Limited myocardial contractile reserve and chronotropic incompetence in patients with chronic Chagas' disease: assessment by dobutamine stress echocardiography

Left ventricular contractile reserve as a determinant of adverse clinical outcomes: a systematic review

An abnormal left ventricular contractile reserve is often seen in patients undergoing stress echocardiogram and may indicate the presence of obstructive coronary artery disease. The techniques and indexes used to identify abnormal left ventricular contractile response and its prognostic value in the absence of known causes has not been well studied. To describe the characteristics and clinical outcomes associated with an abnormal left ventricular contractile response, we performed a systematic review that identified 27 eligible studies. A diverse range of indices were utilised to measure left ventricular contractile reserve, most commonly Δleft ventricular ejection fraction in 11 studies. Dobutamine stress echocardiogram was the most commonly performed modality (19 studies) followed by exercise stress echocardiogram (4 studies), dipyridamole stress echocardiogram (2 studies), invasive hemodynamic measurement (1 study) and dobutamine stress magnetic resonance imaging (1 study). All but one study demonstrated a significant association between the absence of left ventricular contractile reserve and increased rate of cardiovascular events, cardiac death and all-cause mortality.

Chagas Cardiomyopathy: From Romaña Sign to Heart Failure and Sudden Cardiac Death

Despite nearly a century of research and accounting for the highest disease burden of any parasitic disease in the Western Hemisphere, Chagas disease (CD) is still a challenging diagnosis, primarily due to its poor recognition outside of Latin America. Although initially considered endemic to Central and South America, globalization, urbanization, and increased migration have spread the disease worldwide in the last few years, making it a significant public health threat. The international medical community's apparent lack of interest in this disease that was previously thought to be geographically restricted has delayed research on the complex host-parasite relationship that determines myocardial involvement and its differential behavior from other forms of cardiomyopathy, particularly regarding treatment strategies. Multiple cellular and molecular mechanisms that contribute to degenerative, inflammatory, and fibrotic myocardial responses have been identified and warrant further research to expand the therapeutic arsenal and impact the high burden attributed to CD. Altogether, cardiac dysautonomia, microvascular disturbances, parasite-mediated myocardial damage, and chronic immune-mediated injury are responsible for the disease's clinical manifestations, ranging from asymptomatic disease to severe cardiac and gastrointestinal involvement. It is crucial for healthcare workers to better understand CD transmission and disease dynamics, including its behavior on both its acute and chronic phases, to make adequate and evidence-based decisions regarding the disease. This review aims to summarize the most recent information on the epidemiology, pathogenesis, clinical presentation, diagnosis, screening, and treatment of CD, emphasizing on Chagasic cardiomyopathy's (Ch-CMP) clinical presentation and pathobiological mechanisms leading to sudden cardiac death.

Incidence and variables associated with arrhythmias during dobutamine-atropine stress echocardiography among patients with Chagas disease

BACKGROUND

Dobutamine stress echocardiography (DSE) is an important tool in the diagnosis of coronary artery disease. However, there is hesitation in clinical practice for using it in patients with Chagas disease (CD) due to the arrhythmogenic potential of this heart condition. This study aimed to evaluate the incidence and variables associated with arrhythmias during DSE in a population of patients with CD.

METHODS

A population of 205 consecutive patients with CD and suspected coronary heart disease was assessed through a retrospective database analysis. CD was confirmed in all patients by serological testing.

RESULTS

The mean age of the patients selected was 64 years, and 65.4% of the patients were female. Significant arrhythmias occurred as follows: nonsustained ventricular tachycardia in 7.3% of patients; supraventricular tachycardia and sustained ventricular tachycardia in 1%; and atrial fibrillation in 0.5%. Nonsignificant arrhythmias occurred as follows: premature ventricular contractions in 48% of patients and bigeminy in 4.4%. Values for the wall-motion score index at rest greater than 1.12 and 1.18 were independently correlated with the occurrence of nonsignificant arrhythmias (odds ratio [OR] = 2.90, P < 0.001) and significant arrhythmias (OR = 4.23, P = 0.044), respectively.

CONCLUSION

DSE should be considered a safe examination in patients with CD despite the known increased risk of arrhythmias in this group of patients. The occurrence of arrhythmias was low in this study. Abnormal wall-motion score index values at rest were associated with the occurrence of significant and nonsignificant arrhythmias during the test.

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.

Multimodality imaging evaluation of Chagas disease: an expert consensus of Brazilian Cardiovascular Imaging Department (DIC) and the European Association of Cardiovascular Imaging (EACVI)

Aims

To develop a document by Brazilian Cardiovascular Imaging Department (DIC) and the European Association of Cardiovascular Imaging (EACVI) to review and summarize the most recent evidences about the non-invasive assessment of patients with Chagas disease, with the intent to set up a framework for standardized cardiovascular imaging to assess cardiovascular morphologic and functional disturbances, as well as to guide the subsequent process of clinical decision-making.

Methods and results

Chagas disease remains one of the most prevalent infectious diseases in Latin America, and has become a health problem in non-endemic countries. Dilated cardiomyopathy is the most severe manifestation of Chagas disease, which causes substantial disability and early mortality in the socially most productive population leading to a significant economical burden. Prompt and correct diagnosis of Chagas disease requires specialized clinical expertise to recognize the unique features of this disease. The appropriate and efficient use of cardiac imaging is pivotal for diagnosing the cardiac involvement in Chagas disease, to stage the disease, assess patients' prognosis and address management. Echocardiography is the most common imaging modality used to assess, and follow-up patients with Chagas disease. The presence of echocardiographic abnormalities is of utmost importance, since it allows to stage patients according to disease progression. In early stages of cardiac involvement, echocardiography may demonstrate segmental left ventricuar wall motion abnormalities, mainly in the basal segments of inferior, inferolateral walls, and the apex, which cannot be attributed to obstructive coronary artery arteries. The prevalence of segmental wall motion abnormalities varies according to the stage of the disease, reaching about 50% in patients with left ventricular dilatation and dysfunction. Speckle tracking echocardiography allows a more precise and quantitative measurement of the regional myocardial function. Since segmental wall motion abnormalities are frequent in Chagas disease, speckle tracking echocardiography may have an important clinical application in these patients, particularly in the indeterminate forms when abnormalities are more subtle. Speckle tracking echocardiography can also quantify the heterogeneity of systolic contraction, which is associated with the risk of arrhythmic events. Three-dimensional (3D) echocardiography is superior to conventional two-dimensional (2D) echocardiography for assessing more accurately the left ventricular apex and thus to detect apical aneurysms and thrombus in patients in whom ventricular foreshortening is suspected by 2D echocardiography. In addition, 3D echocardiography is more accurate than 2D Simpson s biplane rule for assessing left ventricular volumes and function in patients with significant wall motion abnormalities, including aneurysms with distorted ventricular geometry. Contrast echocardiography has the advantage to enhancement of left ventricular endocardial border, allowing for more accurate detection of ventricular aneurysms and thrombus in Chagas disease. Diastolic dysfunction is an important hallmark of Chagas disease even in its early phases. In general, left ventricular diastolic and systolic dysfunction coexist and isolated diastolic dysfunction is uncommon but may be present in patients with the indeterminate form. Right ventricular dysfunction may be detected early in the disease course, but in general, the clinical manifestations occur late at advanced stages of Chagas cardiomyopathy. Several echocardiographic parameters have been used to assess right ventricular function in Chagas disease, including qualitative evaluation, myocardial performance index, tissue Doppler imaging, tricuspid annular plane systolic excursion, and speckle tracking strain. Cardiac magnetic resonance (CMR) is useful to assess global and regional left ventricular function in patients with Chagas diseases. Myocardial fibrosis is a striking feature of Chagas cardiomyopathy and late gadolinium enhancement (LGE) is used to detect and quantify the extension of myocardial fibrosis. Myocardial fibrosis might have a role in risk stratification of patients with Chagas disease. Limited data are available regarding right ventricular function assessed by CMR in Chagas disease. Radionuclide ventriculography is used for global biventricular function assessment in patients with suspected or definite cardiac involvement in Chagas disease with suboptimal acoustic window and contraindication to CMR. Myocardial perfusion scintigraphy may improve risk stratification to define cardiac involvement in Chagas disease, especially in the patients with devices who cannot be submitted to CMR and in the clinical setting of Chagas patients whose main complaint is atypical chest pain. Detection of reversible ischemic defects predicts further deterioration of left ventricular systolic function and helps to avoid unnecessary cardiac catheterization and coronary angiography.

Conclusion

Cardiac imaging is crucial to detect the cardiac involvement in patients with Chagas disease, stage the disease and stratify patient risk and address management. Unfortunately, most patients live in regions with limited access to imaging methods and point-of-care, simplified protocols, could improve the access of these remote populations to important information that could impact in the clinical management of the disease. Therefore, there are many fields for further research in cardiac imaging in Chagas disease. How to better provide an earlier diagnosis of cardiac involvement and improve patients risk stratification remains to be addressed using different images modalities.

L, Rassi S. Dobutamine Stress Echocardiography Safety in Chagas Disease Patients

BACKGROUND:

A few decades ago, patients with Chagas disease were predominantly rural workers, with a low risk profile for obstructive coronary artery disease (CAD). As urbanization has increased, they became exposed to the same risk factors for CAD of uninfected individuals. Dobutamine stress echocardiography (DSE) has proven to be an important tool in CAD diagnosis. Despite being a potentially arrhythmogenic method, it is safe for coronary patients without Chagas disease. For Chagas disease patients, however, the indication of DSE in clinical practice is uncertain, because of the arrhythmogenic potential of that heart disease.

OBJECTIVES:

To assess DSE safety in Chagas disease patients with clinical suspicion of CAD, as well as the incidence of arrhythmias and adverse events during the exam.

METHODS:

Retrospective analysis of a database of patients referred for DSE from May/2012 to February/2015. This study assessed 205 consecutive patients with Chagas disease suspected of having CAD. All of them had their serology for Chagas disease confirmed.

RESULTS:

Their mean age was 64±10 years and most patients were females (65.4%). No patient had significant adverse events, such as acute myocardial infarction, ventricular fibrillation, asystole, stroke, cardiac rupture and death. Regarding arrhythmias, ventricular extrasystoles occurred in 48% of patients, and non-sustained ventricular tachycardia in 7.3%.

CONCLUSION:

DSE proved to be safe in this population of Chagas disease patients, in which no potentially life-threatening outcome was found.

FUNDAMENTO:

Até poucas décadas atrás, os pacientes chagásicos eram predominantemente trabalhadores rurais, com baixo perfil de risco para doença obstrutiva coronária. Com a crescente urbanização, passaram a ter os mesmos fatores de risco para doença aterosclerótica que indivíduos não infectados. O ecocardiograma sob estresse com dobutamina (EED) é uma importante ferramenta no diagnóstico de coronariopatia. É referido, porém, como um método potencialmente arritmogênico, mas seguro, em pacientes coronarianos não chagásicos. Entretanto, há insegurança na prática clínica de indicá-lo no paciente chagásico, devido ao potencial arritmogênico já intrínseco nesta cardiopatia.

OBJETIVOS:

Analisar a segurança do EED em uma população de chagásicos com suspeita clínica de coronariopatia.

MÉTODOS:

Análise retrospectiva de um banco de dados de pacientes encaminhados para a realização do EED entre maio/2012 e fevereiro/2015. Avaliou-se pacientes consecutivos portadores de doença de Chagas e com suspeita de coronariopatia. Confirmou-se a sorologia para doença de Chagas em todos os pacientes.

RESULTADOS:

A média etária dos 205 pacientes analisados foi de 64 ± 10 anos, sendo a maioria do sexo feminino (65,4%). Nenhum paciente apresentou eventos adversos significativos, como infarto agudo do miocárdio, fibrilação ventricular, assistolia, acidente vascular encefálico, ruptura cardíaca ou morte. Quanto às arritmias, extrassístoles ventriculares frequentes ocorreram em 48% dos pacientes, taquicardia ventricular não sustentada em 7,3%, bigeminismo em 4,4%, taquicardia supraventricular e taquicardia ventricular sustentada em 1% e fibrilação atrial em 0,5%.

CONCLUSÃO:

O EED mostrou ser um exame seguro nessa população de pacientes chagásicos, onde nenhum desfecho grave foi encontrado.

Exercise-induced decrease in myocardial high-energy phosphate metabolites in patients with Chagas heart disease

BACKGROUND

The influence of exercise on cardiac metabolic response in patients with Chagas disease is incompletely understood.

METHODS AND RESULTS

Changes in cardiac energetic metabolism were investigated in Chagas disease patients before and during isometric handgrip exercise with (31)P magnetic resonance spectroscopy (MRS). Twenty-eight patients (10 with systolic dysfunction: group I; 10 with normal systolic function and electrocardiogram (ECG) abnormalities: group II; and 8 asymptomatic without ECG abnormalities: group III) and 8 healthy control subjects (group C) were evaluated by electrocardiogram, echocardiogram, functional tests for coronary artery disease, and image-selected localized cardiac (31)P-MRS. The myocardial phosphocreatine to [β-phosphate]adenosine triphosphate ratio (PCr/β-ATP) was measured at rest and during isometric handgrip exercise. Exercise testing or 99mTc-sestamibi scintigraphy were negative for myocardial ischemia in all individuals. At rest, cardiac PCr/β-ATP was decreased in all Chagas groups (1.23 ± 0.37) versus group C (1.88 ± 0.08; P < .001) and was lower in group I (0.89 ± 0.24) versus groups II (1.44 ± 0.23) and III (1.40 ± 0.37; P < .001). There was no stress-induced change in cardiac PCr/β-ATP (1.88 ± 0.08 at rest vs 1.89 ± 0.08 during exercise; P = NS) in group C. Mean cardiac PCr/β-ATP was 0.89 ± 0.24 and 0.56 ± 0.21 at rest and during exercise, respectively, in group I (37% decrease; P < .001). In group II, PCr/β-ATP was 1.44 ± 0.23 at rest and 0.97 ± 0.37 during exercise (33% decrease; P < .001). In group III, PCr/β-ATP was 1.40 ± 0.37 at rest and 0.60 ± 0.19 during exercise (57% decrease; P < .001).

CONCLUSIONS

Myocardial high-energy phosphates are reduced at rest in Chagas heart disease patients, and the reduction is greater in patients with left ventricular dysfunction. Regardless of left ventricular function, Chagas patients exhibit an exercise-induced decline in cardiac high-energy phosphates consistent with myocardial ischemia, suggesting the possibility that this metabolic approach may offer a tool to probe new interventions in Chagas disease patients.

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.

Chagas heart disease: report on recent developments

Chagas disease, caused by the parasite Trypanosoma cruzi, is an important cause of cardiac disease in endemic areas of Latin America. It is now being diagnosed in nonendemic areas because of immigration. Typical cardiac manifestations of Chagas disease include dilated cardiomyopathy, congestive heart failure, arrhythmias, cardioembolism, and stroke. Clinical and laboratory-based research to define the pathology resulting from T. cruzi infection has shed light on many of the cellular and molecular mechanisms leading to these manifestations. Antiparasitic treatment may not be appropriate for patients with advanced cardiac disease. Clinical management of Chagas heart disease is similar to that used for cardiomyopathies caused by other processes. Cardiac transplantation has been successfully performed in a small number of patients with Chagas heart disease.

Selective decrease of components of the creatine kinase system and ATP synthase complex in chronic Chagas disease cardiomyopathy

Background

Chronic Chagas disease cardiomyopathy (CCC) is an inflammatory dilated cardiomyopathy with a worse prognosis than other cardiomyopathies. CCC occurs in 30 % of individuals infected with Trypanosoma cruzi, endemic in Latin America. Heart failure is associated with impaired energy metabolism, which may be correlated to contractile dysfunction. We thus analyzed the myocardial gene and protein expression, as well as activity, of key mitochondrial enzymes related to ATP production, in myocardial samples of end-stage CCC, idiopathic dilated (IDC) and ischemic (IC) cardiomyopathies.

Methodology/Principal Findings

Myocardium homogenates from CCC (N = 5), IC (N = 5) and IDC (N = 5) patients, as well as from heart donors (N = 5) were analyzed for protein and mRNA expression of mitochondrial creatine kinase (CKMit) and muscular creatine kinase (CKM) and ATP synthase subunits aplha and beta by immunoblotting and by real-time RT-PCR. Total myocardial CK activity was also assessed. Protein levels of CKM and CK activity were reduced in all three cardiomyopathy groups. However, total CK activity, as well as ATP synthase alpha chain protein levels, were significantly lower in CCC samples than IC and IDC samples. CCC myocardium displayed selective reduction of protein levels and activity of enzymes crucial for maintaining cytoplasmic ATP levels.

Conclusions/Significance

The selective impairment of the CK system may be associated to the loss of inotropic reserve observed in CCC. Reduction of ATP synthase alpha levels is consistent with a decrease in myocardial ATP generation through oxidative phosphorylation. Together, these results suggest that the energetic deficit is more intense in the myocardium of CCC patients than in the other tested dilated cardiomyopathies.

Chronic Chagas disease cardiomyopathy (CCC) affects millions in endemic areas and is presenting in growing numbers in the USA and European countries due to migration currents. Clinical progression, length of survival and overall prognosis are significantly worse in CCC patients when compared to patients with dilated cardiomyopathy of non-inflammatory etiology. Impairment of energy metabolism seems to play a role in heart failure due to cardiomyopathies. Herein, we have analyzed energy metabolism enzymes in myocardium samples of CCC patients comparing to other non-inflammatory cardiomyopathies. We found that myocardial tissue from CCC patients displays a significant reduction of both myocardial protein levels of ATP synthase alpha and creatine kinase enzyme activity, in comparison to control heart samples, as well as idiopathic dilated cardiomyopathy and ischemic cardiomyopathy. Our results suggest that CCC myocardium displays a selective energetic deficit, which may play a role in the reduced heart function observed in such patients.

Perioperative management of a patient with Chagas disease having mitral valve surgery

A patient with advanced Chagas disease presented with symptoms attributable to dilated cardiomyopathy and mitral regurgitation. Although esophageal involvement is part of the constellation of findings in Chagas, transesophageal echocardiography was safely used to guide the mitral valve surgery.

Echocardiography in Chagas heart disease

BACKGROUND

Chagas heart disease is a frequent cause of morbidity and mortality in Latin America. Echocardiography provides useful diagnostic and prognostic information and is an important tool in the management of patients with Chagas disease.

METHODS AND RESULTS

A search for relevant publications was obtained from MEDLINE, LILACS, and SCIELO sources. Acute Chagas myocarditis is a rare disorder in which pericardial effusion is frequent. Echocardiography may exclude pericardial tamponade in case of heart failure. Chronic Chagas cardiomyopathy evolves for several decades after the infection. Epidemiological history, positive serology, and suggestive clinical and ECG abnormalities establish the diagnosis. About three quarters of chronic Chagas cardiomyopathy subjects remain asymptomatic with normal (indeterminate form) or abnormal ECGs. Early Doppler abnormalities includes prolongation of isovolumic contraction and relaxation times. Systolic function frequently is normal, but dysfunction may be elicited by stress tests. Half or more of symptomatic patients have a left ventricular apical aneurysm and other segmental contractile abnormalities similar to those seen in coronary heart disease. The dilated nonsegmental form is indistinguishable from dilated cardiomyopathy. Results from univariate and multivariate Cox survival analyses indicate that impaired systolic function and increased ventricular dimensions have significant value in predicting cardiac morbidity and mortality. Cardiac ultrasound commonly is used in the follow-up of patients and in the assessment of various therapeutic modalities.

CONCLUSIONS

Echocardiographic and Doppler techniques provide useful structural and functional information in the detection of early myocardial damage, risk assessment of prognosis, disease progression, and management of patients with Chagas disease.

Clinical aspects of the Chagas' heart disease

Chagas' heart disease, caused by protozoan Trypanosoma cruzi, is a common cause of cardiomyopathy in the Americas. Transmission of T. cruzi occurs through Reduviids, the kissing bugs. Less common ways of transmission are blood transfusion, congenital transmission, organ transplantation, laboratory accident, breastfeeding, and oral contamination. Infestation results in cardiac dysautonomia, myocardial apoptosis, and myocardial fibrosis. In acute phase, death is mostly caused by myocarditis and in chronic phase, it is mostly by irreversible cardiomyopathy. A majority of the patients with Chagas' disease remain in the latent phase of disease for 10 to 30 years or even for life. Specific anti-Chagas' therapy with trypanocide drugs is useful in acute phase but the management of chronic Chagas' heart disease is mostly empirical. The mortality during the acute phase of cardiac Chagas is around 5%. Five-year mortality of chronic Chagas' disease with cardiac dysfunction is above 50%. The clinical aspects of the Chagas' heart disease are concisely reviewed.

Chronotropic incompetence and abnormal autonomic modulation in ambulatory Chagas disease patients

BACKGROUND

Chagas disease (ChD) patients might present chronotropic incompetence during exercise, although its physiopathology remains uncertain. We evaluated the heart rate (HR) response to exercise testing in ChD patients in order to determine the role of autonomic modulation and left ventricular dysfunction in the physiopathology of chronotropic incompetence.

METHODS

ChD ambulatory patients (n = 170) and healthy controls (n = 24) underwent a standardized protocol including Doppler echocardiography, Holter monitoring, HR variability analysis, brain natriuretic peptide (BNP) measurement, and maximal exercise testing. The chronotropic response was calculated as the percentage of predicted HR achieved and the HR increment (DeltaHR) during exercise. ChD patients were divided according to the absence or presence of cardiopathy and chronotropic incompetence (<85% predicted HR).

RESULTS

Chronotropic incompetence was present in 34 (20%) of all ChD patients. The group with cardiopathy displayed reduced DeltaHR (91 +/- 19 bpm) during exercise in comparison with ChD patients without cardiopathy (100 +/- 19 bpm). Both the values observed in ChD groups were significantly different from those of controls (112 +/- 13 bpm). Exercise duration, maximal oxygen consumption, and systolic blood pressure increment were significantly reduced in patients with abnormal chronotropic response. DeltaHR during the exercise was significantly correlated with markers of autonomic control of sinus node, such as rest HR (r =-0.498, P <or= 0.001), peak HR during exercise (r = 0.775, P <or= 0.001), minimal HR during Holter recording (r =-0.231, P = 0.003), and high- and low-frequency components of short-term HR variability (r = 0.188, P = 0.042 and r = 0.203, P = 0.027). Neither left ventricular function nor BNP levels were independently related to the presence of chronotropic incompetence.

CONCLUSIONS

Chronotropic incompetence may be considered an early sign of autonomic dysfunction in ChD patients.

Dyskinesis in Chagasic myocardium: centerline analysis of wall motion using cardiac-gated magnetic resonance images of mice

We report on the use of centerline analysis of cardiac-gated magnetic resonance images to measure wall motion abnormalities in mice infected with Trypanosoma cruzi. To our knowledge, this is the first report of segmental wall motion abnormalities in an animal model of Chagas' disease. Chagas' disease patients with severe cardiac involvement exhibit mild hypokinesis in an extensive region of the left ventricle and dyskinesis in the apical region. We observed dyskinetic segments in a similar region of the hearts of infected wild-type mice. Dyskinesis was not observed in infected mice lacking macrophage inflammatory protein-1alpha, a chemokine that may play an important role in the cardiac remodeling that is normally observed in mouse models of Chagas' disease and in human patients. This study aimed to demonstrate the utility of cardiac-gated magnetic resonance imaging and centerline analysis as a straightforward method for monitoring regional left ventricular wall motion in transgenic and/or diseased mice.

Neuroadrenergic activation and response to dobutamine in congestive heart failure secondary to idiopathic dilated cardiomyopathy

Detection of contractile reserve is important in heart failure patients. To determine if detection of contractile reserve is influenced by neuroadrenergic activation, we examined the relation between dobutamine stress echocardiography (DSE) findings and plasma norepinephrine levels (NE) at rest in 35 patients with nonischemic left ventricular (LV) dysfunction (New York Heart Association class >III in all; LV ejection fraction 0.27 +/- 0.5). Changes in global wall motion score (WMS), and separately in WMS of hypokinetic segments and akinetic segments, were analyzed. A patient was considered to be responsive to dobutamine if the change in global WMS was >/=4. Twenty-three patients were responsive and 12 were not responsive to dobutamine. Plasma NE and baseline heart rate were significantly higher in nonresponsive patients (p <0.001). Changes in global WMS and in hypokinetic segment WMS were inversely related to either plasma NE (r -0.68 and -0.67, respectively) or baseline heart rate (r -0.60 and -0.66, respectively). The change in akinetic segment WMS was related to plasma NE only (r -0.50). Changes in WMS were not related to age, diastolic and systolic LV volume, baseline global WMS, or number of akinetic segments at baseline. Plasma NE >602 pg/ml predicted a blunted or absent contractile reserve at DSE (sensitivity 92%; specificity 87%). Neuroadrenergic activation may influence contractile reserve found at DSE in patients with heart failure due to nonischemic LV dysfunction.