T-wave alternans (TWA) is a cardiac phenomenon associated with the mechanisms leading to sudden cardiac death. In this work, we evaluate different source separation techniques for multilead detection of TWA in the electrocardiogram (ECG). Two periodicity-based techniques - periodic component analysis (πCA) and the newly proposed spectral ratio maximization (SRM) - are compared to two independence-based techniques - FastICA and JADE - and to principal component analysis (PCA). According to simulation results, the best detection performance is obtained with the periodicity-based schemes.