AV Junctional tachycardia
Updated: September 22, 2006
Any tachyarrhythmia arising from the atria or the atrioventricular junction is a supraventricular tachycardia. The term supraventricular tachycardia is usually reserved for atrial tachycardias and arrhythmias arising from the region of the atrioventricular junction as a result of a re-entry mechanism (junctional tachycardias). Junctional tachycardias cause a narrow complex tachycardia.
Impulses originate in the AV junctional pacemaker at a rate 140-220/min and are conducted retrograde to the atria and antegrade to the ventricles. P waves are negative in L2 and positive in AVR and may closely precede, follow or coincide with normal QRS complexes. When P waves precede QRS complexes, the PR interval is less than 0.12 sec; when P waves follow QRS complexes, they appear as splinters deforming the ST segment; when P waves coincide with QRS complexes, they are not discernible. The paroxysmal form of tachycardia is characterized by a ventricular rate 140-220, sudden onset and offset and sudden termination or no change upon vagal stimulation; the nonparoxysmal form is characterized by a ventricular rate 100-140, gradual onset and gradual slowing or no change upon vagal stimulation.
In the US, Junctional rhythms are common in patients with sick sinus syndrome or in patients who have significant bradycardia that allows the AV nodal region to determine the heart rate. Incidence of paroxysmal supraventricular tachycardia is approximately 1-3 per 1000.
Junctional escape rhythms, which are common in younger and/or athletic individuals during periods of increased vagal tone (eg, sleep), occur equally in males and females.
Episodes of atrioventricular nodal re-entrant tachycardia may occur at any age. It commonly presents for the first time in childhood or adolescence, although it may appear at any age. Junctional rhythms during sleep are common in children and in athletic adults.
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