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| AVB | |
|---|---|
| Name | AVB |
| Specialty | Cardiology |
AVB
AVB is a cardiac conduction disorder characterized by impaired electrical conduction between the atria and ventricles. It is recognized in clinical cardiology, electrophysiology, and internal medicine settings and is associated with a spectrum of presentations from asymptomatic conduction delay to syncope and sudden cardiac events. AVB is relevant to practitioners in cardiology, emergency medicine, and geriatrics and intersects with device therapy, infectious disease, and pharmacology.
Atrioventricular block (AVB) denotes pathological impairment of electrical impulse propagation through the atrioventricular nodal region, His bundle, or distal conduction system. Descriptions appear in guidelines from American College of Cardiology, European Society of Cardiology, and American Heart Association as grades of conduction delay with prognostic implications. Historical milestones in understanding conduction block include work by Sunao Tawara on the atrioventricular node, mapping studies by Waldo Lyon and techniques for intracardiac recording developed by Moe and Lewis; device therapy milestones involve innovators like Paul Zoll and Rune Elmqvist.
AVB is classified by degree and site of block. First-degree AVB shows PR prolongation due to delayed conduction at the atrioventricular node or His bundle; second-degree AVB subdivides into Mobitz type I (Wenckebach) often localized to the node and Mobitz type II often involving the His-Purkinje system; third-degree AVB (complete heart block) denotes complete atrioventricular dissociation. Contemporary classification references include consensus statements from Heart Rhythm Society and diagnostic frameworks used in World Health Organization clinical manuals. Electrophysiology mapping differentiates nodal versus infranodal block using techniques pioneered at centers like Mayo Clinic and Cleveland Clinic.
Etiologies of AVB encompass ischemic, inflammatory, degenerative, iatrogenic, and congenital causes. Ischemic causes relate to events such as Myocardial infarction affecting the conduction blood supply; inflammatory causes include infections like Lyme disease, rheumatic processes associated with Rheumatic fever, and myocarditis associated with viruses studied by groups at Johns Hopkins Hospital and Mount Sinai Hospital. Degenerative conduction disease correlates with aging and fibrosis described in pathological series from Massachusetts General Hospital and cohorts from Framingham Heart Study. Iatrogenic causes include postoperative injury after procedures at centers like Cleveland Clinic Foundation and drug-induced block from agents reviewed by Food and Drug Administration safety advisories. Congenital AVB appears in association with maternal autoantibodies in collations analyzed at National Institutes of Health and in genetic syndromes identified by laboratories at Broad Institute.
Clinical features range from asymptomatic ECG findings to syncope, presyncope, fatigue, and signs of low cardiac output described in emergency department series from Mount Sinai Hospital and Royal Infirmary of Edinburgh. Diagnostic evaluation relies on surface electrocardiography, ambulatory monitoring like Holter devices developed by companies linked to Medtronic, and invasive electrophysiological studies performed in tertiary centers such as Karolinska University Hospital. Imaging with echocardiography at institutions like Cleveland Clinic and cardiac magnetic resonance at Mayo Clinic assess structural disease. Laboratory testing for reversible causes includes serology for Borrelia burgdorferi in endemic areas and autoimmune screens informed by work at NIH. Guidelines from European Society of Cardiology and practice statements from American College of Cardiology inform diagnostic thresholds and indications for interventions.
Acute management of high-degree AVB involves temporary pacing measures used in critical care units at Johns Hopkins Hospital and pharmacologic support with agents referenced in Merck Manual and European Resuscitation Council protocols. Long-term therapy centers on permanent pacemaker implantation pioneered in clinical programs at Guy's Hospital and St. Thomas' Hospital and advanced pacing strategies including biventricular pacing developed in trials conducted at Duke University Medical Center and Imperial College London. Device selection, programming, and follow-up practices follow recommendations from Heart Rhythm Society and manufacturers such as Medtronic and Boston Scientific. When reversible causes are identified, targeted therapy—antibiotic therapy for Lyme disease per infectious disease guidelines from Infectious Diseases Society of America or immunomodulation for autoimmune-mediated block per rheumatology centers—may restore conduction.
Prognosis depends on degree, site, etiology, and comorbid conditions documented in cohort studies from Framingham Heart Study and multicenter registries coordinated by National Cardiovascular Data Registry. Third-degree AVB without pacing carries risk of syncope, heart failure, and mortality; pacemaker therapy markedly reduces adverse outcomes in randomized trials such as those conducted at Duke University Medical Center and multicenter studies collated by Cochrane Collaboration. Complications of therapy include device-related infection, lead displacement, and pacing-induced cardiomyopathy discussed in reviews from European Heart Journal and device registries at US Food and Drug Administration.
Epidemiological data derive from population studies like Framingham Heart Study, national registries maintained by Centers for Disease Control and Prevention, and administrative databases from National Health Service systems. Incidence and prevalence increase with age and with prevalence of ischemic heart disease, conduction system fibrosis, and post-operative cardiac procedures tracked in datasets from Organisation for Economic Co-operation and Development. Health system impacts include resource utilization for device implantation and follow-up managed by tertiary centers such as Mayo Clinic and cost analyses performed by Institute for Clinical and Economic Review. Preventive strategies focus on managing ischemic heart disease and infectious risks emphasized by World Health Organization and public health agencies.
Category:Cardiac arrhythmias