Version May 2024
INTRODUCTION — Chagas disease (CD) is caused by Trypanosoma cruzi, a protozoan parasite that can cause acute myopericarditis as well as chronic fibrosing cardiomyopathy. CD is the most common cause of non-ischemic cardiomyopathy in Latin America [1].
Issues related to acute Chagas heart disease will be reviewed here. Issues related to chronic CD including the indeterminate form and chronic Chagas cardiomyopathy are discussed separately. (See "Chagas disease: Chronic Trypanosoma cruzi infection" and "Chronic Chagas cardiomyopathy: Clinical manifestations and diagnosis" and "Chronic Chagas cardiomyopathy: Management and prognosis".)
Issues related to other aspects of Chagas disease are discussed separately. (See "Chagas disease: Acute and congenital Trypanosoma cruzi infection" and "Chagas disease: Antitrypanosomal drug therapy" and "Chagas gastrointestinal disease".)
CLINICAL MANIFESTATIONS
Signs and symptoms — Most patients with acute CD are asymptomatic or have a relatively mild nonspecific illness, with generalized symptoms and signs such as fever and myalgia. A minority of patients have inflammation and swelling at the site of inoculation, known as a "chagoma." When inoculation occurs via the conjunctiva, the patient may present with the Romaña sign, painless unilateral bipalpebral swelling that lasts up to several weeks.
The acute phase of CD begins after an incubation period of one week to two weeks (following vector-borne transmission) or up to four months following transmission via transfusion or organ transplant [2]. The acute phase of CD typically lasts 8 to 12 weeks (figure 1). (See "Chagas disease: Acute and congenital Trypanosoma cruzi infection".)
Symptomatic myocarditis is rare when the transmission is through the vector-borne route (a triatomine bug bite with inoculation of infected vector dejecta into the bite wound or mucous membranes). A diagnosis is rarely (estimated as less than 1 to 5 percent) established during the acute phase acquired via vector transmission, given the high rate of no or mild nonspecific symptoms. In contrast, when patients are infected through the oral route (through the ingestion of food contaminated by large loads of T. cruzi) myocarditis is often severe and carries a higher risk of mortality. In addition, a cluster of acute infections due to a common contaminated source, such as juice, is more likely to lead to etiological testing and recognition of the diagnosis than an isolated vector-borne infection that manifests as an undifferentiated febrile illness [3].
A minority of patients with acute CD present with fulminant disease with acute myocarditis leading to heart failure (HF), pericardial effusion, meningoencephalitis and associated risk of death. HF is associated with significant risk of early mortality. (See "Chagas disease: Acute and congenital Trypanosoma cruzi infection".)
The clinical manifestations of cardiac involvement in acute CD are similar to those of myocarditis or myopericarditis due to other causes; these include dyspnea, fatigue (and other symptoms and signs of HF), chest pain, arrhythmias, and sudden cardiac arrest [2,4,5]. One nonspecific sign of cardiac dysfunction is tachycardia out of proportion to fever [2]. (See "Clinical manifestations and diagnosis of myocarditis in adults" and "Myopericarditis", section on 'Clinical presentation'.)
Factors associated with increased risk of severe acute morbidity (particularly myocarditis) and mortality include infection through the oral route and immunosuppression. The frequency and severity of clinical manifestations in the acute phase, including mortality due to myocarditis and/or meningitis-encephalitis, tend to be more prominent in young children [6]. (See "Chagas disease: Acute and congenital Trypanosoma cruzi infection" and "Chagas disease in the immunosuppressed host".)
Initial test results — During the first weeks of infection, serologic tests for T. cruzi infection are usually negative. Other laboratory findings are nonspecific, such as leukocytosis with an absolute increase in lymphocyte count. Since the level of parasitemia is high in the acute phase, the diagnosis is based upon detection of circulating parasites by a variety of methods. (See "Chagas disease: Acute and congenital Trypanosoma cruzi infection".)
Although symptoms and signs of cardiac disease are commonly lacking, myocardial involvement is likely present in most if not nearly all patients diagnosed with acute CD [7]. Initial cardiac test findings are nonspecific but denote the presence of myocarditis [4,5,8]:
●Electrocardiographic (ECG) findings may include sinus tachycardia, low voltage, atrial and ventricular premature beats, bundle branch block, diffuse ST-T wave changes, prolonged PR interval, or more advanced atrioventricular block (waveform 1). Arrhythmias such as atrial fibrillation and ventricular tachycardia are uncommon. During recovery, the ECG findings resolve in over 90 percent of patients within one year.
●The chest radiograph frequently demonstrates an enlarged cardiac silhouette (cardiac-to-thoracic width ratio above 50 percent), which may be caused by a pericardial effusion or biventricular chamber dilation (image 1).
Echocardiography is a key test to assess cardiac involvement as discussed below. (See 'Diagnosis' below.)
DIAGNOSIS — A diagnosis of acute Chagas myocarditis is based upon identifying recently acquired CD with associated cardiac involvement:
●Acute CD should be suspected in patients who have an epidemiologic exposure (eg, primary residence in an area of the Americas where vector-borne transmission occurs) and nonspecific symptoms such as malaise, fever, and anorexia. Rarely, patients with acute CD may present with a skin "chagoma" or eyelid swelling (Romaña sign). However, many patients are asymptomatic and do not come to clinical attention. (See 'Signs and symptoms' above and "Chagas disease: Epidemiology, screening, and prevention".)
A diagnosis of acute CD is established by detection of circulating parasites by a variety of methods, as discussed separately. Biopsy of a typical "chagoma" is sometimes useful to establish the diagnosis. (See "Chagas disease: Acute and congenital Trypanosoma cruzi infection", section on 'Diagnosis'.)
●Patients with confirmed acute CD should undergo an initial cardiac evaluation including history, physical examination, ECG, and chest radiograph.
●In patients with cardiac symptoms or signs and/or abnormalities on an ECG or chest radiograph, an echocardiogram should be obtained. Diagnosis of cardiac involvement in patients with acute CD is generally confirmed by echocardiography, which is used to evaluate myocardial and pericardial disease and direct specific treatment.
In patients with acute CD, echocardiography often demonstrates a pericardial effusion. Left or right ventricular dilation are less commonly present. Global left ventricular ejection fraction (LVEF) is often normal or near normal, even among patients with regional wall motion abnormalities (anterior and/or apical dyskinesis or septal dyskinesis) or LV dilatation, although a minority have depressed global systolic function. Mild functional mitral regurgitation and/or tricuspid regurgitation are frequently present. Patients with acute CD with HF typically have impaired LV systolic function.
●Endomyocardial biopsy is generally not required to establish the diagnosis, except in patients who have undergone cardiac transplantation, when the distinction between acute Chagas myocarditis and implant rejection is crucial. The frequency of myocardial involvement in symptomatic acute CD was demonstrated by a study of 58 patients with acute CD in which myocarditis was found in all 26 undergoing endomyocardial biopsy, including eight patients with no other evidence of heart disease [4]. Typical findings are inflammatory changes with mild or no fibrosis. Intracellular T. cruzi amastigote nests are occasionally identified (picture 1). Of note, this case series, in which all patients had manifestations severe enough to warrant clinical care, is not representative of the universe of acute CD, which includes many milder cases. (See "Chagas disease in the immunosuppressed host", section on 'Donor-derived acute Chagas in organ transplant recipients'.)
DIFFERENTIAL DIAGNOSIS — Acute Chagas heart disease has a similar presentation to other causes of myocarditis and myopericarditis; these include various infectious agents, cardiotoxins, hypersensitivity reactions, systemic disorders, and radiation (table 1). Acute CD can be distinguished from other types of myocarditis and myopericarditis by detection of parasitemia. In patients with suspected CD with criteria for endomyocardial biopsy, a biopsy may identify or rule out other causes of myocarditis. (See "Clinical manifestations and diagnosis of myocarditis in adults" and "Myopericarditis", section on 'Clinical presentation' and "Endomyocardial biopsy".)
MANAGEMENT — The management of acute CD with cardiac involvement includes antitrypanosomal therapy and management of complications, including HF and pericardial effusion.
●When recognized, acute CD is treated with antitrypanosomal therapy, irrespective of the transmission mechanism. The role of antitrypanosomal drugs in acute disease is discussed in detail separately. (See "Chagas disease: Antitrypanosomal drug therapy" and "Chagas disease: Acute and congenital Trypanosoma cruzi infection", section on 'Management of acute and congenital T. cruzi infection'.)
●HF is treated as appropriate:
•Acute HF is treated according to standard recommendations including diuretic and vasodilator therapy as needed. (See "Treatment of acute decompensated heart failure: General considerations" and "Treatment of acute decompensated heart failure: Specific therapies" and "Management of refractory heart failure with reduced ejection fraction".)
•Patients with HF with reduced ejection fraction (LVEF ≤40 percent) or mid-range ejection fraction (LVEF 41 to 49 percent) should be treated according to standard recommendations. (See "Treatment and prognosis of heart failure with mildly reduced ejection fraction" and "Overview of the management of heart failure with reduced ejection fraction in adults", section on 'Pharmacologic therapy' and "Overview of the management of heart failure with reduced ejection fraction in adults".)
Management of chronic Chagas cardiomyopathy is discussed separately. (See "Chronic Chagas cardiomyopathy: Management and prognosis", section on 'Management'.)
●Patients with asymptomatic LV global systolic dysfunction (LVEF ≤40 percent) should be treated according to standard recommendations. (See "Management and prognosis of asymptomatic left ventricular systolic dysfunction".)
●Pericardial effusion is common in acute CD and occasionally complicated by tamponade (which may occur when the effusion is large or if even a moderate amount of fluid accumulates rapidly), which is treated by urgent pericardiocentesis, as discussed in detail separately. (See "Cardiac tamponade".)
CLINICAL COURSE — Symptoms and signs of acute Chagas myocarditis typically resolve over a period of one to three months with or without etiologic treatment [9]. Valvular regurgitation often resolves after etiologic treatment of CD.
Based upon limited data from old series, mortality for the small minority of untreated individuals with symptomatic acute CD following a triatomine bug bite has been estimated as <5 percent, with the mortality rate highest among younger children and very low in adults [9,10]. For example, in the 1982 Bambuí study, mortality among patients with acute CD was 8.3 percent with mortality of 19.8 percent for patients less than two years and 0 percent for patients 11 years of age and older [6]. Mortality occurs predominantly from refractory HF, with or without encephalitis. (See "Chagas disease: Acute and congenital Trypanosoma cruzi infection".)
As noted above, when the infection is acquired by the oral route, the severity of the acute disease is more pronounced and there is likely a higher risk of mortality which is caused by HF, but comparisons are difficult since limited data are available and the risk of disease varies with age [3,5,11]. In the largest reported outbreak of orally acquired acute CD, infection was confirmed in 103 of 1000 exposed children and adults in a public school community; 75 percent of infected patients were symptomatic, and there was one death in a five-year old child [3]. In a series of 13 patients aged 13 to 61 with acute orally acquired CD, two patients died [5]. In an outbreak in which 40 people were exposed, seven individuals developed cardiac and/or systemic symptoms and two patients died [11]. This is probably related to an enhanced parasite inoculation burden through active invasion mediated by attachment to the gastric mucin layer by gp82, a parasite surface molecule specific to metacyclic trypomastigotes [12,13]. (See 'Clinical manifestations' above and "Chagas disease: Acute and congenital Trypanosoma cruzi infection", section on 'Acute T. cruzi infection'.)
Surviving, untreated patients with acute CD proceed to chronic disease (figure 1 and table 2). The chronic phase includes two forms of disease: an indeterminate (latent, preclinical) form and a determinate (clinical) form, which is subdivided into cardiac, digestive, and cardiodigestive forms. Patients with the indeterminate form have serologic evidence of T. cruzi infection (presence of anti-T. Cruzi antibodies) without overt clinical evidence of cardiac or gastrointestinal disease. (See "Chagas disease: Chronic Trypanosoma cruzi infection", section on 'Natural history'.)
Limited data suggest that patients with acute CD rarely proceed directly to chronic Chagas cardiomyopathy without an intervening indeterminate phase, as described in the endemic area of Bambuí, Brazil [6,9,10]. This phenomenon is likely rare now with high rates of treatment of clinically apparent acute cases. In the hyperendemic Bolivian Chaco region, ECG abnormalities were identified in only 1.1 percent of infected individuals 10 to 19 years of age, suggesting rare direct progression from acute infection to chronic Chagas cardiomyopathy in this population [14]. Approximately one-quarter to one-half of patients with the indeterminate form of CD eventually develop chronic Chagas cardiomyopathy. (See "Chronic Chagas cardiomyopathy: Clinical manifestations and diagnosis".)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Chagas disease".)
SUMMARY AND RECOMMENDATIONS
●Clinical manifestations – Most patients with acute Chagas disease (CD) are asymptomatic or have a relatively mild nonspecific illness with generalized symptoms and signs such as fever and myalgia. A minority of patients with acute CD present with fulminant acute disease with acute myocarditis with heart failure (HF), pericardial effusion, or meningoencephalitis. HF is associated with significant risk of early mortality. (See 'Clinical manifestations' above.)
●Diagnosis – A diagnosis of acute Chagas myocarditis is based upon identifying acute CD with associated cardiac involvement:
•Acute infection – Acute CD should be suspected in patients with nonspecific symptoms such as malaise, fever, and anorexia who have risk factors for infection with Trypanasoma cruzi. A diagnosis of acute CD is generally made by detection of circulating parasites by a variety of methods. (See 'Diagnosis' above.)
•Cardiac disease – Cardiac disease should be suspected in patients with cardiac symptoms or signs on physical examination, ECG (waveform 1), or chest radiograph (image 1). A diagnosis of cardiac involvement is generally confirmed by echocardiography. (See 'Diagnosis' above and "Chagas disease: Acute and congenital Trypanosoma cruzi infection", section on 'Diagnosis'.)
●Differential diagnosis – The differential diagnosis of acute Chagas heart disease includes other causes of myocarditis and myopericarditis (table 1). (See 'Differential diagnosis' above and "Clinical manifestations and diagnosis of myocarditis in adults" and "Myopericarditis".)
●Management – The management of acute Chagas heart disease includes antitrypanosomal therapy and management of complications, including HF and pericardial effusion. (See 'Management' above.)
●Clinical course
•Symptoms and signs of acute Chagas myocarditis typically resolve over a period of one to three months with or without etiologic treatment (figure 1) [9]. (See 'Clinical course' above.)
•Untreated patients with acute CD proceed to the chronic phase which includes an indeterminate (latent) form and a determinate (clinical) form (including cardiac, digestive, and cardiodigestive presentations). Patients with acute CD rarely proceed directly to chronic Chagas cardiomyopathy without an intervening indeterminate (asymptomatic) phase. About one-quarter to one-half of patients with the indeterminate form develop chronic Chagas cardiomyopathy after a latent period ranging from 5 to 30 years. (See 'Clinical course' above.)
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