Ten-Year Incidence of Chagas Cardiomyopathy Among Asymptomatic, T. Cruzi Seropositive Former Blood Donors
What is the natural history of clinical Chagas disease in T. cruzi seropositive blood donors?
The investigators performed a retrospective cohort study among initially healthy blood donors with an index T. cruzi seropositive donation and age, gender-matched, and period-matched seronegatives in 1996-2002 in the cities of Sao Paulo and Montes Claros, Brazil. In 2008-2010, all subjects underwent medical history, physical examination, electrocardiograms (ECGs), and echocardiograms. ECG and echo results were classified by blinded core laboratories, and records with abnormal results were reviewed by a blinded panel of three cardiologists who adjudicated the outcome of Chagas cardiomyopathy. Associations with Chagas cardiomyopathy were tested with multivariate logistic regression.
Mean follow-up time between index donation and outcome assessment was 10.5 years for the seropositives and 11.1 years for the seronegatives. Among 499 T. cruzi seropositives, 120 (24%) had definite Chagas cardiomyopathy, and among 488 T. cruzi seronegatives, 24 (5%) had cardiomyopathy, for an incidence difference of 1.85 per 100 person-years attributable to T. cruzi infection. Of the 120 seropositives classified as having Chagas cardiomyopathy, only 31 (26%) presented with ejection fraction below 50, and only 11 (9%) were classified as New York Heart Association class II or higher. Chagas cardiomyopathy was associated (p < 0.01) with male sex, a past history of abnormal ECG, and the presence of an S3 heart sound.
The authors concluded that there is a substantial annual incidence of Chagas cardiomyopathy among initially asymptomatic T. cruzi seropositive blood donors, although the disease was mild at diagnosis.
This 10-year retrospective cohort study provides strong evidence for a moderate rate of progression to cardiomyopathy (1.85% per year) among persons infected with T. cruzi, but without cardiomyopathy at baseline. Prognostic factors for cardiomyopathy, including male sex, a past history of ECG abnormalities, and S3 gallop, may be useful in deciding which seropositives are at highest risk of cardiomyopathy and potentially eligible for treatment. The false-positive diagnoses of Chagas-like cardiomyopathy among 5% of T. cruzi seronegatives illustrate the difficulty of distinguishing Chagas from other cardiac disease, leading to overestimation of Chagas disease incidence in uncontrolled seropositive cohorts, but the inclusion of a T. cruzi seronegative comparison cohort in this study allowed measurement and elimination of competing morbidity due to other cardiovascular disease.
Keywords: Chagas Disease, Follow-Up Studies, Electrocardiography, New York, Heart Diseases, Incidence, Brazil, Biological Markers, Heart Failure, Cardiovascular Diseases, Chagas Cardiomyopathy, Physical Examination, Echocardiography
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