Prognostic Value of the Spectral Turbulence Analysis of the Signal-averaged Electrocardiogram in Chagas Heart Disease

Admission:

Longitudinal prospective study, with a cohort of 100 consecutive outpatient subjects (34 to 74 years old; 31 females) with Chagas' disease followed-up for at least 10 years at the cardiomyopathy outpatient clinic of University Hospital, Rio de Janeiro, RJ, Brazil, a tertiary care center. Enrollment was from 1995 to 1999. Subjects were born in endemic regions of Minas Gerais, Goias or Bahia States of Brazil and Chagas' disease was diagnosed on basis of two positive serum tests, hemagglutination cruzipain-ELISA and indirect immunofluorescence. All subjects were referred to the arrhythmia for risk stratification. At the time of admission none had received nitroderivative therapy. Subjects were classified according to the severity of heart involvement according to Los Andes classification, and divided into three groups: class I - 28 subjects (group 1), class II - 48 subjects (group 2), and class III - 24 subjects (group 3). Clinical and laboratory data were assessed during a personal interview and review of medical records. On admission, all subjects were in New York Heart Association functional class I or II, had normal sinus rhythm and normal PR intervals. Exclusion criteria at initial enrollment were: any degree of atrioventricular block or non-sinus rhythm, previous documented acute coronary events (unstable angina or myocardial infarction), chronic obstructive pulmonary disease, rheumatic valvular heart disease, alcohol addiction, thyroid dysfunction or abnormal serum electrolytes. Treadmill stress test and/or coronary artery angiogram were indicated in selected subjects to rule out concomitant coronary artery disease. World Health Organization and Helsinki Treaty regulations reviewed in Venice (1983) were followed and all subjects provided informed consent to participate.

Clinical follow-up:

All subjects have been followed-up by the same team of physicians. Medical visits have been scheduled at the outpatient clinics in a three to six-month interval. Medications were prescribed at the discretion of the physician who performed the primary evaluation. Body weight varied <2 kg during follow-up, and serum potassium varied from 3.5 to 5 milliequivalent/L. Mild systemic arterial hypertension (systolic arterial pressure ranging from 140 mmHg and 155 mmHg, or diastolic arterial pressure ranging from 90 mmHg and 105 mmHg) was observed in 41% of the subjects and all received anti-hypertensive medication (converting enzyme inhibitors, diuretics, vasodilators and/or beta-blockers) at the discretion of the physician who performed the primary evaluation in order to reduce blood pressure levels to less than 140/90 mmHg. All regularly followed at scheduled clinical visits. The endpoints were described elsewhere in this registry. All causes of adverse events were ascertained by active search of relatives and review of the medical records.

Resting surface 12-lead ECG and plain chest roentgenogram