title: Value of the Qrs-T angle in predicting the induction of ventricular tachyarrhythmias in patients with Chagas disease.
abstract: BACKGROUND
  The QRS-T angle correlates with prognosis in patients with heart failure and coronary artery disease, reflected by an increase in mortality proportional to an increase in the difference between the axes of the QRS complex and T wave in the frontal plane. The value of this correlation in patients with Chagas heart disease is currently unknown.
  
  
  OBJECTIVE
  Determine the correlation of the QRS-T angle and the risk of induction of ventricular tachycardia / ventricular fibrillation (VT / VF) during electrophysiological study (EPS) in patients with Chagas disease.
  
  
  METHODS
  Case-control study at a tertiary center. Patients without induction of VT / VF on EPS were used as controls. The QRS-T angle was categorized as normal (0-105º), borderline (105-135º) or abnormal (135-180º). Differences between groups for continuous variables were analyzed with the t test or Mann-Whitney test, and for categorical variables with Fisher's exact test. P values < 0.05 were considered significant.
  
  
  RESULTS
  Of 116 patients undergoing EPS, 37.9% were excluded due to incomplete information / inactive records or due to the impossibility to correctly calculate the QRS-T angle (presence of left bundle branch block and atrial fibrillation). Of 72 patients included in the study, 31 induced VT / VF on EPS. Of these, the QRS-T angle was normal in 41.9%, borderline in 12.9% and abnormal in 45.2%. Among patients without induction of VT / VF on EPS, the QRS-T angle was normal in 63.4%, borderline in 14.6% and abnormal in 17.1% (p = 0.04). When compared with patients with normal QRS-T angle, those with abnormal angle had a fourfold higher risk of inducing ventricular tachycardia / ventricular fibrillation on EPS [odds ratio (OR) 4; confidence interval (CI) 1.298-12.325; p = 0.028]. After adjustment for other variables such as age, ejection fraction (EF) and QRS size, there was a trend for the abnormal QRS-T angle to identify patients with increased risk of inducing VT / VF during EPS (OR 3.95; CI 0.99-15.82; p = 0.052). The EF also emerged as a predictor of induction of VT / VF: for each point increase in EF, there was a 4% reduction in the rate of sustained ventricular arrhythmia on EPS.
  
  
  CONCLUSIONS
  Changes in the QRS-T angle and decreases in EF were associated with an increased risk of induction of VT / VF on EPS.
authors.affiliation: Instituto Dante Pazzanese de Cardiologia, São Paulo, SP, Brazil.
authors.forename: Hugo Bizetto
authors.initials: HB
authors.lastname: Zampa
authors.affiliation: Instituto Dante Pazzanese de Cardiologia, São Paulo, SP, Brazil.
authors.forename: Dalmo A R
authors.initials: DA
authors.lastname: Moreira
authors.affiliation: Instituto Dante Pazzanese de Cardiologia, São Paulo, SP, Brazil.
authors.forename: Carlos Alberto Brandão
authors.initials: CA
authors.lastname: Ferreira Filho
authors.affiliation: Instituto Dante Pazzanese de Cardiologia, São Paulo, SP, Brazil.
authors.forename: Charles Rios
authors.initials: CR
authors.lastname: Souza
authors.affiliation: Instituto Dante Pazzanese de Cardiologia, São Paulo, SP, Brazil.
authors.forename: Camila Caldas
authors.initials: CC
authors.lastname: Menezes
authors.affiliation: Instituto Dante Pazzanese de Cardiologia, São Paulo, SP, Brazil.
authors.forename: Henrique Seichii
authors.initials: HS
authors.lastname: Hirata
authors.affiliation: Instituto Dante Pazzanese de Cardiologia, São Paulo, SP, Brazil.
authors.forename: Luciana Vidal
authors.initials: LV
authors.lastname: Armaganijan
mesh_terms: D000367:Age Factors; D000368:Aged; D016022:Case-Control Studies; D014355:Chagas Disease / Q000150:complications / Q000503:physiopathology*; D004452:Echocardiography; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D018709:Statistics, Nonparametric; D013318:Stroke Volume / Q000502:physiology; D017180:Tachycardia, Ventricular / Q000209:etiology / Q000503:physiopathology*; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000209:etiology / Q000503:physiopathology*