Authors: Manal Mirreh, MD AND Asif Padiyath, MD – Children’s Hospital of Philadelphia, Philadelphia, PA
A 14-year-old male with a history of heart transplantation is admitted to the intensive care unit with acute transplant rejection. Due to worsening cardio-respiratory status, he is sedated and intubated. A chest x-ray demonstrates florid bilateral pulmonary edema, and an echocardiogram reveals severe left ventricular dysfunction and moderate mitral regurgitation. A decision is made to place an Impella device in the cardiac catheterization laboratory. Which statement BEST DESCRIBES how an Impella could contribute to hemodynamic improvement in this patient?
EXPLANATION
The Impella® devices first received Food and Drug Administration (FDA) clearance in 2008 and FDA pre market approval as safe and effective in 2015.1 The Impella® system consists of a catheter-based microaxial continuous flow device placed across the aortic valve actively pumping blood from the left ventricle (LV) into the ascending aorta throughout the cardiac cycle, regardless of the heart’s rhythm and cardiac function. It comprises various models with different unloading power and supported flow, including the Impella 2.5® (up to 2.5 L/min; 13F), Impella CP® with Smart Assist (3.5 to 4.3 L/min; 14F), and Impella 5.0® and 5.5® with Smart Assist (up to 6.2 L/min; 23F), with an additional RP model available for right ventricular support (4.0 L/min; 23F). While the 2.5 and CP devices can be percutaneously inserted, the 5.0 and 5.5 require a surgical approach for transfemoral, transaxillary, or trans-subclavian implantation. Currently, Impella® CP, 5.5, and RP are the only commercially available devices. The Smart Assist system, integrated into recent models, uses real-time intelligence to optimize support positioning, management, and weaning. By employing LV-to-aorta support, the Impella® support reduces ventricular workload, enhances cardiac output, and facilitates myocardial recovery in cardiogenic shock.2
Contraindications to placement of Impella CP® include a mechanical aortic valve, LV thrombus, severe aortic stenosis or LV outflow tract obstruction, moderate-to-severe aortic insufficiency, large ventricular septal defect, or severe peripheral arterial disease.
Impella CP® has been approved for pediatric patients weighing ≥52 kg for short-term use up to 4 days, and Impella 5.5® has been approved for pediatric patients weighing ≥30 kg for short-term use up to 14 days.3
The Impella® actively withdraws blood from the LV and ejects it into the ascending aorta, providing forward systemic flow. By continuously removing blood from the LV, the device reduces left ventricular end-diastolic volume and pressure, which in turn lowers LV wall stress and myocardial oxygen demand. Because the left atrium and left ventricle are in series across the mitral valve, decreasing LV pressure increases the pressure gradient from the left atrium to the LV, allowing blood to flow more easily into the ventricle. This results in a secondary reduction of left atrial pressure, relieving pulmonary venous congestion and pulmonary edema. Clinically, this manifests as decreased pulmonary capillary wedge pressure, improved oxygenation, and reduced left-sided filling pressures. Importantly, the Impella® does not directly drain the left atrium or pulmonary veins; the decompression is entirely a consequence of unloading the left ventricle.
REFERENCES
1. Pediatric Cardiology. FDA expands indication for Impella heart pumps for pediatric patients. Published December 18, 2024. Accessed September 3, 2025. https://www.dicardiology.com/content/fda-expands-indication-impella-heart-pumps-pediatricpatients
2. Masiero G, Arturi F, Panza A, Tarantini G. Mechanical circulatory support with Impella: principles, evidence, and daily practice. J Clin Med. 2024;13(16):4586. doi:10.3390/jcm13164586
3. Andropoulos DB, Mossad EB, Miller-Hance WC, eds. Anesthesia for Congenital Heart Disease. 4th ed. Wiley-Blackwell; 2022:759-761. Chapter 32, Mechanical Circulatory Support.
