A common feature in both VT and SVT a the occurrence of ventricular complexes with wide and large deflections, thereby masking the occurrence of the low amplitude P-waves. To identify the presente of atrio-ventricular (AV) dissociation, it becomes necessary to detect the P-waves. The work presented in this article focusses on the detection of the dissociated rhythm of P-waves based on the singular value ratio (SVR) spectrum of a residual signal constructed after subtracting the principal component from the original ECG record. The reliability of our method has been tested on 20 examples of wide QRS type arrhythmia waveforms and verified by comparing the reconstructed waveforms with the corresponding set of intra-atrial recordings.