Purpose: The aim of this study was to investigate whether prolonged myocardial contraction duration in walls of the left ventricle assessed by tissue Doppler imaging (TDI) may serve as risk markers for early detection cardiac events in patients with LQTS. Methods: This was a prospective study being performed in Namazi and Shahid Faghihi Hospitals of Shiraz University of Medical Sciences. Thirty two participants who had a typical electrocardiogram (ECG) with prolong QT pattern were divided into low and high risk groups. High risk group was 21 patients with implantable cardioverter defibrillator (ICD) who had experienced syncope or a QTc longer than 500 milliseconds or a family history of sudden cardiac death or complex ventricular arrhythmias. Low risk group was 11 asymptomatic patients treated with beta blockers who had not experienced syncope, a QTc longer than 500 milliseconds, a family history of sudden cardiac death, and complex ventricular arrhythmias. Myocardial contraction duration in 12 LV segments was obtained using tissue Doppler imaging (TDI) and then was compared between two study groups. Results: The most significant difference regarding the mean of contraction duration between two groups was in base and middle of inferior segment (P = 0.0001). Contraction duration ≥460 ms showed a sensitivity of 71% and a specificity of 82% in the inferior segments of left ventricle. Area under curve was 0.89 in base of inferior segment and, 0.88 in middle of inferior segment. Conclusion: This study showed that myocardial contraction duration can be of important value for early detection cardiac events in patients with LQTS. Prolonged contraction duration in inferior segment was better related to cardiac events compared with other cardiac segment. Finally, we concluded that TD measurements could become part of the routine clinical evaluation and screening for differentiating high risk patients than low risk patients as a new phenotypic marker. Keywords: Long-QT syndrome, Tissue Doppler imaging, Contraction duration