Laser thermal probe recanalization of occluded arteries

Early outcome and intermediate follow-up of vascular stents in the femoral and popliteal arteries without long-term anticoagulation

PURPOSE

The role of arterial stenting in the treatment of femoral and popliteal arterial disease is controversial and has been hampered by recommendations for patients to be given anticoagulants (oral warfarin) for several months or more. This study was undertaken to evaluate the immediate and midterm outcomes of vascular stents implanted percutaneously in the femoral and popliteal arteries, without long-term anticoagulation.

METHODS

Over a 3-year period, 32 patients admitted to a vascular surgery service had arterial stents implanted in the femoral (n = 22) or popliteal (n = 10) artery for the following indications: recurrent stenosis after angioplasty (n = 13), suboptimal result after angioplasty of occluded (n = 12) or calcified stenotic arteries (n = 2), percutaneous transluminal angioplasty-induced thrombosis or dissection (n = 5). Access to the artery was gained by percutaneous insertion of a hemostatic sheath into the ipsilateral common femoral artery. Systemic heparin was given at the time of stent insertion, and patients were prescribed daily low-dose aspirin.

RESULTS

Successful stent implantation was achieved in 31 of the 32 patients. Acute thrombosis (< 30 days) occurred in two patients. There was no incidence of false aneurysm formation, acute leg ischemia, or vessel perforation. All patients were monitored by Doppler scanning index and duplex scanning within 24 hours, and thereafter at 3- to 6-month intervals. The mean ankle-brachial systolic pressure index improved from 0.60 (before treatment) to 0.88 (3 to 6 months after stenting). Stent occlusion has occurred in six patients; two stents were successfully salvaged with urokinase infusion. In follow-up to date (range 3 to 33 months) the primary patency rate by life-table analysis was 75% at 18 months, whereas the secondary patency rate was 89% at the same interval. Restenosis (> 50% lumen diameter) was detected by duplex ultrasonography in seven of 25 patent stents (28%) at a mean interval of 9.5 months (range 4 to 15 months); of these, four patients remained clinically symptom-free despite the ultrasound findings.

CONCLUSIONS

We conclude that vascular stents can be implanted into the femoropopliteal arteries with few complications and with acceptable early and intermediate patency rates, without the need for long-term anticoagulation. Restenosis is not prevented by stents, and the main value of stenting at this site appears to be in salvaging acute complications of percutaneous transluminal angioplasty, or to correct suboptimal results after recanalization of occluded arteries.

Intravascular ultrasound imaging: the new standard for guidance and assessment of endovascular interventions?

Intravascular ultrasound has developed rapidly during the last few years, and provides a unique perspective from which to view vascular disease and the effects of intervention. This catheter-based imaging technique utilizes advances in echographic data processing and computerized image manipulation to produce accurate luminal and transmural images of blood vessels. Although these devices have only been available for a relatively short time, numerous diagnostic and therapeutic applications have been reported. By providing a detailed image of vessels before, during, and after intervention, intravascular ultrasound provides a method for both guidance of endoluminal devices and immediate assessment of the results of therapeutic techniques including balloon angioplasty, atherectomy, laser-assisted angioplasty, and intravascular stent deployment. Intravascular ultrasound also offers exciting possibilities in peripheral vascular research such as investigation of blood vessel compliance, dynamic changes in the vessel wall caused by disease or pharmacologic intervention, and elucidation of the morphologic changes associated with the natural history of atherosclerosis.

Laser angioplasty

Laser energy has the potential for selective ablation of atherosclerotic plaque through minimally invasive means. As currently practiced, laser angioplasty requires the adjunct of balloon angioplasty in most cases and has limited application compared with more conventional methods of revascularization. However, new advances in guidance systems, delivery devices, and laser sources may allow realization of the full benefit of this technology at some point in the future.

Intraoperative peripheral rotary atherectomy: early and late clinical results

Early and late clinical results of intraoperative peripheral atherectomy using the Auth Rotablator are analyzed. Twenty patients (15 males and 5 females age 39-89 years, mean 70 years) underwent 25 atherectomy procedures for peripheral arterial occlusive disease from August 1987 to October 1989. All patients underwent serial history, physical exam, and Doppler pressure measurements preoperatively and then postoperatively at 24 hours, one week, one month, and six months during a follow-up period of 15 to 41 months, mean 27 months. Preoperative and intraoperative completion follow-up arteriography was done in all cases and follow-up arteriography in 19 of 25 cases. Initial arteriographic success was achieved in 23/25 (92%) cases and in 39/41 (93%) arterial segments (superficial femoral artery 12/13, popliteal 14/15, tibial 12/13, profunda-femoral 1/1). Complications included intimal dissection (1), equipment breakage (2), minor emboli (3), major emboli with thigh skin loss (1), transient hemoglobinuria (4), wound hematoma (1), wound infection (1), and limb loss (1). Early thrombosis occurred in five cases to give an in-hospital success rate of 18/25 (72%). Primary patency was 66% at six months but only 12% at two years. Rotary atherectomy effectively recanalizes femoral, popliteal and tibial arteries. However, early thromboembolic complications occurred frequently, and the two year patency was dismal. Rotary atherectomy is not recommended for general use until problems of thromboemboli and intimal hyperplasia are solved.

Intravascular ultrasound guided holmium:YAG laser recanalization of occluded arteries

Current angioplasty devices are limited by arterial wall dissection and perforation, and by early recurrence from inadequate debulking of lesions. This study evaluated intravascular ultrasound (IVUS) as guidance for concentric laser recanalization of arterial occlusions. Twelve, 2-4-cm-long canine iliac artery occlusions were treated at 2 weeks (organizing thrombus) to 12 weeks (firm fibrous lesions) using a Holmium:YAG laser (2,100 nm wavelength) in free running mode, FRM, (250 musec pulse, 5 Hz), n = 9; and Q-switched mode, QSM (200 ns pulse, 6 Hz), n = 3. A 200 microns (n = 2) or 600 microns (n = 10) optic fiber was centered in the artery coaxial to a 5Fr rotating A scan IVUS probe. The fiber was positioned in the center of the artery distal to the lesion and slowly advanced through the obstruction. In 8 occlusions the same fiber was used as a guidewire for passage of either a 1.6-mm-(n = 2) and/or 3.0-mm (n = 6) diameter multifiber catheter (19 x 100 and 19 x 200 microns fibers, respectively) using FRM energy to further debulk the lesion. In all cases, IVUS guidance enabled concentric initial recanalization of occlusions, although 3 vessel perforations resulted from fiber deviation off the center of the lumen at a distance of 2 to 4 cm from the IVUS imaging element. Both QSM and FRM modes ablated tissue, with FRM modes producing more tissue fragmentation and thermal effect. IVUS images accurately diagnosed the location of lesions compared to angioscopic views and pathologic analysis of the specimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Retrograde femoral angioplasty: a new technique

Percutaneous transluminal angioplasty cannot be used for lesions of the superficial femoral artery when the origin of the vessel is occluded. A new technique, retrograde femoral angioplasty, is described in which angioplasty is performed from below via the exposed popliteal artery. In four out of six patients retrograde femoral angioplasty was successfully completed, and three of the four vessels remain patent up to 1 year later. The method provides an alternative to the femoropopliteal bypass graft in some patients.

Intraluminal vascular ultrasound: preliminary report of dimensional and morphologic accuracy

The role of intraluminal ultrasound for diagnosis and monitoring treatment of vascular disease has yet to be defined. This study evaluated the dimensional precision and morphologic accuracy of an intraluminal ultrasound system which consists of a 5.5 French external diameter ultrasonic catheter with a central lumen for passage of a guidewire. Ultrasound images from five in-vitro human and three porcine arterial segments and two in-vivo arteriosclerotic canine arteries were compared to dimensions obtained from arteriograms and from sections of the specimens. Each gross and histological specimen and ultrasound image was scaled, photographed and enlarged up to 20 times and measured for vessel intraluminal and adventitial or outer diameter and wall thickness. Intraluminal and outer diameters and wall thickness from normal in-vitro specimens correlated significantly with dimensions obtained from histologic specimens (r = 0.99, p less than 0.005 for internal and outer diameters and r = 0.73, p less than 0.005 for wall thickness). The mean differences of luminal diameters measured from the vessels supported within a silicone rubber mold was 0.05 +/- 0.09 mm (n = 20). Diameters of outer diameter and wall thickness were less reliably defined, the average margin of error being 0.49 +/- 0.39 mm and 0.29 +/- 0.26 mm, respectively. The mean difference between in-vivo ultrasound and arteriographic diameters was 0.61 +/- 0.38 mm (n = 12). Correlation of luminal diameters between ultrasound and arteriogram was significant (r = 0.76, p less than 0.02). The ultrasound images also differentiated a laminated appearance of normal vessel anatomy from non-uniform or dense signals seen in atherosclerotic lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermal laser probe angioplasty: influence of constant tip temperature, plaque composition, and probe/vessel diameter ratio

Thermal laser angioplasty uses constant laser power, producing widely variable tip temperatures in vivo. Results have been suboptimal. We studied the effect of 50-400 degrees C tip temperatures on depth of ablation at 192 sites on plaqued and normal human aorta in vitro, and the angiographic and histologic response in vivo of 300-400 degrees C at probe/vessel ratios of 0.5-1.0, in 40 normal canine femoral artery segments. In vitro, there was a direct relationship between tip temperature and depth of ablation, r = 0.71 (all segments), r = 0.74 for fibrous plaque, but a poor correlation in fatty plaque r = 0.35. In fibrous plaque, there was proportionately more ablation at tip temperatures greater than 300 degrees C, mean depth 0.62 mm, than at 150-300 degrees C, mean 0.37 mm, (P less than .001). Ablation was similar in plaqued and normal aorta. In vivo, 300 degrees C, 350 degrees C, and 400 degrees C produced similar effects. At probe/vessel ratios less than 0.8, only disruption of internal elastic lamina was observed. At ratios greater than or equal to 0.8, spasm occurred in 39% (7/18), transmural damage in 28% (5/18), and perforation in one of 18. Ablation is not selective for plaque and is highly variable in fatty plaque. Tip temperatures above 300 degrees C produce greater ablation than at lower temperatures. In clinical applications, probe/vessel rations less than or equal to 0.7 may be most appropriate, and it appears that thermal remodeling may contribute more to outcome than plaque ablation.

Experimental and clinical applications of angioscopic guidance for laser angioplasty

The role of angioscopic monitoring and aiming for control of laser intervention in the vascular system was initially investigated in 48 vessels in 33 dogs, and the techniques were then applied to 30 patients undergoing intraoperative or percutaneous laser-probe angioplasty treatment for long atherosclerotic occlusions of the femoral and popliteal arteries or well-localized lesions of the superficial femoral artery. Experimental bare argon fiber laser application in 20 normal canine arteries in vivo demonstrated that small-diameter laser fibers could be accurately aimed by manipulations of the scope. However, advancement of the fiber resulted universally in perforation, with extravasation and thermal damage of surrounding tissues after 2 seconds of argon laser energy at low power. In 28 canine and 2 human veins, angioscopically guided metallic-tipped laserprobes were used to divide 82 valve cusps in preparation for in-situ bypass, with satisfactory aiming and monitoring achieved expeditiously by manipulations of the angioscope. We conclude that angioscopic aiming of lasers is feasible in normal vessels or localized lesions. In contrast, angioscopy has a restricted role for guidance of laser angioplasty in atherosclerotic, occluded arteries, and does not prevent perforation. Postprocedural inspection allows immediate detection of complications and may avert or predict poor outcome.