Principal component analysis of the QRS complex during diagnostic ajmaline test for suspected Brugada Syndrome

We used principal component analysis (PCA) of the QRS complex to assess depolarisation heterogeity during ajmaline test in 96 patients with suspected Brugada Syndrome (BS). PCA was performed on 15-lead ECGs (12 leads +V1, V2 and V3 from 3^rd intercostal space, V1h to V3h using a) V1, V2 and V3 (QRS-PCAstand), b) V1h, V2h and V3h (QRS-PCAhigh), and c) V1 to V3, V1h to V3h (QRS-PCAtotal). Among patients with positive tests (n=23), those with symptoms (n=6) had higher QRS-PCAhigh before (p=0.003) and during maximum drug effect (p=0.001) than those without symptoms (n=17). Following ajmaline, QRS-PCA decreased significantly in patients with negative (n=73) (p=0.00004), but not in those with positive tests (p=0.098). Symptomatic patients with non-diagnostic resting ECGs have increased depolarisation heterogeneity. PCA could detect depolarisation heterogeity and thus help the diagnosis and risk stratification of patients with BS.