Ventricular fibrillation was induced in eight of 10 open-chest dogs by reperfusion after a 15-minute occlusion of the proximal circumflex coronary artery. Simultaneous recordings were made from 27 epicardial electrodes spaced over both ventricles. Analysis of the initial 1.5--2.5 seconds of the transition from sinus rhythm or ventricular tachycardia to fibrillation revealed that ventricular activation occurred in an orderly, rapidly repeating sequence in all hearts. Each activation from arose near the border of the ischemic-reperfused region and passed across the nonischemic portion of the ventricles to the opposite side of the heart as a single, organized wavefront. As the arrhythmia progressed, the time between the appearance of successive activation fronts on the epicardium decreased. Concurrently, the time for each activation front to traverse the ventricles increased. The stimulation increase in rate of appearance and decrease in conduction velocity for each successive cycle resulted in overlapping cycles in which a new activation front arose from the ischemic-reperfused region before the previous front terminated over the right ventricle. The overlap between successive activation fronts increased as the arrhythmia continued. Thus, ventricular activation during the transition to ventricular fibrillation arose near the border of the ischemic-reperfused region and was organized as it passed across the nonischemic tissue, but the body surface ECG appeared disorganized because of variable spacing between successive, coexistent activation fronts.
The effect of digitalis in 21 patients with Wolff-Parkinson-White syndrome was anlayzed with respect to the ventricular response during atrial fibrillation and antegrade and retrograde refractory periods of accessory pathways. Digitalis shortened the cycle length of the most rapid ventricular response (shortest R-R) (i.e., increased the ventricle response) in 6/21 patients, increased the cycle length in 7/21 patients, had no effect on the cycle length in 5/21, and could not be determined in 3/21. Digitalis could be directly related to the onset of ventricle fibrillation resulting from atrial fibrillation in 9/21 patients. Each of these patients had shortest R-R intervals (220 msec or less) during atrial fibrillation in the control data. The results of this study indicate that no a priori prediction about the effect of digitalis on the antegrade conduction of accessory pathways can be made. By elective induction of atrial fibrillation it is possible to separate WPW patients into groups at high and low risk for developing ventricular fibrillation with the administration of digitalis.
(apo B) gene detected with the restriction enzyme EcoRl gives rise to two codominant apo B alleles, one with the EcoRl recognition site (E + ) and the other without it (E"). 1 The E + allele encodes glutamic acid (Glu) at residue 4,154 in apo B-100 (the protein component of low density lipoprotein [LDL]), while the E" allele encodes lysine (Lys) at this position. The EcoRl polymorphism in the apo B gene, which corresponds to the t/z polymorphism of the Ag system, 2 appears to be universally present in humans, with the E" allele occurring at a frequency of between 0.10 and 0.15 in most human populations (see Reference 3). We 4 and others 56 have shown that the frequency of the E" allele is significantly higher in men with coronary artery disease (CAD) than in healthy men from the same population.The major pathway for removal of LDL from the plasma is mediated by high-affinity binding of the apo From the MRC Lipoprotein Team,
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