CLINICAL APPROACH TO WIDE QRS COMPLEX TACHYCARDIAS

Wide QRS complex tachycardia is a frequently encountered arrhythmia in the emergency department (ED). Wide QRS complex tachycardia is define d as tachycardia having QRS duration of greater than 120 msec (0.12 se c)-the upper limit of normal QRS duration.(16) It is important to dete rmine whether the rhythm is ventricular tachycardia (VT), supraventric ular tachycardia (SVT) with aberrancy (usually functional right or lef t bundle branch block), or a preexcited tachycardia using an accessory atrioventricular pathway to activate the ventricles. The problem is n ot merely academic; an incorrect diagnosis can lead to inappropriate t herapy and potentially lethal consequences, especially when VT tachyca rdia is misdiagnosed as SVT.(8,52) Despite the availability of defined clinical and electrocardiographic criteria, the underlying rhythm is often misdiagnosed.(2,3,13,26,31,33,37,50,54,61,62,64) SVT generally c arries a good prognosis, whereas VT can be life threatening if not man aged properly. Physicians tend to underdiagnose VT, favoring a diagnos is of SVT with aberrancy when patients are hemodynamically stable.(11) Akhtar et al(15) found that clinicians diagnosed VT in only 32% of pa tients who presented with a wide QRS tachycardia, when in fact VT was much more common.