Development of online monitoring of myocardiac elastance by imposing dual-frequency minute vibration

It is necessary to determine both ventricular and myocardial mechanical properties for the assessment of cardiac contractility in patients with heart disease. It is important to establish a framework to integrate myocardial properties into ventricular time-varying elastance for understanding the pathophysiology of heart failure. We measured myocardial mechanical properties by imposing minute sinusoidal vibration of different frequencies. Analysis between the amplitude and phase of force relative to those of displacement of at least two frequencies yielded elastance, viscosity, and inertia. Of these, elastance and viscosity were time varying, while inertia was constant during cardiac cycle. Applications of vibration of two different frequencies simultaneously have realized the online monitoring of myocardial properties continuously.