Single beat spectral variance (SBSV): a new method to investigate both constant and time-varying ventricular late potentials

Signal averaging (SA) extinguishes variable late potentials (LP). This might disclose important information for risk stratification of patients prone to ventricular tachycardia (VT). SBSV uses 2-dimensional fast Fourier transform (2D-FFT) to evaluate beat-to-beat variabilities. 2D-FFT shows the frequency contents in the first dimension and the beat-to-beat periodicity in the second dimension. A LP-index function allows the detection of constant and variable LPs. 85 patients (P) after myocardial infarction were investigated: 35 P with VT (group 1) and 50 P without VT (group 2). With SBSV 29/35 P (83%) revealed LP in group 1, 14 of 29 with marked Wenckebach periodicity, and only 5/50 P (10%) in group 2. In comparison, the Simson method after signal averaging detected LP in 18/35 P (51%) in group 1 and 9/50 P (18%) in group 2. Thus, SBSV demonstrated, that variable appearance of LP might be an explanation for negative results after signal averaging.