VIVA I: Xcell Results Presented for Abbott Vascular's Xpert Stent to Treat CLI

October 22, 2009—Six-month clinical results from the VIVA I: Xcell trial were presented for the first time by Krishna J. Rocha-Singh, MD, in the late-breaking trials session at the VIVA: Vascular Interventional Advances meeting in Las Vegas, Nevada.

VIVA I: Xcell is a physician investigational device exemption trial of the feasibility of the Xpert nitinol stent (Abbott Vascular, Santa Clara, CA) for below-the-knee primary stenting in patients with critical limb ischemia (CLI) (Rutherford Class 4-6). The study is sponsored and managed by VIVA Physicians Inc. (VPI, San Jose, CA) with financial support from Abbott Vascular. The study infrastructure includes VPI, Prairie Education & Research Cooperative (Springfield, IL), and three core labs.

According to Dr. Rocha-Singh, the surgical "gold standard" for CLI care is being challenged by new endovascular technologies. However, optimal endovascular strategies are undefined in the medical literature. The growing CLI patient population presents a challenge to clinicians to find less-invasive and cost-effective solutions. Moreover, patient-oriented endpoints ("therapeutic endpoints") require better definition including: freedom from amputation, wound healing, mobility, and quality of life. The study's primary endpoint is amputation-free survival at 12 months in the target limb.

Dr. Rocha-Singh reported that a total of 732 potential CLI patients were screened, with 613 being documented as not meeting clinical or angiographic eligibility criteria. Enrollment of 120 patients (representing 16% of those patients who screened) at 16 sites commenced in July 2006 and was completed on April 3, 2009. The average rate of enrollment was 0.36 patients per site per month.

Of the 120 enrolled patients, 62 (51.7%) were male, 58 female (48.3%) with a mean age of 75.5 ± 9.3 years, and mean serum creatinine levels of 1.2 ± 0.4 mg/dL. Other baseline characteristics included 80 patients (66.7%) with diabetes mellitus, 64 patients (53.3%) with a history of smoking, and 103 patients (85.8%) with hypertension. In terms of severity criteria, 21 patients (17.5%) were Rutherford 4, 82 patients (68.3%) were Rutherford 5, and 17 patients (14.%) were Rutherford 6.

There were 76 patients (63.3%) with one runoff vessel and 44 patients (36.7%) with two or more run-off vessels. Regarding lesion locations, three patients (2.5%) had popliteal lesions, 19 patients (15.8%) had tibioperoneal trunk lesions, 32 patients (26.7%) had peroneal lesions, 18 patients (15%) had posterior tibial lesions, and 48 patients (40%) had anterior tibial lesions. Nine nontarget infrapopliteal vessels were treated during baseline procedures and 72 patients (60%) with non-target inflow were treated during baseline procedures.

Dr. Rocha-Singh reported the 30-day complications of the 120 patients enrolled in the study. There were three (2.5%) target vessel revascularizations, two (1.7%) major amputations, and one (0.8%) cerebrovascular accident. There was one (0.8%) access-site complication requiring transfusion. There were no myocardial infarctions, no target lesion revascularizations and no deaths at 30 days. One patient died at 32 days postprocedure, which was 5 days after the 1-month follow-up visit. This death was attributable to exacerbation of pre-existing congestive heart failure.

At 6-month follow-up in 115 patients, there were a total of 36 (31.3%) target lesion revascularizations, of which 21 (18.3%) were symptomatic. There were seven (6.1%) major amputations, six (5.2%) deaths, four (3.5%) target vessel revascularizations, and one (0.9%) access-site complication requiring transfusion.

Stating that the VIVA I: Xcell trial will give significant insights into wound healing, Dr. Rocha-Singh presented a wound-healing schematic for 159 wounds at baseline. Of 127 analyzable wounds, 68 (53.5%) were 100% healed, 43 (33.9%) had significant decreased wound area, and 16 (12.6%) had increased wound area. This analysis includes 11 patients (16 wounds) that were noted to have decreased or increased compare to baseline, but subsequently went on to have an event (death or major or minor amputation) or a graft placed by 6 months. As this data set is completed, investigators will be able to look into the reasons why some of these wounds heal completely, why some heal at a faster rate than others, and why some wounds get worse, Dr. Rocha-Singh stated.

A secondary analysis of complete wound healing showed significant trends including 68 of 127 wounds (53.5%; in 44 of 77 patients) were 100% healed at 6 months. This included 25 wounds (36.8%) with a baseline area of 3.73 ± 10.6 cm² that were healed at 1 month. There were 22 wounds (32.4%) with a mean baseline area of 7.48 ± 17.75 cm² that were healed at 3 months, and 21 wounds (30.9%) with a mean baseline area of .55 ± .78 cm² that were healed at 6 months. Baseline area calculations were unavailable in 12 patients because of either wound location on toe or site error. Wounds that were treated at a wound care center healed on average in 97.5 ± 59 days versus 101.7 ± 67 days for wounds treated at another location (P = ns), Dr. Rocha-Singh advised.

The VIVA I: Xcell trial results of 40% of patients experiencing complete wound healing at 6 months was approximately equivalent with results shown in the surgical literature. Complete healing was achieved in VIVA I patients at a mean of approximately 100 days, compared to means of approximately 170 to 200 days in the surgical literature.

Dr. Rocha-Singh concluded that use of endovascular revascularization (PTA plus nitinol stenting) is promising with limb salvage rates that are similar to surgery with lower early morbidity and mortality. Surgery carries a higher short-term risk for patients (ie, 0.5–2% 30-day mortality, 10–30% wound complications, 5–8% major systemic complications, 1–2% graft infection). Finally, when compared to surgical literature, the percent of patients with wound healing is similar and the mean time to complete wound healing is shorter with endovascular revascularization.

Dr. Rocha-Singh stated that the interim VIVA I: Xcell data continues to evaluate the association between restoration of flow, angiographically defined restenosis, target lesion revascularization and wound healing. The full angiographic data set may be available by next year.

"I think this trial is going to highlight the extreme importance of looking at other functional and therapeutic endpoints with regard to trials and trial design," commented Dr. Rocha-Singh. "These results highlight that amputation rates through 6 months of the VIVA I: Xcell trial were low. In sicker patients, they were not surprising and anticipated. With the Xcell trial, wounds will continue to be a major source of interest and percutaneous revascularization with the Xpert stent as compared to the surgical literature appears to be quite favorable."