Hi I'm working on a project which takes up ECG signals and tries to evaluate the condition of the patient. For one particular disease (ventricular tachycardia) the ECG looks close to a sine wave. Hence, I find the predominant frequency in the signal. I shift the original signal now by half the time period (calculated from the predominant frequency). Adding the new and the old signal, must give me a value close to zero for this condition only. Problem is, I'm using FFT (512 samples) to determine the predominant frequency component. Is there any better way to find this since FFT eats up a lot of computing time.. Thanks! http://en.wikipedia.org/wiki/File:Lead_II_rhythm_ventricular_tachycardia_Vtach_VT.JPG ^Link for ventricular tachycardia.