Median Fibrillation Frequency in Cardiac Surgery

This study was designed (1) to investigate the effects of normothermic and hypothermic perfusion on the median frequency of the fibrillating myocardium, and (2) to elucidate whether frequency-guided countershock therapy improves countershock success during the reperfusion phase of cardiac surgery. Prospective, randomized study. University hospital cardiac surgery room. Thirty patients (first part of the study) and 38 patients (second part of the study) scheduled for elective coronary artery bypass surgery. During cardiopulmonary bypass, ventricular fibrillation (VF) was induced at a core body temperature of 34.1±0.2°C (normothermia) (n=15) or at a core body temperature of 29.8±0.2°C (hypothermia) (n=15). Using fast Fourier transformation of the ECG signal, median fibrillation frequency was recorded continuously for a period of 120 s. At the end of surgery, countershock was performed as soon as VF was recognized on the ECG monitor (X Hz group; n=19) or countershock was not performed until median fibrillation frequency had increased to the threshold of at least 5 Hz (5 Hz group; n=19). Median fibrillation frequency in the normothermic fibrillation group was statistically higher than in the hypothermic group. In the X Hz and 5 Hz countershock group, median fibrillation frequency before the first countershock attempt was 3.6±0.2 Hz and 5.4±0.1 Hz (p