Echo for Impella®: How to Measure and Determine Proper Position

Michael Galvin, a clinical educator at Abiomed, discusses how to identify Impella components and measure Impella position using echocardiography. Typically, the best echocardiography view for assessing Impella position is the parasternal long-axis view. Begin by looking for the Impella cannula when assessing Impella position under echo. It appears as two parallel lines, often referred to as “railroad tracks,” extending through the aortic valve into the left ventricle. These lines end at the Impella inlet area in the ventricle. 

The stainless steel inlet is the only part of the Impella in this area that is metal. It is usually easy to identify since the metal creates an artifact when imaged with echo. The inlet narrows like a cone and the end of the inlet area, where the stainless steel attaches to the inlet windows, is referred to as “the teardrop” on imaging. Some Impella devices, such as the Impella CP® with SmartAssist®, have a pigtail at the end of the inlet, but this pigtail is often not easy to see on echo.

Michael Galvin discusses when to use echo to assess Impella heart pump position. First, use echo to get a baseline assessment of Impella position when the patient arrives in the ICU/CCU from the cath lab. Then use echo to reassess position if alarms occur, if there are clinical changes or changes in patient positioning or if there are changes in the waveforms on the controller. It is also important to evaluate right ventricular (RV) function with echo if there is a suspicion that RV failure is limiting left ventricular (LV) Impella flow. In addition, echo can help determine how the LV is functioning at different flow levels (P levels), especially during weaning.

When measuring Impella position with echo, first look for the movement of the aortic valve leaflets and then locate the the inlet of the Impella. The parasternal long-axis view is usually the best view for measuring position. The middle of the inlet of the Impella CP® should be approximately 3.5 cm from the aortic valve while the middle of the inlet of the Impella 5.5® with SmartAssist® should be approximately 5 cm from the aortic valve.

Characteristics of good Impella position include not only proper depth within the left ventricle, but also stable position (not rocking or swinging) and good spacing around the inlet and outlet. The inlet should be free-floating, surrounded by blood, and free of mitral valve structures. The outlet should be positioned well above the aortic valve and unobstructed.