightSteelBlue"
| '''Oncologic'''
|bgcolor="Beige"| [[Multiple myeloma]]
|-
|-bgcolor="LightSteelBlue"
| '''Opthalmologic'''
|bgcolor="Beige"| No underlying causes
|-
|-bgcolor="LightSteelBlue"
| '''Overdose / Toxicity'''
|bgcolor="Beige"| No underlying causes
|-
|-bgcolor="LightSteelBlue"
| '''Psychiatric'''
|bgcolor="Beige"| No underlying causes
|-
|-bgcolor="LightSteelBlue"
| '''Pulmonary'''
|bgcolor="Beige"| [[Sarcoidosis]]
|-
|-bgcolor="LightSteelBlue"
| '''Renal / Electrolyte'''
|bgcolor="Beige"| [[Hyperkalemia]], [[hypokalemia]]


=====Inferior ST Elevation MI=====
|-bgcolor="LightSteelBlue"
* Inferior ST elevation [[MI]]: [[AV block]] is more common in patients with inferior [[MI]]s (1/3rd of patients).
| '''Rheum / Immune / Allergy'''
** In 90% of patients the inferior wall is supplied by the [[RCA]] which gives off a branch to the [[AV node]].
|bgcolor="Beige"| [[Ankylosing spondylitis]], [[dermatomyositis]], [[rheumatoid arthritis]], [[scleroderma]], [[SLE]]
** As a rule the [[AV block]] is transient and normal function returns within a week of the acute episode.
|-
|-bgcolor="LightSteelBlue"
| '''Sexual'''
|bgcolor="Beige"| No underlying causes
|-
|-bgcolor="LightSteelBlue"
| '''Trauma'''
|bgcolor="Beige"| No underlying causes
|-
|-bgcolor="LightSteelBlue"
| '''Urologic'''
|bgcolor="Beige"| No underlying causes
|-
|-bgcolor="LightSteelBlue"
| '''Dental'''
|bgcolor="Beige"| No underlying causes
|-
|-bgcolor="LightSteelBlue"
| '''Miscellaneous'''
|bgcolor="Beige"|  [[Amyloidosis]], [[degenerative diseases]],  [[vagus nerve|enhanced  vagal tone]], [[PR interval|normal variants]]
|-
|}


=====Anterior ST Elevation MI=====
===Causes in Alphabetical Order===
* Anterior ST elevation [[MI]]: [[AV block]] may be seen in up to 21%.
{{col-begin|width=80%}}
** The incidence of [[second degree AV block]] and [[third degree AV block]] is 5 to 7%.
{{col-break|width=33%}}
** Block is the result of damage to the interventricular septum supplied by the [[LAD]]
*[[Acute myocardial infarction]]
** There is damage to the bundle branches either in the form of bilateral bundle branch block or [[trifascicular block]].
*[[Acute rheumatic fever]]
** [[RBBB]], [[RBBB]] + [[LAHB]], [[RBBB]] + [[LPHB]] or [[LBBB]] often appear before the development of [[AV block]].
*[[Amyloidosis]]
** The PR is normal or minimally prolonged before the onset of [[second degree AV block]] or [[third degree AV block]].
*[[Ankylosing spondylitis]]
** Although the [[AV block]] is usually transient, there is a relatively high incidence of recurrence or high-degree AV block after the acute event .
*[[ASD]]
** In addition to [[ischemia]], [[fibrosis]] and [[calcification]] of the summit of the ventricular septum that involve the branching part of the bundle branches, may play a role in the genesis of the conduction defect.
*[[Bacterial endocarditis]]
** It used to be thought that CAD was the most frequent cause of chronic [[complete AV block]], but it actually causes only 15% of cases.
*[[Beta-blockers]]
 
*[[Calcific aortic stenosis]]
====Degenerative Diseases====
*[[Calcium channel blockers]]
* Sclerodegenerative disease of the bundle branches first described by Lenegre
*[[Cardiac glycosides]]
* The pathologic process is called idiopathic bilateral bundle branch fibrosis and the heart block is called primary heart block
*[[Cardiac tumors]]
* This is the most common cause of chronic [[AV block]] (46%)
*[[Chagas disease]]
* Lev described similar degenerative lesions, which he referred to as sclerosis of the left side of the cardiac skeleton. There is progressive fibrosis and calcification of the mitral annulus, the central fibrous body, the pars membranacea, the base of the aorta, and the summit of the muscular ventricular septum. Various portions of the [[His bundle]] or the bundle branches may be involved, resulting in [[AV block]].
*[[Cholinesterase inhibitors]]
 
*[[Clonidine]]
====Hypertension====
*[[Degenerative diseases]]
* 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]]
*[[Dermatomyositis]]
 
*[[Digitalis]]
====Diseases of the Myocardium====
*[[Digoxin]]
* [[Acute rheumatic fever]]: PR prolongation is a common (25 to 95% of cases) sign in patients with [[acute rheumatic fever]]
*[[Dilated cardiomyopathy]]
:* [[Type I second degree AV block]] may occur, but [[complete AV block]] is uncommon
*[[Diltiazem]]
:* usually transient, disappears when the patient recovers
*[[Diphtheria]]
* [[Amyloidosis]]
*[[Disopyramide]]
* [[Ankylosing spondylitis]]
*[[Dolasetron]]
* [[Chagas disease]]
*[[Donepezil]]
* [[Dermatomyositis]]
*[[Ebstein anomaly]]
* [[Dilated cardiomyopathy]] results in various degrees of heart block are seen in 15% of patients
*[[Ebstein's anomaly]]
* [[Diphtheria]]
*[[Electrolyte disturbances]]
* [[HCM]]: 3% of patients with [[HCM]] will develop heart block
*[[Emery-Dreifuss muscular dystrophy]]
* [[Hemochromatosis]]
*[[vagus nerve|Enhanced vagal tone in athletes]]  
* [[Lyme disease]]
{{col-break|width=33%}}
* [[Muscular dystrophy]]
*[[Eslicarbazepine acetate]]
* [[Myocarditis]]
*[[Fabry disease]]
* [[Sarcoid]]
*[[Fesoterodine]]
* [[Scleroderma]]
*[[Fingolimod]]
* [[SLE]]
*[[Glycogenosis type 2b]]
* Tumors, primary and secondary
*[[HCM]]
 
* [[Neuromuscular disease|Hereditary neuromuscular disease]]
====Valvular Heart Disease====
*[[Hodgkin lymphoma]]
[[Valvular heart disease|Valvular Diseases]]
*[[Hyperkalaemia]]
* Calcific [[aortic stenosis]] may be accompanied by chronic partial or complete AV block
*[[Carotid sinus hypersensitivity|Hypersensitive carotid sinus syndrome]]
* There is an extension of the calcification to involve the main bundle or its bifurcation, resulting in degeneration and necrosis of the conduction tissue
*[[Hyperthyroidism]]
* May also occur in rheumatic mitral valve disease, but is less common
*[[Hypokalaemia]]
* Occasionally, massive calcification of the mitral annulus as an aging process may cause [[AV block]]
*[[Hypothermia]]
* May also be seen in [[bacterial endocarditis]], especially of the [[aortic valve]]
*[[Ibutilide]]
*[[Ebstein's anomaly]]  may be associated with first-degree AV block.
*[[Ischaemic heart disease]]
 
*[[Kearns-Sayre syndrome]]
====Drugs====
*[[Labetalol]]
* [[Digoxin]] is one of the most common causes of reversible [[AV block]]
*[[Lacosamide]]
:* When [[second degree AV block]] is induced, it is always of the Type I variety
*[[Lanatoside C]]
:* When complete block occurs, the [[QRS complex]]es are narrow because the block is of the AV node
*[[Lenegre's disease]]
:* The ventricular response rate is more rapid than that due to organic lesions, and increased automaticity of the AV junctional pacemaker may be responsible.
*[[Lev's disease]]
* [[Quinidine]] and [[Procainamide]] may produce slight prolongation of the PR
*[[Lyme disease]]
* [[Beta blocker|β blockers]] may cause [[AV block]]
*[[Mitochondrial DNA|Mitochondrial genome inherited conditions]]
* [[Diltiazem]] and [[verapamil]] may cause AV conduction delay and [[PR interval]] prolongation
*[[Multiple myeloma]]
 
*[[Muscular dystrophy]]
====Congenital====
*[[Myocardial bridging]]
* Occurs in the absence of other evidence of organic heart disease
*[[Myocarditis]]
* Site is usually proximal to the bifurcation of the [[His bundle]], most often in the [[AV node]]
*[[Myotonic dystrophy]]
* Narrow [[QRS]] with a rate > 40 beats per minute
*[[Myxedema]]
* Frequently seen in those with corrected [[transposition of the great vessels]], and occasionally in [[ASD]]s and [[Ebstein's anomaly]]
{{col-break|width=33%}}
 
*[[Neonatal lupus erythematosus]]
====Trauma====
*[[prolonged PR interval|Normal variants of PR  prolongation]]
* May be induced during open heart surgery in the area of AV conduction tissue
*[[Paliperidone]]
* Seen in patients operated on for the correction of [[VSD]], [[tetralogy of Fallot]], and [[endocardial cushion defect]].
*[[aortic valve replacement|Post aortic valve replacement ]]
* May be due to [[edema]], transient ischemia, or actual disruption of the conduction tissue. The block may therefore be permanent or transient.
*[[catheter ablation|Post catheter ablation for  arrhythmias]]
* Also reported with both penetrating and non-penetrating trauma of the chest
*[[Ventricular septal defect surgery|Post closure of a ventricular septal defect]]
*[[mitral valve  replacement|Post mitral valve  replacement]]
*[[Procainamide]]
*[[Propoxyphene]]
*[[Propranolol]]
*[[Protozoa|Protozoal infection]]
*[[Quinidine]]
*[[Quinine]]
*[[Rheumatic fever|Rheumatic mitral valve disease]]
*[[Sarcoidosis]]
*[[SLE]]
*[[Systemic sclerosis]]
*[[Terodiline]]
*[[Tetralogy of Fallot]]
*[[periodic  paralysis|Thyrotoxic periodic  paralysis]]
*[[Tolterodine]]
*[[Transposition of the great vessels]]
*[[vagus nerve|Vagal maneuvers]]
*[[Valsalva maneuver]]
*[[Valvular heart disease]]
*[[Verapamil]]
*[[VSD]]
*[[sex linkage|X-linked inherited  conditions]]
{{col-end}}


==References==
==References==
{{Reflist|2}}
{{Reflist|2}}
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[[Category:Up-To-Date cardiology]]
[[Category:Arrhythmia]]
[[Category:Electrophysiology]]
[[Category:Disease]]


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Latest revision as of 04:51, 22 July 2021

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]

Overview

Common causes of first-degree AV block include ischemic heart disease, congenital heart disease, electrolyte abnormalities (particularly hypokalemia and hypomagnesemia), inflammation, infections (endocarditis, rheumatic fever, Chagas disease, Lyme disease, diphtheria), drugs (antiarrhythmic Ia, Ic, II, III, IV and digoxin, β-blockers, calcium channel blockers ), infiltrative diseases (sarcoidosis), collagen vascular diseases (SLE, rheumatoid arthritis, scleroderma), idiopathic degenerative diseases (Lenegre and Lev diseases) and neuromuscular disorders and increased vagal tone in younger patients.

Causes

Life Threatening Causes

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.

Common Causes

Causes by Organ System

Cardiovascular Acute myocardial infarction, acute rheumatic fever, ASD, dilated cardiomyopathy, Ebstein's anomaly, hypersensitive carotid sinus syndrome, hypertension, hypertrophic cardiomyopathy, Lev's disease, myocardial bridging, myocarditis, post aortic valve replacement, post catheter ablation for arrhythmias, post closure of a ventricular septal defect, post mitral valve replacement, tetralogy of Fallot, endocardial cushion defect, transposition of the great vessels, valvular heart disease, VSD
Chemical / poisoning No underlying causes
Dermatologic No underlying causes
Drug Side Effect Amiodarone, beta-blockers, digitalis, calcium channel blockers, cholinesterase inhibitors, disopyramide, dofetilide, dolasetron, donepezil, eslicarbazepine acetate, fesoterodine, fingolimod, flecainide, ibutilide, lacosamide, magnesium, paliperidone, pramipexole, procainamide, propafenone, propoxyphene, quinidine, sotalol, terodiline
Ear Nose Throat No underlying causes
Endocrine Hyperthyroidism, myxedema, thyrotoxic periodic paralysis, hypothyroidism
Environmental Hypothermia
Gastroenterologic Hemochromatosis
Genetic Emery-Dreifuss muscular dystrophy, Fabry disease, glycogenosis type 2b, hereditary neuromuscular disease, Kearns-Sayre syndrome
Hematologic Multiple myeloma
Iatrogenic Post aortic valve replacement, post catheter ablation for arrhythmias, post closure of a ventricular septal defect, post mitral valve replacement
Infectious Disease Acute rheumatic fever, Chagas disease, diphtheria, Lyme disease, myocarditis, neonatal lupus erythematosus, protozoal infection, sarcoidosis, SLE, tuberculosis
Musculoskeletal / Ortho Ankylosing spondylitis, hereditary neuromuscular disease, Kearns-Sayre syndrome, mitochondrial genome inherited conditions, muscular dystrophy
Neurologic No underlying causes
Nutritional / Metabolic Fabry disease, glycogenosis type 2b
Obstetric/Gynecologic No underlying causes
Oncologic Multiple myeloma
Opthalmologic No underlying causes
Overdose / Toxicity No underlying causes
Psychiatric No underlying causes
Pulmonary Sarcoidosis
Renal / Electrolyte Hyperkalemia, hypokalemia
Rheum / Immune / Allergy Ankylosing spondylitis, dermatomyositis, rheumatoid arthritis, scleroderma, SLE
Sexual No underlying causes
Trauma No underlying causes
Urologic No underlying causes
Dental No underlying causes
Miscellaneous Amyloidosis, degenerative diseases, enhanced vagal tone, normal variants

Causes in Alphabetical Order

References


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