Chagas Disease of the Heart

T. cruzi blood infection
T. cruzi blood infection - Chagas disease. Ed Reschke/Getty Images

Chagas disease of the heart is a type of heart failure that is mainly seen in Latin America. In fact, next to coronary artery disease, Chagas disease is the most common cause of heart failure in Latin America.

What Causes Chagas Disease?

Chagas disease of the heart is caused by an infection with a parasite called Trypanosoma cruzi (T. cruzi), which is a protozoan organism. A person contracts Chagas disease after being bitten by the triatomine bug, which has picked up the T.

cruzi parasite by biting an infected animal. Triatomine bugs are common in rural areas, especially in dwellings made of adobe, mud, straw or thatch. People are typically bitten at night while they are asleep.

Chagas disease is not common among city dwellers, and is generally limited to the rural areas of Latin America.

What Happens After Infection Occurs?

After an infection occurs with T. cruzi, Chagas disease usually manifests as an initial acute phase, followed by a chronic phase. Heart problems can occur with either phase, but are more common with the chronic phase of Chagas.

Acute Phase

Once a person is infected with T. cruzi, the acute form of Chagas disease usually begins after one to 16 weeks. Acute Chagas disease is generally a nonspecific, flu-like illness usually characterized by fever and myalgia (muscle aches). Acute Chagas is most often a fairly mild illness, but it can persist for two or three months.

Sometimes acute Chagas disease can affect the heart. People with cardiac involvement have symptoms of acute myocarditis (inflammation of the heart muscle), and may also have acute pericarditis. Symptoms and signs of cardiac involvement may include chest pain, dyspnea (shortness of breath), changes on the ECG, and evidence of a pericardial effusion (fluid collecting around the heart) on an echocardiogram.

Most often, the heart problems seen with acute Chagas disease resolve completely after a few months. However, some people with acute cardiac Chagas disease will progress rapidly to a chronic form heart failure, and about 5 percent will even die from their cardiac disease during the acute illness.

Chronic Phase

After the acute phase of Chagas disease resolves, many people enter what is called the "indeterminate" (or latent) form of the disease. The indeterminate form of Chagas' disease is characterized by a complete lack of illness or symptoms. People with this form of Chagas disease appear and feel entirely normal, and they have a normal cardiac examination (including ECG and echocardiogram). However, blood testing will show that they have a chronic infection with T. cruzi. The indeterminate form of Chagas' disease often lasts for decades, and more than half the people with the indeterminate form of the disease never develop Chagas heart disease.

In addition to the risk of heart disease, those with chronic Chagas may also develop serious disorders of the gastrointestinal system.

In particular, they may experience significant disorders of the esophagus with painful and difficult swallowing, and a particularly severe type of chronic constipation.

Unfortunately, many people with chronic Chagas go on to develop heart disease. Chagas heart disease usually appears at least five years after the acute illness, and it may be delayed much longer than that. Chagas heart disease is a very significant problem, and often results in death or serious disability.

Chagas Heart Disease

Chagas heart disease is a form of dilated cardiomyopathy (cardiac enlargement due to heart muscle weakness). As such, once it occurs its clinical manifestations are largely indistinguishable from any other form of serious heart failure. People with Chagas heart disease often experience disabling dyspnea with exertion, edema (swelling), and extreme fatigue. They are prone to dangerous cardiac arrhythmias - both bradycardias (slow heart rates) and tachycardias (rapid heart rates) - and may experience palpitations, episodes of lightheadedness, and syncope. Sudden death from cardiac arrhythmias is a significant threat for people with Chagas heart disease.

Treating Chagas Heart Disease

The treatment of Chagas disease includes treating the T. cruzi infection, treating the heart failure, treating cardiac arrhythmias, and working to prevent sudden death.

Treating the Infection

Experts agree that it is important to treat patients with acute Chagas disease, and possibly with early indeterminate Chagas disease, with antiparasitic drug therapy aimed at T. cruzi. The two drugs that may be effective against T. Cruzi are called benznidazole and nifurtimox. Both of drugs often cause significant toxicity, and neither is approved for use by the FDA in the United States. In the U.S., doctors needing to treat a patient for T. cruzi must obtain these drugs directly from the CDC.

Evidence is sparse that treating adults who have the indeterminate or chronic forms of Chagas disease with antiparasitic therapy measurably improves the outcome, and most experts do not recommend routinely using these drugs in adults with non-acute Chagas disease. Apparently, by the time Chagas disease becomes chronic, the T. cruzi infection is no longer “active,” and antiparasitic therapy can no longer change the course of the disease. On the other hand, children with the the indeterminate form of Chagas disease appear to benefit from antiparasitic therapy, and most experts recommend treating them.

Treating Heart Failure

Treating the heart failure caused by Chagas disease is very similar to treating heart failure associated with any other cause of dilated cardiomyopathy. Medical therapy usually includes treatment with beta blockersACE inhibitors, and spironolactone. Diuretic therapy is used to help reduce edema and dyspnea.

Cardiac resynchronization therapy (CRT) appears to be as useful in Chagas heart disease as in any other form of heart failure. However, the usefulness of CRT in treating heart failure is largely limited to people who have left bundle branch block, whether they have Chagas disease or any other form of dilated cardiomyopathy. And, unfortunately, in Chagas disease right bundle branch block is more common than left bundle branch block—so CRT is suitable for fewer people with Chagas heart failure than with other kinds of heart failure.

People with Chagas disease appear to do as well with cardiac transplantation as patients with other kinds of heart failure. One concern in performing transplant surgery in Chagas heart disease has been that the immunosuppressive therapy required after transplantation may cause the T. cruzi infection to reactivate. However, clinical studies have shown that reactivation of the infection after transplantation does not appear to be a common problem in Chagas heart disease.

The risk of thromboembolism (a condition that often produces deep venous thrombosispulmonary embolism, or stroke), is increased in anyone with heart failure, but it appears to be an especial risk for people with Chagas heart disease. Most people with Chagas heart disease should be placed on either anticoagulant therapy (with Coumadin or a NOAC drug), or prophylactic aspirin.

Treating Cardiac Arrhythmias and Preventing Sudden Death

Therapy to prevent or treat serious cardiac arrhythmias is often necessary in people with Chagas heart disease, because they are at increased risk for both bradycardias (slow heart rhythms) and tachycardias (fast heart rhythms).

Bradycardias occur with some frequency in people with Chagas disease. The bradycardias are caused both by disease of the sinus node, and by heart block. If the slow heart rhythm is producing symptoms, or if it appears likely to produce severe symptoms such as syncope, therapy with a pacemaker is necessary.

The major concern related to cardiac arrhythmias in people with Chagas heart disease, however, is sudden death caused by ventricular tachycardia or ventricular fibrillation. The risk of having these life-threatening arrhythmias is related to the severity of the cardiac damage that has been done by Chagas.

If cardiac function is depressed to the point that these dangerous arrhythmias are particularly likely to occur, the insertion of an implantable defibrillator should be strongly considered. However, especially in Latin America, where implantable defibrillator therapy is often not readily available, patients with Chagas disease are very likely to be treated with the antiarrhythmic drug amiodarone instead, in an attempt to reduce their risk of sudden death.

Summary

Chagas heart disease is a very serious illness, as is heart failure from any cause. However, just as with any other form of heart failure, symptoms can be substantially reduced, quality of life can be greatly improved, and survival can be prolonged if aggressive, modern treatment strategies are employed.

Sources: 

Bern C. Chagas' Disease. N Engl J Med 2015; 373:456.

Gali WL, Sarabanda AV, Baggio JM, et al. Implantable Cardioverter-Defibrillators for Treatment of Sustained Ventricular Arrhythmias in Patients with Chagas' Heart disease: Comparison With a Control Group Treated With Amiodarone Alone. Europace 2014; 16:674.

Marin-Neto JA, Rassi JR A, Maciel BC, et al. Chagas Heart Disease. In: Evidence-Based Cardiology, 3rd ed, Yusuf S, Cairns J, Camm J, et al. (Eds), 2010. p.823.

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