Background: Wave intensity (WI) is a new hemodynamic index that provides information about the dynamic behavior of the heart and the vascular system and their interaction. WI can be defined at any site in the circulatory system and provide a great deal of information. However, the clinical usefulness of the second peak of WI, which is related to the ability of the left ventricle to activity stop aortic blood flow, has not been fully reported. In previous study, the magnitude of W2 was related to the inertia force of late systolic aortic flow. Also, the higher augmented inertia force, which was calculated with cardiac catheterization, was associated with greater exercise capacity. Then, we hypothesize that WI is correlated to exercise capacity. In this study, we investigated whether WI and the echocardiographic parameters would be correlated with exercise capacity. Methods: A total of 24 patients of heart disease were enrolled. WI was obtained at the right carotid artery using a color Doppler system for blood velocity measurement combined with an echo-tracking method for detecting vessel diameter changes. As echocardiographic parameters, we analyzed ejection fraction (EF), the early (E) and late (A) diastolic mitral velocities, and early (Ea) and late (Aa) diastolic velocities measured using Tissue Doppler imaging. We evaluated exercise capacity (peak VO2, VE/VCO2, and AT). We used Pearson's correlation analysis for statistics. Results: EF, the E/A ratio, and the E/Ea ratio were not correlated to exercise capacity. However, the second peak of WI was significant correlated to the peak VO2 (r=0.50, p<0.05). Conclusion: The second peak of WI is noninvasively obtained, and a clinically useful parameter for exercise capacity in heart disease.