According to a new study published in the New England Journal of Medicine, a fully magnetically levitated centrifugal- flow pump has been found to be superior to a mechanical-bearing axial-flow pump in advanced heart failure patients in terms of survival free of disabling stroke or reoperation for removal in case of device malfunction.
MOMENTUM 3 is the largest left ventricular assist device randomized control trial ever performed looking at the HeartMate technology in the very difficult space of advanced heart failure. The primary end point was a composite of survival at 2 years free of disabling stroke (with disabling stroke indicated by a modified Rankin score of >3) or survival free of reoperation to replace or remove a malfunctioning device. The trial randomised one arm of patients to a traditionally available current device (HeartMate II) which was a continuous flow axial pump with mechanical parts. This made the device prone to wear and tear, with a concerning risk of de novo pump thrombosis. Patients in the second arm received the HeartMate 3 device, a novel device with the unique feature of a fully magnetically levitated rotor. The device was completely frictionless, with no bearings and was not prone to wear and tear. Even if the device fitted into the palm of one’s hand and could be fully implanted into one’s chest, it was engineered to have very wide blood flow paths so red cells entering and exiting the device were not prone to sheer stress. So this was a novel platform that was designed to avert pump thrombosis. In addition to this, the HeartMate 3 actually had a fixed pulse algorithm within it, where it revved itself up and down every 2 seconds creating an artificial pulse, while continuous flow devices rendered the individual pulseless. In the past, the transition from pulsatile to non-pulsatile pumps had occurred as pulsatile devices had to be bulky to accommodate displacement chambers and had valves in them that lacked durability. However, when patients were transitioned to non-pulsatile flow, they had inordinately high rates of gastrointestinal bleeding and angiodysplasia of the colon, mimicking a low pulse pressure state seen in critical Aortic stenosis associated with GI bleeding (Heyde’s syndrome). Hence, MOMENTUM 3 was a trial that aimed to reintroduce pulsatile devices, with the HeartMate 3 generating an intrinsic pseudopulse of 30 bpm.
“We have finally found a forgiving pump, but not a forgettable pump.” -Dr. Mandeep Mehra, M.D. 
Findings in the early analysis of MOMENTUM 3 showed that the new magnetically levitated centrifugal continuous-flow pump was associated with diminished rates of pump thrombosis leading to pump malfunction at 6 months as compared to the axial-flow pump. In order to determine whether the magnetic pump could be used long term as a mechanical circulatory support as a bridge to transplantation or as destination therapy, Dr. Mehra and his colleagues recently published the 2 year prespecified analysis from the MOMENTUM 3 trial.
In the study, Mehra et al found that the primary end point occurred in 79.5% of patients in the centrifugal-flow pump group, as compared with 60.2% in the axial-flow pump group. Reoperation for pump malfunction was less frequent in the centrifugal-flow pump group than in the axial-flow pump group (1.6% vs. 17.0%). Moreover, they found that the overall rate of stroke was lower in the centrifugal-flow pump group than in the axial flow pump group. Therefore, HeartMate 3 in MOMENTUM 3 showed two very important signals. Not only were the rates of pump thrombosis and reoperations from malfunctioning devices significantly diminished, but for the first time ever, there was a clear signal of reduction in strokes (by 53 percent). In fifty years, researchers had not been able to shift stroke rates with left ventricular assist devices. While most strokes were not disabling, the expectation of stroke rates with a device was a minimum of ten percent per year.
In an interview with Dr. Gibson, the primary investigator, Dr. Mandeep Mehra, medical director of the Brigham and Women’s Hospital (BWH) Heart and Vascular Center stresses that, “While the HeartMate 3 design has abrogated issues related to pump thrombosis and has led to significant a reduction of stroke (ischemic strokes being more predominant with left ventricular assist devices than haemorrhagic), low intensity anticoagulation regimens still need to be considered to treat hemorrhagic complications. He adds, “We have finally found a forgiving pump, but not a forgettable pump.” He explains that this is because “you still have a drive line that exits the abdomen, connects into a battery pack that people harness on their shoulders.” This could be challenging as “there’s always a risk of drive line infections and the patient has to be bound to power sources all the time.” When questioned about the next step, he remarks, “The next generation device (HEARTMATE X) will be a fully internalised or fully implantable device where there is no power source that exits the body.” In order to achieve this goal, he believes that free resonance technology has a lot of promise in this field. In addition, novel power sources including hydraulic and thermal power should be considered to internalise these devices. He is also hopeful that future pumps using smart technology will allow the patient to modulate the pulse in response to different activities such as hiking, biking or climbing a flight of stairs.
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