Purge Sidearm Damage: Achilles Heel of New Surgical Circulatory Support System?

The Impella 5.5 (Abiomed, Danvers, MA) was recently approved by the United States Food and Drug Administration for use in patients with cardiogenic shock refractory to medical management. Compared to the Impella 5.0 (Abiomed, Danvers, MA), the Impella 5.5 features more compact motor housing while also delivering maximal forward flow of 6.2 l/min.1 Recently, Ramzy D et al. reported three centers’ initial experiences with 55 patients who underwent Impella 5.5 placement.2 While results were overwhelmingly positive, four patients (7.3%) experienced damage to the purge sidearm, resulting in a pump stop with an inability to restart in two patients. One patient sustained damage from use of isopropyl alcohol to clean the device. The other had damage during broad movement. Our institution is also one of the US limited market release centers for Impella 5.5 implantation. The Impella 5.5 has been implanted in 12 patients thus far. We report one case (8.3%) of purge sidearm damage requiring mechanical circulatory support upgrade. Case A 41-year-old female with a history of postpartum cardiomyopathy and end-stage renal disease was transferred from an outside hospital for heart transplant evaluation. She was not a durable left ventricular assist device candidate due to dialysis dependence. The patient was deemed a candidate for Impella 5.5 placement as a bridge to heart and kidney transplant. Before Impella 5.5 placement, the cardiac index was 2.1 l/min/m2 with a pulmonary capillary wedge pressure of 20 mm Hg on dual inotrope support. After Impella 5.5. implantation, the cardiac index improved to 3.1 l/min/m2 with a pulmonary capillary wedge pressure of 16 mm Hg on postoperative day 1. The patient regained ambulatory status. On day 32 of support, however, the purge sidearm infusion filter cracked due to patient movement and began leaking purge fluid after ambulation (Figure 1). The damaged part was nonexchangeable, and repair using sterile surgical adhesive, sealing, and films, as recommended by the manufacturer, failed. Since the patient was found to have high panel-reactive antibody after Impellor 5.5 insertion, she likely required extended mechanical circulatory support as bridge to transplantation. The Impella 5.5 was replaced with a surgical extracorporeal left ventricular assist device before development of Impella 5.5 pump malfunction.Figure 1.: Consistent purge leak from crack in filter after recommended trouble shooting. The area of the leak is indicated by a red-dashed circle and a red arrow.The Impella 5.5’s purge system diverts antegrade-flowing blood in an oblique direction toward the lumen of the vessel through efflux ports just proximal to the motor’s housing. Purge solution, consisting of heparin sodium dissolved in 5% dextrose per the manufacturer, is pushed in the opposite direction of blood sucked into the impeller at the distal end, thereby creating a pressure barrier that protects the motor from incoming blood.3 Though limited in case numbers, we have experienced a similar incidence of purge sidearm damage in Ramzy et al. The manufacturer has now instituted a purge-sidearm retainer to limit sidearm damage during patient movement or ambulation and further recommends avoiding alcohol-based cleaning products on the purge sidearm to limit any damage to the filter unit. This refinement of device design could lead to further reliable long-term support.