Paroxysmal AV block
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Paroxysmal AV block Microchapters |
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Diagnosis |
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Paroxysmal AV block On the Web |
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American Roentgen Ray Society Images of Paroxysmal AV block |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Akash Daswaney, M.B.B.S[2]
Synonyms and keywords:
Overview
Historical Perspective
Historical Perspective | Famous cases
Classification
Pathophysiology
Intrinsic AV Block | Extrinsic Vagal AV Block | Extrinsic Idiopathic AV Block
Extrinsic Idiopathic AV Block
- The pathogenesis of extrinsic idiopathic paroxysmal AV block (EI-AVB) can be correlated to adenosine plasma levels (APL) and increased affinity of adenosine A1 receptors.
- There is a recurrent history of unexplained syncope, absence of ECG and cardiac abnormalities and a good prognosis.
- Due to innately low APL values seen in these patients, there is an upregulation of A1 receptors, such that even during a mild transient surge in endogenous adenosine levels, AV block occurs.
- A1 receptors, which are present more in the AV node than the SA node, impose an antiadrenergic action by antagonizing β1 receptors, the sympathetic nervous system, hyperpolarizing the SA and AV nodes through potassium channels and lowering intracellular cAMP levels. [1]
- Therefore, in such patients an injection of adenosine or adenosine triphosphate (ATP) may reproduce the attack and adenosine antagonists such as theophylline may be an efficacious treatment option.
- On an ECG, there is an absence of signs of vagal stimulation, atrial/ventricular premature beats and there may be a presence of narrow QRS complexes prior to the period of complete AV Block/ asystole
- Certain studies have also noticed genetic polymorphisms in A2A receptors in a population of people experiencing recurrent unexplained syncope.[2]
Causes
Differentiating Paroxysmal AV block from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Diagnosis
Initial Approach | History and Symptoms | Electrocardiogram, Holter Monitoring, External Loop Recorder | Implantable Loop Recorder | Electrophysiologic studies | Vagal Maneuvers,Carotid Sinus Massage and Tilt Table testing | Laboratory Findings and Stimulation tests | Diagnostic Summary Table |
Treatment
Cardiac Pacing |Treatment for Reflex Syncope|Theopylline |
Case Studies
- ↑ Brignole M, Deharo JC, Guieu R (2015). "Syncope and Idiopathic (Paroxysmal) AV Block". Cardiol Clin. 33 (3): 441–7. doi:10.1016/j.ccl.2015.04.012. PMID 26115830.
- ↑ Saadjian AY, Gerolami V, Giorgi R, Mercier L, Berge-Lefranc JL, Paganelli F; et al. (2009). "Head-up tilt induced syncope and adenosine A2A receptor gene polymorphism". Eur Heart J. 30 (12): 1510–5. doi:10.1093/eurheartj/ehp126. PMID 19386617.