Utility of Conventional Electrocardiographic Criteria in Patients With Idiopathic Ventricular Tachycardia

Objectives: This study sought to determine the ability of conventional electrocardiographic (ECG) criteria to correctly differentiate idiopathic ventricular tachycardia (VT) from supraventricular tachycardia (SVT) with aberrancy.

Background: Previously reported VT ECG criteria were developed from cohorts of patients with structural heart disease and have not been applied to patients with idiopathic VT.

Methods: ECGs of 115 idiopathic VTs, 101 post-myocardial infarction (MI) VTs, and 111 wide QRS SVTs were analyzed using standard criteria. VT was diagnosed in patients when at least 1 criterion was met, SVT when no criteria were met, and indeterminate when there were conflicting criteria.

Results: Standard ECG criteria more frequently diagnosed VT in the post-MI group than the idiopathic group (95% vs. 82%, respectively; p < 0.01). Diagnosis in only 12 of the 111 SVT patients (11%) met the criteria for VT. All patients in the idiopathic VT group with right branch bundle block morphology who did not meet VT criteria demonstrated an rsR' pattern in V₁ (consistent with SVT). Among idiopathic VT patients, Purkinje-associated VT had the lowest sensitivity for correct VT diagnosis in 13 of 23 patients (57%), septal sites of origin were correctly diagnosed in only 56 of 76 patients (74%), whereas nonseptal sites had a high sensitivity in 35 of 35 patients (100%; p < 0.005).

Conclusions: Conventional ECG criteria have reduced sensitivity to distinguish VT from SVT with aberrancy in patients with idiopathic VT. This is most pronounced in VT originating from septal sites, particularly Purkinje sites and the septal outflow tract regions. Clinicians should be aware that application of conventional ECG criteria in idiopathic VT may underdiagnose VT.