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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 beats/min. The AV
node can conduct only every other or every third beat, so that the ventricles are depolarized at 150 or 100 beats/min. 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
Source: Chapter 10. Cardiovascular Disorders: Heart Disease, Pathophysiology of Disease, 6e
connection between the atrium and ventricle exists so that a macroreentrant circuit can be formed with the AV node forming the slow pathway, and the
Citation: McPhee
SJ, Hammer
GD.pathway.
Pathophysiology
6e; 2010 Available
at: http://mhmedical.com/
Accessed:
Mayof02,
2017reentry,
abnormal atrioventricular
connection,
the fast
Finally, of
in Disease,
atrial tachycardia
an abnormal
focus of atrial activity
as a result
either
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triggered activity, or abnormal automaticity can activate the atria in a regular fashion.