Cardiac rotation assessed by gyroscopic sensors: experimental animal trials

During the cardiac cycle, contraction of the helically oriented myocardial fibres results in torsion, a wringing motion as the cardiac apex rotates with respect to the base about the Left Ventricle (LV) long axis. LV twist has been shown to provide a sensitive index of cardiac function. Recently, non-invasive echocardiographic and magnetic resonance imaging techniques have been proposed to quantify cardiac rotation; however, they are not suitable for chronic monitoring of LV twist dynamics. We propose the use of gyroscopic sensors to quantify cardiac rotation. Results from in vivo experiments on four sheep are presented herein. A catheter was placed in the LV to assess LV pressure (LVP) and its first derivative (LVdP/dt). Three gyroscopes were epicardially glued at different levels along the LV long axis (apex, middle, base) to assess LV twist dynamics: Angular Velocity (Ang V) and Angle of cardiac rotation (Angle) were measured and evaluated against hemodynamic measurements (LVP, LVdP/dt), at baseline and after induction of acute alterations of cardiac status (dobutamine infusion and coronary artery ligation). Cardiac rotation assessed at apical level showed the most significant results: compared with baseline values, improvement of contractility (+145% in LVdP/dtMAX) after dobutamine infusion increased both Angle (+11%) and the maximum value of Ang V during systole – defined as Ang VMAX (+155%). After acute impairment of cardiac function caused by coronary ligation, both Ang VMAX and Angle decreased (-31% and -65%, respectively) and a concomitant reduction of LVdP/dtMAX (-35%) was observed. The study demonstrated the feasibility of assessing cardiac rotation and LV twist alterations by means of gyroscopic sensors. A miniaturized gyroscope could be utilized for the chronic monitoring of cardiac function if adequately integrated into a pacemaker or other implantable medical devices.