The major differential diagnosis for VT is supraventricular tachycardia with a wide QRS complex due to aberrant conduction. Although VT may be slightly irregular, gross irregularities, such as those typically seen in atrial fibrillation, are uncommon during VT; such marked irregularities suggest atrial fibrillation. The QRS configuration is helpful in differentiating supraventricular tachycardia from VT. Supraventricular tachycardia with aberration generally produces QRS complexes that are less than 0.14 second in duration, whereas wider complexes are common in VT. The presence of an antiarrhythmic drug may, however, render this criterion unhelpful.
室性心动过速（VT）的主要鉴别诊断是伴有因差异性传导导致的宽QRS波群的室上性心动过速。虽然VT可能稍有不规则，但明显的不规则，如心房颤动中典型所见的那样，在VT时并不常见；这种明显的不规则提示心房颤动。QRS波形态有助于鉴别室上性心动过速和VT。伴有差异性传导的室上性心动过速通常产生时限小于0.14秒的QRS波群，而更宽的QRS波群在VT中很常见。然而，抗心律失常药物的存在可能使这一标准无法适用。
