Human Ventricular Fibrillation During Global Ischemia and Reperfusion: Paradoxical Changes in Activation Rate and Wavefront Complexity
Background—Ischemic ventricular fibrillation (VF) 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. VF was induced by burst pacing. After 30 s, 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 containing 256 unipolar contact electrodes. Dominant frequencies (DF) were calculated using a fast Fourier transform with a moving window. The location of phase singularities (PS) and activation wavefronts were identified at 10 ms intervals. Pre ischemic (perfused) VF was maintained by a disorganised mix of large and small wavefronts. During global myocardial ischemia mean DF decreased from 6.4 Hz to 4.7 Hz at a rate of -0.011 ± 0.002 Hz s-1 (p<0.001) and then increased rapidly to 7.4 Hz within 30 seconds of reflow. In contrast, the average number of epicardial PS increased during ischemia from 7.7 to 9.7 at a rate of 0.013 ± 0.005 PS s-1 (p<0.01), and remained unchanged during reflow at 10.3. The number of wavefronts showed a similar time course to the number of PS.
Conclusions—In human VF, we found an increase in complexity of electrical activation patterns during global myocardial ischemia, and this is not reversed during reflow despite an increase in activation rate.
- Received December 2, 2010.
- Accepted June 22, 2011.
- Copyright © 2011, American Heart Association, Inc. All rights reserved. Unauthorized use prohibited