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First-Degree Atrioventricular Block

A V Block First Degree

In first-degree atrioventricular block, the time for electrical impulse conduction from the sinoatrial node to the ventricles is prolonged. On the electrocardiogram (ECG), this is revealed as lengthening of the PR interval. In the past, first-degree atrioventricular block was regarded a benign condition, but more recent studies show that it can be associated with increased risk of adverse events.


Presentation

For most patients, the diagnosis of first-degree atrioventricular block (AVB) is made by chance on an electrocardiogram (ECG or EKG) [1]. This is because in general, the condition is largely asymptomatic.

Nevertheless, a distinction has to be made based on the extent of PR lengthening. The normal values for the PR interval are between 120 and 200 msec. The definition of first-degree AVB is the lengthening of this period to values of longer than 200 msec [2]. The prolongation is characterized as “marked” if it is greater than 300 msec [3]. Marked first-degree AVB can cause lowered tolerance to exercise, and can have effects similar to those caused by the pacemaker syndrome [3] [4] [5]. Patients with symptomatic marked first-degree AVB should be treated with biventricular pacing [6].

The electrical signal from the sinoatrial node to the ventricles travels through a conduction system consisting of the atrioventricular (AV) node, the bundle of His, the bundle branches, and the Purkinje fibers. There are differences in symptoms depending upon where in this system the defect in conduction is located. Of the above structures, the AV node is the most frequent site of first-degree AVB, but more than one defect in the conduction system is often encountered [1] [7]. An additional defect in the His-Purkinje system is indicated on the ECG by a wide QRS complex.

Early studies on otherwise healthy individuals with first-degree AVB found no negative effects on health prognosis associated with the condition, and first-degree AVB was regarded as benign [8] [9]. Recent works on more diverse populations, including the Framingham Study [1] [3] [10], revealed that first-degree AVB is not a benign condition, but is associated with elevated risks of atrial fibrillation and mortality.

Heart Disease
  • Etiologies include normal physiologic variance, idiopathic bundle branch fibrosis, calcific valvular heart disease, ischemic heart disease, cardiomyopathies, infections resulting in myocarditis, drugs (especially type I antidysrhythmic medications), collagen[ncbi.nlm.nih.gov]
  • Apart from the exclusion of organic heart disease, detailed invasive investigation is not warranted.[ncbi.nlm.nih.gov]
  • Associated electrophysiologic abnormalities and site of delay were studied in 20 patients, aged 1.5 to 16.5 years, with congenital heart disease and first-degree atrioventricular (AV) block (PR interval above the 98th percentile for age and heart rate[ncbi.nlm.nih.gov]
  • However, the clinical significance of first-degree AVB has not been evaluated in patients with stable coronary heart disease.[ncbi.nlm.nih.gov]
  • Abstract The long-term prognosis of first-degree heart block in the absence of organic heart disease has not been clearly defined. We addressed this question in a 30-year longitudinal study of 3983 healthy men.[nejm.org]
Withdrawn
  • If either of these agents was withdrawn, normalization of the P-R interval was controlled by subsequent 12-lead ECG, and patients with secondary normalized P-R interval went in the group with “normal” P-R interval.[anesthesiology.pubs.asahq.org]

Workup

First-degree AVB is often observed by chance on an ECG as a lengthening of the PR interval. Imaging or laboratory tests are not usually indicated. For patients with episodes of syncope, or with ECG showing a wide QRS complex, His bundle ECG could be performed [11].

There are a number of possible underlying causes for first-degree AVB. These include heart disease, myocardial infarction, myocarditis, and AV node disease. Hypokalemia and hypomagnesemia can also cause first-degree AVB. Other conditions associated with first-degree AVB are infectious diseases, rheumatoid arthritis, systemic lupus erythematosus and scleroderma.

Drugs that tend to cause first-degree AVB are antiarrhythmics and cardiac glycosides, such as digoxin. Thus, administration of antiarrhythmics (calcium channel blockers, beta-blockers, and others) and digoxin to people with first-degree AVB requires careful consideration.

First-degree AVB may also occur during adenosine stress testing. This happens in about one tenth of patients tested, when those who already have first-degree AVB may temporarily develop a higher degree of block. These episodes are usually harmless [12].

Prolonged PR Interval
  • Standard 12-lead electrocardiogram showed an uncommon Marked First Degree Atrioventricular Block with an extremely prolonged PR interval of 0.56 s.[ncbi.nlm.nih.gov]
  • PR interval (E) .[bmcresnotes.biomedcentral.com]
  • Electrocardiogram findings of First Degree AV Block First degree AV Block with prolonged PR interval (0.52 sec).[en.my-ekg.com]
  • Prognostic significance of prolonged PR interval in the general population. Eur Heart J 2014;35:123-129.[ahcmedia.com]
  • PR interval or first-degree atrioventricular block. ( 19549974 ) Cheng S....Wang T.J. 2009 24 Reversal of first-degree atrioventricular block in Fabry disease. ( 19901148 ) Blum A....Khasin M. 2009 25 Outcomes in patients with prolonged PR interval or[malacards.org]

Treatment

  • Neither isradipine nor placebo treatment had a statistically significant treatment effect on the change from baseline in P-R interval, QRS duration, Q-T interval (uncorrected), or sinus heart rate at week 7 as measured by 12-lead ECG.[ncbi.nlm.nih.gov]
  • Administration of atropine produced transient disappearance of the block, which disappeared altogether after discontinuing ranitidine treatment.[ncbi.nlm.nih.gov]
  • In this study, six fetuses (8.5%) showed first-degree AVB, and fast normalization of heart function was achieved through maternal treatment with fluorinated steroids.[ncbi.nlm.nih.gov]
  • If there is a need for treatment of an unrelated condition, care should be taken not to introduce any medication that may slow AV conduction.[en.wikipedia.org]
  • Treatment consists of correction of the underlying disorder or discontinuation of the offending medication.[ncbi.nlm.nih.gov]

Prognosis

  • Prognosis [ edit ] Isolated first-degree heart block has no direct clinical consequences. There are no symptoms or signs associated with it. It was originally thought of as having a benign prognosis.[en.wikipedia.org]
  • This study was performed to elucidate long-term prognosis of first-degree AVB in patients with hypertension. We included 3816 patients (mean age, 61.0   10.6 years; men, 47.2%) with hypertension. We reviewed their ECGs and measured the PR interval.[ncbi.nlm.nih.gov]
  • Early studies on otherwise healthy individuals with first-degree AVB found no negative effects on health prognosis associated with the condition, and first-degree AVB was regarded as benign.[symptoma.com]
  • Prognosis Isolated first-degree heart block has no direct clinical consequences. There are no symptoms or signs associated with it. It was originally thought of as having a benign prognosis.[ipfs.io]
  • ., and colleagues examined the prognosis associated with first-degree AVB.[cardiobrief.org]

Etiology

  • Etiologies include normal physiologic variance, idiopathic bundle branch fibrosis, calcific valvular heart disease, ischemic heart disease, cardiomyopathies, infections resulting in myocarditis, drugs (especially type I antidysrhythmic medications), collagen[ncbi.nlm.nih.gov]
  • Block-Mobitz Type II , [[Second Degree Atrioventricular Block-Mobitz Type II]]) Third Degree Atrioventricular Block (Third Degree Heart Block, Complete Heart Block) (see Third Degree Atrioventricular Block , [[Third Degree Atrioventricular Block]]) Etiology[mdnxs.com]
  • Coronary artery disease has been etiologically linked to higher (second and third) degree AVB (37) .[electrophysiology.onlinejacc.org]
  • Etiology First-degree AV block Definition References: [3] [4] [5] Second-degree AV block Mobitz type I / Wenckebach Definition Symptoms/clinical findings Treatment Mobitz type II Definition Symptoms/clinical findings Treatment The second-degree AV block[amboss.com]
  • The etiology of complete heart-block. Br Med K 1963; 2:1149.[acls.com]

Epidemiology

  • : occurs in younger patients (may be hereditary) Physiology : progressive, fibrotic, sclerodegenerative disease of the conduction system Clinical : frequently associated with slow progression to complete heart block Lev’s Disease Epidemiology : occurs[mdnxs.com]
  • Google Scholar Perlman LV, Ostrander LD, Keller JB, Chiang BN: An epidemiologic study of first degree atrioventricular block in Ecumseh, Michigan. Chest. 1971, 59 (1): 40-46. 10.1378/chest.59.1.40.[bmcresnotes.biomedcentral.com]
  • An epidemiological study of PR interval duration in the 4,678 men and women in Tecumseh, Michigan, showed no increase in mortality amongst the 2% of the population with PR 220 ms during mean follow-up of 4 years (3) .[electrophysiology.onlinejacc.org]
Sex distribution
Age distribution

Pathophysiology

  • To describe the results of two recent prospective studies that may indicate how to monitor, diagnose, and treat fetuses with neonatal lupus manifesting with heart involvement and to summarize additional research reports regarding the pathophysiology and[ncbi.nlm.nih.gov]
  • Pathophysiology 1st degree heart block rarely shows any abnormalities of the ECG other than prolonged PR interval (i.e. no QRS widening, no absent QRS etc). This is a result of dysfunction, almost always, at the level of the AV-node.[dundeemedstudentnotes.wordpress.com]

Prevention

  • Prevention requires programming a shorter AV and PVARP that is feasible because retrograde conduction is rare in first-degree AV block patients.[ncbi.nlm.nih.gov]
  • Return from First degree AV block to Cardiac Rhythms Return from First degree AV block to Heart Disease and Prevention Home page[heart-disease-and-prevention.com]
  • Author Affiliations From the Departments of Medicine and Social and Preventive Medicine, University of Manitoba. Address reprint requests to Dr. Mymin at the University of Manitoba Follow-up Study, 770 Bannatyne Ave., Winnipeg, MB R3E 0W3, Canada.[nejm.org]
  • Outcomes in patients with prolonged PR interval or first-degree atrioventricular block. ( 19903913 ) Oh J....Kang S.M. 2009 26 Outcomes in patients with prolonged PR interval or first-degree atrioventricular block. ( 19903912 ) Doraiswamy V.A. 2009 27 Prevention[malacards.org]
  • The BioPace (Biventricular Pacing for Atrio-ventricular Block to Prevent Cardiac Desynchronization) study randomized patients with AVB and mean ejection fraction of 55% to CRT or right ventricular pacing (75) .[electrophysiology.onlinejacc.org]

References

Article

  1. Cheng S, Keyes MJ, Larson MG, et al. Long-term outcomes in individuals with prolonged PR interval or first-degree atrioventricular block. JAMA. 2009;301(24):2571-2577.
  2. John AD, Fleisher LA. Electrocardiography: the ECG. Anesthesiol Clin. 2006;24(4):697-715.
  3. Barold SS, Ilercil A, Leonelli F, Herweg B. First-degree atrioventricular block. Clinical manifestations, indications for pacing, pacemaker management & consequences during cardiac resynchronization. J Interv Card Electrophysiol. 2006;17(2):139-152.
  4. Epstein AE, DiMarco JP, Ellenbogen KA, et al. 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); American Association for Thoracic Surgery; Society of Thoracic Surgeons. ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities: 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) developed in collaboration with the American Association for Thoracic Surgery and Society of Thoracic Surgeons. J Am Coll Cardiol. 2008;51:e1-62.
  5. Dickstein K, Vardas PE, Auricchio A, Daubert JC, Linde C, McMurray J. 2010 focused update of ESC Guidelines on device therapy in heart failure: an update of the 2008 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure and the 2007 ESC guidelines for cardiac and resynchronization therapy. Developed with the special contribution of the Heart Failure Association and the European Heart Rhythm Association. Europace. 2010;12:1526-1536.
  6. Barold SS, Herweg B. Conventional and biventricular pacing in patients with first-degree atrioventricular block. Europace. 2012;14(10):1414-1419.
  7. Schwartzman D. Atrioventricular block and atrioventricular dissociation. In: Zipes D, Jalife J, eds. Cardiac Electrophysiology: From Cell to Bedside. 4th ed. Philadelphia, PA: Saunders. 2004;485–489.
  8. Mymin D, Mathewson FA, Tate RB, Manfreda J. The natural history of primary first-degree atrioventricular heart block. N Engl J Med. 1986;315(19):1183-1187.
  9. Erikssen J, Otterstad JE. Natural course of a prolonged PR interval and the relation between PR and incidence of coronary heart disease. A 7-year follow-up study of 1832 apparently healthy men aged 40–59 years. Clin Cardiol. 1984;7:6–13.
  10. Crisel RK, Farzaneh-Far R, Na B, Whooley MA. First-degree atrioventricular block is associated with heart failure and death in persons with stable coronary artery disease: data from the Heart and Soul Study. Eur Heart J. 2011;32(15):1875-1880.
  11. Haft JI. The His bundle electrogram. Circulation. 1973;47(4):897-911.
  12. Alkoutami GS, Reeves WC, Movahed A. The safety of adenosine pharmacologic stress testing in patients with first-degree atrioventricular block in the presence and absence of atrioventricular blocking medications. J Nucl Cardiol. 1999;6(5):495-497.

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Last updated: 2018-06-21 17:37