Third 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]; Raviteja Guddeti, M.B.B.S. [3]
Overview
Many conditions can cause third degree heart block, but the most common cause is coronary ischemia. Progressive degeneration of the electrical conduction system of the heart can lead to third degree heart block. This may be preceded by first degree AV block, second degree AV block, bundle branch block, or bifascicular block. In addition, acute myocardial infarction may present with third degree AV block.
Third degree heart block may also be congenital and has been linked to the presence of lupus in the mother. It is thought that maternal antibodies may cross the placenta and attack the heart tissue during gestation. The cause of congenital third degree heart block in many patients is unknown.
Causes
Common Causes
- Acute ST elevation MI - Complete heart block occurs in 2.5% to 8% of patients.
- Inferior ST elevation MI: AV block is more common in patients with inferior MIs (1/3rd of patients).
- 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
- Sclerodegenerative disease of the bundle branches was 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 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
- Usually transient, disappears when the patient recovers
- Dilated cardiomyopathy results in various degrees of heart block are seen in 15% of patients
- HCM: 3% of patients with HCM will develop heart block
- Acute rheumatic fever: PR prolongation is a common (25 to 95% of cases) sign in patients with acute rheumatic fever
- 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
- Drugs
- Digoxin is one of the most common causes of reversible AV block
- 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
- Digoxin is one of the most common causes of reversible AV block
- 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 ASD[1], 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), Hypertension, Acute rheumatic fever, Dilated cardiomyopathy, HCM, Myocarditis, Noncampaction cardiomyopathy, Valvular heart disease, Transposition of the great vessels, ASDs, 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 (Oleandrin), Cholinesterase inhibitors, Quinidine,Procainamide |
| Ear Nose Throat | No underlying causes |
| Endocrine | Hypothyroidism |
| Environmental | No underlying causes |
| Gastroenterologic | Hemochromatosis |
| Genetic | No underlying causes |
| Hematologic | Multiple myeloma, Thalassemia major |
| Iatrogenic | No underlying causes |
| Infectious Disease | Acute rheumatic fever, Aspergillosis myocarditis, Chagas disease, Diphtheria, Lyme disease, Myocarditis, Varicella zoster infection |
| Musculoskeletal / Ortho | Ankylosing spondylitis, Muscular dystrophy (Becker muscular dystrophy, myotonic muscular dystrophy), Mitochondrial myopathy |
| Neurologic | No underlying causes |
| Nutritional / Metabolic | No underlying causes |
| Obstetric/Gynecologic | No underlying causes |
| Oncologic | Hodgkin disease, Multiple myeloma, Tumors |
| Opthalmologic | No underlying causes |
| Overdose / Toxicity | No underlying causes |
| Psychiatric | No underlying causes |
| Pulmonary | Sarcoidosis |
| Renal / Electrolyte | Hyperkalemia |
| Rheum / Immune / Allergy | Ankylosing spondylitis, Dermatomyositis, Reiter's syndrome, Relapsing polychondirtis, 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, Nail-patella syndrome |
Causes in Alphabetical Order
- Acute myocardial infarction (especially acute inferior MI)
- Acute rheumatic fever
- Amyloidosis
- Ankylosing spondylitis
- ASD
- Aspergillosis myocarditis
- AV nodal disease
- Beta-blockers
- Calcium channel blockers
- Cardiac glycosides (Oleandrin)
- Chagas disease
- Cholinesterase inhibitors
- Dermatomyositis
- Digitalis
- Dilated cardiomyopathy
- Diphtheria
- Ebstein's anomaly
- Endocardial cushion defect
- Enhanced vagal tone (for example in athletes)
- HCM
- Hemochromatosis
- Hodgkin disease
- Hyperkalemia
- Hypertension
- Hypothyroidism
- Lyme disease
- Multiple myeloma
- Muscular dystrophy (Becker muscular dystrophy, myotonic muscular dystrophy)
- Myocarditis
- Mitochondrial myopathy
- Nail-patella syndrome
- Noncampaction cardiomyopathy
- Normal variants
- Procainamide
- Quinidine
- Reiter's syndrome
- Relapsing polychondirtis
- Sarcoidosis
- Scleroderma
- SLE
- Tetralogy of Fallot
- Thalassemia major[2]
- Transposition of the great vessels
- Trauma[3]
- Varicella zoster infection
- Valvular heart disease
- VSD
References
- ↑ Chen Q, Cao H, Zhang GC; et al. (2012). "Atrioventricular block subsequent to intraoperative device closure atrial septal defect with transthoracic minimal invasion; a rare and serious complication". PLoS ONE. 7 (12): e52726. doi:10.1371/journal.pone.0052726. PMC 3532427. PMID 23285170.
- ↑ Maleki AR, Nikyar B, Hosseini SM (2012). "Third-Degree Heart Block in Thalassemia major: A Case Report". Iran J Pediatr. 22 (2): 260–4. PMC 3446065. PMID 23056897. Unknown parameter
|month=ignored (help) - ↑ Thakar S, Chandra P, Pednekar M, Kabalkin C, Shani J (2012). "Complete heart block following a blow on the chest by a soccer ball: a rare manifestation of commotio cordis". Ann Noninvasive Electrocardiol. 17 (3): 280–2. doi:10.1111/j.1542-474X.2012.00518.x. PMID 22816548. Unknown parameter
|month=ignored (help)