A narrow QRS does not predict a normal left ventricular function in Chagas' disease

Left ventricular (LV) systolic dysfunction is a major prognostic determinan t in Chagas' disease (ChD), a potentially fatal disorder which affects near ly 20 million individuals in Latin America. Therefore, reliable screening m ethods are needed to identify patients in need of a detailed evaluation of LV function. Since previous reports have suggested that a prolonged QRS dur ation may be an accurate predictor of LV dysfunction, the relationship betw een QRS duration and LV function was evaluated in ChD patients, in order to determine whether a narrow QRS on surface electrocardiogram (ECG) predicts a normal LV function. Ninety-eight patients with ChD and no other cardiac or systemic illness were underwent standard 12-lead ECG and Doppler echocar diogram (echo) examination. An investigator (blinded to the echo data) meas ured manually the QRS duration. LV dysfunction was defined by the presence of LV dilatation (LV diastolic dimension > 55 mm), depressed LV ejection fr action (LVEF < 0.50), segmental contractile abnormalities (SCA) or LV aneur ysm. QRS duration was significantly correlated with LV diastolic dimension (r = 0.44, P = 0.000) and LVEF (r = 0.24, P = 0.016). A significant percent age of patients with QRS < 100 ms had abnormal systolic LV parameters, incl uding LV dilatation (8.1%), reduced EF (10.2%), SCA (42.8%) and LV aneurysm (14.2%). A narrow QRS does not exclude the presence of significant global and segmental LV dysfunction in ChD patients. Since these abnormalities hav e prognostic and therapeutic implications, further evaluation of LV systoli c performance is desirable in such patients.