Correct diagnosis of wide complex tachycardia (WCTs) can be challenging. With EMS providers' ever-expanding scope of practice, it is no longer safe to label any rhythm that is wide and fast as ventricular tachycardia (VT). Though many paramedic curricula do not address advanced cardiac dysrhythmias and treatments, several EMS departments have protocols that require advanced training in 12-lead ECG interpretation and treatment of specific cardiac dysrhythmias.

     With the introduction of new pharmacological interventions that target specific areas of the cardiac conduction system, it has become increasingly important for EMS providers to make an accurate interpretation of an ECG. Though most paramedics have no difficulty distinguishing VT from narrow complex supraventricular tachycardia (SVT), some might fall victim to the "wide + fast = VT" trap when looking at SVT with aberrant conduction. Although VT and SVT with aberrant conduction look similar, they vary greatly in terms of origin, pathophysiology and treatment. Mislabeling dysrhythmias can have severe consequences. Improper identification of VT could place a patient in grave danger by delaying indicated pharmacological and electrical interventions.

     A common aphorism among advanced practitioners is, "When in doubt whether a WCT is VT or SVT, treat patients as if they are experiencing VTs."1 This stems from a statistic showing that approximately 80% of all WCTs are VT.1 Though this aphorism is generally a good rule of thumb, it is also important to acknowledge that one in five WCTs is not VT and therefore requires different treatment regimens. One must possess the proper diagnostic tools and knowledge to decide whether a WCT is VT or SVT with aberrant conduction. EMS providers should be able to differentiate VT and SVT with aberrant conduction with confidence and a high degree of certainty. In order to understand the visual differences between VT and SVT with aberrant conduction, one must first understand the basic pathophysiology behind the two dysrhythmias.

Ventricular tachycardia

There are several types of VT caused by many different mechanisms.

     Polymorphic VTs, like torsade de pointes (TDP), have their own footprints that distinguish them from SVTs and are not pertinent to this particular article. Here we address the most common form of VT (monomorphic VT) and the means by which it may be distinguished from SVT with aberrancy.