Clinical usefulness of wave intensity analysis

Wave intensity (WI) is a hemodynamic index, which can evaluate the working condition of the heart interacting with the arterial system. It can be defined at any site in the circulatory system and provides a great deal of information. However, we need simultaneous measurements of blood pressure and velocity to obtain wave intensity, which has limited the clinical application of wave intensity, in spite of its potential. To expand the application of wave intensity in the clinical setting, we developed a real-time non-invasive measurement system for wave intensity based on a combined color Doppler and echo-tracking system. We measured carotid arterial WI in normal subjects and patients with various cardiovascular diseases. In the coronary artery disease group, the magnitude of the first peak of carotid arterial WI (W ₁) increased with LV max. dP/dt (r = 0.74, P < 0.001), and the amplitude of the second peak (W ₂) decreased with an increase in the time constant of LV pressure decay (r = −0.77, P < 0.001). In the dilated cardiomyopathy group, the values of W ₁ were much lower than those in the normal group (P < 0.0001). In the hypertrophic cardiomyopathy group, the values of W ₂ were much smaller than those in the normal group (P < 0.0001). In mitral regurgitation before surgery, W ₂ decreased or disappeared, but after surgery W ₂ appeared clearly. In the hypertension group, the magnitude of reflection from the head was considerably greater than that in the normal group (P < 0.0001). We also evaluated hemodynamic effects of sublingual nitroglycerin in normal subjects. Nitroglycerin increased W ₁ significantly (P < 0.001). WI can be obtained non-invasively using an echo-Doppler system in the clinical setting. This method will increase the clinical usefulness of wave intensity.