Aims To test the hypothesis that Qr in V, is a predictor of pulmonary embolism, right ventricutar strain, and adverse clinical outcome. Methods and Results ECG's from 151 patients with suspected pulmonary embolism were blindly interpreted by two observers. Echocardiography, troponin 1, and pro-brain natriuretic peptide levels were obtained in 75 patients with pulmonary embolism. Qr in V-1 (14 vs 0 in controls; p<0.0001) and ST elevation in V-1 greater than or equal to1 mV (15 vs 1 in controls; p=0.0002) were more frequently present in patients with pulmonary embolism. Sensitivity and specificity of Qr in V-1 and T wave inversion in V, for predicting right ventricular dysfunction were 31/97% and 45/94%, respectively. Three of five patients who died in-hospital and 11 of 20 patients with a complicated course, presented with Qr in V-1. After adjustment for right ventricular strain including ECG, echocardiography, pro-brain natriuretic peptide and troponin I levels, Qr in V-1 (OR 8.7, 95%CI 1.4-56.7; p=0.02) remained an-independent predictor of adverse outcome. Conclusions Among the ECG signs seen in patients with acute pulmonary embolism, Qr in V-1 is closely related to the presence of right ventricutar dysfunction, and is an independent predictor of adverse clinical outcome. (C) 2003 The European Society of Cardiology. Published by Elsevier Science Ltd. All rights reserved.