Análise temporal da variabilidade da freqüência cardíaca no estado basal em idosos chagásicos na forma indeterminada em área endêmica

Cardiac autonomic modulation and long-term use of amiodarone in patients with chronic Chagasic cardiopathy

BACKGROUND

Patients with chronic Chagas cardiopathy (CCC), which may be associated with cardiac arrhythmias, frequently use amiodarone, an antiarrhythmic drug that, experimentally, appears to modulate the cardiac autonomic function.

OBJECTIVE

The present cross-sectional observational study aimed to evaluate autonomic cardiac modulation in patients with CCC undergoing chronic amiodarone therapy.

METHODS

Three groups were investigated: Group 1 included patients with CCC not treated with amiodarone (n = 27); Group 2 included patients with CCC with prolonged use (at least 6 months) of amiodarone (n = 16); and Group 3 included non-Chagasic control patients (n = 23). All patients underwent a complete clinical and laboratory assessment, followed by autonomic function tests, consisting of a basal continuous electrocardiogram in the resting supine position for 10 minutes, followed by a change the orthostatic posture for a further 5 minutes. Heart rate variability (HRV) parameters (median and interquartile interval) were quantified using linear methods in the time- and frequency-domains (autoregressive spectral analysis) and nonlinear methods, including symbolic analysis.

RESULTS

Patients with CCC using amiodarone had changes in HRV suggestive of an offset in the sympatho-vagal balance with a vagal modulation predominance (normalized HF, 49.7[27.4] vs 31.1[22.8] [P < 0.05]; and percentage 2V, 40.1 [14.6] vs 21.5 [13.4] [P < 0.05] vs untreated CCC group). These changes were further accompanied by increases in parameters indicative of greater complexity of HRV.

CONCLUSIONS

The deviation in the sympatho-vagal balance and the increase in the complexity of HRV strongly suggest that amiodarone may have a cardioprotective effect, in addition to its antiarrhythmic effects, which could increase the survival of these patients.

[Heart rate variability: analysis of time-domain indices in patients with chronic Chagas disease before and after an exercise program]

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' heart rate target zone during training, and their rating of perceived exertion was assessed by the modified Borg scale.

RESULTS

There were no statistically significant differences (p>0.05) in SDNN, pNN50 and rMSSD, probably due to the large standard deviation observed, patients' poor adherence to the program and their low socioeconomic status, resulting in a small sample, and the short duration of the program.

CONCLUSION

Heart rate variability parameters in patients with CCC did not undergo statistically significant changes after a six-month cardiac rehabilitation program.

Study on Chagas disease occurrence in the municipality of Monte Negro, State of Rondônia, Brazilian Amazon

INTRODUCTION: Studies on Chagas disease deal with the perspective of its occurrence in the Amazon region, which is directly correlated to the population growth and the spread of the bug biotope. The state of Rondônia has an immense source of vectors (Triatomine) and reservoirs of Trypanosoma cruzi. Environmental changes brought forth by the deforestation in the region may cause vector behavior changes and bring these vectors to a closer contact with humans, increasing the probability of vector infection. METHODS: This study was carried out to check the occurrence of Chagas disease in the municipality of Monte Negro, Rondônia, Brazil, based on a random sampling of the farms and people wherein blood collection from the population and capturing triatomines were done. The blood samples were submitted to serologic tests to detect antibodies of the IgG class against T. cruzi. The triatomines that were collected had their digestive tract checked for the presence of trypanosomatidae with morphology resembling that of the T. cruzi. RESULTS: The population examined was mostly from other states. From the 322 bugs examined on the microscope, 50% showed parasites with morphology compatible with T. cruzi. From the serology of 344 random samples of human blood, 1.2% was found positive, 6% showed inconclusive results, and 92.8% were negative. CONCLUSIONS: Monte Negro shows low prevalence of human infection by T. cruzi and none active vector transmission; however, preventive and surveying measures, which are not performed until now, shall be taken due to the abundance of vectors infected by trypanosomatidae.

The relationship between heart rate variability and serum cytokines in chronic chagasic patients with persistent parasitemia

BACKGROUND

Persistent parasitemia, immunological, and autonomic nervous system impairments may play an important role in the evolution and clinical outcome of the chronic phase of Chagas' disease by triggering functional cardiovascular changes.

METHODS

Three groups were evaluated: 17 chronic chagasic patients with the indeterminate form (IChD), 12 chronic chagasic patients with cardiac forms (ChHD), and 29 individuals as a healthy control group. Parasitemia was assessed by polymerase chain reaction; hemoculture, heart rate variability by linear and nonlinear methods, and interleukin (IL)-1β, IL-4, IL-6, IL-10, IL-12, IL-13, IL-17, and tumor necrosis factor-α, and interferon (IFN)-γ serum cytokines were assessed by enzyme-linked immune assay.

RESULTS

Twenty-nine chronic chagasic patients were positive for parasitemia (17 IChD and 12 ChHD). Heart rate variability parameters in baseline condition and after cold face test were significantly decreased in chagasic patients compared to controls. Tilt tests showed no alteration. However, using nonlinear indices, ChHD patients presented lower values compared to IChD and controls. Differences in the expression of serum cytokines were observed between chagasic patients and controls. However, among the groups, ChHD presented higher median values of IL-10 and lower of IFN-γ compared to IChD.

CONCLUSION

Both chagasic groups present an autonomic impairment using linear methods. The nonlinear methods revealed that the ChHD group had a higher cardiovascular risk. Serum cytokine concentrations between chagasic patients were similar. However, ChHD showed higher concentrations of IL-10 and lower of IFN-γ, suggesting some established process of immune regulation.

The Valsalva maneuver in Chagas disease patients without cardiopathy

OBJECTIVES

To perform a meta-analysis of studies using the Valsalva ratio (VR) in Chagas disease (ChD) patients without cardiopathy in comparison to control subjects in order to determine if vagal heart modulation is impaired in early forms of ChD.

METHODS

The medical literature was systematically searched and reviewed for cross-sectional studies in humans in which the Valsalva maneuver was used to evaluate the autonomic modulation of the heart in ChD patients without cardiopathy. The Hedges g statistic (software Medcalc v.9.4.0.0) was used to combine the results of all studies through the calculation of the summary standardized mean difference (SMD): the mean VR in controls minus the mean VR in ChD patients, divided by the pooled and adjusted standard deviation. The sample size necessary to detect this SMD with 80% of power was calculated using the G*Power software v.3.0.

RESULTS

The meta-analysis included 396 patients in 7 studies. Summary mean VRs were 1.87 +/- 0.39 ms in controls versus 1.74 +/- 0.40 ms in ChD without cardiopathy, leading to a statistically significant summary SMD of -0.310 (95% CI -0.513 to -0.106). Considering the summary SMD of -0.31, an alpha error of 0.05 and a 1:1 ratio of ChD and control patients, the estimated total sample size for a study with 80% power was 330 patients.

INTERPRETATION

ChD patients without cardiopathy have reduced VR values compared to healthy controls, indicating early vagal dysfunction. Most previous studies could not detect this impairment due to small study samples and insufficient statistical power.

Vagal impairment in elderly Chagas disease patients: a population-based study (the Bambuí study)

BACKGROUND

Chagas disease (ChD) will become predominantly a disease of the elderly, as a consequence of the effectiveness of control measures in many Latin American countries. The effects of the disease in old age have received little attention. We investigated the effects of ageing in the association between cardiac vagal impairment, a typical feature of ChD, and chronic Trypanosoma cruzi infection.

METHODS

The study sample of this cross-sectional study consists of 1014 subjects ≥ 60 years old (mean age = 68.3; SD = 6.9) residing in Bambuí City (Southeast Brazil). ECG was recorded and one-breath sinus arrhythmia test was performed. Maximal expiratory over the minimal inspiratory (E:I) ratio and heart rate variability (HRV) measurements were calculated. Ordinal logistic regression was used to assess the relation between vagal indexes and chronic T. cruzi infection.

RESULTS

The prevalence of T. cruzi infection was 32.0% and of major ECG abnormalities, 43.4%. Among individuals aged 60-69 years, T. cruzi infection was significantly and independently associated with reduced SDNN (OR 0.38; 95% CI 0.27-0.53), RMSSD (OR 0.48; 0.34-0.67) and EI: ratio (OR 0.45; 95% CI 0.33-0.63). Among individuals aged >70 years, no significant odds ratios were found in either the unadjusted or the adjusted analysis. The presence of major ECG abnormalities did not affect the association between vagal indexes and T. cruzi infection.

CONCLUSIONS

Disease-specific vagal cardiac dysfunction was observed in ChD individuals below 70. However, further ageing interferes significantly with vagal heart modulation, attenuating the difference of HRV indexes between ChD and non-ChD subjects.