Ventricular arrhythmias and left ventricular myocardial function in chronic chagasic patients

Vagal dysautonomia in patients with Chagas disease and mortality: 14-year results of a population cohort of the elderly

INTRODUCTION

Great part of Chagas disease (ChD) mortality occurs due to ventricular arrhythmias, and autonomic function (AF) may predict unfavorable outcomes. We aimed to evaluate the predictive value of AF indexes in ChD patients.

METHODS

The Bambuí Study of Aging is a prospective cohort of residents ≥60 years at study onset (1997), in the southeastern Brazilian city of Bambuí (15,000 inhabitants). Consented participants underwent annual follow-up visits, and death certificates were tracked. AF was assessed by the maximum expiration on minimum inspiration (E:I) ratio during ECG acquisition and by heart rate variability indices: SDRR (standard deviation of adjacent RR intervals) and RMSSD (square root of the mean of the sum of squares of the differences between adjacent RR intervals)), calculated using a computer algorithm. Cox proportional hazards regression was performed to access the prognostic value of AF indexes, expressed as terciles, for all-cause mortality, after adjustment for demographic, clinical and ECG variables.

RESULTS

From 1742 qualifying residents, 1000 had valid AF tests, being 321 with ChD. Among these, median age was 68 (64-74) years, and 32.5% were men. In Cox survival analyses, only SDRR was associated with all-cause mortality in non-adjusted models: SDRR (hazard ratio (HR): 1.26 (95% CI 1.08-1.47), p < 0.001), E:I ratio (HR: 1.13 (95% CI 0,98-1.31), p = 0.10) and RMSSD (HR: 0.99 (0.86-1.16), p = 0.95). After adjustment for sex and age, none of the indexes remained as independent predictors.

CONCLUSION

Among elderly patients with ChD, AF indexes available in this cohort were not independent predictors of 14-year mortality.

Exploring the Historical Background and Clinical Implications of Electrocardiogram in the Context of Chagas Disease Research

Chagas disease (CD) remains one of the most significant endemic diseases in Latin America. Approximately 30% of individuals with CD develop the cardiac form, the main determinant of morbidity and mortality, which is characterized by typical electrocardiogram (ECG) changes caused by chronic chagasic cardiopathy (CCC). This review accentuates to how crucial it is for research teams and reference centers that treat patients with CD to standardize ECG in CCC. This was a non-systematic review of the literature. ECG is the most widely used examination in the diagnosis and evaluation of CCC, and it is also employed in epidemiological surveys, risk stratification for cardiovascular events and death, and monitoring the clinical progression of the disease. Carlos Chagas and Eurico Villela published the first work addressing CCC in 1922. Other works followed, including the study by Evandro Chagas' which was the first to perform ECG in CD, culminating in Francisco Laranja's seminal work in 1956. Since the 1980s, standardizations and ECG reading codes for CD have been established. This standardization aimed to code complex arrhythmias and characteristic ventricular conduction disorders and standardize ECG readings for clinical and epidemiological studies in CD. Nearly all existing electrocardiographic abnormalities can be found in CD, with a predominance of abnormalities in the formation and conduction of cardiac stimuli. The complex and heterogeneous substrate of CD with varied electrocardiographic manifestations poses a significant challenge when comparing studies involving patients with CCC, emphasizing the need for ECG standardization in CD.

Management of Cardiovascular Disease in Patients With COVID-19 and Chronic Chagas Disease: Implications to Prevent a Scourge Still Larger

Cardiovascular diseases (CVD) are the most important cause of morbidity and mortality in the general population. Because the high prevalence of COVID-19 and chronic Chagas disease (CCD) where the latter is endemic, all such diseases will likely be observed in the same patient. While COVID-19 can provoke generalized endotheliitis, which can lead to a cytokine storm and a hyper-coagulable state culminating into in-site and at a distance thrombosis. Therefore, small-vessel coronary artery disease (CAD), cerebrovascular disease, thromboembolism, and arrhythmias are prominent findings in COVID-19. In CCD, small-vessel CAD, cardioembolic stroke, pulmonary embolism, heart failure and arrhythmias are frequently observed as a result of a similar but less intense mechanism. Consequently, the association of CCD and COVID-19 will likely increase the incidence of CVD. Thus, doctors on the frontline should be on the alert for this diagnostic possibility so that the proper treatment can be given without any delay.

Advanced Therapies for Ventricular Arrhythmias in Patients With Chagasic Cardiomyopathy: JACC State-of-the-Art Review

Chagas disease is caused by infection from the protozoan parasite Trypanosoma cruzi. Although it is endemic to Latin America, global migration has led to an increased incidence of Chagas in Europe, Asia, Australia, and North America. Following acute infection, up to 30% of patients will develop chronic Chagas disease, with most patients developing Chagasic cardiomyopathy. Chronic Chagas cardiomyopathy is highly arrhythmogenic, with estimated annual rates of appropriate implantable cardioverter-defibrillator therapies and electrical storm of 25% and 9.1%, respectively. Managing arrhythmias in patients with Chagasic cardiomyopathy is a major challenge for the clinical electrophysiologist, requiring intimate knowledge of cardiac anatomy, advanced training, and expertise. Endocardial-epicardial mapping and ablation strategy is needed to treat arrhythmias in this patient population, owing to the suboptimal long-term success rate of endocardial mapping and ablation alone. We also describe innovative approaches to improve acute and long-term clinical outcomes in patients with refractory ventricular arrhythmias following catheter ablation, such as bilateral cervicothoracic sympathectomy and bilateral renal denervation, among others.

Cardiac magnetic resonance imaging in Chagas' disease: a parallel with electrophysiologic studies

Chagas' disease (CD), caused by the parasite Trypanosoma cruzi, is the leading cause of cardiac disability from infectious diseases in Central and South America. The disease progresses through an extended, asymptomatic form characterized by latency without clinical manifestations into a symptomatic form with cardiac and gastro-intestinal manifestations. In the terminal phase, chronic Chagas' myocarditis results in extensive myocardial fibrosis, chamber enlargement with aneurysms and ventricular tachycardia (VT). Cardiac magnetic resonance imaging (CMR) has proven useful in characterizing myocardial fibrosis (MF). Sub-epicardial and mid-wall fibrosis are less common patterns of MF in CHD than transmural scar, which resembles myocardial infarction. Commonly involved areas of MF include the left ventricular apex and basal infero-lateral wall, suggesting a role for watershed ischemia in the pathophysiology of MF. Electrophysiology studies have helped refine the relationship between MF and VT in this setting. This article reviews the patterns of MF in CHD and correlate these patterns with electrogram patterns to predict risk of ventricular arrhythmias and sudden death.

Chagas Cardiomyopathy: An Update of Current Clinical Knowledge and Management: A Scientific Statement From the American Heart Association

Background:

Chagas disease, resulting from the protozoan Trypanosoma cruzi , is an important cause of heart failure, stroke, arrhythmia, and sudden death. Traditionally regarded as a tropical disease found only in Central America and South America, Chagas disease now affects at least 300 000 residents of the United States and is growing in prevalence in other traditionally nonendemic areas. Healthcare providers and health systems outside of Latin America need to be equipped to recognize, diagnose, and treat Chagas disease and to prevent further disease transmission.

Methods and Results:

The American Heart Association and the Inter-American Society of Cardiology commissioned this statement to increase global awareness among providers who may encounter patients with Chagas disease outside of traditionally endemic environments. In this document, we summarize the most updated information on diagnosis, screening, and treatment of T cruzi infection, focusing primarily on its cardiovascular aspects. This document also provides quick reference tables, highlighting salient considerations for a patient with suspected or confirmed Chagas disease.

Conclusions:

This statement provides a broad summary of current knowledge and practice in the diagnosis and management of Chagas cardiomyopathy. It is our intent that this document will serve to increase the recognition of Chagas cardiomyopathy in low-prevalence areas and to improve care for patients with Chagas heart disease around the world.

Innate immune receptors over expression correlate with chronic chagasic cardiomyopathy and digestive damage in patients

Chronic chagasic cardiomyopathy (CCC) is observed in 30% to 50% of the individuals infected by Trypanosoma cruzi and heart failure is the important cause of death among patients in the chronic phase of Chagas disease. Although some studies have elucidated the role of adaptive immune responses involving T and B lymphocytes in cardiac pathogenesis, the role of innate immunity receptors such as Toll-like receptors (TLRs) and Nod-like receptors (NLRs) in CCC pathophysiology has not yet been determined. In this study, we evaluated the association among innate immune receptors (TLR1-9 and nucleotide-binding domain-like receptor protein 3/NLRP3), its adapter molecules (Myd88, TRIF, ASC and caspase-1) and cytokines (IL-1β, IL-6, IL-12, IL-18, IL-23, TNF-α, and IFN-β) with clinical manifestation, digestive and cardiac function in patients with different clinical forms of chronic Chagas disease. The TLR8 mRNA expression levels were enhanced in the peripheral blood mononuclear cells (PBMC) from digestive and cardiodigestive patients compared to indeterminate and cardiac patients. Furthermore, mRNA expression of IFN-β (cytokine produced after TLR8 activation) was higher in digestive and cardiodigestive patients when compared to indeterminate. Moreover, there was a positive correlation between TLR8 and IFN-β mRNA expression with sigmoid and rectum size. Cardiac and cardiodigestive patients presented higher TLR2, IL-12 and TNF-α mRNA expression than indeterminate and digestive patients. Moreover, cardiac patients also expressed higher levels of NLRP3, ASC and IL-1β mRNAs than indeterminate patients. In addition, we showed a negative correlation among TLR2, IL-1β, IL-12 and TNF-α levels with left ventricular ejection fraction, and positive correlation between NLRP3 with cardiothoracic index, and TLR2, IL-1β and IL-12 with left ventricular mass index. Together, our data suggest that high expression of innate immune receptors in cardiac and digestive patients may induce an enhancement of cytokine expression and participate of cardiac and digestive dysfunction.

Chronic Chagas Heart Disease Management: From Etiology to Cardiomyopathy Treatment

Trypanosoma cruzi (T. cruzi) infection is endemic in Latin America and is becoming a worldwide health burden. It may lead to heterogeneous phenotypes. Early diagnosis of T. cruzi infection is crucial. Several biomarkers have been reported in Chagas heart disease (ChHD), but most are nonspecific for T. cruzi infection. Prognosis of ChHD patients is worse compared with other etiologies, with sudden cardiac death as an important mode of death. Most ChHD patients display diffuse myocarditis with fibrosis and hypertrophy. The remodeling process seems to be associated with etiopathogenic mechanisms and neurohormonal activation. Pharmacological treatment and antiarrhythmic therapy for ChHD is mostly based on results for other etiologies. Heart transplantation is an established, valuable therapeutic option in refractory ChHD. Implantable cardioverter-defibrillators are indicated for prevention of secondary sudden cardiac death. Specific etiological treatments should be revisited and reserved for select patients. Understanding and management of ChHD need improvement, including development of randomized trials.

Arrhythmias in chagasic cardiomyopathy

Chagas disease, a chronic parasitosis caused by the protozoa Trypanosoma cruzi, is an increasing worldwide problem because of the number of cases in endemic areas and the migration of infected individuals to more developed regions. Chagas disease affects the heart through cardiac parasympathetic neuronal depopulation, immune-mediated myocardial injury, parasite persistence in cardiac tissue with secondary antigenic stimulation, and coronary microvascular abnormalities causing myocardial ischemia. A lack of knowledge exists for risk stratification, management, and prevention of ventricular arrhythmias in patients with chagasic cardiomyopathy. Catheter ablation can be effective for the management of recurrent ventricular tachycardia.

Rehabilitation practice patterns for patients with heart failure: the South American perspective

Heart failure (HF) is an important public health issue in South America. Economic impacts are substantial. Chagas heart disease is a prevalent HF etiology; it is caused by the protozoan Trypanosoma cruzi. Cardiac rehabilitation (CR) is an integral component of HF care. The benefits of CR in HF patients need to be assessed. The effectiveness and safety of CR delivery, such as home-based interventions, should be explored. Strategies to improve adherence in CR are imperative. We describe past and current CR trends for HF patients and discuss the future of this important intervention.

Chagas disease: an overview of clinical and epidemiological aspects

Chagas disease, caused by the parasite Trypanosoma cruzi, is a serious health problem in Latin America and is an emerging disease in non-endemic countries. In recent decades, the epidemiological profile of the disease has changed due to new patterns of immigration and successful control in its transmission, leading to the urbanization and globalization of the disease. Dilated cardiomyopathy is the most important and severe manifestation of human chronic Chagas disease and is characterized by heart failure, ventricular arrhythmias, heart blocks, thromboembolic phenomena, and sudden death. This article will present an overview of the clinical and epidemiological aspects of Chagas disease. It will focus on several clinical aspects of the disease, such as chronic Chagas disease without detectable cardiac pathology, as well as dysautonomia, some specific features, and the principles of treatment of chronic cardiomyopathy.

Diagnosis and management of Chagas disease and cardiomyopathy

Chagas cardiomyopathy is the most severe and life-threatening manifestation of human Chagas disease--a 'neglected' tropical disease caused by the protozoan parasite Trypanosoma cruzi. The disease is endemic in all continental Latin American countries, but has become a worldwide problem because of migration of infected individuals to developed countries, mainly in Europe and North America. Chagas cardiomyopathy results from the combined effects of persistent parasitism, parasite-driven tissue inflammation, microvascular and neurogenic dysfunction, and autoimmune responses triggered by the infection. Clinical presentation varies widely according to the extent of myocardial damage, and manifests mainly as three basic syndromes that can coexist in an individual patient: heart failure, cardiac arrhythmia, and thromboembolism. NYHA functional class, left ventricular systolic function, and nonsustained ventricular tachycardia are important prognostic markers of the risk of death. Management of Chagas cardiomyopathy focuses on the treatment of the three main syndromes. The use of β-blockers in patients with Chagas disease and heart failure is safe, well tolerated, and should be encouraged. Most specialists and international institutions now recommend specific antitrypanosomal treatment of patients with chronic Chagas disease, even in the absence of evidence obtained from randomized clinical trials. Further research on the management of patients with Chagas cardiomyopathy is necessary.

Pathogenesis of Chagas disease cardiomyopathy

Chagas disease, or American trypanosomiasis, is a parasitic infection caused by the flagellate protozoan Trypanosoma cruzi. Chagas disease is mainly affecting rural populations in Mexico and Central and South America. The World Health Organization estimates that 300 000 new cases of Chagas disease occur every year and approximately 20 000 deaths are attributable to Chagas. However, this organisation classified Chagas disease as a neglected tropical disease. The economic burden of this disease is significant. In many Latin American countries, the direct and indirect costs, including the cost of health care in dollars and loss of productivity, attributable to Chagas disease ranges from $40 million to in excess of $800 million per nation per annum. So, it remains a contemporary public health concern. In chronic phase, mortality is primarily due to the rhythm disturbances and congestive heart failure that result from the chronic inflammatory cardiomyopathy (CCC) due to the persistence presence of parasites in the heart tissue. Mechanisms underlying differential progression to CCC are still incompletely understood. In the last decades immunological proteomic genetic approaches lead to significant results which help to disperse the veil covering the knowledge of the pathogenic process. Here, we reported these significant progresses.

Epicardial Ablation of Ventricular Tachycardia in Chagas Heart Disease

Chagas heart disease is a chronic diffuse inflammatory cardiomyopathy with focal aspects. A wide spectrum of cardiac involvement can be found over time and these pathologic aspects determine different clinical presentations of the disease. The peculiar progress of the anatomic substrate may predispose the patient to a progressive cardiomyopathy, complex arrhythmias, and thromboembolic phenomena. Chagas ventricular tachycardia is a reentrant and scar-related tachycardia, and epicardial circuits are frequently found that substrate predominantly related to the inferior and lateral basal walls. Combining endocardial and epicardial mapping and ablation could improve the results of conventional endocardial ventricular tachycardia ablation.

Chagas cardiomyopathy--where do we stand after a hundred years?

A hundred years from its description, Chagas cardiomyopathy remains a challenging disease. Although successful vector-control strategies have decreased the incidence of Chagas disease in several Latin American countries, both migration to urban areas and immigration have spread the disease worldwide; and now, blood transfusion, organ transplantation, and vertical transmission are a concern. The pathogenesis of Chagas cardiomyopathy involves complex host-parasite interactions, where low-grade but incessant systemic infection and triggered autoimmune reaction are the main mechanisms for its development, with the contribution of autonomic damage and microvascular disturbances. Chagas cardiomyopathy is the most important clinical presentation of Chagas disease and comprises a wide range of manifestations, including heart failure, arrhythmias, heart blocks, sudden death, thromboembolism, and stroke. Recently, simple clinical prognostic scores have been developed to identify high-risk patients and help with management. The treatment of Chagas cardiomyopathy focuses mostly on managing heart failure, arrhythmias, and thromboembolism. The role of specific antiparasitic therapy in the chronic form is not yet defined, and a randomized trial is now under way to address this crucial point. In this article, we review the main clinical aspects of Chagas cardiomyopathy and underscore some upcoming challenges for the appropriate control, diagnosis, and management of this complex disease.

An update on the management of Chagas cardiomyopathy

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, infects nearly 18 million people in Latin America and mainly affects the heart, causing heart failure, arrhythmias, heart block, thromboembolism, stroke and death. In this review, the clinical diagnosis and management of Chagas cardiomyopathy are discussed. Particular emphasis is placed on the clinical staging of patients and the use of various diagnostic tests that may be useful in individualizing treatment of the two most relevant clinical syndromes, that is, heart failure and arrhythmias. The relevance of specific treatments are discussed, stressing the important role of parasite persistence in disease pathogenesis. We also discuss new therapy modalities that may have a role in the treatment of Chagas cardiomyopathy.

Right ventricular dysfunction is an independent predictor of survival in patients with dilated chronic Chagas' cardiomyopathy

BACKGROUND

Right ventricular (RV) involvement is a typical feature of Chagas' disease. In patients with congestive heart failure of other etiologies, RV dysfunction is a strong indicator of poor prognosis. However, the prognostic value of RV dysfunction in patients with Chagas' cardiomyopathy has not been reported. This study sought to investigate the prognostic value of RV dysfunction, apart from other well established risk factors, in patients with Chagas' cardiomyopathy.

METHODS

The study enrolled 158 patients (99 men; mean age of 48+/-12 years) from a tertiary center for Chagas' disease. Patients were selected if found to have both the diagnosis of Chagas' disease and cardiomyopathy. All patients underwent a comprehensive Doppler echocardiogram and the global RV function was quantitatively assessed using the RV index of myocardial performance (Tei index).

RESULTS

Most of the patients were in NYHA classes I and II (79%). During a mean follow up of 34+/-23 months, 44 patients (28%) died: 24 (55%) patients died of progressive heart failure and 16 (36%) of sudden death. RV Tei index emerged as an independent predictor of survival (hazard ratio 5.75, 95% confidence interval 1.69 to 19.51). Kaplan-Meier survival curves showed a higher cumulative mortality among patients in the highest quartile of RV Tei index, compared with other 3 quartiles (log-rank statistic 21.87, p<0.001). After adjustment for clinical data and LV ejection fraction, RV Tei index in the highest quartile (>0.56) remained a significant predictor of death (hazard ratio 5.29, 95% confidence interval 2.43 to 11.52).

CONCLUSIONS

RV function assessed by the Tei index added significant prognostic information, incremental to the NYHA clinical classification and to the standard echocardiographic evaluation of LV systolic function. A simple measure of a Doppler index, which allows analysis of both systolic and diastolic function of the RV, appears to be a useful non-invasive tool for risk stratification in patients with dilated chronic Chagas' cardiomyopathy.

Oxidative stress in chronic cardiopathy associated with Chagas disease

BACKGROUND

Chagas disease is characterized by chronic inflammation similar to autoimmune diseases. The imbalance between prooxidant and antioxidant defenses is known as oxidative stress, and is often associated with inflammatory processes of many diseases.

METHODS

The present work measured some components of the antioxidant system present in the blood of four groups of patients in different stages of chronic Chagas heart disease (n=10 each group), according to the modified Los Andes clinical-hemodynamic classification. Each group of chagasic patients was compared with four groups of healthy subjects, and chagasic group IV was compared to group V, characterized by rheumatic cardiac disease, giving a total of 90 subjects. Antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), and the contents of reduced (GSH), oxidized (GSSG) and total glutathione (TG) were assayed.

RESULTS

SOD, CAT and GR activities showed essentially no differences among the four groups, however, intraerythrocytic GSH concentrations showed decreased values parallel to the progression of the disease. In addition, the glutathione peroxidase (GPx) activities were higher in groups III and V and lower in groups I, II and IV, also suggesting an antioxidant depletion with progression of the disease. In contrast, except for SOD and CAT activities, patients from group V showed a generally higher antioxidant capacity compared to the chagasic group IV.

CONCLUSION

The results indicate a general increase of oxidative stress parallel to the progression of Chagas disease.

Teste ergométrico e o Holter de 24 horas na detecção de arritmias ventriculares complexas em diferentes estádios da cardiopatia chagásica crônica

Comparou-se o teste ergométrico com Holter de 24 horas na detecção de arritmias ventriculares complexas em diferentes estádios da cardiopatia chagásica crônica. Avaliados 71 pacientes sem outras doenças associadas, idade=51±10,3, metade mulheres. Divididos em quatro grupos conforme o grau de acometimento cardíaco. A estatística esta discriminada no corpo do trabalho. Ao Holter, no grupo IA as arritmias ventriculares complexas foram detectadas em 4,3%, IB em 25%, II em 55% e no grupo III em 90%. Nos grupos II e III não houve diferença entre os exames na detecção de arritmias ventriculares complexas (p=NS). Nos grupos IA e IB, houve uma concordância de 100% no teste ergométrico na não detecção de arritmias ventriculares complexas entre dois observadores. No grupo II, a concordância foi de 70% (kappa=0,368, p=0,003) e de 90% (kappa=0,78, p=0,002) no grupo III. Foi observado diferenças na presença de arritmias ventriculares complexas entre os pacientes dos grupos em fase inicial e avançada da cardiopatia chagásica crônica. Nos pacientes dos grupos II e III não houve diferença entre os dois exames na detecção das arritmias ventriculares complexas. Pacientes dos grupos IA e IB é razoável indicar Holter e/ou o teste ergométrico na ocorrência de progressão da doença.

Sera from chronic chagasic patients depress cardiac electrogenesis and conduction

We report results obtained with sera from 58 chronic chagasic patients that were evaluated for effects on heart rate and atrioventricular (AV) conduction in isolated rabbit hearts and screened for the presence of muscarinic and beta-adrenergic activity. We show that sera from 26 patients decreased heart rate, while 10 increased it and 22 had no effect. Additionally, sera from 20 of the 58 patients blocked AV conduction. Muscarinic activation seems to be involved in both effects, but is not the only mechanism, since atropine did not antagonize the decrease in heart rate in 23% of sera or AV block in 40%. Sera from patients with complex arrhythmias were significantly more effective in depressing both heart rate and AV conduction. Sera that induce increases in heart rate seem to operate exclusively through beta-adrenergic activation. Two of these sera, evaluated with respect to intercellular communication in primary cultures of embryonic cardiomyocytes were able to block gap junction conductance evaluated by a dye injection technique after 24-h exposure. The mechanisms underlying this uncoupling effect are currently being investigated.

[Indeterminate form of Chagas disease: considerations about diagnosis and prognosis]

The indeterminate form of Chagas' disease is defined by the absence of clinical, radiological and electrocardiographic manifestations of cardiac or digestive involvement in Trypanosoma cruzi chronic infected persons. When submitted to advanced cardiovascular tests, these patients may present significant abnormalities. However, the indeterminate form concept was reaffirmed as valid, since diagnostic criteria are simple and prognosis is benignant. In clinical practice, diagnostic difficulties are frequent, related to subjectivity and uncertain meaning of clinical, electrocardiographic and radiological findings. Moreover, indeterminate form prognosis is not equally good: after five to 10 years, a third of patients will have cardiopathy. Sudden death, a rare complication, may be the first manifestation of Chagas' disease. It is necessary to reappraise indeterminate form concept, redefining diagnostic criteria and therapeutic management. Clinical and noninvasive evaluation may allow individual risk stratification; therapeutic interventions may be beneficial in high risk groups. Since etiologic treatment may prevent cardiopathy, its role in indeterminate form management must be reassessed.

Sera from chronic chagasic patients with complex cardiac arrhythmias depress electrogenesis and conduction in isolated rabbit hearts

BACKGROUND

Immune dysfunction has long been proposed as a mechanism for the etiopathogenesis of the chronic phase of Chagas' disease. Antibodies of chagasic patients have been shown to interfere with electric and mechanical activity of embryonic myocardial cells in culture. Here, we demonstrate that antibodies derived from a group of chronic chagasic patients are able to induce disturbances in the electrogenesis and conduction in isolated adult rabbit hearts.

METHODS AND RESULTS

Sera from chronic chagasic patients with complex cardiac arrhythmias (ChA+) decreased heart rate (from 131+/-26 to 98+/-37 bpm [mean+/-SD]; n=6; P<.05) in isolated rabbit hearts when perfused at a dilution of 1:100 (vol:vol) by the Langendorff method. Sera from another experimental group of four chronic chagasic patients without complex arrhythmias (ChA-) and two control groups composed of five Wolff-Parkinson-White (WPW) syndrome patients and five orthopedic surgery patients did not affect heart rate when tested under similar conditions. In addition, sera from five of six ChA+ patients and from one WPW patient induced AV conduction blockade. Effects of the sera from ChA+ patients are due to their IgG fractions. Both serum and IgG effects are blocked by atropine (10 micromol/L).

CONCLUSIONS

Antibodies of ChA+ patients decrease heart rate and induce AV conduction block in isolated adult rabbit hearts through activation of muscarinic receptors.

Electrocardiography in Chagas' heart disease

Conventional ECG still plays an important role in the overall knowledge of Chagas' cardiopathy, because of its importance in longitudinal and epidemiological studies, its diagnostic value, and its utility in prognostic evaluation. The authors discuss these aspects, as well as the use of eCG in the acute phase and the significance of a normal ECG in Chagas' disease. Correlations were made between ECG and Hemodynamic/angiographic variables among 1010 patients with positive laboratory tests for Chagas' disease: a) in the group with normal ECG there was no significant differences between symptomatic and non-symptomatic patients with regard to ejection fraction and angiographic abnormalities; b) slight abnormalities on the ECG corresponded to an intermediate level of severity of the disease, that is, between normal ECG and ECG with significant abnormalities C) fibrosis on the ECG was not predictive of akinesia in the related area on the angiography; d) combined ECG abnormalities generally correlated with greater myocardial compromises compared to isolated abnormalities; e) under multiple regression analysis the ECG abnormalities that independently correlated with depressed ejection fraction were: premature ventricular beats, ventricular tachycardia, left bundle branch block, atrial fibrillation, complete AV block, and anterior and inferior fibrosis. Male sex, cardiac insufficiency and cardiomegaly on the throat radiography were also significantly related.

Holter monitoring in Chagas' heart disease

Electrocardiographic rhythm disturbance evaluation by Holter monitoring is increasingly becoming a useful methodologic tool for risk stratification as well as for therapeutic assessment in patients with Chagas' disease. Furthermore, late potential analyses, now being directly obtained from Holter recording has promising perspectives in enhancing identification of patients with high risk profiles for development of malignant ventricular arrhythmias. In addition, recently incorporated to Holter studies, heart rate variability analysis will certainly contribute to a better understanding of the characteristic autonomic nervous system disarray that commonly affects chagasic patients.

Ventricular function in Chagas' heart disease

Invasive and noninvasive methods used to evaluate ventricular function in Chagas's disease are reviewed. The traditional indices of overall ventricular performance reflect the interaction of preload, contractility, afterload and heart rate. Therefore, they are unable to distinguish changes in contractility from modifications of loading conditions. The role of ventricular function as a predictor of mortality in chronic Chagas' heart disease is discussed. Ventricular function abnormalities in patients with indeterminate and digestive forms of Chagas' disease are especially emphasized. Finally, the evidence of early impairment of diastolic performance in digestive forms of Chagas' disease are especially emphasized. Finally, the evidence of early impairment of diastolic performance in patients with Chagas' disease is presented.

Electrophysiologic study in chronic Chagas' heart disease

Cardiac arrhythmias are common in chagasic patients. Electrophysiologic study is an invasive procedure for the investigation of sinus node function, atrioventricular node conduction and intraventricular (His-Purkinje) conduction and the mechanism of tachycardias. It is useful in elucidating syncope, dizziness and tachycardiac palpitations that remain unexplained by non-invasive diagnostic methods. It is fundamental in directing non-pharmacological therapy, especially in "sudden death" survivors. Chagasic patients may benefit from electrophysiologic study after a critical clinical evaluation.

Prognostic implications of clinical, electrocardiographic and hemodynamic findings in chronic Chagas' disease

To evaluate the prognostic importance of 19 clinical, electrocardiographic and hemodynamic variables, 556 chronic chagasic patients were submitted to an extensive protocol, including left cineventriculogram and Holter monitoring, and followed for up to 15 years. The protagonist role of the magnitude of the myocardial compromise in the evolution of chagasic patients is underscored by our results, which indicated the independent prognostic value of an ejection fraction below 0.30 (P < 0.001), a heart rate higher than 89 beats/min (P < 0.01), grade IV functional capacity (P < 0.05), end systolic stress > 120 g/cm2 (P < 0.05), and end diastolic volume index > 200 ml/m2 (P < 0.05). When only patients with an ejection fraction over 0.29 were considered, variables with independent prognostic value were: the cardio-thoracic ratio (P < 0.01), functional capacity (P < 0.05) and heart rate (P < 0.05). Survival analysis demonstrated that the presence of complex (Lown III, IV) ventricular arrhythmias increased mortality significantly (P < 0.01) only in patients with an ejection fraction over 0.29. Therefore, preservation of myocardial function is the capital measure in the treatment of chronic chagasic patients.

[A longitudinal electrocardiogram study of Chagas' disease from the acute phase]

Several studies have been done to analyse the relationship between the characteristics of the electrocardiogram (ECG) and mortality in the several stages of the disease, using different methods like multiple case and longitudinal studies. We analysed the ECG from the acute stage up to twenty years of follow-up (+/- 9 years) in 42 patients with Chagas' disease to determine their evolution and it's value like an index for therapeutic evaluation. The 42 patients (18 female, 24 males) were originally from the north of the State of Minas Gerais (Brazil) and the initial stage was mainly in the first two decades of age. All bad cardiac involvement and received full specific treatment. We utilized the following criteria for the ECG analyses: Modified Minnesota Code for Chagas' disease; WHO/ISFC TASK FORCE for inter ventricular conduction disturbances and Pieretti criteria for inactive electrical areas. We conclude that: a) The electrocardiogram changes tend to get worse with evolution into the chronic stage; b) The electrocardiogram is not a good index for therapeutic valuation.

Arrhythmias in heart failure--therapeutic challenges

Electrophysiologic disorders are common at all stages of heart failure due to myocardial mechanical factors, neuroendocrine disturbances, electrolyte abnormalities, or ischemia, and also because of cardiovascular drugs. The prevalence of various forms of heart block, bradycardias, and arrhythmias in heart failure is largely unknown, as is their relationship to the etiology of the syndrome. Complex and multiform ventricular premature beats and nonsustained ventricular tachycardia are common, and their frequency is broadly related to the severity of heart failure. Supraventricular arrhythmias are also common features of the syndrome. The heart failure syndrome has an ominous prognosis. Approximately half the patients die suddenly, but the causal relationship between preexisting arrhythmias and sudden death is not known. Equally vital is knowledge of the influence of drug therapy on the arrhythmias of heart failure, but at present this is scarce and needs further study.