First degree AV block causes: Difference between revisions
Jump to navigation
Jump to search
| Line 6: | Line 6: | ||
===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. | 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. | ||
* Normal Variants | |||
* [[PR prolongation]] can be found in 0.5% of healthy patients. | ** [[PR prolongation]] can be found in 0.5% of healthy patients. | ||
* | ** Transient AV block can occur with [[vagal maneuvers]]. | ||
* Transient AV block can occur with [[vagal maneuvers]]. | |||
* Acute ST elevation MI | |||
** [[First degree block]] occurs in 8% to 13% of patients. | |||
* [[First degree block]] occurs in 8% to 13 | |||
* Inferior ST elevation MI | |||
* Inferior ST elevation [[MI]]: [[AV block]] is more common in patients with inferior [[MI]]s (1/3rd of patients). | ** Inferior ST elevation [[MI]]: [[AV block]] is more common in patients with inferior [[MI]]s (1/3rd of patients). | ||
** In 90% of patients the inferior wall is supplied by the [[RCA]] which gives off a branch to the [[AV node]]. | *** In 90% of patients the inferior wall is supplied by the [[RCA]] which gives off a branch to the [[AV node]]. | ||
** As a rule the [[AV block]] is transient and normal function returns within a week of the acute episode. | *** As a rule the [[AV block]] is transient and normal function returns within a week of the acute episode. | ||
* Anterior ST elevation MI | |||
* Anterior ST elevation [[MI]]: [[AV block]] may be seen in up to 21%. | ** Anterior ST elevation [[MI]]: [[AV block]] may be seen in up to 21%. | ||
** The incidence of [[second degree AV block]] and [[third degree AV block]] is 5 to 7%. | *** The incidence of [[second degree AV block]] and [[third degree AV block]] is 5 to 7%. | ||
** Block is the result of damage to the interventricular septum supplied by the [[LAD]] | *** Block is the result of damage to the interventricular septum supplied by the [[LAD]] | ||
** There is damage to the bundle branches either in the form of bilateral bundle branch block or [[trifascicular block]]. | *** There is damage to the bundle branches either in the form of bilateral bundle branch block or [[trifascicular block]]. | ||
** [[RBBB]], [[RBBB]] + [[LAHB]], [[RBBB]] + [[LPHB]] or [[LBBB]] often appear before the development of [[AV block]]. | *** [[RBBB]], [[RBBB]] + [[LAHB]], [[RBBB]] + [[LPHB]] or [[LBBB]] often appear before the development of [[AV block]]. | ||
** The PR is normal or minimally prolonged before the onset of [[second degree AV block]] or [[third degree AV block]]. | *** The PR is normal or minimally prolonged before the onset of [[second degree AV block]] or [[third degree AV block]]. | ||
** Although the [[AV block]] is usually transient, there is a relatively high incidence of recurrence or high-degree AV block after the acute event . | *** Although the [[AV block]] is usually transient, there is a relatively high incidence of recurrence or high-degree AV block after the acute event. | ||
** 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. | *** 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. | ||
** 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. | *** 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. | ||
* Degenerative diseases | |||
* Sclerodegenerative disease of the bundle branches first described by Lenegre | ** Sclerodegenerative disease of the bundle branches first described by Lenegre | ||
* The pathologic process is called idiopathic bilateral bundle branch fibrosis and the heart block is called primary heart block | ** The pathologic process is called idiopathic bilateral bundle branch fibrosis and the heart block is called primary heart block | ||
* This is the most common cause of chronic [[AV block]] (46%) | ** This is the most common cause of chronic [[AV block]] (46%) | ||
* 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]]. | ** 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]]. | ||
* 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]] | ** 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]] | ||
* Diseases of the myocardium | |||
* [[Acute rheumatic fever]]: PR prolongation is a common (25 to 95% of cases) sign in patients with [[acute rheumatic fever]] | ** [[Acute rheumatic fever]]: PR prolongation is a common (25 to 95% of cases) sign in patients with [[acute rheumatic fever]] | ||
:* [[Type I second degree AV block]] may occur, but [[complete AV block]] is uncommon | :** [[Type I second degree AV block]] may occur, but [[complete AV block]] is uncommon | ||
:* Usually transient, disappears when the patient recovers | :** Usually transient, disappears when the patient recovers | ||
* [[Amyloidosis]] | ** [[Amyloidosis]] | ||
* [[Ankylosing spondylitis]] | ** [[Ankylosing spondylitis]] | ||
* [[Chagas disease]] | ** [[Chagas disease]] | ||
* [[Dermatomyositis]] | ** [[Dermatomyositis]] | ||
* [[Dilated cardiomyopathy]] results in various degrees of heart block are seen in 15% of patients | ** [[Dilated cardiomyopathy]] results in various degrees of heart block are seen in 15% of patients | ||
* [[Diphtheria]] | ** [[Diphtheria]] | ||
* [[HCM]]: 3% of patients with [[HCM]] will develop heart block | ** [[HCM]]: 3% of patients with [[HCM]] will develop heart block | ||
* [[Hemochromatosis]] | ** [[Hemochromatosis]] | ||
* [[Lyme disease]] | ** [[Lyme disease]] | ||
* [[Muscular dystrophy]] | ** [[Muscular dystrophy]] | ||
* [[Myocarditis]] | ** [[Myocarditis]] | ||
* [[Sarcoid]] | ** [[Sarcoid]] | ||
* [[Scleroderma]] | ** [[Scleroderma]] | ||
* [[SLE]] | ** [[SLE]] | ||
* Tumors, primary and secondary | ** Tumors, primary and secondary | ||
* Valvular Heart Disease | |||
[[Valvular heart disease|Valvular Diseases]] | [[Valvular heart disease|Valvular Diseases]] | ||
* Calcific [[aortic stenosis]] may be accompanied by chronic partial or complete AV block | ** 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 | ** 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 | ** 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]] | ** 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]] | ** May also be seen in [[bacterial endocarditis]], especially of the [[aortic valve]] | ||
*[[Ebstein's anomaly]] may be associated with first-degree AV block. | ** [[Ebstein's anomaly]] may be associated with first-degree AV block. | ||
* Drugs | |||
* [[Digoxin]] is one of the most common causes of reversible [[AV block]] | ** [[Digoxin]] is one of the most common causes of reversible [[AV block]] | ||
:* When [[second degree AV block]] is induced, it is always of the Type I variety | :** When [[second degree AV block]] is induced, it is always of the Type I variety | ||
:* When complete block occurs, the [[QRS complex]]es are narrow because the block is of the AV node | :** When complete block occurs, the [[QRS complex]]es are narrow because the block is of the AV node | ||
:* The ventricular response rate is more rapid than that due to organic lesions, and increased automaticity of the AV junctional pacemaker may be responsible. | :** 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 | ** [[Quinidine]] and [[Procainamide]] may produce slight prolongation of the PR | ||
* [[Beta blocker|β blockers]] may cause [[AV block]] | ** [[Beta blocker|β blockers]] may cause [[AV block]] | ||
* [[Diltiazem]] and [[verapamil]] may cause AV conduction delay and [[PR interval]] prolongation | ** [[Diltiazem]] and [[verapamil]] may cause AV conduction delay and [[PR interval]] prolongation | ||
* 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 [[ASD]]s 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=== | ===Causes by Organ System=== | ||
Revision as of 18:42, 1 February 2013
|
First degree AV block Microchapters |
|
Diagnosis |
|---|
|
Treatment |
|
Case Studies |
|
First degree AV block causes On the Web |
|
American Roentgen Ray Society Images of First degree AV block causes |
|
Risk calculators and risk factors for First degree AV block causes |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2]
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 inhibitors.
- Normal Variants
- PR prolongation can be found in 0.5% of healthy patients.
- Transient AV block can occur with vagal maneuvers.
- Acute ST elevation MI
- First degree block occurs in 8% to 13% of patients.
- Inferior ST elevation MI
- Anterior ST elevation MI
- Anterior ST elevation MI: AV block may be seen in up to 21%.
- The incidence of second degree AV block and third degree AV block is 5 to 7%.
- Block is the result of damage to the interventricular septum supplied by the LAD
- There is damage to the bundle branches either in the form of bilateral bundle branch block or trifascicular block.
- RBBB, RBBB + LAHB, RBBB + LPHB or LBBB often appear before the development of AV block.
- The PR is normal or minimally prolonged before the onset of second degree AV block or third degree AV block.
- Although the AV block is usually transient, there is a relatively high incidence of recurrence or high-degree AV block after the acute event.
- 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.
- 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.
- Anterior ST elevation MI: AV block may be seen in up to 21%.
- Degenerative diseases
- Sclerodegenerative disease of the bundle branches first described by Lenegre
- The pathologic process is called idiopathic bilateral bundle branch fibrosis and the heart block is called primary heart block
- This is the most common cause of chronic AV block (46%)
- 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.
- 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 byhypertension
- Diseases of the myocardium
- Acute rheumatic fever: PR prolongation is a common (25 to 95% of cases) sign in patients with acute rheumatic fever
- Type I second degree AV block may occur, but complete AV block is uncommon
- Usually transient, disappears when the patient recovers
- Amyloidosis
- Ankylosing spondylitis
- Chagas disease
- Dermatomyositis
- Dilated cardiomyopathy results in various degrees of heart block are seen in 15% of patients
- Diphtheria
- HCM: 3% of patients with HCM will develop heart block
- Hemochromatosis
- Lyme disease
- Muscular dystrophy
- Myocarditis
- Sarcoid
- Scleroderma
- 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.
- When second degree AV block is induced, it is always of the Type I variety
- When complete block occurs, the QRS complexes are narrow because the block is of the AV node
- 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
- 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) |
| Chemical / poisoning | No underlying causes |
| Dermatologic | No underlying causes |
| Drug Side Effect | Calcium channel blockers, Beta-blockers, Digitalis, Cardiac glycosides, Cholinesterase inhibitors |
| Ear Nose Throat | No underlying causes |
| Endocrine | No underlying causes |
| Environmental | No underlying causes |
| Gastroenterologic | No underlying causes |
| Genetic | No underlying causes |
| Hematologic | No underlying causes |
| Iatrogenic | No underlying causes |
| Infectious Disease | No underlying causes |
| Musculoskeletal / Ortho | No underlying causes |
| 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 | No underlying causes |
| Renal / Electrolyte | No underlying causes |
| Rheum / Immune / Allergy | No underlying causes |
| Sexual | No underlying causes |
| Trauma | No underlying causes |
| Urologic | No underlying causes |
| Dental | No underlying causes |
| Miscellaneous | Enhanced vagal tone (for example in athletes) |