BBI Contributing Writer
SCOTTSDALE, Arizona The 17th annual International Congress for Endovascular Interventions, hosted here by the Arizona Heart Institute and Hospital (AHI; Phoenix, Arizona) in late January, is one of the largest medical conferences of its kind in the world. The series updates interventionalists and allied healthcare personnel on new endovascular technologies and techniques. As is an emerging trend in other meetings, particularly those in cardiovascular disciplines, this meeting featured live video feeds of interventional procedures interspersing standard podium presentations. The live video came from Arizona Heart Institute. Scientific discussions during the meeting covered all aspects of endovascular disease and included considerable attention devoted to the future of related gene therapy.
Critical limb ischemia (CLI) is an extreme form of peripheral vascular disease. The prognosis for CLI is poor. Within three months of presentation, 9% of patients will die, 1% will have a myocardial infarction, 1% will suffer from stroke, 12% will have an amputation and 18% will have persistent CLI. This disease is a marker for premature death, with mortality rates at 21% at one year from diagnosis and 31.6% at two years. During the meeting, Giancarlo Biamino, MD, of the University of Leipzig Heart Center (Leipzig, Germany), presented his findings from 10 years of personal experience using laser atherectomy for CLI and other less-serious femoropopliteal arterial problems.
According to Biamino, the laser catheters initially used for arterial disobliteration were connected to lasing sources transmitting continuous waves of laser energy, with a long tissue interaction time that provoked what he said was an unacceptable increase in the local endovascular temperature. That type of thermal continuous-wave lasers were abandoned in the early 1990s. Today's CVX-300 excimer laser from Spectranetics (Colorado Springs, Colorado) uses an extremely short pulse duration and limited penetration, which in turn limits the thermal effect of the absorbed energy to the irradiated tissue. In more than 95% of the cases in his experience, an occlusion was transformed into a stenosis, which in turn, facilitated definitive dilation or easy placement of a stent. In 10% to 20% of the procedures, the intervention was concluded as a stand-alone procedure.
Another example of "cool" laser use was noted in the six-month results for Spectranetics' Laser Angioplasty for Critical Limb Ischemia (LACI) trial. This work may validate the resurrection of laser technology in treating peripheral vascular disease. The study, published in the October 2003 issue of Endovascular Today, showed that excimer laser-assisted endovascular intervention in CLI resulted in high procedural success with few in-hospital complications. This work allowed treatment of complex disease characterized by multiple stenosis and occlusions. The study concluded that excellent limb salvage rates in excess of 90% can be achieved with a very low incidence of surgical reintervention in high-risk patients who are poor candidates for surgical revascularization.
Other new devices are available for complicated peripheral vascular disease. Sonya Noor, MD, of the Arizona Heart Institute, also presented work benefiting patients with percutaneous plaque. From June to November 2003, she and her colleagues treated 80 limbs in 72 patients using the SilverHawk percutaneous atherectomy device from FoxHollow Technologies (Redwood City, California). Technical success was achieved in 95% of the patients. Follow-up with periodic duplex imaging has found no stenosis or occlusion at up to six months.
According to Noor, the SilverHawk atherectomy device provides excellent debulking. There are significant gains in vessel lumen occur without the barotrauma injury or plaque effacement characteristic of standard balloon angioplasty and stenting. She noted, "This user-friendly device, with a relatively low profile, can be used safely and may become a stand-alone treatment for this disease."
Gene therapy research
Gene therapy technology is being hailed as the next revolution in medicine, offering treatment for many serious chronic diseases. The goal of gene therapy is to eliminate disease by replacing faulty or missing genes with normal or modified ones so that the body can make the right proteins or enzymes needed to function normally. During a luncheon presentation at the congress, Ted Dietrich, MD, also of the Arizona Heart Institute, said, "We continue to search for the least possible invasive method for treating disease. It appears that gene and cell nanotechnology may be the future in this pursuit." He predicted a majority of diseases may eventually be cured through microbiological therapies guided by gene identification.
About 1.5 million patients suffer a myocardial infarction each year. There are 2 million patients treated each year for congestive heart disease. Both these disease states result from a loss of cardiomyocytes (precursors for cardiac muscle). The Arizona Heart Institute is one of four U.S. medical centers participating in early clinical safety trials of skeletal muscle cell transplants in combination with coronary bypass graft surgery. The trial is being completed in collaboration with GenVec (Gaithersburg, Maryland), which develops transplantable cells to treat disease characterized by cell dysfunction or death.
The myoblast transplant begins with a biopsy of muscle cells from the patient's thigh. A marble-sized section of the muscle is removed while the patient is under local anesthesia. The section of muscle is then taken to a special cell laboratory where the myoblasts are isolated and multiplied. The multiplied cells are later injected directly into areas of the heart muscle that have suffered past damage from heart attacks and coronary artery disease. The myocytes convert naturally to cardiocytes. The injection/ transplant is accomplished in conjunction with standard coronary artery bypass surgery.
Joseph Wagner, of Neuronyx (Malvern, Pennsylvania) described his company's approach for cardiocyte stimulation using autologous bone-marrow derived stem cells. These adult stem cells are recruited to the damaged heart muscle area to assist in the natural tissue repair process through dynamic secretion of pro-regenerative trophic factors and cytokines. "An important advantage of stem cells from adult donors is that they have an advanced safety profile as compared to fetal and embryonic tissues," Wagner noted. The stem cell transplantation results in improved systolic cardiac function and reduced severity of the infarcted tissue. The stem cells encourage the regeneration of original heart muscle.
Device evolution continues
Booths representing 44 vendors demonstrated such devices as the "cool" laser, a mechanical atherectomy device and several new stents and grafts to the 800 attendees at the congress. Among those vendors were Spectranetics, FoxHollow Technologies and Vascular Architects (also Redwood City).
Spectranetics is responding to the need for improved minimally invasive options in peripheral vascular disease. The company has expanded its excimer laser technology to treat critical limb ischemia. Currently undergoing clinical trials in the U.S., the technology has the European CE mark. The excimer technology is designed to dissolve thrombus and ablate atherosclerotic material in the legs with a low complication and high success rate.
The laser provides a short pulse duration (120 ms) and limited penetration of 10 micrometers to 20 micrometers. The XeCI laser delivers energy in a time span much shorter than it takes for the heat to diffuse. This permits the obstructive material to absorb enough energy per pulse without thermal damage, hence, the "cool" laser.
Spectranetics' laser is the only system approved by the FDA for multiple cardiovascular procedures, including atherectomy and removal of problematic pacemaker and defibrillator leads.
FoxHollow Technologies has developed the SilverHawk family of coronary and peripheral catheters to excise plaque in vessels from 2.0 to 6.0 mm. The company says the single-operator, monorail catheter with a powerful, effective carbide cutter consistently and efficiently excises large volumes of plaque from both de novo and restenotic lesions producing large luminal gains without barotrauma to the vessel wall.
During plaque excision, the SilverHawk cutter is mechanically apposed to the plaque wall without balloon dilatation of the vessel. Calcification is attacked by a carbide cutter 3.5 times stronger than stainless steel and 23 times stronger than calcium. The operator not the device design determines the cut length. The ability to continuously shave plaque longitudinally enables efficient treatment of long lesions. A single device can be used to treat multi-focal and multi-vessel disease.
Staging Revascularization is the term used to describe the four-stage process promoted by Vascular Architects. Physicians using this process can use less-invasive procedures first, postponing more invasive strategies until later, preserving use of important conduits. Stage One is identification and analysis of the patient's disease. Stage Two is peripheral angioplasty with or without stenting.
Stage Three is a remote endarerectomy. The Moll Ring Cutter a debulking device is designed for minimally invasive removal of plaque from arterial walls. This non-motorized, hand-held device consisting of a stainless steel tube and double ring cutters with angled blades is inserted through a one-inch incision in the leg and advanced through the artery accomplishing a remote endartarectomy. Once the occlusion has been separated from the arterial wall, the cutter is placed at the distal end of the plaque. The blades separate the plaque from the vessel wall and contain it as the device is removed.
In Stage Four surgical bypass the aSpire Covered Stent and 718 Delivery System is the technique of choice. The aSpire Covered Stent uses a double helix design. The spiral shape provides flexibility and conformability. Side branch protection is provided by the unique design coupled with controllable deployment. This protects vital side branches of the vessel. A crush-resistant nitinol frame is fully covered by ePTFE for significantly enhanced luminal coverage.