High Concentrations of Chlorantraniliprole Reduce Its Compatibility with a Key Predator, Hippodamia convergens (Coleoptera: Coccinellidae).

Diamides are a novel insecticide group that act by disrupting insect muscle contraction. Recommended field rates (FRs) vary greatly among target pests and cropping systems, leading to variable risks for non-target organisms. We evaluated the toxicity of chlorantraniliprole to the predator Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae) by exposure to residues, topical application, and consumption of contaminated food. We also estimated lethal concentrations (LCs) of chlorantraniliprole in two target pests, cotton leafworm, Alabama argillacea (Hübner) (Lepidoptera: Erebidae), and tobacco budworm, Chloridea virescens (F.) (Lepidoptera: Noctuidae), by exposing larvae to treated cotton, Gossypium hirsutum L., leaves and assessed residual activity at various intervals after application to cotton plants. Exposure to dried residues and ingestion of treated moth eggs resulted in similar toxicity to H. convergens, whereas topical application was a less toxic route of exposure. Regardless of exposure route, the LC50s and LC90s obtained for H. convergens were higher than those calculated for the pests. Residues at the upper limit of the LC90 for C. virescens remained effective against this pest for up to 16 d, while exhibiting minor impacts on H. convergens. In contrast, the FR concentration of C. virescens caused significant mortality in H. convergens. The results suggest that the current FR for C. virescens is too high to be safe for H. convergens, and given the LCs observed for this pest in the present study, trials to explore the potential efficacy of lower FRs are justified. Depending on the concentration and route of exposure, this insecticide has the potential to be compatible with H. convergens.

A cluster of Rickettsia rickettsii infection at an animal shelter in an urban area of Brazil.

Rickettsia rickettsii infection is being increasingly recognized as an important cause of fatal acute illness in Brazil, where this tick-borne disease is designated Brazilian spotted fever (BSF). In this study we report five fatal cases of BSF in employees of an animal shelter in an urban area in the municipality of Rio de Janeiro in southeast Brazil after a natural disaster on 11 January 2011. Four of the cases occurred from 27 January to 11 April 2011, while the fifth fatal case was identified in April 2012. Three cases were confirmed by molecular analysis and two by epidemiological linkage. An investigation of BSF was performed in the animal shelter, and blood samples were collected from 115 employees and 117 randomly selected dogs. The presence of high levels (1024-4096) of antibodies against spotted fever group rickettsiae was found in three (2·6%) employees and 114 (97·5%) dogs. These findings emphasize the need to consider BSF as a possible cause of undifferentiated febrile illness, especially dengue and leptospirosis, in patients occupationally exposed to dogs heavily infested by ticks, mainly working at kennels and animal shelters that have inadequate space for the animals housed and frequently providing an environment conducive to exposure to pathogens such as R. rickettsii.

Performance of the Striped Mealybug Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae) under Variable Conditions of Temperature and Mating.

Mealybugs have strong associations with their host plants due to their limitations for dispersal. Thus, environmental conditions and host quality may impact the biological traits of mealybugs. To the best of our knowledge, we are the first to report on the biology of a Brazilian population of the striped mealybug Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae), which has recently been reported to infest cotton in Brazil. We evaluated the development and reproductive performance of F. virgata reared under different temperatures (25, 27, and 28°C) and mating status. The type of reproduction was also studied with insects reared on a factitious host and on cotton plants. Shorter development was obtained at 28°C as follows: nymphs generating males and females exhibited three and four instars with a mean duration of 19.1 and 20.5 days, respectively. The nymphal viability ranged from 77 to 96%, and was highest at 25°C. Females reared at 28°C initiated reproduction earlier (16.4 days), but the reproductive period was similar in all temperatures (∼16.2 days). Females produced more nymphs at 27 and 28°C (440 and 292 neonates) than at 25°C (277 neonates), although they lived longer at 25°C (63 days). Ferrisia virgata females exhibited only sexual reproduction. Thus, only mated females produced offspring, whereas unmated females died without reproducing. Therefore, the studied population of F. virgata exhibited only sexual reproduction with high survival and offspring production when fed cotton. Furthermore, pumpkin is a feasible host for mass rearing this mealybug species in the laboratory, an opening avenue for future studies.

Effect of aerobic conditioning on ventricular activation: a principal components analysis approach to high-resolution electrocardiogram.

BACKGROUND: The athlete's heart represents a reversible structural and functional adaptations of myocardial tissue developed through physical conditioning. Surface electrocardiogram (ECG) has the capability to detect myocardial hypertrophy but has limited performance in monitoring physical conditioning-induced myocardial remodeling. The aim of this study was to develop an ECG-derived test for detecting incipient myocardial hypertrophy in well-conditioned athletes based on a principal components (PC) analysis. METHODS: Two groups of study composed of 14 sedentary healthy volunteers (CONTROL GROUP) and 14 professional long distance runners (Athlete group) had their maximal metabolic equivalents (MET) estimated (mean ± SD: CONTROL GROUP: 9 ± 2 METs vs. Athlete group: 20 ± 1 METs, p<0.05). All participants had their high-resolution ECG (HRECG) recorded, and a 120 ms segment starting at the QRS complex onset and ending in the ST segment was extracted to build a data matrix for PC analysis. The Mahalanobis distance was evaluated by a logistic regression model to determine the optimal separation threshold between groups. HRECG was also analyzed using the classical time domain approach. The comparison of areas under the receiver operating characteristic curve (c-statistic) in 10,000 bootstrap re-samplings measured how well each method detected physical conditioning (α<0.05). RESULTS: Average bootstrap c-statistic for PC analysis and time domain approaches were 0.98 and 0.79 (p<0.05), respectively. PC analysis and maximal oxygen consumption exhibited comparable performances to distinguish between groups. DISCUSSION: The PC analysis method applied to HRECG signals appropriately discriminates well-conditioned athletes from healthy, sedentary subjects.

Utility of a novel risk score for prediction of ventricular tachycardia and cardiac death in chronic Chagas disease - the SEARCH-RIO study.

The SEARCH-RIO study prospectively investigated electrocardiogram (ECG)-derived variables in chronic Chagas disease (CCD) as predictors of cardiac death and new onset ventricular tachycardia (VT). Cardiac arrhythmia is a major cause of death in CCD, and electrical markers may play a significant role in risk stratification. One hundred clinically stable outpatients with CCD were enrolled in this study. They initially underwent a 12-lead resting ECG, signal-averaged ECG, and 24-h ambulatory ECG. Abnormal Q-waves, filtered QRS duration, intraventricular electrical transients (IVET), 24-h standard deviation of normal RR intervals (SDNN), and VT were assessed. Echocardiograms assessed left ventricular ejection fraction. Predictors of cardiac death and new onset VT were identified in a Cox proportional hazard model. During a mean follow-up of 95.3 months, 36 patients had adverse events: 22 new onset VT (mean±SD, 18.4±4/year) and 20 deaths (26.4±1.8/year). In multivariate analysis, only Q-wave (hazard ratio, HR=6.7; P<0.001), VT (HR=5.3; P<0.001), SDNN<100 ms (HR=4.0; P=0.006), and IVET+ (HR=3.0; P=0.04) were independent predictors of the composite endpoint of cardiac death and new onset VT. A prognostic score was developed by weighting points proportional to beta coefficients and summing-up: Q-wave=2; VT=2; SDNN<100 ms=1; IVET+ =1. Receiver operating characteristic curve analysis optimized the cutoff value at >1. In 10,000 bootstraps, the C-statistic of this novel score was non-inferior to a previously validated (Rassi) score (0.89±0.03 and 0.80±0.05, respectively; test for non-inferiority: P<0.001). In CCD, surface ECG-derived variables are predictors of cardiac death and new onset VT.

Utility of a novel risk score for prediction of ventricular tachycardia and cardiac death in chronic Chagas disease - the SEARCH-RIO study

The SEARCH-RIO study prospectively investigated electrocardiogram (ECG)-derived variables in chronic Chagas disease (CCD) as predictors of cardiac death and new onset ventricular tachycardia (VT). Cardiac arrhythmia is a major cause of death in CCD, and electrical markers may play a significant role in risk stratification. One hundred clinically stable outpatients with CCD were enrolled in this study. They initially underwent a 12-lead resting ECG, signal-averaged ECG, and 24-h ambulatory ECG. Abnormal Q-waves, filtered QRS duration, intraventricular electrical transients (IVET), 24-h standard deviation of normal RR intervals (SDNN), and VT were assessed. Echocardiograms assessed left ventricular ejection fraction. Predictors of cardiac death and new onset VT were identified in a Cox proportional hazard model. During a mean follow-up of 95.3 months, 36 patients had adverse events: 22 new onset VT (mean±SD, 18.4±4‰/year) and 20 deaths (26.4±1.8‰/year). In multivariate analysis, only Q-wave (hazard ratio, HR=6.7; P<0.001), VT (HR=5.3; P<0.001), SDNN<100 ms (HR=4.0; P=0.006), and IVET+ (HR=3.0; P=0.04) were independent predictors of the composite endpoint of cardiac death and new onset VT. A prognostic score was developed by weighting points proportional to beta coefficients and summing-up: Q-wave=2; VT=2; SDNN<100 ms=1; IVET+=1. Receiver operating characteristic curve analysis optimized the cutoff value at >1. In 10,000 bootstraps, the C-statistic of this novel score was non-inferior to a previously validated (Rassi) score (0.89±0.03 and 0.80±0.05, respectively; test for non-inferiority: P<0.001). In CCD, surface ECG-derived variables are predictors of cardiac death and new onset VT.

Markers of insulin resistance and sedentary lifestyle are predictors of preeclampsia in women with adverse obstetric results

Some thrombophilias and severe preeclampsia may increase the risk for preterm deliveries and fetal death due to placental insufficiency. Our objective was to evaluate clinical and laboratory data as predictors of preeclampsia in a population of mothers with 3rd trimester fetal losses or preterm deliveries. In a longitudinal retrospective study, 54 consecutive women (age range: 16 to 39 years) with normotensive pregnancies were compared to 79 consecutive women with preeclampsia (age range: 16 to 43 years). Weight accrual rate (WAR) was arbitrarily defined as weight gain from age 18 years to the beginning of pregnancy divided by elapsed years. Independent predictors of preeclampsia were past history of oligomenorrhea, WAR >0.8 kg/years, pre-pregnancy or 1st trimester triglyceridemia >150 mg/dL, and elevated acanthosis nigricans in the neck. In a multivariate logistic regression model, two or more predictors conferred an odds ratio of 15 (95 percentCI [5.9-37]; P < 0.001) to develop preeclampsia (85 percent specificity, 73 percent sensitivity, c-statistic of 81 ± 4 percent; P < 0.0001). Clinical markers related to insulin resistance and sedentary lifestyles are strong independent predictors of preeclampsia in mothers with 3rd trimester fetal losses or preterm deliveries due to placental insufficiency. Women at risk for preeclampsia in this particular population might benefit from measures focused on overcoming insulin resistance.

Markers of insulin resistance and sedentary lifestyle are predictors of preeclampsia in women with adverse obstetric results.

Some thrombophilias and severe preeclampsia may increase the risk for preterm deliveries and fetal death due to placental insufficiency. Our objective was to evaluate clinical and laboratory data as predictors of preeclampsia in a population of mothers with 3rd trimester fetal losses or preterm deliveries. In a longitudinal retrospective study, 54 consecutive women (age range: 16 to 39 years) with normotensive pregnancies were compared to 79 consecutive women with preeclampsia (age range: 16 to 43 years). Weight accrual rate (WAR) was arbitrarily defined as weight gain from age 18 years to the beginning of pregnancy divided by elapsed years. Independent predictors of preeclampsia were past history of oligomenorrhea, WAR >0.8 kg/years, pre-pregnancy or 1st trimester triglyceridemia >150 mg/dL, and elevated acanthosis nigricans in the neck. In a multivariate logistic regression model, two or more predictors conferred an odds ratio of 15 (95%CI [5.9-37]; P < 0.001) to develop preeclampsia (85% specificity, 73% sensitivity, c-statistic of 81 ± 4%; P < 0.0001). Clinical markers related to insulin resistance and sedentary lifestyles are strong independent predictors of preeclampsia in mothers with 3rd trimester fetal losses or preterm deliveries due to placental insufficiency. Women at risk for preeclampsia in this particular population might benefit from measures focused on overcoming insulin resistance.

The effect of configuration parameters of time-frequency maps in the detection of intra-QRS electrical transients of the signal-averaged electrocardiogram: impact in clinical diagnostic performance.

Time-frequency maps of signal-averaged electrocardiogram based on a short time Fourier transform (STFT) technique analysis was employed to assess the presence of high frequency electrical transients (turbulence) and arrhythmia risk assessment. The optimal configuration set of STFT variables aiming at risk stratification for sustained monomorphic ventricular tachycardia (SMVT) is still undetermined. Different configuration variables, including analyzing time-window widths, starting positions, relative displacements, and zero-padding for STFT time-frequency maps constructions were combined on each analyzing averaged signal from 18 healthy controls and 18 subjects presenting inducible SMVT. Spectral turbulence analysis (STA) was, thus, carried out according to conventional procedures. The optimal configuration set of variables for STA was obtained by assessing the total diagnostic accuracy of all combinations of parameters. The optimal diagnostic performance was found at 86% total diagnostic accuracy as compared to 56% using previous defined normality thresholds (p=0.01). Present configuration set of variables is distinctive from previously defined set of variables and improves risk stratification.

Circadian cardiac autonomic function in perinatally HIV-infected preschool children.

The 24-h heart rate variability and QT-interval adaptation was investigated in perinatally HIV-infected preschool children classified according to immunological status in order to assess autonomic function at early stages of infection. Thirty-five perinatally HIV-infected and clinically stable children (4.8 +/- 0.3 years) were enrolled after approval of the study by the University Hospital Pedro Ernesto Ethics Committee and written informed parental consent was obtained. The children were classified according to peripheral CD4+ count (cells/microL) as follows: group 1, N = 11 (>or=1000); group 2, N = 7 (>or=500 and <1000); group 3, N = 17 (<500). Left ventricular ejection fraction (>55%), 24-h RR interval variability (RRV) indexes (NN, SDANN, SDNN index, r-MSSD) and 24-h QT and Bazett-corrected QT (QTc) were determined, and groups were matched for age, body surface area, and left ventricular ejection fraction, reducing biases in RRV. The peak differences () between the highest and lowest RRV and QT indexes were extracted from nocturnal (1 am-6 am) and daytime (1 pm-6 pm) hourly assessed segments, respectively. Pearsons correlation (r) and Kruskal-Wallis ANOVA were used to compare groups. CD4+ count correlated positively with NN (r = 0.45; P = 0.003). There were no significant differences in daytime NN among groups. Nighttime SDNN index (P = 0.01), nighttime r-MSSD (P = 0.003), NN (P = 0.01), SDNN index (P = 0.03) and r-MSSD (P = 0.004) were significantly lower in group 3 than in the other groups. Expected nighttime QTc-interval lengthening was not observed in all groups. In perinatally HIV-infected preschool children with preserved left ventricular systolic function, parasympathetic-mediated autonomic dysfunction parallels immune status, impairing both RRV and circadian QTc interval adaptation.

Circadian cardiac autonomic function in perinatally HIV-infected preschool children

The 24-h heart rate variability and QT-interval adaptation was investigated in perinatally HIV-infected preschool children classified according to immunological status in order to assess autonomic function at early stages of infection. Thirty-five perinatally HIV-infected and clinically stable children (4.8 ± 0.3 years) were enrolled after approval of the study by the University Hospital Pedro Ernesto Ethics Committee and written informed parental consent was obtained. The children were classified according to peripheral CD4+ count (cells/µL) as follows: group 1, N = 11 (≥1000); group 2, N = 7 (≥500 and <1000); group 3, N = 17 (<500). Left ventricular ejection fraction (>55%), 24-h RR interval variability (RRV) indexes (NN, SDANN, SDNN index, r-MSSD) and 24-h QT and Bazett-corrected QT (QTc) were determined, and groups were matched for age, body surface area, and left ventricular ejection fraction, reducing biases in RRV. The peak differences (∆) between the highest and lowest RRV and QT indexes were extracted from nocturnal (1 am-6 am) and daytime (1 pm-6 pm) hourly assessed segments, respectively. Pearson’s correlation (r) and Kruskal-Wallis ANOVA were used to compare groups. CD4+ count correlated positively with ∆NN (r = 0.45; P = 0.003). There were no significant differences in daytime NN among groups. Nighttime SDNN index (P = 0.01), nighttime r-MSSD (P = 0.003), ∆NN (P = 0.01), ∆SDNN index (P = 0.03) and ∆r-MSSD (P = 0.004) were significantly lower in group 3 than in the other groups. Expected nighttime QTc-interval lengthening was not observed in all groups. In perinatally HIV-infected preschool children with preserved left ventricular systolic function, parasympathetic-mediated autonomic dysfunction parallels immune status, impairing both RRV and circadian QTc interval adaptation.

Mechanical cardiac remodeling and new-onset atrial fibrillation in long-term follow-up of subjects with chronic Chagas' disease.

Atrial fibrillation (AF) affects subjects with Chagas' disease and is an indicator of poor prognosis. We investigated clinical, echocardiographic and electrocardiographic variables of Chagas' disease in a long-term longitudinal study as predictors of a new-onset AF episode lasting >24 h, nonfatal embolic stroke and cardiac death. Fifty adult outpatients (34 to 74 years old, 62% females) staged according to the Los Andes classification were enrolled. During a follow-up of (mean +/- SD) 84.2 +/- 39.0 months, 9 subjects developed AF (incidence: 3.3 +/- 1.0%/year), 5 had nonfatal stroke (incidence: 1.3 +/- 1.0%/year), and nine died (mortality rate: 2.3 +/- 0.8%/year). The progression rate of left ventricular mass and left ventricular ejection fraction was significantly greater in subjects who experienced AF (16.4 +/- 20.0 g/year and -8.6 +/- 7.6%/year, respectively) than in those who did not (8.2 +/- 8.4 g/year; P = 0.03, and -3.0 +/- 2.5%/year; P = 0.04, respectively). In univariate analysis, left atrial diameter >/=3.2 cm (P = 0.002), pulmonary arterial hypertension (P = 0.035), frequent premature supraventricular and ventricular contraction counts/24 h (P = 0.005 and P = 0.007, respectively), ventricular couplets/24 h (P = 0.002), and ventricular tachycardia (P = 0.004) were long-term predictors of AF. P-wave signal-averaged ECG revealed a limited long-term predictive value for AF. In chronic Chagas' disease, large left atrial diameter, pulmonary arterial hypertension, frequent supraventricular and ventricular premature beats, and ventricular tachycardia are long-term predictors of AF. The rate of left ventricular mass enlargement and systolic function deterioration impact AF incidence in this population.

Mechanical cardiac remodeling and new-onset atrial fibrillation in long-term follow-up of subjects with chronic Chagas' disease

Atrial fibrillation (AF) affects subjects with Chagas' disease and is an indicator of poor prognosis. We investigated clinical, echocardiographic and electrocardiographic variables of Chagas' disease in a long-term longitudinal study as predictors of a new-onset AF episode lasting >24 h, nonfatal embolic stroke and cardiac death. Fifty adult outpatients (34 to 74 years old, 62 percent females) staged according to the Los Andes classification were enrolled. During a follow-up of (mean ± SD) 84.2 ± 39.0 months, 9 subjects developed AF (incidence: 3.3 ± 1.0 percent/year), 5 had nonfatal stroke (incidence: 1.3 ± 1.0 percent/year), and nine died (mortality rate: 2.3 ± 0.8 percent/year). The progression rate of left ventricular mass and left ventricular ejection fraction was significantly greater in subjects who experienced AF (16.4 ± 20.0 g/year and -8.6 ± 7.6 percent/year, respectively) than in those who did not (8.2 ± 8.4 g/year; P = 0.03, and -3.0 ± 2.5 percent/year; P = 0.04, respectively). In univariate analysis, left atrial diameter ≥3.2 cm (P = 0.002), pulmonary arterial hypertension (P = 0.035), frequent premature supraventricular and ventricular contraction counts/24 h (P = 0.005 and P = 0.007, respectively), ventricular couplets/24 h (P = 0.002), and ventricular tachycardia (P = 0.004) were long-term predictors of AF. P-wave signal-averaged ECG revealed a limited long-term predictive value for AF. In chronic Chagas' disease, large left atrial diameter, pulmonary arterial hypertension, frequent supraventricular and ventricular premature beats, and ventricular tachycardia are long-term predictors of AF. The rate of left ventricular mass enlargement and systolic function deterioration impact AF incidence in this population.

Association between decreased vitamin levels and MTHFR, MTR and MTRR gene polymorphisms as determinants for elevated total homocysteine concentrations in pregnant women.

OBJECTIVES: To examine the association between methylenetetrahydrofolate reductase (MTHFR) (C677T and A1298C), methionine synthase (MTR) A2756G and methionine synthase reductase (MTRR) A66G gene polymorphisms and total homocysteine (tHcy), methylmalonic acid (MMA) and S-adenosylmethionine/S-adenosylhomocysteine (SAM/SAH) levels; and to evaluate the potential interactions with folate or cobalamin (Cbl) status. SUBJECTS/METHODS: Two hundred seventy-five healthy women at labor who delivered full-term normal babies. Cbl, folate, tHcy, MMA, SAM and SAH were measured in serum specimens. The genotypes for polymorphisms were determined by PCR-restriction fragment length polymorphism (RFLP). RESULTS: Serum folate, MTHFR 677T allele and MTR 2756AA genotypes were the predictors of tHcy levels in pregnant women. Serum Cbl and creatinine were the predictors of SAM/SAH ratio and MMA levels, respectively. The gene polymorphisms were not determinants for MMA levels and SAM/SAH ratios. Low levels of serum folate were associated with elevated tHcy in pregnant women, independently of the gene polymorphisms. In pregnant women carrying MTHFR 677T allele, or MTHFR 1298AA or MTRR 66AA genotypes, lower Cbl levels were associated with higher levels of tHcy. Lower SAM/SAH ratio was found in MTHFR 677CC or MTRR A2756AA genotypes carriers when Cbl levels were lower than 142 pmol/l. CONCLUSIONS: Serum folate and MTHFR C677T and MTR A2576G gene polymorphisms were the determinants for tHcy levels. The interaction between low levels of serum Cbl and MTHFR (C677T or A1298C) or MTRR A66G gene polymorphisms was associated with increased tHcy.

Noninvasive prognostic markers for cardiac death and ventricular arrhythmia in long-term follow-up of subjects with chronic Chagas' disease.

The objective of the present study was to investigate clinical, echocardiographic and electrocardiographic (12-lead resting ECG, 24-h ambulatory ECG monitoring and signal-averaged ECG (SAECG)) parameters in subjects with chronic Chagas' disease in a long-term follow-up as prognostic markers for adverse outcomes. Fifty adult outpatients (34 to 74 years old, 31 females) staged according to Los Andes class I, II or III and complaining of palpitation were enrolled in a longitudinal study. SAECG was analyzed in time and frequency domains and the endpoint was a composite of cardiac death and ventricular tachycardia. During a follow-up of 84.2 +/- 39.0 months, 34.0% of the patients developed adverse outcomes (9 cardiac deaths and 11 episodes of ventricular tachycardia). After optimal dichotomization, in a stepwise multivariate Cox-hazard regression model, apical aneurysm (HR = 3.7; 95% CI = 1.2-1.3; P = 0.02), left ventricular ejection fraction <62% (HR = 4.60; 95% CI = 1.39-15.24; P = 0.01) and incidence of ventricular premature contractions >614 per 24 h (hazard ratio = 6.1; 95% CI = 1.7-22.6; P = 0.006) were independent predictors of the composite endpoint. Although a high frequency content in SAECG demonstrated association with the presence of left ventricular dysfunction and myocardial fibrosis, its predictive value for the composite endpoint was not significant. Apical aneurysms, reduced left ventricular function and a high incidence of ventricular ectopic beats over a 24-h period have a strong predictive value for a composite endpoint of cardiac death and ventricular tachycardia in subjects with chronic Chagas' disease.

The effect of an aerobic training program on the electrical remodeling of heart high-frequency components of the signal-averaged electrocardiogram is a predictor of the maximal aerobic power.

Increased heart rate variability (HRV) and high-frequency content of the terminal region of the ventricular activation of signal-averaged ECG (SAECG) have been reported in athletes. The present study investigates HRV and SAECG parameters as predictors of maximal aerobic power (VO2max) in athletes. HRV, SAECG and VO2max were determined in 18 high-performance long-distance (25 +/- 6 years; 17 males) runners 24 h after a training session. Clinical visits, ECG and VO2max determination were scheduled for all athletes during the training period. A group of 18 untrained healthy volunteers matched for age, gender, and body surface area was included as controls. SAECG was acquired in the resting supine position for 15 min and processed to extract average RR interval (Mean-RR) and root mean squared standard deviation (RMSSD) of the difference of two consecutive normal RR intervals. SAECG variables analyzed in the vector magnitude with 40-250 Hz band-pass bi-directional filtering were: total and 40-microV terminal (LAS40) duration of ventricular activation, RMS voltage of total (RMST) and of the 40-ms terminal region of ventricular activation. Linear and multivariate stepwise logistic regressions oriented by inter-group comparisons were adjusted in significant variables in order to predict VO2max, with a P < 0.05 considered to be significant. VO2max correlated significantly (P < 0.05) with RMST (r = 0.77), Mean-RR (r = 0.62), RMSSD (r = 0.47), and LAS40 (r = -0.39). RMST was the independent predictor of VO2max. In athletes, HRV and high-frequency components of the SAECG correlate with VO2max and the high-frequency content of SAECG is an independent predictor of VO2max.

The effect of an aerobic training program on the electrical remodeling of the heart: high-frequency components of the signal-averaged electrocardiogram are predictors of the maximal aerobic power

Increased heart rate variability (HRV) and high-frequency content of the terminal region of the ventricular activation of signal-averaged ECG (SAECG) have been reported in athletes. The present study investigates HRV and SAECG parameters as predictors of maximal aerobic power (VO2max) in athletes. HRV, SAECG and VO2max were determined in 18 high-performance long-distance (25 ± 6 years; 17 males) runners 24 h after a training session. Clinical visits, ECG and VO2max determination were scheduled for all athletes during thew training period. A group of 18 untrained healthy volunteers matched for age, gender, and body surface area was included as controls. SAECG was acquired in the resting supine position for 15 min and processed to extract average RR interval (Mean-RR) and root mean squared standard deviation (RMSSD) of the difference of two consecutive normal RR intervals. SAECG variables analyzed in the vector magnitude with 40-250 Hz band-pass bi-directional filtering were: total and 40-æV terminal (LAS40) duration of ventricular activation, RMS voltage of total (RMST) and of the 40-ms terminal region of ventricular activation. Linear and multivariate stepwise logistic regressions oriented by inter-group comparisons were adjusted in significant variables in order to predict VO2max, with a P < 0.05 considered to be significant. VO2max correlated significantly (P < 0.05) with RMST (r = 0.77), Mean-RR (r = 0.62), RMSSD (r = 0.47), and LAS40 (r = -0.39). RMST was the independent predictor of VO2max. In athletes, HRV and high-frequency components of the SAECG correlate with VO2max and the high-frequency content of SAECG is an independent predictor of VO2max.

Noninvasive prognostic markers for cardiac death and ventricular arrhythmia in long-term follow-up of subjects with chronic Chagas' disease

The objective of the present study was to investigate clinical, echocardiographic and electrocardiographic (12-lead resting ECG, 24-h ambulatory ECG monitoring and signal-averaged ECG (SAECG)) parameters in subjects with chronic Chagas' disease in a long-term follow-up as prognostic markers for adverse outcomes. Fifty adult outpatients (34 to 74 years old, 31 females) staged according to Los Andes class I, II or III and complaining of palpitation were enrolled in a longitudinal study. SAECG was analyzed in time and frequency domains and the endpoint was a composite of cardiac death and ventricular tachycardia. During a follow-up of 84.2 ± 39.0 months, 34.0 percent of the patients developed adverse outcomes (9 cardiac deaths and 11 episodes of ventricular tachycardia). After optimal dichotomization, in a stepwise multivariate Cox-hazard regression model, apical aneurysm (HR = 3.7; 95 percent CI = 1.2-1.3; P = 0.02), left ventricular ejection fraction <62 percent (HR = 4.60; 95 percent CI = 1.39-15.24; P = 0.01) and incidence of ventricular premature contractions >614 per 24 h (hazard ratio = 6.1; 95 percent CI = 1.7-22.6; P = 0.006) were independent predictors of the composite endpoint. Although a high frequency content in SAECG demonstrated association with the presence of left ventricular dysfunction and myocardial fibrosis, its predictive value for the composite endpoint was not significant. Apical aneurysms, reduced left ventricular function and a high incidence of ventricular ectopic beats over a 24-h period have a strong predictive value for a composite endpoint of cardiac death and ventricular tachycardia in subjects with chronic Chagas' disease.