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For heart-assist patients, there's no place like home
By Anissa Anderson Orr

Antonio Fonseca

On Dec. 30, 2002, 55-year-old Antonio Fonseca checked out of The Methodist Hospital, a month after he suffered a massive heart attack that tore a hole in his heart muscle.

As he got into the car, he took with him what resembled a rolling, overnight suitcase. But inside was something far more precious than a change of clothes: a machine that powered a heart-assist device implanted in his chest. The Thoratec left ventricular assist device pumped blood to his body in place of his ailing heart, keeping him alive and giving his heart time to heal. And because the device's power supply was portable, Fonseca enjoyed the holidays at home with his family and friends.

On Jan. 23, 2003, Fonseca underwent surgery to have the device removed. His heart healed enough to pump on its own.

"Sending patients home on these devices is safe and greatly promotes the recovery process," said Matthias Loebe, MD, PhD, an assistant professor in the Michael E. DeBakey Department of Surgery at Baylor College of Medicine and a co-investigator of the clinical trial that uses the portable LVAD. "This technology is an enormous step forward in treating people with heart failure."

Baylor is one of twelve centers in the United States studying the portable driver for the Thoratec LVAD, the only heart-assist device approved by the Federal Drug Administration as both a bridge to transplant and a bridge to recovery. Fonseca was the first patient in Houston to be sent home with a Thoratec LVAD. But as surgeons and researchers perfect smaller, more portable heart-assist devices, patients may be spending more time recovering from heart failure at home.

Portable means practical

Heart-assist devices have come a long way since Michael E. DeBakey, MD, implanted one of the first LVADs into a female heart failure patient in 1967. The original LVADs were huge contraptions, tethered to even bigger contraptions that powered them.

Pictured are, from left, Javier Lafuente, MD, George Noon, MD, and Antonio Loebe, MD, PhD

"LVADs that are pneumatically driven like the Thoratec need an external driver that's pretty big," Loebe said. "Usually these things are the size of a small family refrigerator. In the old days, the size didn't really matter because patients were put on a device and stayed in the hospital. Then they were quickly transplanted. Now they have to wait longer for a transplant and it is really important to get them walking around out of the hospital and out of bed."

The next generation of heart-assist devices is smaller, and powered by battery controllers carried in a pack next to the body, or implanted under the skin. The MicroMed DeBakey VAD, developed by DeBakey and George Noon, MD, chief of the division of transplant surgery and assist devices and a professor in the department of surgery at Baylor, in collaboration with the National Space and Aeronautics Agency, is one of the smallest models being implanted. The device itself weighs less than four ounces and features a controller and carrying case that weighs less than five pounds. To date, 175 DeBakey VADs have been implanted in 14 heart centers in the United States and around the world.

The secret behind the DeBakey VAD's small size is its rotary axial flow design. While pulsatile design heart-assist devices use pumps to mimic the pumping action of the heart, rotary axial pumps use a propeller or rotor to push the blood continuously. The axial flow pump uses only one moving part, making it less bulky and less prone to mechanical problems.

Nosé's "two-year" biventricular pump

One of the originators of the continuous flow approach to designing heart-assist devices is Yukihiko Nosé, MD, PhD, professor in the department of surgery and a pioneer in the field of artificial organs and assist devices. Funded by a contract from the Japanese government, Nosé, who is also director of Baylor's artificial organs research laboratory, has been working during the last 12 years on four models of heart-assist devices using a pump design that uses centrifugal force to pump the blood. While not as small as the DeBakey VAD, all could fit in the palm of your hand.

Yukihiko Nosé, MD, PhD

Nosé's "two-day" Nikkiso pump is used in 20 percent of all open-heart surgery cases in Japan as a cardiopulmonary bypass pump. The pump is also distributed in the United States by Cobe Laboratory. In Japan, his "two-week" Kyocera pump has been implanted in an estimated 1,000 patients who need more time to heal from heart failure. While this pump requires a large console, it can support the patient for up to one month. The third model pump is nicknamed the 'three-month' pump. The HTMAC pump can be implanted in a patient for up to a year. Both the power source and pump system are wearable outside the skin.

Nosé is also working on a pump for longer-term use, called the "two-year" biventricular pump, which supports both of the heart's ventricles. This pump system is totally implantable. Constructed of lightweight and durable titanium, the device can sustain a patient for up to two years.

"By using a continuous flow design instead of a pulsatile design, we can make the device much smaller and comfortable for the patient," Nosé said. "The power pack can be worn by the patient in a small package attached to the chest."
Nosé plans to apply for FDA approval for the device in two years and to market the device in the United States in five years.

Waste not, want not

Research shows that heart-assist devices help speed recovery in some patients. Now scientists at Baylor are analyzing heart tissue removed during the implantation surgery to determine why.

"When you put in an assist device, you core out a piece of their heart," said Javier Lafuente, MD, an assistant professor in the department of surgery at Baylor and principal investigator for the Thoratec trial. "From that core piece you are able to make assumptions about what changes happen to the heart during heart failure and investigate the different possibilities for patients with different types of cardiac disease to recover with the device."

Heart-assist devices seem to stem the damage caused by a heart attack. When the heart fails, the muscle becomes inflamed. The inflammation destroys vital heart muscle cells, which are then replaced by scar tissue composed of collagen. Implanting a heart-assist device interrupts the transformation into collagen and allows the repair mechanism to take over. As a result, no more muscle is destroyed, scar formation is minimized and the heart muscle may recover.

"We want to find out what this healing mechanism and how to use it to the advantage of patients who have heart failure," Lafuente said. "That's the next step."

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