Human Ventricular Fibrillation During Global Ischemia and Reperfusion

Abstract

Background-Ischemic ventricular fibrillation in experimental models has been shown to progress through a series of stages. Progression of ischemic VF in the in vivo human heart has not been determined. Methods and Results-We studied 10 patients undergoing cardiac surgery. Ventricular fibrillation was induced by burst pacing.After 30 seconds, global myocardial ischemia was induced by aortic cross-clamp and maintained for 2.5 minutes, followed by coronary reflow. Epicardial activity was sampled (1 kHz) with a sock that contained 256 unipolar contact electrodes. Dominant frequencies were calculated with a fast Fourier transform with a moving window. The locations of phase singularities and activation wavefronts were identified at 10-ms intervals. Preischemic (perfused) ventricular fibrillation was maintained by a disorganized mix of large and small wavefronts. During global myocardial ischemia, mean dominant frequencies decreased from 6.4 to 4.7 Hz at a rate of Ϫ0.011Ϯ0.002 Hz s Ϫ1 (PϽ0.001) and then increased rapidly to 7.4 Hz within 30 seconds of reflow. In contrast, the average number of epicardial phase singularities increased during ischemia from 7.7 to 9.7 at a rate of 0.013Ϯ0.005 phase singularities per second (PϽ0.01) and remained unchanged during reflow, at 10.3. The number of wavefronts showed a similar time course to the number of phase singularities. Conclusions-In human ventricular fibrillation, we found an increase in complexity of electric activation patterns during global myocardial ischemia, and this was not reversed during reflow despite an increase in activation rate. (Circ Arrhythm Electrophysiol. 2011;4:684-691.)

Unraveling the Underlying Arrhythmia Mechanism in Persistent Atrial Fibrillation

“…To remove power line interference and low-frequency components, the atrial signals were then filtered with a fourth-order Butterworth band pass filter with passband from 1 to 30 Hz, applied in forward and reverse mode so as to minimize phase distortion. 7 The dominant frequency of the electrogram at each electrode was identified from signal spectra obtained using the Welch method. Briefly, the 10-second recordings were divided into 4 epochs, each overlapping the preceding epoch by half its length.…”

Effect of Global Cardiac Ischemia on Human Ventricular Fibrillation: Insights from a Multi-scale Mechanistic Model of the Human Heart

“…For this reason, experimental studies on human hearts are extremely important for understanding underlying mechanisms. Recently this gap has partially been filled by studies in isolated myopathic hearts [11], [12], and studies in the in-situ human heart [13].…”

Spatiotemporal Progression of Early Human Ventricular Fibrillation

“…Whether this scenario is applicable to all VF episodes and what other mechanisms may cause the increased stability of the spiral waves remains unclear. Of note, however, reports have suggested that zones of ischemia and scars might play a prominent role in the maintenance of VF (20–23). Furthermore, the reduced thickness of the RV has been hypothesized to permit only stable rotors whereas the thicker LV tissue tends to exhibit diverse activation patterns (24), consistent with these results.…”

“…Fourth, the ASI metric has not been validated beyond the scope of this study. Finally, VF is a dynamic condition in which electrophysiological properties such as dominant frequency (27), action potential duration, conduction velocity, and tissue ischemia continually progress (28). In this study, VF was terminated at 11±3 seconds for patient safety, and thus the results of this study may only be applicable in early VF.…”