The predictive value of ventricular fibrillation electrocardiogram signal frequency and amplitude variables in patients with out-of-hospital cardiac arrest

We evaluated ventricular fibrillation frequency and amplitude variables to predict successful countershock, defined as pulse-generating electrical act ivity. We also elucidated whether bystander cardiopulmonary resuscitation ( CPR) influences these electrocardiogram (ECG) variables. In 89 patients wit h out-of-hospital cardiac arrest, ECG recordings of 594 countershock attemp ts were collected and analyzed retrospectively. By using fast Fourier trans formation analysis of the ventricular fibrillation ECG signal in the freque ncy range 0.333-15 Hz (median [range]), median frequency, dominant frequenc y, spectral edge frequency, and amplitude were as follows: 4.4 (2.4-7.5) Hz , 4.0 (0.7-7.0) Hz, 7.7 (3.7-13.7) Hz, and 0.94 (0.24-1.95) mV, respectivel y, before successful countershock (n = 59). These values were 3.8 (0.8-7.7) Hz (P = 0.0002),3.0 (0.3-9.7) Hz (P < 0.0001), 7.3 (2.0-14.0) Hz (P < 0.05 ), and 0.53 (0.03-3.03) mV (P < 0.0001), respectively, before unsuccessful countershock (n = 535). In patients in whom bystander CPR was performed (n = 51), ventricular fibrillation frequency and amplitude before the first de fibrillation attempt were higher than in patients without bystander CPR (n = 38) (median frequency, 4.4 [2.4-7.5] vs 3.7 [1.8-5.3] Hz, P < 0.0001; dom inant frequency, 3.8 [0.9-7.7] vs 2.6 [0.8-5.9] Hz, P < 0.0001; spectral ed ge frequency, 8.4 [4.8-12.9] vs 7.2 [3.9-12.1]Hz, P < 0.05; amplitude, 0.79 [0.06-4.72] vs 0.67 [0.16-2.29] mV, P = 0.0647). Receiver operating charac teristic curves demonstrate that successful countershocks will be best disc riminated from unsuccessful countershocks by ventricular fibrillation ampli tude (3000-ms epoch). At 73% sensitivity, a specificity of 67% was obtained with this variable.