Isolated T wave alternans

Navarro-López, F; Cinca, Juan; Sanz, Ginés; Periz, Alberto; Magriñá, J; Betriu, Amadeo

doi:10.1016/0002-8703(78)90369-1

Cited by 54 publications

(7 citation statements)

References 13 publications

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“…13 There is limited evidence that vagus nerve stimulation can reduce TWA in humans, 30 but ours is the first study to evaluate the effects of selective parasympathetic blockade on TWA while simultaneously controlling for heart rate. We did not observe any effect of atropine on TWA, suggesting that tonic vagal activity does not exert an important influence on TWA among patients with ischemic heart disease and left ventricular dysfunction.…”

Section: Twa and The Parasympathetic Nervous Systemmentioning

confidence: 93%

Effects of Selective Autonomic Blockade on T-Wave Alternans in Humans

et al. 2002

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Background-T-wave alternans (TWA) is an important noninvasive measure of ventricular arrhythmia vulnerability. This study tested the hypothesis that the autonomic nervous system influences TWA measurement in high-risk subjects with coronary artery disease. Methods and Results-T-wave alternans was measured in 60 patients with coronary artery disease, left ventricular dysfunction, and inducible sustained ventricular tachycardia during electrophysiological studies. All patients had TWA measured at baseline with atrial pacing at 100 bpm (600 ms), 109 bpm (550 ms), and 120 bpm (500 ms). After a 10-minute recovery period, TWA was measured again after sympathetic blockade (esmolol, nϭ20), parasympathetic blockade (atropine, nϭ20), or no intervention (control subjects, nϭ20). The prevalence of significant TWA was unchanged compared with baseline after atropine infusion and in the control group. In contrast, the amplitude of TWA in the vector magnitude lead was significantly reduced after esmolol infusion (PϽ0.001), and the number of positive TWA tests was reduced by 50% (70% versus 35%, PϽ0.05). Conclusions-Our findings have important implications for the use of TWA to risk-stratify patients for life-threatening ventricular arrhythmias and provide a new potential mechanism for the reduction in sudden cardiac death conferred by ␤-blockers among patients with coronary artery disease and congestive heart failure.

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Section: Twa and The Parasympathetic Nervous Systemmentioning

confidence: 93%

Effects of Selective Autonomic Blockade on T-Wave Alternans in Humans

et al. 2002

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“…Sequential beat‐to‐beat changes in the morphology of the ST segment and T wave (electrical alternans) and in cardiac contraction (mechanical alternans) is a phenomenon that has been observed in several pathological settings (cardiomyopathy, ischaemia, heart failure and atrial fibrillation; Navarro‐Lopez et al 1978 b ; Pastore et al 1999; Qu et al 2000; Hiromoto et al 2005), heralding the occurrence of atrial fibrillation (Hiromoto et al 2005; Gong et al 2007) and severe ventricular arrhythmias (Rosenbaum et al 1994; Kodama et al 2001; Shusterman et al 2006). Alternation in the amplitude and duration of the action potential is commonly the underlying mechanism of electrical alternans (Pastore et al 1999), and experimentally, alternation of the action potential can be induced by artificially increasing the heart rate (Cinca et al 1978; Narayan et al 2002; Hiromoto et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Sarcoplasmic reticulum and L‐type Ca²⁺ channel activity regulate the beat‐to‐beat stability of calcium handling in human atrial myocytes

Llach

Molina

Fernandes

et al. 2011

The Journal of Physiology

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Non-technical summary Cardiac arrhythmias occur when the heart is unable to beat rhythmically, and can be induced if the heart is forced to work in excess of its capacity. Here we examine how cells isolated from the atrial chamber of the human heart respond when their beating rate is increased. Our results show that there are differences in the ability of individual heart cells to respond rhythmically when they are forced to beat fast. Moreover, we find that mechanisms that regulate the level of calcium ions in the heart cells determine their ability to respond rhythmically. These results show that pharmacological control of calcium levels in heart cells might be useful in the treatment of people who suffer cardiac arrhythmias during excessive exercise.Abstract Irregularities in intracellular calcium on a beat-to-beat basis can precede cardiac arrhythmia, but the mechanisms inducing such irregularities remain elusive. This study tested the hypothesis that sarcoplasmic reticulum (SR) and L-type calcium channel activity determine the beat-to-beat response and its rate dependency. For this purpose, patch-clamp technique and confocal calcium imaging was used to record L-type calcium current (I Ca ) and visualize calcium in human atrial myocytes subjected to increasing stimulation frequencies (from 0.2 to 2 Hz). The beat-to-beat response was heterogeneous among a population of 133 myocytes, with 30 myocytes responding uniformly at all frequencies, while alternating and irregular responses were induced in 78 and 25 myocytes, respectively. Myocytes with uniform responses had the lowest frequency of calcium wave-induced transient inward currents (I TI ; 0.4 ± 0.2 min −1 ), I Ca density (1.8 ± 0.3 pA pF −1 ) and caffeine-releasable calcium load (6.2 ± 0.5 amol pF −1 ), while those with alternating responses had the highest I TI frequency (1.8 ± 0.3 min −1 , P = 0.003) and I Ca density (2.4 ± 0.2 pA pF −1 , P = 0.04). In contrast, the calcium load was highest in myocytes with irregular responses (8.5 ± 0.7 amol pF −1 , P = 0.01). Accordingly, partial I Ca inhibition reduced the incidence (from 78 to 44%, P < 0.05) and increased the threshold frequency for beat-to-beat alternation (from 1.3 ± 0.2 to 1.9 ± 0.2 Hz, P < 0.05). Partial inhibition of SR calcium release reduced the I TI frequency, increased calcium loading and favoured induction of irregular responses, while complete inhibition abolished beat-to-beat alternation at all frequencies. In conclusion, the beat-to-beat response was heterogeneous among human atrial myocytes subjected to increasing stimulation frequencies, and the nature and stability of the response were determined by the SR and L-type calcium channel activities, suggesting that these mechanisms are key to controlling cardiac beat-to-beat stability.

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“…, 1979;German6 er d . , 1980;Haiat el al., 1976;Johnson er al., 1982;MacAlpin, 1980a,b;Maseri et al, 1978;Navarro et al, 1978;Previtali et al, 1980;Schang and Pepine, 1977;Sellier et al, 1978;Selwyn et al, 1978;Stern et al, 1975). Furthermore, we can also exclude any influence of hyperkalemia or other electrolyte changes known to affect the electrocardiographic repolarization phase (Chawla et al, 1978) as our patients had normal serum values for potassium, sodium, chloride, and calcium.…”

Section: Discussionmentioning

confidence: 99%

Asymptomatic myocardial ischemia in patients with stable and typical angina pectoris

Cocco

Strozzi

Leishman

et al. 1982

Clinical Cardiology

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Summary:The existence of transient niyocardial ischemia (TMI) and the value of the serial dynamic electrocardiogram (DCG) in patients with variant or unstable angina pectoris are known. However, less information is available on the frequency and characteristics of TMI in patients with stable angina pectoris. For this study, we selected 40 patients with stable and typical angina pectoris. The presence of coronary artery disease and the ejection fraction were evaluated by means of angiocardiography. The DCG monitoring was performed with bichannel portable recorders for three 24-h periods at 7-day intervals. The patients were on optimal doses of beta blockers and isosorbidilate throughout the study.We detected 788 episodes of TMI in 22 of the 40 patients. The ejection fraction was poorer in the 22 patients with ST-Tchanges than in the 18 without such changes. The repolarization changes were: ( I ) ST elevation (55 symptomatic and 87 asymptomatic episodes, (2) ST depression ( 1 38 symptomatic and 236 asymptomatic episodes. and (3) T-wave changes (83 symptomatic and 164 asymptomatic episodes). All 22 patients with TMI prcsented a combination of the above changes. It appears, therefore, that ST-T changes are more frequent in patients with stable angina pectoris than was hitherto suspected. The DCG is valuable in assessing these

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Isolated T wave alternans

Cited by 54 publications

References 13 publications

Effects of Selective Autonomic Blockade on T-Wave Alternans in Humans

Effects of Selective Autonomic Blockade on T-Wave Alternans in Humans

Sarcoplasmic reticulum and L‐type Ca²⁺ channel activity regulate the beat‐to‐beat stability of calcium handling in human atrial myocytes

Asymptomatic myocardial ischemia in patients with stable and typical angina pectoris

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Isolated T wave alternans

Cited by 54 publications

References 13 publications

Effects of Selective Autonomic Blockade on T-Wave Alternans in Humans

Effects of Selective Autonomic Blockade on T-Wave Alternans in Humans

Sarcoplasmic reticulum and L‐type Ca2+ channel activity regulate the beat‐to‐beat stability of calcium handling in human atrial myocytes

Asymptomatic myocardial ischemia in patients with stable and typical angina pectoris

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Sarcoplasmic reticulum and L‐type Ca²⁺ channel activity regulate the beat‐to‐beat stability of calcium handling in human atrial myocytes