Changes in autonomic activity and ventricular repolarization

Shusterman, Vladimir; Beigel, Anna; Shah, Syed Afaq Ali; Aysin, Benhur; Weiss, Raul; Gottipaty, Venkateshwar; Schwartzman, David; Anderson, Kelley P.

doi:10.1016/s0022-0736(99)90078-x

Cited by 19 publications

(13 citation statements)

References 18 publications

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“…Fiducial points, including the onset of the Q wave, the end of the S wave, and the beginning (T-onset), peak (T-peak), and end (T-end) of the T wave were identified as described elsewhere. 17 Data segments with uninterrupted streams of consecutive T waves were used for TWA analysis. The dynamics of TWA were examined with the use of 2 independent time-domain techniques: the intrabeat average (IBA) and the modified moving average (MMA) analyses (Figures 1 and 2).…”

Section: Repolarization Analysismentioning

confidence: 99%

Upsurge in T-Wave Alternans and Nonalternating Repolarization Instability Precedes Spontaneous Initiation of Ventricular Tachyarrhythmias in Humans

2006

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Background-Analysis of repolarization instability, manifested by T-wave alternans (TWA), has proved useful for arrhythmia risk assessment. However, temporal relations between TWA and the spontaneous initiation of ventricular tachyarrhythmias (VTA) in humans are unknown. We examined continuous dynamics of repolarization in Holter electrocardiograms with spontaneous sustained (Ͼ30 seconds) VTA. Methods and Results-Ambulatory electrocardiograms from 42 patients (79% with ischemic heart disease; left ventricular ejection fraction, 37Ϯ15%) were digitized, and the lead with the highest magnitude of the T wave was selected for analysis. TWA was examined by the modified moving average and intrabeat average analyses. To examine non-TWA (longer-period) oscillations in the repolarization segment, spectral energy of oscillations of consecutive T-wave amplitudes was calculated with the use of the short-time Fourier transform. Heart rate variability was assessed with the Fourier transform as well. TWA increased before the onset of VTA and reached a peak value of 23.6Ϯ11.7 V 10 minutes before the event (Pϭ0.0007). Spectral power of the oscillations of consecutive T-wave amplitudes increased nonuniformly, with the greatest increase in the respiratory range (2.6 V 2 ; Pϭ0.005). In the TWA range, the change was smaller but highly pronounced relative to the 60-to 120-minute level (65%; Pϭ0.003). The low-frequency and high-frequency heart rate variability power declined before the arrhythmia (Pϭ0.04 and Pϭ0.06, respectively). Conclusions-The magnitude of repolarization instability, manifested by TWA and beat-to-beat oscillations of T-wave amplitudes at other frequencies, increased before the onset of VTA. Tracking of these dynamics can facilitate timely detection of high-risk periods and may be useful for initiation of preventive treatments.

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Section: Repolarization Analysismentioning

confidence: 99%

Upsurge in T-Wave Alternans and Nonalternating Repolarization Instability Precedes Spontaneous Initiation of Ventricular Tachyarrhythmias in Humans

2006

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“…Because the data were collected using single-lead telemetry devices, analysis of the spatial distribution of these changes on the cardiac surface was not feasible. Nevertheless, it is important to note that a similar disparity between the patterns of changes in these repolarization indexes in response to the sympathetic stimulation has been observed in patients with structural heart disease compared with those without it (41).…”

Section: Min (Peak Effect) After the Injection Of Isoproterenolmentioning

confidence: 70%

“…Since the changes in repolarization are complex and highly variable among individual animals and no single parameter on the surface ECG can reliably represent the entire spectrum of repolarization changes (23), we used a set of several descriptors in addition to TWA, including the duration of the QT interval, mean T-wave amplitude, and T-wave area, as previously described (41).…”

Section: Methodsmentioning

confidence: 99%

“…Thus, the changes in the T wave amplitude and area observed in FVB mice could also be related to the alterations of the repolarization sequence induced by adrenergic stimulation and associated changes in CLs. In contrast, the lack of changes in these parameters in both humans with heart failure and TNF-␣ mice might reflect a diminished responsiveness to adrenergic stimulation due to the underlying exhaustion of repolarization reserve or chronically high levels of sympathetic activity accompanying the development of heart failure (37,41). Since these patterns of repolarization dynamics were similar in TNF-␣ mice compared with those observed in humans with chronic heart disease, our results provide further evidence of electrophysiological similarities between this genetic mouse model and the chronic heart failure phenotype in humans.…”

Section: Min (Peak Effect) After the Injection Of Isoproterenolmentioning

confidence: 99%

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Adrenergic stimulation promotes T-wave alternans and arrhythmia inducibility in a TNF-α genetic mouse model of congestive heart failure

Shusterman

McTiernan

Goldberg

et al. 2010

American Journal of Physiology-Heart and Circulatory Physiology

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T-wave alternans (TWA) is a proarrhythmic repolarization instability that is common in congestive heart failure (CHF). Although transgenic mice are commonly used to study the mechanisms of arrhythmogenesis in CHF, little is known about the dynamics of TWA in these species. We hypothesized that TWA is present in a TNF-alpha model of CHF and can be further promoted by adrenergic stimulation. We studied 16 TNF-alpha mice and 12 FVB controls using 1) in vivo intracardiac electrophysiological testing and 2) ambulatory telemetry during 30 min before and after an intraperitoneal injection of isoproterenol. TWA was examined using both linear and nonlinear filtering applied in the time domain. In addition, changes in the mean amplitude of the T wave and area under the T wave were computed. During intracardiac electrophysiological testing, none of the animals had TWA or inducible arrhythmias before the injection of isoproterenol. After the injection, sustained TWA and inducible ventricular tachyarrhythmias were observed in TNF-alpha mice but not in FVB mice. In ambulatory telemetry, before the isoproterenol injection, the cardiac cycle length (CL) was longer in TNF-alpha mice than in FVB mice (98 +/- 9 and 88 +/- 3 ms, P = 0.04). After the injection of isoproterenol, the CL became 8% and 6% shorter in TNF-alpha and FVB mice (P < 10(-4)); however, the 2% difference between the groups in the magnitude of CL changes was not significant. In TNF-alpha mice, the magnitude of TWA was 1.5-2 times greater than in FVB mice both before and after the isoproterenol injection. The magnitude of TWA increased significantly after the isoproterenol injection compared with the baseline in TNF-alpha mice (P = 0.003) but not in FVB mice. The mean amplitude of the T wave and area under the T wave increased 60% and 80% in FVB mice (P = 0.006 and 0.009) but not in TNF-alpha mice. In conclusion, TWA is present in a TNF-alpha model of CHF and can be further promoted by adrenergic stimulation, along with the enhanced susceptibility for ventricular arrhythmias.

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“…Linear, hybrid and nonlinear methods (MA, NARMAX and PP, respectively) show significant differences between normal and long QT interval, although they give us P LF /P HF and SD 12 ratios superior to 1 in both cases; this means the LF component was predominating in the rr and qt series, but its value is larger in the long QT interval than the normal case. Several authors [13,14] refer to the spectral components having a relationship with the autonomic nervous system, which directly influences the activity of the heart; this contracts automatically under the action of the node sinus, in fact it is connected to the nervous system autonomous (SNA) via sympathetic system corresponding to high frequencies (HF) (0.15-0.4 Hz) and via the parasympathetic system corresponding to the low frequency (LF) (0.04-0.15 Hz), whereas very low frequencies (VLF) (0.0033-0.04 Hz) were attributed to physical activity; this confirms that the sympathetic activities affect RR and QT intervals in the normal and long QT intervals cases. On the other hand, the ratio P LF /P HF has a similar repartition between the rr series and qt series in each case; which means that the intervals RR and QT change by the same rate.…”

Section: Discussionmentioning

confidence: 99%

Analysis of the QT-RR variability interactions using the NARMAX model

Baakek

Reguig

Slimane

2012

Journal of Medical Engineering & Technology

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In this paper a new approach is used in order to evaluate and quantify the interactions between the QT and RR intervals. This is achieved after the identification of the RR and QT series with a hybrid model (the non-linear autoregressive moving average with exogenous input (NARMAX)). This identification follows two steps: the first is a linear parametric identification corresponding to the MA model, whereas the second is a non-linear identification using the NARX model. The power spectral density PSD of RR and QT is computed by using the monovariate part of this model (MA model). The QT-related RR series is obtained by using the bivariate part corresponding to the NARX model and its PSD is determined by using the autoregressive method. Then a cross-spectral and the coherence function were determined in order to confirm the obtained results. Different heart pathology cases were selected to evaluate the approach: the normal case, the cases which represent long QT intervals and some other cases which represent short QT intervals. They were taken from the MIT BIH database. The results show that every case illustrates two frequencies; the first in the low frequency band LF and the second in the high frequency band HF. In the normal case and long QT interval cases, the LF was predominating in the QT, RR and in QT-related RR power spectral density PSD. In the short QT interval cases the HF was much larger in all cases. The obtained results were compared to the poincaré plot method which confirms it; however, the NARMAX model can distinguish between normal and pathologic cases with a great precision (p < 0.001). In addition, the QT variability index QTVI is computed and represented by a box plot which expresses the relationship between QT and RR intervals. The QTVI shows a large variability in the short QT interval cases, whereas it shows a small and a negative variability in the long QT interval case.

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Changes in autonomic activity and ventricular repolarization

Cited by 19 publications

References 18 publications

Upsurge in T-Wave Alternans and Nonalternating Repolarization Instability Precedes Spontaneous Initiation of Ventricular Tachyarrhythmias in Humans

Upsurge in T-Wave Alternans and Nonalternating Repolarization Instability Precedes Spontaneous Initiation of Ventricular Tachyarrhythmias in Humans

Adrenergic stimulation promotes T-wave alternans and arrhythmia inducibility in a TNF-α genetic mouse model of congestive heart failure

Analysis of the QT-RR variability interactions using the NARMAX model

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