Cardiology In Critical Care

Arrhythmia Recognition

Junctional 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.

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