Self-contained left-ventricular assist device reduces infection risk
Destination therapy’ for when transplant is not an option
(Last month, CHF Disease Management described devices in clinical trials that offer hope for your end-stage patients by pacing and resynchronizing the heart. This month, the newsletter presents a new left-ventricular assist device that avoids infection and an innovative type of temporary heart assist pump.)
A new heart assist device being tested in Europe may increase the options doctors give their patients who are ineligible for transplant. The LionHeart device awaits approval of the Food and Drug Administration (FDA), after which widespread clinical trials will begin in this country. The device has the potential to improve cardiac function with a lower risk of infection, compared to similar devices.
The LionHeart heart assist device is designed to be a permanent implant — so-called destination therapy — for patients with progressive, irreversible, end-stage Class IV heart failure. Not intended as a bridge to transplant, it is a permanent alternative to transplant.
What makes the device different from other short-term assist devices, the bridges, is that its components are fully implantable, eliminating need for drive and venting lines.
"Currently all assist pumps have drive lines or external tethers that stick out from the body," explains lead investigator Walter E. Pae Jr., MD, a cardiothoracic surgeon and professor of surgery at Penn State’s College of Medicine in Hershey. "These lines often cause infections, and we think this device will greatly reduce the risk of infection."
Pae says the device, developed at his facility in conjunction with Reading, PA-based Arrow International, marks a major step forward in heart-assist technology. "This new device is totally implantable, and there are no other fully implantable heart assist devices in clinical trials. It is not a bridge to transplant or temporary heart helper, but rather, a permanent therapy for end-stage heart failure in patients who are not candidates for heart transplant."
Danger of infection from LVADs
Assist devices that act as a bridge to transplant, such as the LVAD (left ventricular assist device) made by Thoratec, says Pae, are not fully implantable and not meant to be permanent. Cannulas come out through the skin, and they are a constant source of infection.
"Also, the patient is less able to take a shower or submerge himself in water [with traditional LVADs]. All these devices are pulsatile; they take blood out of the left ventricle through a unidirectional valve in a pump, and pump it down to the ascending aorta," he says. By doing that, the pumps take over the work of the left side of the heart. That lowers pressure inside the lungs and provides appropriate forward flow of blood to organs.
"The defining feature of the LionHeart system is the use of pulsatile technology and improving it by combining the control system with the battery and putting it all inside the body," says Pae. "Then it allows energy to pass across the skin through transcutaneous energy transmission. We’re able to recharge the batteries to provide a constant source of power without a break in the skin." The patient can untether himself from the wand for 20 minutes and go swimming or take a shower. "That not only eliminates the possibility of infection but also improves a patient’s quality of life."
The strong point of the LionHeart system is that it avoids infection, says Richard Pozen, MD, FACC, national medical director of Vivra Heart Services in Fort Lauderdale, FL. "But if something goes wrong with the implanted devices that have external leads, you can unhook them. It seems that this device would be harder to get to [because] it’s totally implanted. You’d have to go into the patient to get at it."
"We recognize that heart transplantation is a limited and expensive way to treat advanced heart failure," says Marc Silver, MD, who runs the CHF center at Christ Hospital in Chicago, a division of Advocate Healthcare.
"We have learned from using LVADs that we can safely support people for a long time, if needed, and that many people can recover significant heart function. Growing out of these observations are two strategies: bridges to recovery and destination therapy. What is open for debate now is which approach is more practical and economical." Silver says that having a totally implantable device without a break in the skin overcomes one of the major limitations of LVAD therapy — risk of infection.
"Now we await the longer term outcome studies of this approach," he says. "It should certainly reduce the infections, but may not reduce them altogether since a foreign body always increases this risk."
The concept of shorter term support with current LVADs for a period of time that reduces the risk of infection, but still allows some recovery, is another approach being taken at several centers. Silver and Pozen note they have no connection to the company that produces LionHeart.
"We clearly have better medium- and long-term options for patients with advanced heart failure today," adds Silver.
Pae, also director of transplantation at The Milton S. Hershey (PA) Medical Center, assisted German surgeons at Herzentrum Nordrhein-Westflaen hospital in Bad Oeyn-hausen when they implanted the LionHeart device in a 67-year-old man last October. The patient had a diagnosis of dilated cardiomyopathy and was considered ineligible for transplantation.
Patients can untether for a shower
The LionHeart device incorporates a power transmitter/coil feature that transfers energy across intact skin to implanted batteries, allowing patients to be "untethered" for approximately 20 minutes.
Percutaneous drive lines and external tethers are eliminated. The power transmitter/coil is connected to a power pack that can be pulled on a handcart or, if the patient is able, worn on the belt or carried in a backpack or shoulder harness.
The device weighs about 8 pounds when loaded with two rechargeable battery packs, each of which provides two to three hours of power for mobile operation. (See illustration of placement of the device, at left.)
"This is for patients with end-stage heart failure who are not transplant candidates," says Pae. "There is a very large population of patients with Class IV heart failure. The trial is designed to pick a very sick population who have prognostic indicators of one-year survival — patients who, if treated medically, would have survival chances of less than 50%. And it is for patients who are not transplant candidates due to age or comorbidities that prohibit them from taking anti-rejection drugs."
Pae says donor organs are a scarce resource. "It’s not feasible to give a 30-year-old’s heart to a 70-year-old recipient with diabetes who probably won’t live more than a couple of years, when that same heart could be put into another 30-year-old. This leaves an underserved population with poor quality of life."
Pae, a consultant for Arrow, says that at the same time LionHeart is being submitted to the FDA for approval, investigators are working on coming up with lighter, more compact energy sources to power the device to make it more convenient for these end-stage patients.