Padrão circadiano dos episódios de taquicardia ventricular em portadores de cardiopatia chagásica

Abstract

SummaryChronic Chagas´ cardiomyopathy (CCM) causes ventricular arrhythmias and sudden death, and constitutes the most frequent cause of death in many endemic areas 1,2 . The circadian variation in the incidence of ventricular arrhythmias and sudden death differs according to the substrate (e.g., morning and evening peaks in ischemic heart disease and non-Chagasic dilated cardiomyopathy). Third generation implantable cardioverter defibrillators (ICDs) have the ability to store the time and date of each ventricular tachycardia (VT) episode, enabling the patterns of ventricular tachyarrhythmia occurrence to be analyzed. The aim of our study was to evaluate the circadian variation of spontaneous VT in recipients of an ICD with CCM. MethodsThis was a retrospective cohort study in the whole population of patients with CCM who have undergone ICD implantation in our institution since May 1998. All patients (n=22) had 2 out of 3 specific serologic tests positive for Chagas´ disease (enzyme-linked immunosorbent assay, indirect immunofluorescence reaction and indirect hemagglutination). The presence of ischemic heart disease was ruled out by negative stress testing or coronary angiography before ICD implantation.Seven different types of ICDs were implanted in the study patients (ICD models 1746(ICD models , 1782(ICD models , 1810(ICD models , 1821(ICD models , 1831(ICD models , 1851(ICD models and 1861 Guidant Corp., St. Paul, MN, USA). A single and a dual chamber ICD were implanted in 8 and 7 patients, respectively.Spontaneous VT was defined as a sudden change in rate with stable cycle length that does not fluctuates > 10% during tachycardia. VT discrimination was based on the configuration and stability of the intracardiac ECG, the RR interval analysis, and the first post pacing interval variability. Only VT that were successfully terminated by the device were accepted. Since ventricular fibrillation and polymorphic VT may have different substrates and precipitants, these episodes were not considered for study.The distribution of VT detection time was examined and classified into four 6-hour time periods of the day. To avoid data bias in individuals with multiple therapies in a relatively short time frame, episodes within a 1-hour period were counted only once, and upper limits of the first 30 consecutive SMVT events per patient were used for this analysis. Tachyarrhythmias with an RR cycle length < 300 ms were classified as rapid tachyarrhythmia, those with an RR ≥ 300 were classified as less rapid tachycardia.Follow-up visits were scheduled for the first month following hospital discharge and then every 6 months. Clinical and ICD data were obtained by a cardiologist at each visit. All episodes were stored on floppy disks and reviewed by two independent observers. Consensus about the diagnosis of the episodes was obtained in cases of discrepancy.Continuous variables were expressed as mean ± SD or as median and interquartile range, according to the appropriate distribution type. The level of significance was set ...

Sudden Cardiac Death in Chagas Disease

“…In contrast with ischemic heart disease, the circadian variation reveals that deaths occur predominantly during the evening between 12 am to 6 pm. 6 Confirmation of the exact mechanism of sudden death in Chagas disease is extremely difficult and complex. All reports on the mechanisms of sudden death in Chagas disease are mainly based on observations, hypotheses and inferences.…”