Challenging Cases of Wide Complex Tachycardias: Use and Limits of Algorithms

Electrocardiographic algorithms are particularly useful to differentiate, in the presence of a wide complex tachycardia, between supraventricular aberrancy and ventricular tachycardias (VT). There are numerous limitations to the sensitivity and specificity of these algorithms including the presence of accessory pathways, use of antiarrhythmic drugs, congenital heart diseases, electrolytes impairments, and artificial pacing. Once the diagnosis of VT has been reached, other algorithms can help in localizing the origin of the ventricular arrhythmia. These approaches are also limited by the anatomic structure of where the arrhythmia originates. This article illustrates the difficulties in applying common algorithms in many clinical circumstances.