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.
Impella® Device — Indication & Safety Information
INDICATIONS FOR USE
The Impella 2.5® and Impella CP® Systems are temporary (≤ 6 hours) ventricular support devices indicated for use during high-risk percutaneous coronary interventions (PCI) performed in elective or urgent, hemodynamically stable patients with severe coronary artery disease, when a heart team, including a cardiac surgeon, has determined high-risk PCI is the appropriate therapeutic option. Use of the Impella 2.5 and Impella CP Systems in these patients may prevent hemodynamic instability, which can result from repeat episodes of reversible myocardial ischemia that occur during planned temporary coronary occlusions and may reduce peri- and post-procedural adverse events.
The Impella 2.5®, Impella CP®, Impella 5.0®, and Impella LD® Catheters, in conjunction with the Automated Impella Controller (collectively, “Impella® System Therapy”), are temporary ventricular support devices intended for short term use (≤ 4 days for the Impella 2.5 and Impella CP, and ≤ 6 days for the Impella 5.0, and Impella LD) and indicated for the treatment of ongoing cardiogenic shock that occurs immediately (< 48 hours) following acute myocardial infarction or open heart surgery or in the setting of cardiomyopathy, including peripartum cardiomyopathy, or myocarditis as a result of isolated left ventricular failure that is not responsive to optimal medical management and conventional treatment measures (including volume loading and use of pressors and inotropes, with or without IABP). The intent of Impella System Therapy is to reduce ventricular work and to provide the circulatory support necessary to allow heart recovery and early assessment of residual myocardial function.
Important Risk Information for Impella devices
The Impella 2.5, Impella CP, Impella 5.0 and Impella LD are contraindicated for use with patients experiencing any of the following conditions: Mural thrombus in the left ventricle; Presence of a mechanical aortic valve or heart constrictive device; Aortic valve stenosis/calcification (equivalent to an orifice area of 0.6 cm2 or less); Moderate to severe aortic insufficiency (echocardiographic assessment graded as ≥ +2); Severe peripheral arterial disease precluding placement of the Impella System; Significant right heart failure*; Combined cardiorespiratory failure*; Presence of an Atrial or Ventricular Septal Defect (including post-infarct VSD)*; Left ventricular rupture*; Cardiac tamponade*
* This condition is a contraindication for the cardiogenic shock indication only.
POTENTIAL ADVERSE EVENTS
Acute renal dysfunction, Aortic valve injury, Bleeding, Cardiogenic shock, Cerebral vascular accident/Stroke, Death, Hemolysis, Limb ischemia, Myocardial infarction, Renal failure, Thrombocytopenia and Vascular injury
In addition to the risks above, there are other WARNINGS and PRECAUTIONS associated with Impella devices. Visit http://www.abiomed.com/important-safety-information to learn more.