ACC 2009: Pint-Sized "Partial" Ventricular-Assist Pump Debuts to Hopeful Reviews

from <a href="" target="_blank">Heart<i>wire</i></a> &#151; a professional news service of WebMD

April 03, 2009

April 3, 2009 (Orlando, Florida) — Weighing 25 g and smaller than a man's thumb, a rotor-based pump (Synergy; CircuLite, Saddle Brook, NJ) provided "partial ventricular support," boosting hemodynamics rather than taking it over, in a 16-patient "first-in-human" experience reported here at the American College of Cardiology 2009 Scientific Sessions. Investigators think that the small patient series has shed some light on at least two questions that are important for such a device: can it safely provide long-term circulatory assistance, and for what kind of patient is it useful?

The pump's "minimally invasive" nature--it sits in a subcutaneous pocket and ties into the circulation through small intercostal openings--suggests potential in patients with debilitating heart failure who aren't sick enough to justify the risks of currently available full-support ventricular-assist devices or aren't large enough to accommodate them, according to the pump's lead investigator, Dr Daniel Burkhoff (Columbia University, New York, NY).

"Partial support interrupts the progressive hemodynamic deterioration typical of late-stage heart failure, so we believe that this pump has the potential to expand the use of mechanical circulatory support to a much larger population of patients with severe medically refractory heart failure," according to Burkhoff, who is chief medical officer for CircuLite.

Implanted in men and women with recurrent advanced heart failure (INTERMACS level 4), ambulatory and not on inotropic therapy, who were either listed or otherwise suitable for a heart transplant, the Synergy pump made the patients feel markedly better, improved their mean arterial and capillary-wedge pressures and cardiac index the first day of implantation, and sustained the benefits over an average of about 11 weeks in the current analysis.

Burkhoff told heartwire that the longest continuous duration of Synergy support in a patient has been seven months, "and we have multiple patients now approaching six months. These patients will get transplanted, ultimately. But we're now enrolling patients who are either not eligible for transplantation or expected to have a very long duration of support. Our goal is that this will be used as a permanent implant."

The Synergy pump's apparent success at improving hemodynamics was balanced by a few complications, but little definitive can be said about outcomes in either direction based on a handful of cases. Important adverse events included a few pocket hematomas, sepsis, a driveline infection, a problem with clotting on the device itself that apparently resolved with design changes, according to Burkhoff, a lead fracture within the pump that led to its replacement, an instance of renal failure, and one stroke.

"These initial results find, I think, proof of concept in a few patients, at least, that partial support will provide important long- or intermediate-term hemodynamic support in the less-sick [patients] of the INTERMACS class 4 group," panelist Dr Michael A Acker (University of Pennsylvania, Philadelphia) said after Burkhoff's presentation."

Unquestionably, Acker said, the ability to implant the device through a minithoracotomy without cardiopulmonary bypass support "should lower the bar of implantation if the problem of thrombosis has been truly overcome and if complication rates remain low." Whether the device improves quality of life "with no safety issues and no decrement in stroke-free survival" should also be explored, he said.

As described for heartwire by surgeon Dr Andre Simon (Hannover Medical School, Germany), the Synergy implantation procedure takes only about one to 1.5 hours and "theoretically, you don't even have to take the patient to the ICU, you can take them to a normal ward, and they need just two to three days of healing. At this point, of course, we keep the patients longer, but it has an immediate effect, and you could discharge them very quickly."

Measured prior to surgery and during the 24-hour postoperative period, the group averages for mean artery pressure went up 5 mm Hg (p=0.02) and cardiac index climbed by 1.3 L/min/m2 (p<0.001). The average pulmonary artery diastolic pressure fell by 9 mm Hg (p=0.01), Burkhoff reported.

Those three hemodynamic parameters remained significantly improved (p=0.01, 0.005, and 0.02, respectively) in nine of the patients over 11 weeks, with an average pump flow rate of 2.8 L/min. Mean peak VO2 increased from 9.6 mL/kg/min to 14.1 mL/kg/min (p=0.01).

Speaking to the panel after his presentation, Burkhoff said he expects that "the amount of reverse remodeling we'll get with this device will be less than with a full-support device. Having said that, I think that the hemodynamic data, which show a progressive increase in blood pressure despite a progressive decrease in pulmonary capillary wedge pressure, are indicative of some degree of recovery of function." But, he said, "I'm not sure we'll see, even though we're intervening at an earlier stage of disease, a profound increase in the number of patients who demonstrate recovery."

Burkhoff is CircuLite chief medical officer; both he and coauthor Dr Bart Meyns (University Hospital Leuven, Belgium) report being consultants to and shareholders in the company, which funded the study. Simon had no disclosures. Acker reports receiving consulting fees or honoraria from Acorn Cardiovascular.

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