Association between circadian Holter ECG changes and sudden cardiac death in patients with Chagas heart disease
Résumé
Objective: Chagas disease (ChD) is a parasitic illness, largely spread over South America. ChD usually causes progressive myocardium damage, either by direct parasite action or through autoimmune response. Sudden cardiac death (SCD) is prevalent in the early disease stages, being associated with a high variety of ectopic cardiac beats. This study aims at applying heart rate variability (HRV) and heart rate turbulence (HRT) techniques over Holter electrocardiogram (ECG) records to investigate association with SCD in Chagas heart disease (ChHD). Approach: From a retrospective evaluation of a local database, the Holter records from 78 outpatients (34 female) were divided into groups: SCD deaths (20) and alive patients (56). To consider circadian autonomic changes, the analysis was performed in three periods: a) Entire 24 h record; b) 12 h daylight period; and c) the remaining 12 h including the night rest. Eight variables were extracted using HRV and HRT approaches from each record and analysed together with the left ventricular ejection fraction (LVEF) estimated by echocardiography. Main results: The set of parameters was reduced by both forward and backward stepwise and classification was performed using k-nearest neighbours method and a leave-one-out cross-validation in a set of 10 bootstrap, where SCD data were randomly taken with reposition for balancing groups. The best 24 h model predicted SCD with 89.9 ± 0.9% accuracy using three HRV variables. The use of 12 h segments increased accuracy up to 91.0 ± 1.2% in a model with the standard deviation parameter measured during day (SDNNday) and night (SDNNnight). Although considered as playing a major role in SCD, LVEF did not show association with SCD in this sample. Significance: The degree of HRV and its circadian changes are associated with sudden cardiac death in Chagas heart disease patients.