Age and QT variability index during free breathing, controlled breathing and tilt in patients with chronic heart failure and healthy control subjects

Piccirillo, Gianfranco; Magnanti, Marzia; Matera, Sabrina; Carlo, Silvia Di; Laurentis, Tiziana De; Torrini, A; Marchitto, Nicola; Ricci, Renato Pietro; Magrì, Damiano

doi:10.1016/j.trsl.2006.02.001

Cited by 51 publications

(57 citation statements)

References 34 publications

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“…This study identified a positive linear relationship between RT variance and tilt table inclination. Since sympathetic tone and modulation increase during head-up tilt (11,14,23,32), the gradual increase of RT variability with tilt table inclination supports the existence of a relationship between RT variance and ventricular sympathetic tone and/or modulation (26,39) and the opportunity of using the level of RT variability as an index proportional to the magnitude of ventricular sympathetic control. This result, combined with recent findings suggesting that QT variability is unrelated to sympathetic tone (4), suggests that the relationship between RT variance and ventricular sympathetic control should be limited to the amplitude of ventricular sympathetic modulation (i.e., the amplitude of the fluctuations of the sympathetic discharge around its mean value) and/or, as suggested by Berger (6), to ventricular sympathetic tone when its values are elevated, as occurs at the highest tilt table inclinations.…”

Section: Discussionmentioning

confidence: 79%

RT variability unrelated to heart period and respiration progressively increases during graded head-up tilt

Porta

Tobaldini

Gnecchi‐Ruscone³

et al. 2010

American Journal of Physiology-Heart and Circulatory Physiology

104

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Porta A, Tobaldini E, Gnecchi-Ruscone T, Montano N. RT variability unrelated to heart period and respiration progressively increases during graded head-up tilt. Am J Physiol Heart Circ Physiol 298: H1406 -H1414, 2010. First published February 12, 2010 doi:10.1152/ajpheart.01206.2009.-Open-loop linear parametric models were exploited to describe ventricular repolarization duration (VRD) variability during graded head-up tilt. Surface ECG and thoracic movements were recorded in 15 healthy humans (age: 24 -54 yr, median: 28 yr; 6 women and 9 men). Tilt table inclinations ranged from 15 to 90°and were varied in steps of 15°. All subjects underwent recordings at every step in random order. Heart period was assessed as the time difference between two consecutive R-wave peaks (RR) and the respiratory signal (R) as the sampling of the thoracic movement signal at the R-wave peaks. VRD was measured automatically as the temporal difference between the R-wave peak and T-wave apex (RT a) or T-wave end (RTe). The best model decomposed RT variability as due to RR changes (RR-related RT variability) to direct respiratory-related inputs (R-related RT variability) and to unknown rhythmical sources unrelated to RR changes and R (RR-R-unrelated RT variability). Using this model, RTe variability was found to be less predictable than RTa variability and composed of a smaller fraction of RR-related RT variability and a larger fraction of RR-R-unrelated RT variability. Predictability progressively decreased with tilt table angles, suggesting increased complexity of RT regulation. RT variance progressively increased with tilt table inclination. This increase was characterized by a gradual rise of the amount of RR-R-unrelated RT variability, whereas the amount of RR-related RT variability remained unchanged. These results suggest that the amount of RT variability, complexity of RT dynamics, and amount of RR-Runrelated RT variability increase with the magnitude of the sympathetic drive directly related to tilt table inclination. We propose the utilization of the amount of RR-R-unrelated RT variability instead of overall RT variability as an indirect measure of autonomic regulation directed to ventricles. QT measurement; QT variability; QT-RR relationship; modelling; autonomic nervous system THERE IS INCREASING INTEREST in quantifying the amount of the beat-to-beat changes of ventricular repolarization duration (VRD), i.e., VRD variability (2,4,6,12,15,20,27,40). This interest is based on the original suggestion that VRD variability provides an indirect measure of the autonomic regulation directed to ventricles (7). VRD variability is usually computed from the surface ECG as the variability of the time interval between the Q-wave onset and T-wave end (QT interval) under the hypothesis that the variability of the ventricular depolarization period is negligible with respect to that of VRD. Since variability of the heart period, computed as the temporal difference between two consecutive R-wave peaks on the ECG (RR), provides indexes of the ...

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Section: Discussionmentioning

confidence: 79%

RT variability unrelated to heart period and respiration progressively increases during graded head-up tilt

Porta

Tobaldini

Gnecchi‐Ruscone³

et al. 2010

American Journal of Physiology-Heart and Circulatory Physiology

104

View full text Add to dashboard Cite

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“…Therefore, the present study analyzed the possible relationships between some markers of spatial and temporal myocardial repolarization dispersion and CMR-derived data in a se- beat-to-beat fluctuations in QT interval variability proposed by Berger et al 26 To avoid probable confounding from the influence of respiration on RR interval and QT variables, 24, 25 we analyzed RR and QT intervals only from the last 5-min beat segments recorded during the controlled breathing. QT and RR mean (QTm and RRm), as well as their variances (QTv and RRv), were automatically calculated in order to obtain QTv normalized for QTm (QTVN) and QTVI according to the following 2 standard formulas (Figure 1) Last, a standard 12-lead surface ECG at 50 mm/s was used to manually measure the QT interval length in every lead with a digital caliper.…”

Section: Subjectsmentioning

confidence: 99%

“…Software for data acquisition, storage, and analysis were designed and produced by our research group and are described in detail elsewhere. 19-22,24, 25 To calculate the RR and QT intervals and to make the end of the T wave easier to identify, we used software that our laboratory developed based on the algorithm for quantification of QT Variability and LGE in HCM mial regression is based on the same principles as basic linear regression, except that the relationship between the independent and dependent variables is non-linear. It is used to fit nonlinear (eg, curvilinear) data into a least-squares linear regression model.…”

Section: Rr and Qt Interval Data Analysismentioning

confidence: 99%

Myocardial Repolarization Dispersion and Late Gadolinium Enhancement in Patients With Hypertrophic Cardiomyopathy

Magrì

Cecco

Piccirillo

et al. 2014

Circ J

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Background: Growing evidence suggests that late gadolinium enhancement (LGE) at cardiac magnetic resonance (CMR) is an additive marker of disease severity, and possibly of arrhythmic risk, in hypertrophic cardiomyopathy (HCM). We investigated the possible relationship between LGE and markers of myocardial repolarization dispersion in HCM. Methods and Results:Eighty-five HCM outpatients underwent CMR and short-period electrocardiogram analysis to calculate the temporal myocardial repolarization dispersion through the QT variance normalized for QT mean (QTVN) and the QT variability index (QTVI). The QT dispersion in the spatial domain was also obtained. Patients with LGE (62%) had higher left atrial volume, maximum wall thickness, and left ventricular mass (P<0.0001), as well as a greater prevalence of non-sustained ventricular tachycardia (P<0.0001) and hypotensive blood pressure response (P=0.044). Both QTVN and QTVI were higher in the group with LGE (P<0.0001). At multivariate analysis, using QTVI as the dependent variable, %LGE (P<0.0001), age (P<0.0001), left ventricular outflow obstruction (P=0.038), and sudden cardiac death risk factor burden (P=0.020) reached statistical significance. Otherwise, only %LGE (P=0.005) and left ventricular mass index (P=0.015) remained associated with QTVN. Conclusions:Temporal myocardial repolarization dispersion correlates with LGE extent. Whether these variables could be useful in HCM clinical management warrants confirmation by larger prospective studies. (Circ J 2014; 78: 1216 -1223

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“…Conversely, a lower value is indicative of a more stable myocardium. The QTVI has been reported to be elevated in several conditions, including dilated cardiomyopathy 39 hypertension, 44 heart failure, 70 anxiety and depression. 71 In addition, Atiga et al 40 reported that the QTVI was a sensitive predictor of future arrhythmia and a more accurate predictor of sudden cardiac death compared with spatial QT dispersion, HRV and ejection fraction in patients with heart disease.…”

Section: Clinical Utility Of Cardiac Autonomic Measuresmentioning

confidence: 99%

Non-invasive electrocardiographic assessments of cardiac autonomic modulation in individuals with spinal cord injury

et al. 2015

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Study design: Review. Objectives: The purpose of this review is to discuss the utility of linear and non-linear heart rate variability (HRV) as well as the QT-variability index (QTVI) as indices of cardiac autonomic control in individuals with spinal cord injury (SCI). Setting: Brock University, Department of Kinesiology, St Catharines, Ontario, Canada. Brock-Niagara Centre for Health and Well-being, St Catharines, Ontario, Canada. Methods: Literature review. Conclusion: Non-invasive markers determined from the electrocardiogram, such as linear and non-linear HRV, and, more recently, the QTVI have all shown some promise as indices of cardiac autonomic regulation in the SCI population. However, there are inconsistencies in the literature that call to question their true validity in this regard. Studies using pharmacological blockade, sympathetic manoeuvres and exercise suggest that both linear and non-linear HRV reflect cardiac parasympathetic activity, whereas their ability to quantify cardiac sympathetic outflow remains uncertain. The QTVI, although a novel method, correlates with both limbs of the autonomic nervous system and therefore may hold value as a measure of both cardiac sympathetic and parasympathetic activity in individuals with SCI; however, more research is required to confirm its utility.

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Age and QT variability index during free breathing, controlled breathing and tilt in patients with chronic heart failure and healthy control subjects

Cited by 51 publications

References 34 publications

RT variability unrelated to heart period and respiration progressively increases during graded head-up tilt

RT variability unrelated to heart period and respiration progressively increases during graded head-up tilt

Myocardial Repolarization Dispersion and Late Gadolinium Enhancement in Patients With Hypertrophic Cardiomyopathy

Non-invasive electrocardiographic assessments of cardiac autonomic modulation in individuals with spinal cord injury

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