Measurement and spectral analysis of fibrillation in the normothermic and hypothermic myocardium

The amplitude of the fibrillation waveform transduced from the myocardium was found to decrease as the heart was cooled from 37°C to 8°C. The administration of potassium-rich cardioplegia to the hypothermic myocardium further reduced the fibrillation amplitude by a factor of 100 compared with the normothermic amplitude. A measurement system is presented which is capable of reliably monitoring fibrillation waveforms in the cold cardioplegia arrested myocardium. This measurement system is shown to be impervious to the omnipresent electrical and mechanical artefacts which normally mask low-level signals. Subjecting the fibrillation waveforms to spectral analysis revealed that only the fundamental and the first six harmonics of the waveform are of significance. The results and methodology provide a means of correlating the temperature of the myocardium and the concentration of the potassium in the perfused cardioplegia, with the presence or absence of electrical activity in the myocardial cells.