Wide complex tachycardia.

Abstract

Wide complex tachycardias present diagnostic challenges for emergency physicians. The history, physical examination, and ECG provide information required to arrive at the correct diagnosis. When a previous history of heart disease exists, VT should be suspected; however, no single clinical feature is sufficiently reliable for distinguishing VT from SVT. Patients with VT may tolerate their dysrhythmias for several hours and maintain hemodynamic stability. ECG analysis is the most useful process in differentiating SVT and VT. Characteristics suggestive of VT include evidence of AV dissociation, QRS duration of longer than 0.16 seconds, and QRS axis between -90 degrees +/- 180 degrees. Predictive QRS morphologic criteria also have been established for VT. A four-step approach to ECG analysis has been reported to accurately identify patients with VT, but prospective validation in an ED setting is lacking. The initial approach to treating patients with wide QRS tachycardias depends on hemodynamic stability. Until the identify of a dysrhythmia is certain, consider all patients to be suffering from VT. Unstable patients require immediate cardioversion. Acute treatment of stable patients includes lidocaine or procainamide. Adenosine is appropriate when wide QRS SVT is the diagnosis, and it also has been used as a diagnostic aid to identify dysrhythmias. Reports of complications with the use of adenosine as a diagnostic agent have not yet appeared but may occur after sufficient numbers of cases have accumulated. Magnesium sulfate may be useful in refractory cases of VT and torsades de pointes. Chronic treatment of patients prone to VT may include complex pharmacotherapy and AICDs. Development of new class III agents and enhancement of AICD technology may result in improved patient outcomes and the availability of more choices for emergent therapy of wide QRS tachycardias.