Cryoplasty Appears to Help Below-Knee Arterial Occlusion

BY SHERRY BOSCHERT

SEATTLE -- Cryoplasty seems to be a viable alternative to surgical treatment of below-the-knee arterial obstructive lesions in patients with critical limb ischemia, according to interim results from a study of 108 patients.

Cryoplasty combines transient freezing of the vessel wall and balloon dilatation. All patients in the Below-the-Knee Chill study had occlusion of infrapopliteal arteries; the patients could also have had above-knee occlusions. A total of 68% of patients had diabetes. Ulceration or gangrene was present in approximately two-thirds of patients, and 34% had complete occlusions.

Of the 108 patients in the study when enrollment closed, 81 have 1-year follow-up data available. The mean follow-up lasted 393 days, with a maximum of 708 days. Eight patients have died; there were 12 major amputations. At 6 months after cryoplasty, 93% of survivors retained their limbs, as did 85% of survivors at 1 year, Dr. Thomas O. McNamara reported at the annual meeting of the Society of Interventional Radiology.

Among all patients, 79% were free of amputation at 1 year, said Dr. McNamara of the University of California, Los Angeles. His institution receives funding from Boston Scientific Corp., which makes the cryotherapy system studied.

The results are comparable to those of a multicenter, randomized comparison of balloon angioplasty or surgery to treat 452 patients similar to those in his own study, Dr. McNamara noted. In the Bypass Versus Angioplasty in Severe Ischemia of the Leg (BASIL) trial, 71% of patients treated with balloon angioplasty were alive with intact limbs after 1 year, as were 68% after surgical treatment of below-the-knee arterial obstructive lesions with critical limb ischemia, he noted (Lancet 2005;366:1903-82)

A physician in the audience questioned whether the 79% limb salvage rate with cryoplasty is worth the extra effort and expense for that procedure when balloon angioplasty offers a 71% limb salvage rate. Dr. McNamara replied that "once you've used it a few times," the cryoplasty system "doesn't seem like much of a hassle."

In the current study, cryoplasty was more effective in patients with less severe disease. Amputation within 1 year was needed in no patients who had Rutherford class 4 critical limb ischemia, in 12% who were class 5, and in 40% who were class 6. All eight deaths were among class 6 patients, who made up approximately one-quarter of the cohort. The amputation rate was 20% among 71 patients with diabetes and 4% in those without diabetes. Eleven percent of smokers died, compared with 4% of nonsmokers.

Another physician in the audience criticized the medical device industry for not funding higher-quality studies that compare treatments and yield more useful information than the current study presented. "We get new, expensive technology but not randomized, controlled trials," he said.