Can specific ECG markers identify a pharmacologically induced type 1 Brugada pattern? Insights from a large, single-center cohort.

Background: In patients with a type 2 or 3 Brugada pattern, the pharmacological (IC drugs) induction of a type 1 pattern confirms the diagnosis of Brugada syndrome.

Objective: To evaluate the value of various ECG markers in predicting IC drug test results.

Methods: We retrospectively analysed 443 consecutive patients referred to our Center (from January 2010 to December 2019) to undergo Ajmaline/Flecainide testing; all had a type 2 or 3 Brugada pattern or were relatives with Brugada syndrome. Clinical parameters and ECG markers (rV and SV duration and amplitude, QRSV/QRSV duration, V and V ST amplitude) were independently evaluated for their association to pharmacological test positivity, and a logistic regression model was applied.

Results: The drug test was positive in 151 (34%) patients. On multivariate logistic regression analysis, age > 45 years, female gender, HR >60 bpm, QRSV/QRSV duration >1 and non-isoelectric pattern in V were associated with a positive test. The percentage of patients who tested positive increased according to the presence of the above ECG markers (from 11.3% in the absence to 57.6% in the presence of both factors). During long-term follow-up, the clinical event rate was higher in patients with predictive ECG markers and very low in those without.

Conclusions: In our population we confirmed the ability of QRSV/QRSV duration >1 and of a non-isoelectric pattern in V to predict a pharmacologically induced type 1 Brugada pattern. Patients with neither of these ECG markers had a rather low event rate during follow-up.