Management/Diagnostic Testing of Tachycardia The gold standard for arrhythmia diagnosis is a 12- or 15-lead EKG Using the EKG, the rhythm may be classified into narrow or wide, and regular or irregular The mechanism can be discerned from the rate and the P wave relationship to the QRS Extremely regular tachycardia suggests a re-entrant circuit as the mechanism Any irregularity of the rate or rhythm may reveal the mechanism of the arrhythmia and therefore these irregularities should be recorded on an EKG for scrutiny after the patient is stabilized When a patient presents to the ED with tachycardia a standard approach should be taken First, determine if the patient is stable or unstable An unstable patient should rapidly be prepared for cardioversion or defibrillation according to Pediatric Advanced Life Support (PALS) guidelines A simple rhythm strip should be recorded through the external defibrillator If the patient is pulseless, high-quality CPR should be initiated, airway and IV access should be secured Unstable nonsinus tachycardia should be cardioverted or defibrillated Synchronization should be employed in all rhythms except ventricular fibrillation (VF) to prevent the shock from being delivered at a vulnerable time on the T wave, potentially inducing VF If tachycardia persists, the shock should be repeated with higher energy according to PALS guidelines (see Chapter Cardiopulmonary Resuscitation ) After delivery of the shock, CPR should resume immediately One provider should check the rhythm strip while another team member re-assesses the patient If the rhythm has converted to normal sinus rhythm and the patient is stable, obtain an EKG, and assess for CHF The patient should constantly be monitored for any deterioration in condition or change in rhythm Inotropes are arrhythmogenic, so if necessary they should be initiated with care Consult cardiology and admit to an intensive care unit skilled in care of dysrhythmias If the patient is stable, obtain an EKG with long rhythm strip to determine whether the QRS is narrow or wide and whether the rhythm is regular or irregular That information drives subsequent actions Narrow Complex, Irregular Tachycardia An irregularly, irregular, narrow QRS rhythm, is almost always atrial fibrillation (or less commonly, atrial flutter/IART with variable conduction) These rhythms will respond to synchronized cardioversion (0.5 to J/kg), or medication for rate control Due to the risk of stroke, one should avoid cardioversion in a patient who has been in atrial fibrillation for 48 hours or more, or who is unable to tell when tachycardia started Either beta-blockers or calcium channel blockers may be used (but not in