Fig. 2

Hysteresis estimation across contractile states. Hysteresis can reflect changes in cardiac state and can be estimated using an algorithm employing device signals alone. a Representative animal data show how hysteresis can increase with contractility from a baseline (blue) to a high inotropy (purple). Instead of direct measurement (circles), hysteresis can be accurately estimated at each point during the systolic phase using a motor current relation derived from Euler’s fluid equations (squares). b Correlation and Bland–Altman analysis are performed to compare quantification of the systolic phase from direct measurement and estimated hysteresis. The results from hysteresis estimation are well-matched to direct measurement in animals undergoing various acute interventions, with improved limits of agreement when considering ranges typical for cardiogenic shock. c A similar comparison is performed using data from patients undergoing percutaneous coronary intervention with results that are consistent with animal results. Notably, patients had more varied baselines, but individually less inotropic variation compared to animal studies with acute interventions