Role of Echocardiography and Impella® in Cardiogenic Shock
Impella trainer Michael Galvin, BS, RDCS, discusses the role of echocardiography and Impella in cardiogenic shock. He begins by explaining what cardiogenic shock is and the role of Impella in managing cardiogenic shock. He then defines echo values and measurements that help diagnose shock and evaluate Impella's position, including where to measure and which structures are important to identify. He also discusses echocardiographic findings in right heart failure and the role of echo in weaning Impella support.
Mike defines cardiogenic shock as “inadequate blood supply due to ventricular failure” that may result from conditions such as acute heart failure from myocardial infarction (MI) or cardiomyopathy. Echocardiography provides a non-invasive and rapid assessment of hemodynamics to help diagnose and optimize treatment in these patients. Echo features of cardiogenic shock include low ejection fraction (EF), regional or global hypokinesia, dilated left ventricle (LV) and/or right ventricle (RV), worsening mitral regurgitation, and low cardiac output (CO).
Mike describes the hemodynamic effects of Impella, explaining that Impella effectively increases blood flow and mean arterial pressure (MAP) to increase end-organ perfusion. Impella also reduces left ventricular end-diastolic pressure (LVEDP) and volume (LVEDV), reducing the mechanical work of the heart and its demand for oxygen, leading to unloading and myocardial recovery.
A pre-implant echo evaluation is useful before initiating Impella support. This evaluation can include baseline LV and RV function, LV and RV diameter in diastole, left atrial size, valve function, and inferior vena cava (IVC) size and collapsibility. In addition, Mike emphasizes the importance of evaluating left ventricular ejection fraction (LVEF) and mitral valve function, noting “the biggest predictors of mortality in shock are your ejection fraction and the severity of mitral valve regurgitation.”
Mike recommends using echo at ICU/CCU check-in; if you suspect catheter migration, poor position, or RV failure; in conjunction with repositioning; to assess myocardial recovery while on support, especially when weaning; and after removing Impella to compare LV and RV size and function to before Impella support.
When looking at echo images of Impella in the heart, the middle of the inlet should be located 3.5 cm below the aortic valve annulus, or 5 cm below the annulus for the Impella 5.5® with SmartAssist®. Mike shows several echo images, presents correct Impella position checklists for TTE and TEE, and explains how to make these measurements.
Mike also discusses the importance of identifying RV failure in patients with cardiogenic shock, noting that Impella RP®—which provides support to the right side of the heart—is used most often in patients with cardiogenic shock. He emphasizes that without the RV providing adequate preload, left-sided pump flows will not be optimal and may result in suction alarms, hemolysis, and poor pump flows. He describes anatomic signs of RV failure and corresponding echo features, including tricuspid annular plane systolic excursion (TAPSE), the motion of the tricuspid valve annulus over time.
Finally, Mike discusses how echo assists with weaning. “Knowing when a patient can be weaned off support is really a key component to our care,” he emphasizes, describing how patients should be weaned off inotropic and vasopressor support before weaning and how hemodynamics should be maintained as Impella flow is reduced. He concludes with the reminder: “Echo plays a critical role in every step of care for the cardiogenic shock patient.”