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In supraventricular tachycardia, the QRS is narrow because the ventricles are depolarized over the normal specialized conduction tissues (light blue
region). Five possible arrhythmias are commonly encountered. First, in atrial fibrillation, multiple microreentrant circuits can lead to chaotic activation of the
atrium. Because impulses are reaching the AV node at irregular intervals, ventricular depolarization is irregular. Second, in atrial flutter, a macroreentrant
circuit, traveling up the interatrial septum and down the lateral walls, can activate the atria in a regular fashion at approximately 300 bpm. The AV node can
conduct only every other or every third beat, so that the ventricles are depolarized at 150 or 100 bpm. In AV nodal reentrant tachycardia, slow and fast
pathways exist in the region of the AV node and a microreentrant circuit can be formed. Fourth, in atrioventricular reentry, an abnormal connection
Source: Cardiovascular Disorders: Heart Disease, Pathophysiology of Disease: An Introduction to Clinical Medicine, 7e
between the atrium and ventricle exists so that a macroreentrant circuit can be formed with the AV node forming the slow pathway, and the abnormal
Citation:
Hammer
Pathophysiology
of Disease:
An Introduction
to atrial
Clinical
Medicine,
7e; 2013
Available
at: triggered activity,
atrioventricular
connection,
the GD,
fast McPhee
pathway.SJ.
Finally,
in atrial tachycardia
an abnormal
focus of
activity
as a result
of either
reentry,
http://mhmedical.com/
Accessed:
May
05,
2017
or abnormal automaticity can activate the atria in a regular fashion.
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