Electrical Alternation in Experimental Coronary Artery Occlusion.

Hellerstein, Herman K.; Liebow, Irving M.

doi:10.3181/00379727-70-16857

Cited by 13 publications

(14 citation statements)

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“…In contrast to concordant alternans, discordant alternans is a less studied phenomenon 13,27 in cardiac tissue where its mechanism is unknown. In the present study, we focused on the conditions necessary to produce dis- cordant alternans in spatially uniform tissue.…”

Section: Discussionmentioning

confidence: 99%

Mechanisms for Discordant Alternans

Watanabe

Fenton

Evans

et al. 2001

Cardiovasc electrophysiol

307

360

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Discordant Alternans Mechanism. Introduction: Discordant alternans has the potential to produce larger alternans of the ECG T wave than concordant alternans, but its mechanism is unknown. Methods and Results:We demonstrate by one-and two-dimensional simulation of action potential propagation models that discordant alternans can form spontaneously in spatially homogeneous tissue through one of two mechanisms, due to the interaction of conduction velocity and action potential duration restitution at high pacing frequencies or through the dispersion of diastolic interval produced by ectopic foci. In discordant alternans due to the rst mechanism, the boundaries marking regions of alternans with opposite phase arise far from the stimulus site, move toward the stimulus site, and stabilize. Dynamic splitting of action potential duration restitution curves due to electrotonic coupling plays a crucial role in this stability. Larger tissues and faster pacing rates are conducive to multiple boundaries, and inhomogeneities of tissue properties facilitate or inhibit formation of boundaries.Conclusion: Spatial inhomogeneities of electrical restitution properties are not required to produce discordant alternans.

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Section: Discussionmentioning

confidence: 99%

Mechanisms for Discordant Alternans

Watanabe

Fenton

Evans

et al. 2001

Cardiovasc electrophysiol

307

360

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“…Moreover it has been suggested that intracellular calcium increases during acute ischaemia, and that this is related to arrhythmia generation (Clusin, Buchbinder & Harrison, 1983). Mechanical alternans has been reported coupled with electrical alternans, and there is evidence for a link between 'odd type' alternans and both calcium entry and calcium cycling (Hellerstein & Liebow, 1950;Hirata et al 1980;Wohlfahrt, 1982;Hashimoto et al 1983;Bateman et al 1987). During steady electromechanical alternans the high force can be associated with the short action potential.…”

Section: Possible Mechanisms Of Ischaemic Alternansmentioning

confidence: 99%

“…J. LAB monophasic action potentials (Lab & Woollard, 1978) and the electrocardiogram (Hellerstein & Liebow, 1950;Hashimoto, Suzuki, Miyake & Nakashima, 1983;Carson et al 1986) has been noted to occur during ischaemia in the intact preparation.…”

Section: Electrical Restitution Curvesmentioning

confidence: 99%

Electrophysiological alternans and restitution during acute regional ischaemia in myocardium of anaesthetized pig.

Dilly

Lab

1988

The Journal of Physiology

129

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SUMMARY1. Alternate long and short action potential durations, or electrical alternans, has only been sporadically observed in ischaemic myocardium in situ. We systematically studied alternans in the latter to characterize the phenomenon, relate it to ventricular arrhythmia and suggest possible mechanisms.2. Sixteen Landrace pigs were anaesthetized (Azaperone, N20 and 02), ventilated and the hearts exposed. A branch of the left coronary artery was ligated. Left intraventricular and systemic pressures were monitored. Monophasic action potentials were recorded simultaneously with up to five suction electrodes in and around the proposed ischaemia area.3. A computer measured the duration of every action potential, at several phases of repolarization, throughout the first hour of ischaemia. This allowed the systematic study of the alternans. Measurements during defined stimulus protocols were also made for the construction of electrical restitution curves.4. Alternans was found in all recordings within the ischaemic area and in twothirds of those in the 'border' area. There was no alternans in non-ischaemic areas.5. The alternans, when action potential duration was plotted for every beat, appeared as an oscillation which was pleomorphic. It could be: (a) stable for hundreds of beats; (b) switched or triggered (by one extraneous beat having a different cycle length) between one stable state with high and one with low or absent alternans; (c) damped; (d) undamped to take a crescendo form, sometimes preceding ventricular fibrillation.6. The alternans in general showed an ill-defined peak incidence between about 200 to 1500 beats after the onset of ischaemia, and a clearer late peak at about 3000 beats. These periods occurred at about 2-7 min and 15-40 min, corresponding to socalled phase 1 A and 1 B arrhythmia respectively. Only the late peak was seen with triggered alternans.7. The electrical restitution curve for the action potential duration during ischaemia when compared with curves, constructed with data from non-ischaemic myocardium, showed a progressive depression in plateau, a reduction in magnitude and was flattened at I h. However, there was a reversal or reduction in decline at about 15-45 min.S. G. DILLY AND M. J. LAB 8. We propose that electrical alternans is a distinctive electrophysiological characteristic of ischaemic myocardium which may be causally related to ventricular arrhythmia and fibrillation, and that at least two mechanisms contribute to the alternans: (i) electrical restitution of the action potential and (ii) changes in intracellular calcium cycling.

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“…Development of the giant R wave in stationary epicardial "mat" electrodes positioned across the ischemic zone . The unipolar electrocardiograms were recorded simultaneously from 14 epicardial electrodes (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) with an inter-electrode distance of 1mm and also from a reference unipolar intra-left ventricular electrode (Ref.…”

Section: Baselinementioning

confidence: 99%