Research ArticleCardiology

Mechanical circulatory support device-heart hysteretic interaction can predict left ventricular end diastolic pressure

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Science Translational Medicine  28 Feb 2018:
Vol. 10, Issue 430, eaao2980
DOI: 10.1126/scitranslmed.aao2980

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Predicting pressure from a pump

Mechanical ventricular assist devices help the heart pump blood after cardiac surgery or while awaiting heart transplant. Chang et al. show that the motor current and pressure head recorded by the Impella, a temporary assist device placed within the left ventricle, can be used to measure left ventricular end diastolic pressure (LVEDP). LVEDP indicates cardiac function and is used to titrate mechanical pump support. Chang and colleagues found that Impella-based LVEDPs matched left heart catheter-based LVEDPs more closely than pulmonary capillary wedge pressure–inferred LVEDPs. After testing in a mock circulatory loop and a pig model of cardiac dysfunction, they confirmed their findings with patient data. This method does not require any modification of the Impella assist device, suggesting that it could be easily adopted into clinical practice.

Abstract

The full potential of mechanical circulatory systems in the treatment of cardiogenic shock is impeded by the lack of accurate measures of cardiac function to guide clinicians in determining when to initiate and how to optimally titrate support. The left ventricular end diastolic pressure (LVEDP) is an established metric of cardiac function that refers to the pressure in the left ventricle at the end of ventricular filling and immediately before ventricular contraction. In clinical practice, LVEDP is typically only inferred from, and poorly correlates with, the pulmonary capillary wedge pressure (PCWP). We leveraged the position of an indwelling percutaneous ventricular assist device and advanced data analysis methods to obtain LVEDP from the hysteretic operating metrics of the device. We validated our hysteresis-derived LVEDP measurement using mock flow loops, an animal model of cardiac dysfunction, and data from a patient in cardiogenic shock to show greater measurement precision and correlation with actual pressures than traditional inferences via PCWP. Delineation of the nonlinear relationship between device and heart adds insight into the interaction between ventricular support devices and the native heart, paving the way for continuous assessment of underlying cardiac state, metrics of cardiac function, potential closed-loop automated control, and rational design of future innovations in mechanical circulatory support systems.

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