Recanalization of Peripheral Total Occlusions
The results of the GRIP Registry study of the Safe-Cross Radiofrequency Total Occlusion Crossing System show that this device can safely achieve distal lumen positioning.
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Total occlusions in the superficial femoral artery (SFA) represent approximately half of the lesions found in peripheral arteries. Recanalization is often approached with stiff wires or hydrophilic wires. Recent studies in the treatment of SFAs show that crossing the lesion is feasible in approximately 68% to 100% of cases.1-10 Lesion length appears to be one factor affecting success rates; longer lesions (>10 cm), obviously, have lower success rates than shorter lesions (<10 cm). Furthermore, lesions with densely dystrophic calcific changes are also unpredictable in terms of successful passage of the wire across the occlusion site. An evaluation of the ability of the multiple methods for crossing total occlusions in the SFA has been described, but there has been no consistency in the success for any single approach. The Guided Radio Frequency in Peripheral Total Occlusions (GRIP) Registry study was designed to evaluate the safety and effectiveness of a new guidewire system to traverse total occlusions in the peripheral arteries of the lower extremities.
MATERIALS AND METHODS
Thirteen investigational sites enrolled a total of 72 consecutive patients (75 lesions) undergoing definitive percutaneous therapy of a total occlusion in native, peripheral arteries of the lower extremities. The Safe-Cross Radiofrequency Total Occlusion Crossing System (Figure 1A-C) was the investigational device used to attempt crossing of the total occlusion after a failed attempt to cross using conventional guidewires. The mean age of patients in the study was 66.1 ± 11.5 years. Sixty-eight percent of the patients were male. Patients were eligible for study participation if they satisfied all requirements established by the inclusion/exclusion criteria in the study protocol. Patient demographics and clinical characteristics are presented in Table 1. The key inclusion criteria were that the total occlusion be in a native, lower extremity and that the total occlusion could not be crossed with conventional guidewires after a minimum of 10 minutes of guidewire manipulation. The primary endpoints were based on the technical success of the procedure to cross the occlusion site, in addition to an assessment of claudication before and after the procedure, as well as measurements of the ankle-brachial index (ABI) scores and any procedure-related complications. An independent safety monitoring committee reviewed adverse events throughout the study and in aggregate at the conclusion of the study.
The primary efficacy endpoint of the GRIP Registry study was achievement of distal luminal wire position. The primary safety endpoint was evaluation of the rate, nature, and severity of adverse events affiliated with the procedure. Secondary endpoint analysis included assessment of final peripheral blood flow using the ABI scores compared to preprocedural ABI scores.
The OCR technology uses near-infrared light to distinguish between plaque, blood, tissue, thrombus, and the arterial wall. A light beam of known intensity is introduced through a fiber optic in the 0.014-inch or 0.035-inch guidewire and illuminates the area adjacent to the tip of the guidewire. Algorithms have been devised based on variable absorption rates and different scattering coefficients that will distinguish the normal arterial wall from the occlusive material. Radiofrequency energy can be delivered at the tip of the guidewire to ablate through refractory occlusions. The Safe-Cross System is currently pending FDA 510(k) clearance.
Preliminary safety and effectiveness results for the study cohort are displayed in Table 2. The device success rate, defined as the achievement of distal lumen position, was 76%, satisfying the requirements of the statistical endpoint analysis in the protocol (Figure 2A,B). The safety endpoint (clinical success), defined as the achievement of distal lumen position with no occurrence of vessel perforation, dissection (grade C or greater), or distal embolization, was achieved in 74.7% of the lesions treated (Table 3). Table 4 shows the rates of improvement in ABI score (preprocedural vs postprocedural) for lesions that were successfully crossed. For the 56 lesions that were recanalized, the mean preprocedural ABI was 0.59; the mean postprocedural ABI was 0.86. The difference between the preprocedural and postprocedural ABI scores is statistically significant (P<.001; Student t test). The two patients who had normal ABI values before the procedure had normal ABI values after the procedure. Of the 18 patients who presented with mild claudication before the procedure, nine (50%) had normal ABI values after the procedure and nine (50%) had mild claudication after the procedure. Of the 29 patients who had moderate claudication before the procedure, 14 (48%) had normal ABI values, 10 (34%) had mild claudication, and five (17%) had moderate claudication after the procedure. Of the seven patients who had severe claudication before the procedure, two (29%) had mild claudication and five (71%) had moderate claudication after the procedure. All patients in the severe-claudication ABI range before the procedure had improvement in their ABI after the procedure.
The GRIP study is one of the first peripheral-device studies to focus on the challenges of total occlusion recanalization. The results of the study provide scientific evidence to establish that the device met the study’s objectives. With the goal of complete revascularization of the affected vascular bed, the Safe-Cross System provides the interventionist with a guidance system to achieve distal lumen position in the initial phase of the revascularization procedure.
Mark H. Wholey, MD, is Chairman of the Pittsburgh Vascular Institute, UPMC-Shadyside, Pittsburgh, Pennsylvania. He holds no financial interest in any product or manufacturer mentioned herein. Dr. Wholey may be reached at (412) 623-2083; firstname.lastname@example.org.
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