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1 University of Toronto, Canada
2 University of Toronto, Canada; Medicine/Cardiology, University Health Network, Toronto, Canada
3 University of Toronto, Canada; Medicine, University of Toronto, Toronto, Canada
4 Medicine, University of Toronto, Toronto, Canada
* To whom correspondence should be addressed. E-mail: k.nanthakumar{at}uhn.on.ca.
Ventricular fibrillation (VF) is an important cause of sudden cardiac death and cardiovascular mortality in patients with cardiomyopathy. Though it was generally believed that chaotic re-entrant wavefronts underlie VF in humans, there is emerging evidence of spatio-temporal organization during early VF. The mechanism of this organization of electrical activity in early VF is unknown in myopathic hearts. We studied early VF in-vivo, intra-operatively in five cardiomyopathic patients. Simultaneous electrograms were obtained from the epicardium and endocardium in left ventricular cardiomyopathy and the endocardium in right ventricular myopathy. The Hilbert transform was used to derive phase of the electrograms. Rotors were identified by isolating phase singularity points. Rotors were present in all of the myopathic hearts studied during VF, and cumulatively lasted a mean of 3.2±2.0 s of the 7.0±4.0 s of the VF segments analyzed. For each surface mapped 3.6±2.9 rotors were identified for the duration mapped. The average number of cycles completed by these rotors was 4.9±4.9. The longest rotor lasted 10.2±6.2 rotations and lasted 2.0±1.2 s. The rotors on the endocardium had a cycle length of 192±33 ms compared to 220±15 on the epicardium (p=0.08). There is centrifugal activation of electrical activity from these rotors and they give rise to domains that activate at faster rates with evidence of conduction block at the border with slower domains. These rotors frequently localized to border regions of myocardium with bipolar electrogram amplitude <0.5mV. The organization of electrical activity during early VF in myopathic human hearts is characterized by wavefronts emanating from a few rotors.
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