Session S64.3

QRS&T Wave Alternans and Beat-to-Beat Ventricular Repolarization Variability Assessed from 12-Lead Holters in Patients with Suspected Brugada Syndrome

G Bortolan*, II Ivaylo, VN Batchvarov, ER Behr

Institute of Biomedical Engineering
Padova, Italy

Background: Microvolt 2:1 T wave alternans (TWA) and increased beat-to-beat repolarization variability have been reported in Brugada syndrome (BS) and could be related to increased arrhythmic risk. We hypothesized that among patients with suspected BS, those with positive diagnostic ajmaline test (i.e. likely carriers of BS genotype) have greater TWA or beat-to-beat repolarization variability on 24-hour Holter recordings that those with negative tests.
Methods: Ambulatory 24-hour 12-lead Holter recordings (1000 Hz, 5 µV resolution) were acquired in 14 patients with suspected BS and positive (n=7, 4 male, age 41±20 years) or negative (n=7, 3 male, age 29±16 years) ajmaline tests. In each patient, six 5-minute nighttime (10pm-6am) electrocardiograms (ECG) (42 ECGs in each group) were analyzed for a) 2:1 alternans of the QRS and T (QRS-WA, TWA) using a validated method based on amplitude and principal component analysis (PCA: ratio of 2nd to 1st eigenvalue) of the QRS and T waves (Computers in Cardiology Challenge 2008) and b) PCA variability measured as standard deviation of PCA of all QRS and T waves in leads V1, V2 and V3 (PCA-QRS_var and PCA-T_var). All parameters were calculated on the whole 5-min ECG (global indices) and on selected windows of 120 RR intervals (local indices).
Results: Regular QRS-WA was observed more frequently in patients with positive than in those with negative ajmaline tests (e.g. local QRS-WA: 15/42 (36%) vs 4/42 (9.5%) recordings, p=0.004, correlation coefficient R=0.27, p=0.013), whereas TWA was not significantly different between the 2 groups (16/42 (38.1%) vs 11/42 (26.2%), p=0.24). PCA-T_var was significantly higher in patients with positive compared to those with negative tests (0.032±0.048 vs 0.015±0.013, p=0.029).
Conclusions: Beat-to-beat repolarization variability, but not 2:1 TWA is increased in patients with positive ajmaline tests which suggest that in BS repolarization variability occurs more commonly in a non 2:1 (irregular) pattern. Regular QRS alternans is increased in patients with positive ajmaline tests. These results can help to improve the diagnosis of BS.

(Abstract Control Number: 6)