A method and system for choosing suitable sites for catheter delivery ablative energy is provided that includes a catheter/ablation structure that is positioned on a potential ablation site on a heart. The catheter/ablation structure produces one or more electrograms recorded at the potential ablation site. A signal processing unit receives from the catheter/ablation structure the recorded one or more intercardiac electrograms from the potential ablation site and performing Fast Fourier Transform (FFT) on the recorded one or more intercardiac electrograms as so to produce one or more spectral power distributions of the potential ablation site. A display unit displays the one or more spectral power distributions so as to determine whether the potential RF ablation site exhibit necessary spectral properties for the delivery of the ablative energy. A ablative energy generator unit provides the ablative energy to the potential ablation site using the catheter/ablation structure.