Electrical Alternans of the ST Segment in Non‐PrinzmetaPs Angina

Demidowich, George; Werres, Roland; Rothfeld, D; Becker, Julie

doi:10.1111/j.1540-8159.1980.tb05579.x

Cited by 11 publications

(2 citation statements)

References 7 publications

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“…The mechanism of ST segment and T-wave alternans is unclear. ST-T alternans on surface ECG has been associated with vasospastic angina [3,4], classical angina [ 5 ] , exercise testing [ 6 ] , and acute myocardial infarction [7]. Surawicz and Fisch [8] reported that this phenomenon is the failure of an ischemic area to depolarize on alternate beats because of variations in conduction and refractoriness between the ischemic and nonischemic areas.…”

Section: Discussionmentioning

confidence: 99%

Intracoronary ST‐T alternans during coronary balloon angioplasty

Kwan

Feit

Chadow

et al. 1995

Cathet. Cardiovasc. Diagn.

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To evaluate the presence and clinical significance of electrical alternans during PTCA, intracoronary electrocardiography (ic-ECG) was performed in 65 consecutive lesions. ST-T alternans, defined as a beat-to-beat difference in the ST elevation > or = 1 mm, was present in five lesions (7.7%), all in the proximal left anterior descending (LAD) coronary artery. The phenomenon was seen only after 130 sec (mean 174 +/- 57) of balloon inflation. Only two of the five showed ST-T alternans simultaneously on both surface and ic-ECG. One of five patients had premature ventricular contractions following ST-T alternans. Three of these five lesions required a second balloon inflation with duration of > or = 300 sec; there was no ST-T alternans on the second inflation in any of these lesions. We conclude: (1) the detection of ST-T alternans during PTCA is enhanced by use of ic-ECG, (2) electrical alternans during PTCA was seen only in proximal LAD lesions, implicating a large amount of ischemic myocardium as a requisite for the phenomenon, (3) electrical alternans is not immediate, requiring a certain duration of balloon occlusion and hence ischemia to occur, and (4) the absence of ST-T alternans during second balloon inflations suggests ischemic preconditioning may abolish this phenomenon.

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Section: Discussionmentioning

confidence: 99%

Intracoronary ST‐T alternans during coronary balloon angioplasty

Kwan

Feit

Chadow

et al. 1995

Cathet. Cardiovasc. Diagn.

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“…1,2 In particular, there is considerable clinical evidence that alternans is a frequent occurrence during episodes of acute myocardial ischemia. [2][3][4][5][6][7][8][9][10][11][12][13] There is also overwhelming experimental evidence for electrical alternans during ischemia. 5,6,9,12, The onset of alternans is very rapid, typically occurring within the first few minutes following coronary artery occlusion, and ventricular arrhythmias, including premature beats and ventricular tachycardia and fibrillation, often start soon after the onset of alternans.…”

Section: Introductionmentioning

confidence: 99%

Alternans and higher-order rhythms in an ionic model of a sheet of ischemic ventricular muscle

Arce

González

et al. 2000

Chaos: An Interdisciplinary Journal of Nonlinear Science

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Life-threatening arrhythmias such as ventricular tachycardia and fibrillation often occur during acute myocardial ischemia. During the first few minutes following coronary occlusion, there is a gradual rise in the extracellular concentration of potassium ions ([K(+)](0)) within ischemic tissue. This elevation of [K(+)](0) is one of the main causes of the electrophysiological changes produced by ischemia, and has been implicated in inducing arrhythmias. We investigate an ionic model of a 3 cmx3 cm sheet of normal ventricular myocardium containing an ischemic zone, simulated by elevating [K(+)](0) within a centrally-placed 1 cmx1 cm area of the sheet. As [K(+)](0) is gradually raised within the ischemic zone from the normal value of 5.4 mM, conduction first slows within the ischemic zone and then, at higher [K(+)](0), an arc of block develops within that area. The area distal to the arc of block is activated in a delayed fashion by a retrogradely moving wavefront originating from the distal edge of the ischemic zone. With a further increase in [K(+)](0), the point eventually comes where a very small increase in [K(+)](0) (0.01 mM) results in the abrupt transition from a global period-1 rhythm to a global period-2 rhythm in the sheet. In the peripheral part of the ischemic zone and in the normal area surrounding it, there is an alternation of action potential duration, producing a 2:2 response. Within the core of the ischemic zone, there is an alternation between an action potential and a maintained small-amplitude response ( approximately 30 mV in height). With a further increase of [K(+)](0), the maintained small-amplitude response turns into a decrementing subthreshold response, so that there is 2:1 block in the central part of the ischemic zone. A still further increase of [K(+)](0) leads to a transition in the sheet from a global period-2 to a period-4 rhythm, and then to period-6 and period-8 rhythms, and finally to a complete block of propagation within the ischemic core. When the size of the sheet is increased to 4 cmx4 cm (with a 2 cmx2 cm ischemic area), one observes essentially the same sequence of rhythms, except that the period-6 rhythm is not seen. Very similar sequences of rhythms are seen as [K(+)](0) is increased in the central region (1 or 2 cm long) of a thin strand of tissue (3 or 4 cm long) in which propagation is essentially one-dimensional and in which retrograde propagation does not occur. While reentrant rhythms resembling tachycardia and fibrillation were not encountered in the above simulations, well-known precursors to such rhythms (e.g., delayed activation, arcs of block, two-component upstrokes, retrograde activation, nascent spiral tips, alternans) were seen. We outline how additional modifications to the ischemic model might result in the emergence of reentrant rhythms following alternans. (c) 2000 American Institute of Physics.

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Exercise-induced ST segment alternans

Ring

Fenster

1986

American Heart Journal

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Electrical Alternans of the ST Segment in Non‐PrinzmetaPs Angina

Cited by 11 publications

References 7 publications

Intracoronary ST‐T alternans during coronary balloon angioplasty

Intracoronary ST‐T alternans during coronary balloon angioplasty

Alternans and higher-order rhythms in an ionic model of a sheet of ischemic ventricular muscle

Exercise-induced ST segment alternans

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