ANAHEIM, California – New heart implantation devices and techniques for primary bypass grafting are among recent surgical advances against heart disease and have the potential to help thousands of patients each year, according to research presented during the American Heart Association's (AHA; Dallas, Texas) annual scientific sessions in November.One of the surgeons who helped implant the first self-contained artificial heart, Robert Dowling, MD, from the University of Louisville and Jewish Hospital (Louisville, Kentucky), said the success of the clinical trials shows the promise of the mechanical circulatory support device. At that point, five patients had been implanted with the AbioCor device, manufactured by Abiomed (Danvers, Massachusetts), with the first of them, Robert Tools, surviving for more than 130 days at the time of Dowling's presentation. (Since then, two of the AbioCor recipients have died, along with another who died during the implantation procedure.)
"The AbiCor device can be used to treat many of the increasing number of patients with end-stage heart failure," Dowling said. "It has exceeded our expectations in every way."
The success of a new left ventricular assist device, the Jarvik 2000 developed by Jarvik Heart (New York), shows its broad application for heart failure patients, according to O.H. Frazier, MD, of the Texas Heart Institute at St. Luke's Episcopal Hospital (both Houston, Texas). "The small size of the pump and the ease of implantation, together with the capability to return patients to full, active lives, indicate that this technology could benefit many, many patients," Frazier said.
Frazier and his associates evaluated the hemodynamic status and quality-of-life variables in 16 patients with severe heart failure who received the Jarvik 2000 as a bridge to transplant. Nine underwent successful transplantation and remained well after an average follow-up of 7.9 months, indicating that partially pulsatile systemic flow is well tolerated in patients who are supported by a continuous flow LVAD over prolonged periods of support, he said."This also suggests that complete rehabilitation is possible and heart function may also improve after unloading with the pump," Frazier noted.
It is possible that such pumps, currently used for bridge to transplant, may soon be used as an avenue for primary treatment. Another study, REMATCH, demonstrated the effectiveness of such systems, particularly the device being studied, the Thoratec (Pleasanton, California) HeartMate VE.
Also discussed at the AHA news conference were innovative "sutureless" techniques for use in coronary artery bypass surgery. These techniques were discussed by Marc Buijsrogge, MD, from the Heart and Lung Center (Utrecht, the Netherlands), and Thierry Carrel, MD, of University Hospital (Bern, Switzerland). Buijsrogge described a new mechanical device that uses an adhesive material to connect and seal blood vessels, and Carrel discussed research involving a new stainless steel device with an expendable clip that balloons out to connect the bypass vessel to the coronary artery.
Other trial results
Guidant (Indianapolis, Indiana) laid out the results of the INHIBIT (INtimal Hyperplasia Inhibition with Beta In-stent Trial) study involving its Galileo Intravascular Radiotherapy System, which is designed to make it easier for physicians to treat longer coronary lesions (that is, blockages) by incorporating an automatic stepping function. The system is designed to deliver radiation therapy starting at the far end of the blockage and automatically stepping the radiation treatment through a catheter to treat the programmed length of the artery needing therapy. John Capek, PhD, president of Guidant's Vascular Interventions unit, said the results "build on the momentum" of the U.S. clearance of the system earlier in November for treating restenosis.
Ron Waksman, MD, associate director of the division of cardiology and director of experimental angioplasty and vascular brachytherapy at Washington Hospital Center (Washington), was the principal investigator in the INHIBIT trial. He said the Galileo system enables physicians "to more easily perform radiotherapy procedures by automatically determining the number of steps required to treat a particular lesion and automatically performing those steps."
The INHIBIT trial enrolled 135 patients in 10 centers worldwide. The Galileo system uses a new 20 mm source to produce equivalent source lengths of 40 mm to 60 mm. Guidant said the trial results would be used to file a premarket approval application supplement for the system.
Waksman also reported on another approach to the problem of restenosis, presenting the results of preclinical studies using Miravant Medical Technologies' (Santa Barbara, California) intracoronary PhotoPoint photodynamic therapy (PDT) as an adjunct procedure to balloon angioplasty and/or stent deployment. In two studies in advanced coronary restenosis models, PhotoPoint PDT significantly inhibited the aggressive cell overgrowth post-angioplasty and prevented negative vessel wall remodeling, or constriction. "[We] saw both a dramatic inhibition of cellular proliferation and positive vessel wall remodeling in these studies," Waksman said.
The therapy uses a light-sensitive drug to target the precursor cells of restenosis within the artery wall and/or target proliferative cells in existing restenotic lesions. In the two-step PDT procedure, the drug is administered systemically and localizes in the vessel wall after a period of time. Non-thermal, non-ionizing light is selectively delivered to the treatment site using Miravant's endovascular light delivery catheter. The company has developed both the pharmaceutical and device components of the intracoronary procedure, and Robert Scott, MD, president, Miravant Cardiovascular, said that the results "have encouraged us to move forward with accelerated development programs for restenosis and atherosclerosis."
Kristine Guleserian, MD, fellow in cardiothoracic surgery at Barnes-Jewish Hospital and Washington University School of Medicine (both St. Louis, Missouri), described work she had done at Children's Hospital (Boston, Massachusetts) using human umbilical cord blood as a source for endothelial progenitor cells to engineer cardiovascular tissue. Guleserian and her colleagues proposed that early stage endothelial cells, called endothelial progenitor cells (EPCs), taken from human umbilical cord blood could be used to create endothelial layers for cardiovascular tissue engineering.
Guleserian said she envisions many exciting possibilities for this new cell source, including "banking" the cells for future use. She said that there is also the possibility that while a mother is still pregnant, cord blood cells could be used to create a tissue-engineered structure needed to correct a cardiac birth defect diagnosed prenatally. Theoretically, this new tissue could be ready to use when the baby is born – or even before birth for potential prenatal/surgical repair.
Hiroaki Matsubara, MD, PhD, of Kansai Medical University (Osaka, Japan), discussed the results of a study designed to determine the efficacy and safety of therapeutic angiogenesis using bone marrow cell implantation for critical limb ischemia in 11 patients with peripheral artery disease. Matsubara and his colleagues injected bone marrow cells from each patient into areas of their legs where tissue was dying due to lack blood flow.
"Complete relief of leg pain was reported by 10 of the patients, who also were able to walk on a treadmill for longer periods without experiencing pain." He added that he believes this new bone marrow transplant may be a "safe new strategy" for treating patients with ischemic limbs.