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Introduction: invasive electrophysiology studies and radiofrequency ablation of accessory pathway in patients with WPW syndrome have become routine methods. Noninvasive techniques for localization of the accessory pathway (AP) might help to guide mapping procedures and ablation techniques. Several noninvasive modalities have been used to predict pathway location, however, these methods have modest diagnostic accuracy.Aims: In this study we sought to examine the diagnostic accuracy of strain imaging as a new noninvasive mapping procedure for localization of accessory pathway in patients with Wolff-Parkinson-White syndrome.Methods: We prospectively studied 25 patients (mean age 32±17 years, 58.3% men) who had recurrent supraventricular tachycardia with the evidence of pre-excitation by ECG. All subjects were in sinus rhythm and had normal LV function before electrophysiologic endocardial mapping for radiofrequency ablation of accessory pathway. Complete transthoracic echocardiography and Doppler tissue imaging, strain and strain rate imaging were done in all patients. Localization of the accessory pathway was determined by the myocardial region with the shortest electromechanical interval. We measured time difference between onset of delta wave (δ) to onset(δ-So) and peak systolic (δ-Sm) myocardial contraction, time difference between onset of the delta wave and regional strain (δ-[Latin Small Letter Open E]), peak strain (δ-[Latin Small Letter Open E]p), peak strain rate (δ-SRp). Prediction of the localization of the accessory pathway from standard 12-lead ECG was made by using 3 previously described algorithms after performing echocardiography.The site of successful radiofrequency ablation was used as the precise location of accessory pathway and compared with echocardiographic and electrocardiographic data.Results: ECG has the highest positive predictive value (PPV) for localization of AP in RAS and LPS (100%), RPS (75%), and LL (83.3%) and the lowest for RL (0%). (δ-So) has the highest PPV for localization of AP in LPS (100%) and LL (91.6%) and the lowest one in RL and RAS (50%) and RPS (0%). The PPV of (δ-[Latin Small Letter Open E]) for localization of AP in LPS, RAS, RPS, and RL was 100% versus 66.6% in LL. In general we found a PPV of 56% for TDI (δ-So) and 84% for strain imaging (δ-[Latin Small Letter Open E]) for accurate localization of AP in patients with WPW. Our study showed that strain imaging is superior to ECG in localization of AP (84% versus 76%).Conclusion: TDI derived parameters such as onset of systolic velocity (δ-So) and strain (δ-Strain) have better diagnostic yield than ECG for noninvasive localization of accessory pathway in patients with WPW syndrome.