EXPLANATION


The Impella® is a short-term ventricular assist device (VAD) used to provide ventricular support in the setting of cardiogenic shock following acute myocardial infarction, acute transplant rejection, cardiac surgery, high-risk percutaneous coronary interventions or for the management of cardiomyopathy. The Impella® can be used in patients on extracorporeal membrane oxygenation (ECMO) for left ventricular unloading. The Impella 5.5® is also used as a bridge to heart transplantation. The Impella 5.5® is placed surgically via a direct transaortic approach or through right or left axillary artery cutdown and graft. It is placed within the left ventricle (LV), across the aortic valve, and utilizes a catheter-based microaxial pump to displace blood from the LV into the ascending aorta, providing up to 6 L/ min of flow. Other iterations of the Impella® include the Impella CP®, which is placed percutaneously through the femoral artery and allows flows up to 4.3 L/min, and the Impella RP®, which is used for right ventricular support and provides a flow rate of up to 4 L/min.


Placement of an Impella 5.5® is contraindicated in patients with severe aortic stenosis or calcification with a valve area less than 0.6 cm², LV thrombus, moderate or severe aortic insufficiency, presence of an atrial or ventricular septal defect, and presence of a mechanical aortic valve. Complications of the Impella® include damage to the aortic valve, ascending aorta, aortic root, and coronary sinuses, stroke, hemolysis, acute renal failure, and thrombocytopenia.


The Impella 5.5® can be used in the pediatric population if the patient can accommodate the 21 French (Fr) cannula that crosses the aortic valve. The device is 114 mm in length and is mounted on a 9 Fr catheter for implantation. While large studies do not exist in pediatric patients, there are published case reports of Impella® implantation in pediatric patients with most utilizing computed tomography or fluoroscopy for measurement and modeling of the aortic annulus, ascending aorta, aortic arch vessels, and LV cavity in conjunction with guided navigation for implantation. The Impella 5.5® and CP® have recently been approved by the U.S. Food and Drug Administration for use in pediatric patients weighing greater than or equal to 30 kg and greater than or equal to 52 kg respectively. However, the Impella® continues to be used off-label in smaller patients using vessel and LV size for guidance.


The patient described in this case underwent a Bentall procedure. In this case, he received a mechanical aortic valve which excludes him from Impella 5.5® implantation, making C. the correct answer. As discussed above, this patient’s age and weight do not exclude Impella 5.5® use. However, measurements of the aortic valve annulus and aortic arch vessels, along with a three-dimensional rendering of LV size can help to determine if an Impella 5.5® catheter can be positioned appropriately in pediatric patients regardless of age or weight.


REFERENCES


Abiomed. Impella® 5.5 with SmartAssist© instructions for use. https://d1edr79mp9g5zc.cloudfront.net/5eb0affe-1991-449b-bfc0-a5a0516548bf/cb8ef4bf-4fb9-46ed-91d7-6117f06bb18e/cb8ef4bf-4fb9-46ed-91d7-6117f06bb18e_source__v.pdf . Accessed February 6, 2025.


Glazier JJ, Kaki A. The Impella Device: Historical Background, Clinical Applications and Future Directions. Int J Angiol. 2019;28(2):118-123. doi:10.1055/s-0038-1676369


Oelkers B, Schumer E, Lambert AN, Alsoufi B, Kozik D, Wilkens SJ. The Use of Impella 5.5 Reduces Pulmonary Vascular Resistance as Bridge to Heart Transplant in a Pediatric Patient. ASAIO J. 2025;71(3): e46-e47. doi:10.1097/MAT.0000000000002256


Pediatric Cardiology. FDA Expands Indication for Impella Heart Pumps for Pediatric Patients. December 18, 2024. Accessed February 6, 2025. https://www.dicardiology.com/content/fda-expands-indication-impella-heart-pumps-pediatric-patients