Use of Impella® Device to Assess Left Ventricular Function: A Proof-of-Concept Study
Left ventricular end-diastolic pressure (LVEDP) refers to the pressure in the LV at the end of diastolic filling and immediately before ventricular contraction.1 It is a useful measure to assess cardiac function and is typically inferred from pulmonary capillary wedge pressure (PCWP). However, PCWP is prone to significant errors and some studies report discordance of PCWP from measured LVEDP by more than 6 mm Hg.1,2
The current study was undertaken to investigate the possibility of measuring LVEDP using an indwelling ventricular assist device, Impella CP®.
Study Objective and Design
The Impella CP is a catheter-based ventricular assist device inserted into the LV across the aortic valve to supports heart function by pulling blood from LV into aorta. Impella maintains a constant motor speed by varying the motor current in response to changes in pressures of aorta and LV.1 The device performance metrics in response to cardiac contractions produces a characteristic hysteresis loop.
In this study published in Science Translational Medicine, Chang et al used the hysteresis loop (relationship between device motor current and pressure gradient across aorta and LV) to determine LVEDP.1 The Impella-derived LVEDP was verified in a mock circulatory loop under simulated physiological conditions. It was also validated in a porcine model of cardiac dysfunction. The clinical applicability and validity of Impella-derived LVEDP was determined by direct comparison with PCWP readings from a patient in cardiogenic shock on mechanical support.
The experiments conducted using mock circulatory loop demonstrated the change in shape of hysteresis loop in response to the changing cardiac state. In addition, it showed that LVEDP can be predicted from the hysteresis loop as it appears as an inflection point when Impella encounters a change in the LV during diastolic filling to active contraction.
In the porcine model of cardiac dysfunction, Impella-derived LVEDP correlated well with direct catheter measurement (R2=0.96) and was 5-fold more accurate than PCWP measurements.
The Impella-derived LVEDP was comparable with PCWP readings of a patient in cardiogenic shock on mechanical support. This finding suggests clinical applicability and validity of hysteresis-derived LVEDP measurement.
The study authors concluded that “the motor current-pressure head relationship of Impella can be used to determine LVEDP”. This is the first study to demonstrate the diagnostic utility of the Impella. Based on the findings of this study, the authors speculate that mechanical support devices may be used for continuous monitoring of cardiac functioning with potential closed-loop feedback control and titration, with future validation.
Since this proof-of-concept study was validated in a porcine model following rapid and acute changes in LVEDP, additional experiments modeling chronic changes in LVEDP and device variability is needed to broaden the scope of these findings.
1 Chang BY, Keller SP, Bhavsar SS et al. Mechanical circulatory support device-heart hysteretic interaction can predict left ventricular end diastolic pressure. Sci Transl Med. 2018; Feb 28;10(430).
2 Ryan JJ, Rich JD, Thiruvoipati T et al. Current practice for determining pulmonary capillary wedge pressure predisposes to serious errors in the classification of patients with pulmonary hypertension. Am Heart J.2012;163(4):589-94.
To learn more about the Impella® platform of heart pumps, including important risk and safety information associated with the use of the devices, please visit: abiomed.com/important-safety-information