PACS 87.19.Hh -Cardiac dynamics PACS 82.39.Rt -Reactions in complex biological systems PACS 05.10.-a -Computational methods in statistical physics and nonlinear dynamics Abstract -Ventricular fibrillations (VFs) in isolated hearts induced by fast pacing are studied in a Langendorff preparation by measuring the electrical signals from the right atrium (Va) and the ventricle (Vv). We find that when there is a strong component of Vv detected in Va during VF, the induced VFs are usually not self-terminating. Criteria for the prediction of self-terminating VFs are developed based on the analysis of Vv and Va by the cross-wavelet power spectrum and cross-Fourier power spectrum methods. The success rate of our prediction criteria is about 80-90%. Our findings suggest that a heart under VF can recover its sinus rhythm only when the sino-atrial node of the heart is not under strong influence of the VF from its ventricle.