[Ventricular tachycardia masquerading as supraventricular tachycardia]

Area of Science:

• Cardiology
• Electrophysiology

Background:

• Differentiating supraventricular tachycardia (SVT) with aberrancy from ventricular tachycardia (VT) is clinically significant.
• Preexisting bundle branch block (BBB) often simplifies this differentiation; identical QRS morphology suggests SVT, while different morphology suggests VT.

Observation:

• Two cases of wide-complex tachycardia in patients with pre-existing BBB are presented.
• In both cases, the QRS morphology during tachycardia was nearly identical to the QRS morphology at rest.

Findings:

• Despite similar QRS morphology, findings such as atrioventricular dissociation and response to adenosine and lidocaine strongly indicated VT.
• These cases demonstrate VT masquerading as SVT due to identical QRS morphology in the context of BBB.

Implications:

• Identical QRS morphology during wide-complex tachycardia in BBB patients does not exclude VT.
• Careful evaluation for AV dissociation and response to specific medications is crucial to avoid misdiagnosis of VT as SVT.