|
|
| (20 intermediate revisions by 5 users not shown) |
| Line 1: |
Line 1: |
| | __NOTOC__ |
| {{Infobox_Disease | | | {{Infobox_Disease | |
| Name = {{PAGENAME}} | | | Name = {{PAGENAME}} | |
| Image = First Degree AV Block.jpg | | | Image = First Degree AV Block.jpg | |
| Caption = | | | Caption = | |
| DiseasesDB = |
| |
| ICD10 = {{ICD10|I|44|0|i|30}}-{{ICD10|I|44|3|i|30}} |
| |
| ICD9 = {{ICD9|426.0}}-{{ICD9|426.1}} |
| |
| ICDO = |
| |
| OMIM = |
| |
| MedlinePlus = |
| |
| eMedicineSubj = |
| |
| eMedicineTopic = |
| |
| MeshID = D006327 |
| |
| }} | | }} |
| {{SI}} | | {{Atrioventricular block}} |
| {{CMG}}
| | '''For patient information, click [[Heart block (patient information)|here]]''' |
|
| |
|
| {{SK}} AV block | | {{CMG}}; {{AE}} {{EdzelCo}} |
|
| |
|
| ==Overview==
| | {{SK}} AV block; AV nodal block |
| 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.<ref>{{Dorlands|b_16|12188991}}</ref> It usually involves the [[atrioventricular node]], but it can involve other structures too. Atrioventricular (AV) block is caused by one of the following mechanisms i.e. fibrosis or degeneration of the conduction system, [[ischemic heart disease]], or medications. AV block is categorized by degree and site of conduction. 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). Second-degree AV block can be of one of the two types: Mobitz I and Mobitz II. Mobitz I, or [[Wenckebach block]], consists of progressive prolongation of PR interval, until loss of conduction to the ventricle occurs (missed beat). Mobitz I block is rarely symptomatic and does not require treatment. On the other hand, Mobitz II AV block is characterized by a constant PR interval with intermittent missed beats. The missed beats can occur with varying frequency such as occasional to 3:1 or 2:1.
| |
|
| |
|
| == Classification == | | == [[Atrioventricular block overview|Overview]] == |
| * [[First Degree AV Block]],
| |
| *:* Prolongation of [[PR interval]]
| |
| * [[Second Degree AV Block]] also known as [[Mobitz I]] and [[Mobitz II]]
| |
| *:* Type I AV Block ([[Wenchebach]])
| |
| *:*:* Progressive prolongation of the [[PR interval]] before dropped beat.
| |
| *:*:* Usually block is in the [[AV node]]
| |
| *:* Type II AV Block
| |
| *:*:* No change in [[PR interval]] before dropped beat
| |
| *:*:* Usually infranodal
| |
| * [[Complete or Third-Degree AV Block|Third Degree AV Block]] also known as complete heart block
| |
| *:* No relationship between Atrial and ventricular activity.
| |
|
| |
|
| ==Pathophysiology== | | == [[Atrioventricular block historical perspective|Historical Perspective]] == |
| ==== Intrinsic Etiology ====
| |
| * Congenital
| |
| * Degenerative (Lev’s and Lenegre’s)
| |
| * Ischemia
| |
| * Infiltrative ([[Sarcoidosis]], [[Amyloidosis]], [[Hemochromatosis]])
| |
| * Inflammatory ([[systemic lupus erythematosus]] ([[SLE]]), [[Scleroderma]], [[rheumatoid arthritis]] ([[RA]]))
| |
| * Myopathic ([[Myotonic Dystrophy]], Erbs Palsy)
| |
| * Infectious (Lyme, [[Endocarditis]], [[Chagas]])
| |
| * Trauma (Valve Replacement, Line insertions)
| |
|
| |
|
| ==== Extrinsic Etiology ==== | | == [[Atrioventricular block classification|Classification]] == |
| * Autonomic (Carotid hypersensitivity, situational, vasovagal)
| |
| * Medications ([[Beta blockers]], [[calcium-channel blocker]] (CCB), [[Digoxin]], [[Clonidine]], [[antiarrhythmics]])
| |
| * Hypothyroidism
| |
| * Hypothermia
| |
| * Neurologic
| |
| * Electrolytes (Hyperkalemia, Hypokalemia)
| |
|
| |
|
| ==Differential Diagnosis of AV Block in General== | | == [[Atrioventricular block pathophysiology|Pathophysiology]] == |
| ===Normal Variants===
| |
| # [[PR prolongation]] can be found in 0.5% of healthy patients
| |
| # [[Second degree block type I]] may be seen in healthy patients during sleep
| |
| # Transient AV block can occur with vagal maneuvers
| |
|
| |
|
| ===ST Elevation MI=== | | == [[Atrioventricular block causes|Causes]] == |
| In acute ST elevation [[MI]]:
| |
| * [[First degree block]] occurs in 8% to 13%
| |
| * [[Second degree block]] in 3.5% to 10%
| |
| * [[Complete heart block]] in 2.5% to 8%
| |
|
| |
|
| ====Inferior ST Elevation MI==== | | == [[Atrioventricular block differential diagnosis|Differentiating Atrioventricular block from other Diseases]] == |
| * 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]]
| |
| # As a rule the [[AV block]] is transient and normal function returns within a week of the acute episode
| |
|
| |
|
| ====Anterior ST Elevation MI==== | | == [[Atrioventricular block epidemiology and demographics|Epidemiology and Demographics]] == |
| * Anterior ST elevation [[MI]]: [[AV block]] may be seen in up to 21%
| |
| # 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
| |
|
| |
|
| ===Degenerative Diseases=== | | == [[Atrioventricular block risk factors|Risk Factors]] == |
| * 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=== | | == [[Atrioventricular block natural history, complications and prognosis|Natural History, Complications and Prognosis]] == |
| * 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=== | | == Diagnosis == |
| * [[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===
| | [[Atrioventricular block history and symptoms|History and Symptoms]] | [[Atrioventricular block physical examination|Physical Examination]] | [[Atrioventricular block laboratory findings|Laboratory Findings]] | [[Atrioventricular block electrocardiogram|Electrocardiogram]] | [[Atrioventricular block EKG examples|EKG Examples]] | [[Atrioventricular block chest x ray|Chest X Ray]] | [[Atrioventricular block echocardiography|Echocardiography]] | [[Atrioventricular block other diagnostic studies|Other Diagnostic Studies]] |
| [[Valvular heart disease|Valvular Diseases]] | |
| * 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]]
| |
| | |
| ===Drugs===
| |
| * [[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 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.
| |
| * [[Quinidine]] and [[Procainamide]] may produce slight prolongation of the PR
| |
| * [[Beta blocker|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 [[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
| |
|
| |
|
| == Treatment == | | == Treatment == |
| * Remove extrinsic causes
| |
| * Treat reversible intrinsic causes
| |
|
| |
|
| == Pharmacotherapy ==
| | [[Atrioventricular block medical therapy|Medical Therapy]] | [[Atrioventricular block surgery|Surgery]] | [[Atrioventricular block primary prevention|Primary Prevention]] | [[Atrioventricular block secondary prevention|Secondary Prevention]] | [[Atrioventricular block cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] | [[Atrioventricular block future or investigational therapies|Future or Investigational Therapies]] |
|
| |
|
| === Acute Pharmacotherapies === | | ==Case Studies== |
| * Pharmacologic interventions (Atropine, Isoproterenol, Theophylline)
| |
|
| |
|
| == Surgery and Device Based Therapy ==
| | [[Atrioventricular block case study one|Case #1]] |
| * Temporary Pacing
| |
| * Permant Pacing
| |
|
| |
|
| === Indications for Surgery and Device Based Therapy ===
| | {{WikiDoc Help Menu}} |
| '''Indications for Permanent Pacemaker in Acquired Atrioventricular Block in Adults (AHA, 1998)'''
| | {{WikiDoc Sources}} |
| <br>
| | [[CME Category::Cardiology]] |
| * ''Class I''
| |
| *:* Third-degree AV block plus:
| |
| *:*:* Symptoms related to bradycardia
| |
| *:*:* Arrhythmia or other condition requiring nodal blockers
| |
| *:*:* Asystole > 3 seconds (while awake), ventricular rate <40
| |
| *:*:* Neuromeuscular disease
| |
| *:* Second Degree AV block plus:
| |
| *:*:* Symptomatic Bradycardia
| |
| * ''Class II''
| |
| *:* Asymptomatic Third-degree AV Block with HR >40
| |
| *:* Asymptomatic Type II, second-degreee AV Block
| |
| *:* Asymptomatic Type I, second-degree AV Block (with wide complex)
| |
| * ''Class III''
| |
| *:* Asymptomatic Type I, second-degree AV block (with narrow complex)
| |
| | |
| ==ACC / AHA Guidelines- Recommendations for Acquired Atrioventricular Block in Adults (DO NOT EDIT) <ref name="Epstein"> Epstein AE, DiMarco JP, Ellenbogen KA, Estes NAM III, Freedman RA, Gettes LS, Gillinov AM, Gregoratos G, Hammill SC, Hayes DL, Hlatky MA, Newby LK, Page RL, Schoenfeld MH, Silka MJ, Stevenson LW, Sweeney MO. ACC/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices). Circulation. 2008; 117: 2820–2840. PMID 18483207 </ref>==
| |
| {{cquote| | |
| ===Class I===
| |
| 1. Permanent [[pacemaker]] implantation is indicated for [[third-degree AV block|third-degree]] and advanced [[second-degree AV block]] at any anatomic level associated with [[bradycardia]] with symptoms (including [[heart failure]]) or [[ventricular arrhythmias]] presumed to be due to [[AV block]]. ''(Level of Evidence: C)''
| |
| | |
| 2. Permanent [[pacemaker]] implantation is indicated for [[third-degree AV block|third-degree]] and advanced [[second-degree AV block]] at any anatomic level associated with [[arrhythmias]] and other medical conditions that require drug therapy that results in symptomatic [[bradycardia]]. ''(Level of Evidence: C)''
| |
| | |
| 3. Permanent [[pacemaker]] implantation is indicated for [[third-degree AV block|third-degree]] and advanced [[second-degree AV block]] at any anatomic level in awake, symptom-free patients in [[sinus rhythm]], with documented periods of asystole greater than or equal to 3.0 seconds86 or any escape rate less than 40 bpm, or with an escape rhythm that is below the [[AV node]]. ''(Level of Evidence: C)''
| |
| | |
| 4. Permanent [[pacemaker]] implantation is indicated for [[third-degree AV block|third-degree]] and advanced [[second-degree AV block]] at any anatomic level in awake, symptom-free patients with [[AF]] and [[bradycardia]] with 1 or more pauses of at least 5 seconds or longer. ''(Level of Evidence: C)''
| |
| | |
| 5. Permanent [[pacemaker]] implantation is indicated for [[third-degree AV block|third-degree]] and advanced [[second-degree AV block]] at any anatomic level after [[catheter ablation]] of the AV junction. ''(Level of Evidence: C)''
| |
| | |
| 6. Permanent [[pacemaker]] implantation is indicated for [[third-degree AV block|third-degree]] and advanced [[second-degree AV block]] at any anatomic level associated with postoperative [[AV block]] that is not expected to resolve after [[cardiac surgery]]. ''(Level of Evidence: C)''
| |
| | |
| 7. Permanent [[pacemaker]] implantation is indicated for [[third-degree AV block|third-degree]] and advanced [[second-degree AV block]] at any anatomic level associated with [[neuromuscular disease]]s with [[AV block]], such as [[myotonic muscular dystrophy]], [[Kearns-Sayre syndrome]], [[Erb dystrophy]] ([[limb-girdle muscular dystrophy]]), and [[peroneal muscular atrophy]], with or without symptoms. ''(Level of Evidence: B)''
| |
| | |
| 8. Permanent [[pacemaker]] implantation is indicated for [[second-degree AV block]] with associated symptomatic [[bradycardia]] regardless of type or site of block. ''(Level of Evidence: B)''
| |
| | |
| 9. Permanent [[pacemaker]] implantation is indicated for asymptomatic persistent [[third-degree AV block]] at any anatomic site with average awake ventricular rates of 40 bpm or faster if [[cardiomegaly]] or [[LV dysfunction]] is present or if the site of block is below the [[AV node]]. ''(Level of Evidence: B)''
| |
| | |
| 10. Permanent pacemaker implantation is indicated for [[second-degree AV block|second-]] or [[third-degree AV block]] during exercise in the absence of [[myocardial ischemia]]. ''(Level of Evidence: C)''
| |
| | |
| ===Class IIa===
| |
| 1. Permanent [[pacemaker]] implantation is reasonable for persistent [[third-degree AV block]] with an escape rate greater than 40 bpm in asymptomatic adult patients without [[cardiomegaly]]. ''(Level of Evidence: C)''
| |
| | |
| 2. Permanent [[pacemaker]] implantation is reasonable for asymptomatic [[second-degree AV block]] at intra- or infra-His levels found at electrophysiological study. ''(Level of Evidence: B)''
| |
| | |
| 3. Permanent [[pacemaker]] implantation is reasonable for [[first-degree AV block|first-]] or [[second-degree AV block]] with symptoms similar to those of [[pacemaker syndrome]] or hemodynamic compromise. ''(Level of Evidence: B)''
| |
| | |
| 4. Permanent [[pacemaker]] implantation is reasonable for asymptomatic type II [[second-degree AV block]] with a narrow QRS. When type II [[second-degree AV block]] occurs with a wide QRS, including isolated [[right bundle-branch block]], pacing becomes a Class I recommendation. (See Section 2.1.3, “Chronic Bifascicular Block.”) ''(Level of Evidence: B)''
| |
| | |
| ===Class IIb===
| |
| 1. Permanent [[pacemaker]] implantation may be considered for [[neuromuscular disease]]s such as [[myotonic muscular dystrophy]], [[Erb dystrophy]] ([[limb-girdle muscular dystrophy]]), and [[peroneal muscular atrophy]] with any degree of [[AV block]] (including [[first-degree AV block]]), with or without symptoms, because there may be unpredictable progression of AV conduction disease. ''(Level of Evidence: B)''
| |
| | |
| 2. Permanent [[pacemaker]] implantation may be considered for [[AV block]] in the setting of drug use and/or drug toxicity when the block is expected to recur even after the drug is withdrawn. ''(Level of Evidence: B)''
| |
| | |
| ===Class III===
| |
| 1. Permanent [[pacemaker]] implantation is not indicated for asymptomatic [[first-degree AV block]]. ''(Level of Evidence: B)'' (See Section 2.1.3, “Chronic Bifascicular Block.”)
| |
| | |
| 2. Permanent [[pacemaker]] implantation is not indicated for asymptomatic type I [[second-degree AV block]] at the supra-His ([[AV node]]) level or that which is not known to be intra- or infra-Hisian. ''(Level of Evidence: C)''
| |
| | |
| 3. Permanent [[pacemaker]] implantation is not indicated for [[AV block]] that is expected to resolve and is unlikely to recur (e.g., drug toxicity, [[Lyme disease]], or transient increases in vagal tone or during [[hypoxia]] in [[sleep apnea syndrome]] in the absence of symptoms). ''(Level of Evidence: B)''}}
| |
| | |
| ==Examples==
| |
| | |
| <div align="left">
| |
| <gallery heights="225" widths="225">
| |
| Image:LAE.jpg|First degree AV block is a misnomer in that every P wave is conducted to the ventricles, however, with a PR interval exceeding 200 msec. Prolonged PR conduction, a more appropriate classification for this conduction disturbance, may be the result of conduction delay within the atrium, AV node, bundle of His or bundle branches. Prolongation of the PR interval most often indicates AV nodal conduction delay.
| |
| Image:2to1AVBlock1.jpg|Two-to-one AV block can represent benign block within the AV node or disease of the His-Purkinje system. Certain electrocardiographic features and maneuvers can help in distinguishing where the location of block exists. A long PR interval with a narrow QRS suggests an intranodal block. A short PR interval with intraventricular conduction delay or bundle branch block suggests disease below the node. Responses to atropine, exercise and carotid sinus massage can be helpful in diagnosis. Atropine will improve AV nodal conduction but will worsen block within diseased His-Purkinje fibers. Exercise has a similar effect, improving conduction in cases where block exists only in the node, but worsening when block is subnodal. Alternatively, Carotid Sinus Massage will slow conduction when block occurs in the AV node, but will improve conduction in diseased His-Purkinje tissue by allowing for refractoriness to recover
| |
| </gallery>
| |
| </div>
| |
| | |
| ==Sources==
| |
| * The ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities <ref name="Epstein"> Epstein AE, DiMarco JP, Ellenbogen KA, Estes NAM III, Freedman RA, Gettes LS, Gillinov AM, Gregoratos G, Hammill SC, Hayes DL, Hlatky MA, Newby LK, Page RL, Schoenfeld MH, Silka MJ, Stevenson LW, Sweeney MO. ACC/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices). Circulation. 2008; 117: 2820–2840. PMID 18483207 </ref>
| |
| | |
| ==References==
| |
| {{Reflist|2}}
| |
|
| |
|
| [[Category:Cardiology]] | | [[Category:Cardiology]] |
| [[Category:Electrophysiology]] | | [[Category:Electrophysiology]] |
| [[Category:Emergency medicine]]
| |
| [[Category:Disease]] | | [[Category:Disease]] |
|
| |
| {{WikiDoc Help Menu}}
| |
| {{WikiDoc Sources}}
| |
