Impella Education, Patient Management, AMI Cardiogenic Shock, Protected PCI
Best Practices for Patients Supported with Impella® (Part 2): Impella Waveforms, Positioning, and Repositioning
“Position assessment is very important every day,” Behnam Tehrani, MD, FSCAI emphasizes in this discussion of Impella® heart pump waveforms, positioning, and repositioning best practices. When Impella is correctly positioned, the inlet area of the device is about 3.5 centimeters below the aortic valve and the outlet area is in the aorta.
Dr. Tehrani explains that a key element of ensuring proper Impella positioning is having 3 people at the bedside in the CCU: 2 people for patient care and hygiene and 1 person dedicated to watching the waveforms on the Impella console and ensuring that the centimeter position on the catheter doesn’t change as the patient is moved.
Waveforms. “Understanding the waveforms is really important,” states Dr. Tehrani. He explains that the red placement signal waveform on the Impella console “displays a pressure measurement that is very useful and helpful in determining the location of the open pressure area of the catheter with respect to the aortic valve” and that the green motor current waveform “is essentially a measure of the energy intake of the Impella catheter and so it varies with speed and the pressure difference between the inlet and outlet areas of the cannula.”
What do the waveforms look like for different Impella positions?
Correctly positioned Impella: Aortic placement signal waveform and pulsatile motor current waveform
Impella too far into the ventricle: Ventricular placement signal waveform and dampened motor current waveform
Impella too far out of the ventricle: Aortic placement signal waveform and dampened motor current waveform
The Impella console also displays alarms at the top of the display if Impella is not correctly positioned.
Position Assessment. Dr. Tehrani emphasizes the need for assessing Impella position daily and documenting position to prevent device migration and potential problems. If, for example, Impella is sitting on the anterior mitral valve leaflet, it may cause functional mitral stenosis, mitral regurgitation, or hemolysis. It may also lead to problems if it is abutting the posterior medial papillary muscle or entangled under subvalvular apparatus.
Repositioning. Dr. Tehrani offers the following best practices for repositioning Impella:
“Always do it under imaging guidance.” Use fluoroscopic guidance when repositioning in the cath lab and echo guidance (parasternal long axis TTE or long axis TEE) in the CCU
Reduce P-level to P2 when repositioning Impella
Ensure that the inlet is ~3.5 cm below aortic valve
Ensure that the catheter is not abutting the anterior mitral valve leaflet, subvalvular apparatus, or papillary muscles
Remove all slack to prevent inward migration
Lock down the Tuohy to help prevent device migration
After repositioning, resume prior P-level setting and reassess final position with imaging
Dr. Tehrani also emphasizes the importance of PA catheter placement. “Never have a patient come upstairs from the cath lab without at PA catheter,” he states. “It’s really important as part of your weaning or escalation strategies to make sure a PA catheter is in place.”