Prognosis And Natural History

Infection with T cruzi significantly shortens the life expectancy of affected persons. Mortality rates vary greatly between geographic regions, suggesting that environmental factors, comorbid infections, or trypanosome strain may influence the severity or progression of disease.170 In a rural Venezuelan population with a prevalence of infection of 47% studied for 4 years, heart disease developed in initially seropositive patients at a rate of 1.1%/year.171 Mortality due to Chagas heart disease in this period was 7% in those younger than age 50 years and 3% in the entire group, accounting for 69% of all deaths. Death typically results a minimum of 15 years after infection, with most persons dying of Chagas heart disease between age 25 and 45 years. Chagas disease is by far the leading cause of death in this young age group in endemic areas, making it a major public health problem.

The cause of death in Chagas heart disease is sudden cardiac death in approximately 50% of patients, congestive heart failure in 40%, and cerebral embolism in 10%. Among the patients in our series, 9 of the 11 deaths were sudden. Sudden death is more frequent than death from congestive heart failure in younger patients, in stage II patients (segmental wall motion abnormalities without heart failure),172 and in those with complex and sustained ectopy on ambulatory ECG.173 Sudden death in Chagas heart disease, usually due to ventricular tachycardia or fibrillation, is frequent in endemic countries; autopsy studies of fatal traffic accidents and sudden death often reveal that Chagas heart disease is the sole finding.172 Half of those dying suddenly are asymptomatic before death, and death is the first sign of Chagas disease. Nearly all such individuals have significant, often extensive, ventricular abnormalities and conduction system disease.174'175

The presence of congestive heart failure is the strongest predictor of subsequent mortality in all studies. Mortality in such patients is high, probably higher than in patients with congestive heart failure from other etiologies.176 Ten-year survival in a typical study was 9% after development of congestive heart failure (stage III) compared with 65% in those with ECG abnormalities without heart failure (stage II), and it was normal in seropositive patients with a normal ECG (stage I).177 Among those who have congestive heart failure, maximum oxygen consumption, functional class, and ejection fraction predict survival.178 In our series (average follow-up, 56 ±9 months), 5-year survival was 64%38 (Fig. 20-12). Five-year survival was 30% in those with left ventricular dysfunction versus 88% in those with normal function. No deaths occurred in patients without either ventricular aneurysm or systolic dysfunction versus 42% survival in patients having either one. Factors associated with decreased survival are shown in Table 20-6. Congestive heart failure at initial presentation and its occurrence during follow-up were the 2 historical features most strongly associated with a fatal outcome. In a multivariate model, initial congestive heart failure and the presence of either left ventricular aneurysm or systolic dysfunction (P = 0.03) were the only independent predictors of subsequent death.

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ON=17 15 986666555431

• N=25 20 14 97555555444421

Your Heart and Nutrition

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