Impella 5.5® with SmartAssist® versus CentriMag™: Head-to-Head Comparison of Device Hemocompatibility

Marvin Slepian, MD, reviews his recently published paper in which he compares the hemocompatibility of Impella 5.5® with SmartAssist® to CentriMag™.

Overview

Dr. Slepian acknowledges that he, like many clinicians, thought about the speed at which the microaxial Impella 5.5 pump rotates compared to the rotary CentriMag pump, and wondered: “Wouldn’t that speed actually cause more issue with the blood?” Yet through his research he explains, “We came out with a very different result than what I thought. That actually Impella was not as activating on many aspects of blood compared to the CentriMag.”

For their research, Dr. Slepian and his colleagues created standard circulatory loop systems that circulated freshly obtained porcine blood under standard operating conditions using CentriMag or Impella 5.5 with SmartAssist. They looked at four broad study endpoint variables: hemolysis, platelet activation, microparticlegeneration, and von Willebrand factor (vWF) alteration.

Hemolysis

Dr. Slepian describes hemolysis in terms of plasma free hemoglobin and lactate dehydrogenase (LDH), noting that they did not see any significant differences between Impella 5.5 with SmartAssist and CentriMag. He explains that even though Impella 5.5 with SmartAssist spins at a speed that is an order of magnitude faster than CentriMag, “You may actually be imparting the same degree of shear to the blood. It’s not that number… that’s actually going to cause the problem. It’s not that. It’s the absolute interaction of that propulsive element with the blood.” Dr. Slepian also points to earlier research he’s published delving deeper into the mechanisms contributing to thrombosis in continuous flow ventricular assist devices.

Platelet Activation

Dr. Slepian discusses the dynamic process of platelet activation, looking at β-thromboglobulin and P-selectin as well as soluble P-selectin and annexin V. He explains how there will be a certain degree of activation after 4 hours of circulation in the loop, but he emphasizes, “The level of activation is exactly the same for Impella versus CentriMag.”

Microparticle Generation

Dr. Slepian spends some time discussing microparticles, which he defines as “a fragmented piece of a cell which is blown off.” When a microparticle is generated, its surface contains substances that activate platelets and bind vWF. “In simple terms,” Slepian explains, “it’s got all the adhesive stuff, super concentrated, almost 7-fold on these little microparticles which really – it’s like gasoline on a fire for thrombosis. So, the microparticle situation is actually very important.” In this paper, Slepian and colleagues observed more microparticle generation with CentriMag than Impella 5.5 with SmartAssist and he concludes, “I think that being able to blow out and reduce microparticles is the next ‘goal’ of advanced engineering of mechanical circulatory support.”

vWF

With regard to von Willebrand factor, Dr. Slepian explains that his research revealed a slight effect, however he notes, “that’s not really where the money is with these devices.”

Summary

“If I have to summarize the study,” says Dr. Slepian, “it was an eye opener that actually it's not just about the rate and speed of a device causing an issue. That in fact, with Impella, we do not see any untoward hemolysis compared to the CentriMag… As far as platelet activation, we do not see a lot of activation with these devices, though we do see a little bit more generation of microparticles with—about 20% more—with the CentriMag device. And that is an area that we are going to keep our eye on because that is a long-term driver of thrombosis or long-term events that can occur in a patient.”

Looking ahead, Dr. Slepian identifies future research in the areas of the mechanisms that govern the generation of microparticles, ways to mitigate and reduce the generation of microparticles by changing the mechanical properties of platelets, and the interaction with inflammatory cytokines, which has become important during the COVID-19 era.