Chronic Heart Disease

Symptoms of chronic Chagas’ disease are insidious and progressive (see Figure 8). After recovering from acute phases, many people, perhaps the majority, remain asymptomatic for the rest of their lives, while others remain in good health for many years before developing symptoms and signs of the chronic stage of disease. The chronic phase is characterized by widespread damage to the organ(s) and the multiform chagasic syndrome, with its digestive (aperistalsis, megaesophagus, megacolon), respiratory (megatrachea, bronchiectasis), urinary (megaloureter), cardiac (denervation), and neurological (myelopathy, encephalopathy) components (Köberle 1968, Iosa 1994).

Cardiac abnormalities range from types of rhythm disturbances to various forms of heart block, including right‑ and left‑bundle branch block, hemiblocks and atrioventricular blocks (see Andrade 1994, Iosa 1994). Some tested patients show a normal electrocardiogram (ECG) reading, particularly in the early stages, but stress testing may reveal ECG abnormalities such as heart block or arrhythmias which might not be seen in resting ECGs. Sometimes available in urban centers, echocardiography may also be useful in evaluating cardiac chamber size and left‑ventricular function and in following the progression of the disease.

Although electrocardiographic abnormalities related to Chagas’ disease have been estimated as high as 87 percent (Hurst 1986:1170), 33 percent seems a more reasonable figure from studies in Brazil. Almost one‑third of 2,000 subjects examined by ECG in endemic areas of Brazil indicated abnormalities, and 9 percent of chest x‑rays showed enlargement of the cardiac shadow (Braunwald 1988:1447; Hurst 1986:1170).

Pedro Jáuregui and Alberto Casanovas (1987:30‑33) analyzed electrocardiographs from people living in endemic chagasic areas throughout Bolivia to see how many indicated electrocardiographic abnormalities characteristic of chagasic‑related heart disease. They studied 4,108 electrocardiographs from patients of rural communities in the Departments of La Paz (280), Tarija (258), Potosí (311), Cochabamba (1,818), Santa Cruz (1,185), and Chuquisaca (256). They found that 436 (9.4 percent) strongly indicated Chagas’ disease from the total number of 853 (20.8 percent) of ECG abnormalities. Of the 853 total abnormalities found, 469 (55 percent) were in men and 384 (45 percent) were in women, with 761 (89 percent) being adults and 92 (11 percent) being youths.

Criteria used to indicate chronic chagasic myocarditis among the ECG abnormalities were left anterior hemiblock (29 percent), block of the right bundle branch (27 percent), and sinal bradycardia (16 percent). There were 152 patients who had combined abnormalities of block of the right bundle branch and left anterior hemiblock. Including other abnormalities, 61 percent suffered from heart block, 22 percent from arrhythmias, 10 percent from repolarization disorders, 2 percent from overcharges, and 2 percent from other alterations. Youths indicated light disorder of conduction of the right bundle branch or sinal bradycardia with repolarization suggestive of vagotonia. Vagotonia is a disorder that results from overstimulation of the vagus nerve, causing a slowing of the heart rate, fainting, and dizziness.

Diagnostic tests were not given to verify what percentage of these people were infected with T. cruzi, so conclusions are indefinite; however, some hypotheses can be suggested, such as the relationship of altitude to chagasic heart disease. Altitude appears to affect the manifestations of chronic chagasic heart disease. Lesser oxygen intake at high altitude (hypoxia) puts additional stress on chronic chagasic patients emigrating from lower to higher regions of Bolivia. Twenty‑three percent of ECG alterations were found in patients from mesothermic zones as compared to 14 percent from those in subtropical zones. Mesothermic zones in Bolivia are mountains, plateaus, and valleys at altitudes from 8,000 to 14,000 feet. Although triatomine vectors are infrequently found above 13,000 feet, Bolivians move from the lower areas where they were infected to higher altitudes where hypoxia combines with chagasic stress to produce ECG abnormalities.

Although research is needed to correlate the incidence of ECG abnormalities with seropositive chagasic patients in higher altitudes, one clinical conclusion is that patients with myocarditis in La Paz are at greater risk than those at lower altitudes. The aerobic effect of living at high altitude that has traditionally endowed Andeans with strong hearts is counterproductive to Andeans suffering with hearts infected with T. cruzi. Traditionally, Andeans have referred to leishmaniasis as “el mal de los Andes”; it now appears that Chagas’ disease may be the curse of Andeans.

Therapeutically, patients with chronic Chagas’ disease stand a better chance of living longer at lower altitudes if they can avoid becoming superinfected. However, at lower altitudes there is a greater risk of superinfection, as there are more vinchucas and infected people. This leads to an auxiliary research question: to what degree does superinfection precipitate chronic Chagas’ disease myocarditis among lowland Bolivians? Apparently, it has a limited negative effect, considering that only 14 percent of patients from mesothermic zones had ECG abnormalities.