Dynamic Coupling Between Ventricular Repolarization Duration and RR:Interval Phase:Rectification Analysis in Chagas Disease (original) (raw)
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2015 Computing in Cardiology Conference (CinC), 2015
This study investigated dynamic atrio-ventricular duration (AVD) and phase-rectification-driven RRinterval coupling to assess AV conduction facilitation in healthy and chronic Chagas disease (ChD) subjects. All subjects were in sinus rhythm and underwent 60 min head-up tilt table test under ECG recording. ChD group underwent MIBG scintigraphy and confirmed sympathetic denervation. Histogram of RR-interval series was calculated, with 100 ms class, ranging from 600 ms to 1200 ms. For each class, mean of normal RR-intervals (MRR) and mean of the peak-to-peak P-to-R wave interval (MPR), representing AVD, were analyzed in RRintervals pairs of acceleration (AC) and deceleration (DC) phases, reflecting sympathetic and parasympathetic influences on heart rate, respectively. Regression lines of MPR vs. MRR were computed in the whole series, and in DC and AC phases, and respective slopes calculated (sMPR T , sMPR DC and sMPR AC). Student t-test compared groups. MRR and MPR were larger in ChD group. In healthy subjects, sMPR T , sMPR DC and sMPR AC significantly increased as a function of MRR in all phases. In subjects with Chagas disease, however, PRinterval increases only in DC phase, confirming loss of sympathetic driven RR-interval variation.
Pace-pacing and Clinical Electrophysiology, 2003
Electrocardiographic repolarization parameters are potential markers of arrhythmogenic risk and have not been evaluated in Chagas' disease. The aim of this report was to investigate their associations with LV systolic function assessed by two-dimensional echocardiography. In a cross-sectional study involving 738 adult outpatients in the chronic phase of Chagas' disease, maximal QTc and T wave peak-to-end (TpTe) intervals, and QT, QTapex (QTa), JT and TpTe interval dispersions, and variation coefficients were measured and calculated from 12-lead standard ECGs. Clinical, radiological, ECG, and echocardiographic data were recorded. In bivariate statistical analysis, all repolarization parameters were significantly increased in patients with moderate or severe LV systolic dysfunction, and these patients showed more clinical, radiologic, and ECG abnormalities. Receiver operating characteristic curve analysis demonstrated that isolatedly QTd had the best predictive performance for LV dysfunction, with an 80% specificity and 67% sensitivity for values >60 ms in the subgroup of chagasic patients with abnormal ECGs and no heart failure. Multivariate logistic regression selected, as the best predictive model for LV dysfunction in this subgroup of patients, the presence of cardiomegaly on chest X ray (OR 14.06, 95% CI,), QTd > 60 ms (OR 9.35, 95% CI, male gender (OR 7.70, 95% CI,) and the presence of frequent premature ventricular contractions (PVCs) on ECG (OR 4.06, 95% CI,. This model showed 90% specificity and 71% sensitivity. In conclusion, QTd was associated to LV systolic function and could be used to predict asymptomatic dysfunction in chronic Chagas' disease. The presence of cardiomegaly, frequent PVCs, and male sex refined LV function stratification in these patients. (PACE 2003; 26:1-10)
Journal of Electrocardiology, 2009
Introduction: Cardiac autonomic dysfunction occurs in Chagas' indeterminate and heart disease, but comparison of this disturbance between both forms was not yet performed. Methods: Time-and frequency-domain 5-minute heart rate variability in supine and standing positions were evaluated in 17 subjects with Chagas' disease with the indeterminate form, 13 with heart disease and 15 controls. Trend of variability indices across the groups was also tested. Results: In the supine position, reduced time-domain and absolute frequency-domain indices reflecting overall autonomic modulation were observed in both Chagas' disease groups. In the standing position, the coefficient of variation and those frequency-domain indices were also reduced, and the other time-domain indices were reduced only in the cardiac group. Heart rate variability indices hypothesized to reflect relative sympathetic and parasympathetic activity showed no alteration. A significant graded reduction was observed in the altered indices in both postures, from the control to the Chagas' indeterminate and heart disease groups. Conclusion: Cardiac autonomic dysfunction, with preserved putative measures of sympathetic and parasympathetic modulation in relative terms, was less severe or absent in the indeterminate and pronounced in cardiac form of Chagas' disease.
American Journal of Cardiology, 2001
The traditional methods of analyzing heart rate (HR) variability have failed to predict imminent ventricular fibrillation (VF). We sought to determine whether new methods of analyzing RR interval variability based on nonlinear dynamics and fractal analysis may help to detect subtle abnormalities in RR interval behavior before the onset of life-threatening arrhythmias. RR interval dynamics were analyzed from 24-hour Holter recordings of 15 patients who experienced VF during electrocardiographic recording. Thirty patients without spontaneous or inducible arrhythmia events served as a control group in this retrospective case control study. Conventional time-and frequency-domain measurements, the short-term fractal scaling exponent (␣) obtained by detrended fluctuation analysis, and the slope () of the power-law regression line (log power ؊ log frequency, 10 ؊4 ؊10 ؊2 Hz) of RR interval dynamics were determined. The short-term correlation exponent ␣ of RR intervals (0.64 ؎ 0.19 vs 1.05 ؎ 0.12; p <0.001) and the power-law slope  (؊1.63 ؎ 0.28 vs ؊1.31 ؎ 0.20, p <0.001) were lower in the patients before the onset of VF than in the control patients, but the SD and the low-frequency spectral components of RR intervals did not differ between the groups. The short-term scaling exponent performed better than any other measurement of HR variability in differentiating between the patients with VF and controls. Altered fractal correlation properties of HR behavior precede the spontaneous onset of VF. Dynamic analysis methods of analyzing RR intervals may help to identify abnormalities in HR behavior before VF.
Power-law behavior of heart rate variability in Chagas’ disease
American Journal of Cardiology, 2002
Beta slope is a nonlinear index derived from the powerlaw analysis of 24-hour heart rate variability (HRV); in healthy subjects, the  index is typically near ؊1, suggesting a fractal behavior of HRV. There is scarce data on HRV in Chagas' disease. This transversal study intends to describe power-law and linear HRV patterns in different forms of Chagas' disease. Patients and healthy controls (n ؍ 26) without other diseases were submitted to a standardized protocol, including electrocardiography, echocardiography, and 24-hour Holter monitoring. Patients with Chagas' disease were divided into groups according to their left ventricular (LV) systolic function: normal (group 1, n ؍ 85), segmental abnormalities (group 2, n ؍ 49), and reduced ejection fraction (group 3, n ؍ 26). The temporal series were carefully processed to obtain the HRV indexes and  slope. Despite the differences in the LV systolic function, the 3 groups were comparable in terms of long-term HRV index values. After adjustment for covariates, short-term HRV index values were consistently reduced in the Chagas' disease groups. The -index values were also diminished in Chagas' disease groups (group 1: ؊1.09 ؎ 0.03, group 2: ؊1.11 ؎ 0.06; group 3: ؊1.14 ؎ 0.03; and controls: 0.95 ؎ 0.03, p <0.001). This breakdown of fractal long-range correlation of RR interval dynamics, a strong predictor of mortality in other cardiomyopathies, may reflect cardiac dysautonomia that may have gone undetected in long-term time-domain analysis. This abnormality may explain the increased risk for arrhythmic sudden death found in Chagas' disease even in the absence of signs of LV dysfunction. ᮊ2002 by Excerpta Medica, Inc.
Computers in Cardiology 2000. Vol.27 (Cat. 00CH37163), 2000
Heart rate variability (HRV) and ventricular repolarization duration (VRD) variability are reflexes of autonomic activity and balance. HRV is dependent on aging, presence of disease, and use of drugs. The objective of this study is to assess the influence of the instantaneous RR interval on HRV and VRD variability. High resolution ECG signals of 20 normal adult were analyzed, respectively, by the normal RR interval series and by detecting the distance between the peaks of R-and T-waves (RTm). HRV and VRD variability were assessed by the mean (M), the standard deviation (SO) and rootmean-squared difference (M S) of consecutive normal RR and RTm intervals, stratlfied according to RR interval histogram. Results indicate that HRV reduces as mean RR interval shortens while the VRD variability paradoxically increases.
Revista Portuguesa de Cardiologia (English Edition), 2013
Chagas disease (CD) is an infection caused by the protozoan flagellate Trypanosoma cruzi, and transmitted by insects of the genera Triatoma, Rhodnius and Panstrongylus. The heart is affected to varying degrees by inflammatory and destructive lesions in atrial and ventricular myocardial fibers. Several studies have demonstrated the benefits of exercise in patients with congestive heart failure (CHF), including reduced sympathetic tone and increased parasympathetic tone, the result of reduced epinephrine and norepinephrine levels, both at rest and during exercise, including at submaximal levels. It has been hypothesized that the increase in sympathetic arousal during exercise improves peripheral muscle metabolism. Objectives: The objectives of this study were to select patients with chronic Chagas cardiomyopathy (CCC) with dysautonomia on 24-h Holter monitoring, assess autonomic function after rehabilitation, and determine whether it resulted in reduced daytime levels of SDNN and increased daytime and nighttime levels of pNN50 and rMSSD. Methods: We analyzed time-domain indices of heart rate variability through 24-h Holter monitoring before and after a supervised exercise program. We studied 18 CCC patients (five men), mean age 57.33 ± 9.73 years, followed at the CD outpatient clinic of the National Institute of Cardiology and IPEC/Fiocruz in Rio de Janeiro, Brazil, between April 2009 and November 2010. The following tests were used to assess the severity of CCC: clinical examination, functional evaluation by cardiopulmonary stress testing, electrocardiogram and conventional Doppler echocardiography. The exams were performed within a month of the start and end of the exercise program, which consisted of 60-min sessions of aerobic exercise on a treadmill and resistance training three times a week for six months. The goal was to reach the patients' ଝ Please cite this article as: Amaral da Silva Souza MV, et al. Variabilidade da frequência cardíaca: análise dos índices no domínio do tempo em portadores de cardiopatia chagásica crónica, antes e após um programa de exercícios. Rev Port Cardiol. 2013. http://dx.et al.