A novel sensor to continuously monitor cardiac apex rotation

The left ventricular (LV) rotation is a key component of cardiac mechanics as recently shown by advanced imaging techniques. In healthy subjects, the cardiac rotation follows a specific pattern within the cardiac cycle in order to be effective: during isovolumic contraction all short-axis levels, from base to apex, rotate counterclockwise, when viewed from the apex, during ejection, the apex continues counterclockwise while the base reverses direction; thus cardiac apex rotation angle (CAR) reaches the maximum at End of Systole (ES). In diastole, the shearing forces built up during systole by cardiac rotation result in rapid untwisting which is thought to contribute to diastolic suction. Alterations in the normal pattern or magnitude of the cardiac rotation have been associated with cardiovascular diseases, such as chronic heart failure, tachycardia-induced dilated cardiomyopathy, dilated cardiomyopathy, hypertrophic cardiomiopathy, myocardial infarction and aortic stenosis. The analysis of CAR signal with respect to systolic and diastolic phases could be useful for the monitoring of cardiac function in patients with various degrees of heart failure as there are often delay and/or dyssynchrony phenomena which considerably reduce the overall mechanical efficiency of the heart. If an altered rotational dynamics determines a delay of maximum CAR into the Isovolumic Relaxation Period (IRP), the effective contribution of left ventricular twisting to systole must be considered the CAR value at the time of ES (CARES). Continuous monitoring of LV rotation has not been attempted so far but may provide important information for long term management of heart failure patients. We propose the use of an implantable gyroscopic sensor for the continuous monitoring of CAR. We evaluated in animals the CAR signal with respect to the systolic timing (CARES) and we tested its ability to reflect changes of LV function during acute ischemia.