A Wolff in Sheep’s Clothing: ECG Predictors of Ventricular Pre-excitation in Patients with Subtle Findings

Background: Patients with abnormal ECGs concerning for ventricular pre-excitation (VPE) necessitate testing to formally diagnose VPE. These patients may undergo a number of minimally invasive test to diagnose the presence of an accessory pathway (AP). The purpose of this study was to determine if any findings present on the resting 12 lead ECG in patients with subtle VPE (sVPE) reliably predict the presence of VPE.

Methods: An international, multicenter, retrospective review of patients with baseline ECG findings of sVPE. Inclusion criteria: Patients <21 years of age, baseline ECG and confirmatory testing. Exclusion criteria: Patients with incomplete demographics, lack of a baseline ECG or confirmatory testing. Patient demographics, all ECG measurements (PR interval, QRS duration, presence or absence of δ-waves ECGs and abnormal T-waves) were reviewed and confirmatory testing analyzed.

Results: We identified 78 patients of which 24 (31%) were identified as having VPE (Group I), 54 (69%) did not (Group II). No differences were noted between Group I and Group II in regards to sex, age, race, PR duration, QRS axis or presence/absence of Q-waves existed. Significant differences were noted between Group I and Group II in regards to multiple δ-waves on the ECG (ƿ < 0.001) with ≥ 7 δ-waves having a sensitivity 0.83, specificity 0.65, NPV 0.9 and PPV 0.51. A δ-wave in aVL was found more often in Group I when compared to Group II ƿ < 0.001, sensitivity 0.83, specificity 0.78, NPV 0.91 and PPV 0.63. The QRS duration > normative for age also predicted the presence of VPE when comparisons were made between Group I and Group II (ƿ < 0.05).

Conclusion: Semi-reliable predictors of VPE from abnormal ECGs include 1. ≥7 δ-waves, 2. Presence of δ-wave in lead aVL and 3. Prolonged QRS for age. Reviewing abnormal ECGs for signs of sVPE did not yield significant findings capable of reliable ECG screening, thus necessitating further diagnostic testing.