Usefulness of microvolt T-wave alternans for predicting outcome in patients with Chagas disease with implantable cardioverter defibrillators.

BACKGROUND: Chagas disease (ChD) may lead to life-threatening heart disease, including malignant ventricular arrhythmias. The use of implantable cardioverter defibrillators (ICDs) has become the main therapeutic strategy for secondary prevention of SCD in Chagas disease (ChD). Microvolt T-wave alternans (MTWA) is a direct measure of ventricular repolarization instability and has emerged as a potentially useful way of determining arrhythmia vulnerability. However, this methodology has not been evaluated in patients with ChD. OBJECTIVE: To evaluate the predictive value of MTWA testing for appropriate therapy or death in ChD patients with ICDs. METHODS: This prospective study included consecutive patients who received ICD implantations in a Brazilian tertiary referral center. RESULTS: Seventy-two patients were followed for a median time of 422 (range 294-642) days. Thirty-three patients had ChD. The MTWA was non-negative (positive or indeterminate) in 27 (81.8%) of ChD patients. The combined primary outcome (appropriate ICD therapy or death) occurred in 29 patients (40.3%); 17 out 33 ChD patients presented the primary outcome. There was a statistically significant difference in event-free survival between ChD patients with negative and non-negative MTWA results (p=0.02). Non-negative MTWA tests nearly triple the risk of appropriate ICD therapy or death (HR=2.7, 95% CI: 1.7-4.4, p=0.01) in patients with ChD and was the only variable associated with outcomes. The sensitivity and the negative predictive value was 100% in ChD patients. CONCLUSIONS: MTWA may be useful in recognizing high-risk ICD patients who may require adjunctive therapies with antiarrhythmic drugs or catheter ablation.

Heart rate recovery in asymptomatic patients with Chagas disease.

BACKGROUND: Chagas disease patients with right bundle-branch block (RBBB) have diverse clinical presentation and prognosis, depending on left ventricular (LV) function. Autonomic disorder can be an early marker of heart involvement. The heart rate recovery (HRR) after exercise may identify autonomic dysfunction, with impact on therapeutic strategies. This study was designed to assess the HRR after symptom-limited exercise testing in asymptomatic Chagas disease patients with RBBB without ventricular dysfunction compared to patients with indeterminate form of Chagas disease and healthy controls. METHODS: One hundred and forty-nine subjects divided into 3 groups were included. A control group was comprised of healthy individuals; group 1 included patients in the indeterminate form of Chagas disease; and group 2 included patients with complete RBBB with or without left anterior hemiblock, and normal ventricular systolic function. A symptom-limited exercise test was performed and heart rate (HR) response to exercise was assessed. HRR was defined as the difference between HR at peak exercise and 1 min following test termination. RESULTS: There were no differences in heart-rate profile during exercise between healthy individuals and patients in indeterminate form, whereas patients with RBBB had more prevalence of chronotropic incompetence, lower exercise capacity and lower HRR compared with patients in indeterminate form and controls. A delayed decrease in the HR after exercise was found in 17 patients (15%), 9% in indeterminate form and 24% with RBBB, associated with older age, worse functional capacity, impaired chronotropic response, and ventricular arrhythmias during both exercise and recovery. By multivariable analysis, the independent predictors of a delayed decrease in the HRR were age (odds ratio [OR] 1.11; 95% confidence interval [CI] 1.03 to 1.21; p = 0.010) and presence of RBBB (OR 3.97; 95% CI 1.05 to 15.01; p = 0.042). CONCLUSIONS: A small proportion (15%) of asymptomatic Chagas patients had attenuated HRR after exercise, being more prevalent in patients with RBBB compared with patients in indeterminate form and controls.