Marcadores eletrocardiográficos para detecção precoce de doença cardíaca em pacientes com talassemia beta maior

Abstract

Objective: To comparatively evaluate P-wave dispersion (PWD) in patients with β-thalassemia major (TM) and healthy control subjects for the early prediction of arrhythmia risk.Methods: Eighty-one children with β-TM, aged 4-19 years, and 74 healthy children (control group) underwent routine electrocardiography and transthoracic echocardiography for cardiac evaluation. PWD was calculated as the difference between the maximum and the minimum P-wave duration.Results: There was a statistically significant difference between study and control groups in peak early (E) mitral inflow velocity and E/late (A) velocity ratio. Maximum P-wave duration and PWD were found to be significantly higher in β-TM patients than in control subjects. Conclusions:Increased PWD in our β-TM patients might be related to depression of intra-atrial conduction due to atrial dilatation and increased sympathetic activity. These patients should be closely followed up for risk of lifethreatening arrhythmias.J Pediatr (Rio J). 2010;86(2):159-162: Thalassemia major, P-wave dispersion, ferritin, cardiac involvement. Original article0021-7557/10/86-02/159 Jornal de PediatriaCopyright © 2010 by Sociedade Brasileira de Pediatria IntroductionCardiac failure and sudden death, the latter probably due to arrhythmias, remain the major causes of death in β-thalassemia major (TM). 1 Disease prognosis, however, has been modified with regular blood transfusions and iron chelation therapy with deferoxamine. 2 P-wave dispersion (PWD) is a simple electrocardiographic marker that has been reported to be associated with inhomogeneous and discontinuous propagation of sinus impulses. It has been defined as the difference between the maximum and the minimum P-wave duration. 3-4 Prolonged P-wave duration and increased PWD have been shown to carry an increased risk for atrial fibrillation. 4 Cardiomyopathy is associated with a four-to six-fold increase in the risk of developing atrial fibrillation. 5 The present study aimed to comparatively investigate these electrocardiographic markers in patients with β-TM and healthy control subjects for the early prediction of arrhythmia risk. MethodsThe study population consisted of two groups: Group I -81 children with β-TM; and group II -74 healthy children Peak mitral inflow velocities in early diastole (E) and after atrial contraction (A) were expressed as cm/s. Deceleration time of peak E filling velocity was measured in milliseconds.Overall LV diastolic dysfunction was defined as the presence of any abnormality of the mitral valve. Twelve-lead electrocardiogram (ECG) was recordedfor each patient and control subject at a rate of 50 mm/s.At the time of electrocardiographic recording, all subjects were in sinus rhythm and none were taking any type of antiarrhythmic agent. P-wave duration was measured manually by two of the investigators who were blinded to the participants' clinical status. All measurements were performed using calipers and magnifying lens to improve accuracy. The onset of P-wave was defined as the junctio...