- Trifascicular block
DiseaseDisorder infobox
Name = Trifascicular heart block
ICD10 = ICD10|I|45|3|i|30
ICD9 = ICD9|426.54Trifascicular block is a problem with the electrical conduction of the
heart . It is diagnosed on anelectrocardiogram (ECG/EKG) and has three features: [GPnotebook|1161101334]* prolongation of the (
first degree AV block )
*right bundle branch block
* eitherleft anterior fascicular block orleft posterior fascicular block Alternatively, trifascicular block is suggested by alternating
right bundle branch block andleft bundle branch block .Fact|date=August 2007Differential diagnosis
Trifascicular block is important to diagnose because it is difficult to tell based on the surface ECG whether the prolonged PR interval is due to disease in the AV node or due to diffuse distal conduction system disease.
* In the former case, if the block at the AV node level becomes complete, the escape rhythm will originate from the
bundle of His , which typically will generate heart rates in the 40s, allowing the individual to survive and complain of symptoms of fatigue or near-syncope to their physician.* In the latter case, however, because the conduction system disease is diffuse in nature, the escape rhythm may be fascicular or ventricular, which may be at rates that are life-threateningly low.
Diagnosis
The diagnosis of whether the PR prolongation is due to AV nodal disease or diffuse conduction system disease is typically made by an
electrophysiologic study of the conduction system. In an electrophysiologic study, trifascicular block due to AV nodal disease is represented by a prolonged AH interval (denoting prolonged time from impulse generation in the atria and conduction to thebundle of His ) with a relatively preserved HV interval (denoting normal conduction from the bundle of His to the ventricles). Trifascicular block due to distal conduction system disease is represented by a normal AH interval and a prolonged HV interval.Treatment
The treatment for diffuse distal conduction system disease is insertion of a pacemaker. If the PR prolongation is due to AV nodal disease, a case may be made for observation, as it may never progress to complete heart block with life threateningly low heart rates.
Regardless of where in the conduction system the block is, if the block is believed to be the cause of
syncope in an individual, a pacemaker is an appropriate treatment.References
External links
* http://library.med.utah.edu/kw/ecg/mml/ecg_0293_mod.html
* http://www.ecglibrary.com/trifas.htmlee also
*
Bifascicular block
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