Evaluation of baseline ECG in patients undergoing Oral Flecainide Challenge test for suspected Brugada Syndrome: An analysis of lead II

• Main Authors: Maneesh K. Rai, MD, DM, Mukund A. Prabhu, MD, DM, Jayaprakash Shenthar, MD, DM, FACC, Natarajan Kumaraswamy U, MD, DM, Ritesh Vekariya, MD, Padmanabh Kamath, MD, DM, Narasimha Pai, MD, DM, FACC, Ramanath L. Kamath, MD, DM, Vivek Pillai, MD, DM
• Format: Article
• Language: English
• Published: Elsevier 2017-07-01
• Series: Indian Pacing and Electrophysiology Journal
• Subjects: Brugada syndrome; Flecainide challenge; Electrocardiographic findings; Inferior leads; ST elevation
• Online Access: http://www.sciencedirect.com/science/article/pii/S0972629217300219
• ISSN: 0972-6292

Background and Objectives: We analyzed Lead II in patients undergoing an Oral Flecainide Challenge test (FCT), to identify any pointers that could predict a positive FCT and thereby help in recognition of latent BS. Methods: The following parameters in lead II were retrospectively analyzed from the pre-test ECG in 62 patients undergoing FCT for suspected BS: The presence or absence of S waves, S wave amplitude, duration and upslope duration; J point parameters- Early repolarization, QRS notch, and QRS Slur; ST segment parameters-lack of isoelectric ST segment, ST duration and QT interval. Results: 48 had positive FCT (Group-1) while 14 were negative for FCT(Group-2). Lack of an isoelectric ST segment (50% vs 14.29%, p = 0.018) and slurring of QRS (33.33% vs 0%, p = 0.014) was more common in Group-1 than Group-2. Group-1 had shorter ST segment duration (median 81.5 (IQR 64–103.5) vs 110 (IQR 90–132), p = 0.002) and shorter ST: QT ratio (median 0.28 (IQR 0.22–0.35) vs 0.23 (0.18–0.27), p = 0.007). QRS notch/depressed J point (87.5%), QRS slur (100%), and lack of isoelectric ST segment (92.31%) had high sensitivity for predicting an inducible Type 1 Brugada pattern. Combining two parameters- ST: QT ratio<0.24 and lack of isoelectric ST segment-considerably improved the specificity (73.3%), and the positive predictive value of the test to 76%. The results remained accurate when validated in a small prospective cohort. Conclusion: Shortened ST segment in Lead II, lack of isoelectric ST segment, slurred QRS and ST/QT ratio <0.24 are predictive of underlying Brugada pattern in baseline ECG.