Laser-Thermal Recanalization Using Short Interrupted Bursts of Energy in Peripheral Arterial Occlusions

The efficacy of a new laser thermal probe is being tested in patients with chronic total occlusion of the ilio-femoropopliteal arteries. The new probes utilize short interrupted bursts of laser energy while the probe is in direct contact with the obstruction. Ten patients (mean age 68 years) with occlusions had claudication walking one block or less; the mean length of 11 occlusions was 6.5 cm. Angiographic luminal patency and ankle brachial index were evaluated in each patient. Luminal patency (1.0 = no narrowing) increased from 0 to 0.64 ± 0.08 after laser thermal recanalization (P < 0.001), and further increased to 0.88 ± 0.05 after laser-balloon angioplasty (P < 0.01). Ankle brachial index increased from a baseline of 0.60 ± 0.03 to 0.82 ± 0.03 after laser balloon angioplasty (P < 0.001). No arterial perforation, spasm, thrombosis, or embolism occurred; and there was no damage of guidewire or metal probe of the catheter. These data suggest that short interrupted bursts of thermal energy are effective in recanalizing peripheral vascular occlusions; long-term evaluation is underway to determine whether such debulking by laser thermal revascularization lowers the late restenosis/reocclusion rate of balloon angioplasty. (J Interven Cardiol 1989:2:4)     

Modified Fiber Tips for Laser Angioplasty: Mechanisms of Action

Laser angioplasty with modified fiber tips has become a common procedure for the recanalization of totally occluded peripheral arteries. We evaluated the contribution of optical, thermal, and mechanical effects to the mechanism of recanalization of various probes, theoretically and experimentally. Temperature behavior and tissue penetration were measured in relation to axial force exerted by metal laser probes, and optical contact probes coupled to continuous-wave and pulsed Nd:YAG lasers. Modified fiber tips only penetrated tissue when the contact surface of the probe exceeded a temperature threshold of about 225°C in the fatty tissue model used. Metal laser probes had to be insulated from a liquid environment to attain this temperature. Optical probes needed to have an absorbing layer of carbonized tissue particles to attain this temperature. Tissue penetration by modified fiber tips was force dependent, especially with optical probes. Since the diameter of the probe was larger than the ablative laser beam, the atraumatic probe had to distend soft tissues mechanically. Because the metal laser probes delivered their energy in all directions, undesired heating in the radial direction has to be reduced by motion. The recanalization mechanism of modified fiber tips will depend on the properties of the obstruction. Sometimes the probes will recanalize the obstruction without the use of laser energy (Dotter effect). Moderate heating of the tissue by either direct absorption of light, or by heat conduction from the heated surface of the probe, may help to remodel the obstruction. Tissue temperatures around 100°C will vaporize the water compound, and temperatures higher than 225°C will ablate the solid compounds of the tissue creating a channel. The present unsteerable probes will not penetrate heavily calcified obstructions. Calcific deposits may deflect the probe into the wall with the risk of perforation.     

Endoscopic Retrograde Pancreatography and Brushing Cytology Using a Guidewire with Special Reference to the Recanalization Method in Patients with Main Pancreatic Duct Obstruction

Abstract: We attempted endoscopic retrograde cholangiopancreatography (ERCP) using guidewires on 32 patients: 16 with main pancreatic duct (MPD) stricture and 16 with MPD obstruction which had been detected by ordinary ERCP. We also performed brushing cytology for pancreatic ductal lesions in 24 of these patients. In 15 of the 16 patients with a MPD stricture, an ERCP catheter was inserted up to the stricture and then the catheter was passed into the proximal MPD through the stricture using a guidewire (recanalization method). In 14 of the 16 patients with a MPD obstruction, the lesion was reached using guidewires. In addition, the recanalization method was possible in 12 of these 14 patients and the pancreatic ductal system proximal to the obstruction was visualized. ERCP using guidewires, especially using the recanalization method, allowed us to obtain detailed information, not only about the lesion itself but also on the pancreatic ductal system proximal to the lesion. Employing these methods, we obtained pancreatograms cliaracteristic of chronic pancreatitis or pancreatic cancer with a high detection rate and could evaluate whether the lesion was benign or malignant even in cases difficult to diagnose using ordinary ERCP. Furthermore, an assessment of the lesion expansion was possible to some degree with the recanalization method. The diagnostic accuracy of brushing cytology of the ductal lesion using guidewires was 79%. Although one subject experienced acute pancreatitis after these procedures, she recovered following conservative treatment. No other serious complications were observed.     

Laser-assisted thermal angioplasty in human peripheral artery occlusions: mechanism of recanalization

Recanalization of completely occluded superficial femoral or popliteal arteries was attempted in 18 patients with use of an Argon laser-mediated thermal probe. The length of the occluded segments varied between 0.5 and 26.0 cm, but 67% of the occlusions were greater than 9 cm long. The initial success rate was 67%. Arterial perforation occurred in six patients but was not associated with major complications. To study the mechanism of the laser-mediated thermal probe, thermal recanalization was performed on 11 human arterial segments in vitro obtained after amputation, and mechanical recanalization was performed in vitro in 10 human peripheral arteries with use of a guide wire and catheter technique. An additional four arteries were studied with the laser probe as a non-heated mechanical device. Both the mechanical and thermal devices appear to follow a similar pathway through a complete obstruction. These studies suggest that the thermal probe burns through soft fibrous tissue but is mechanically deflected away from hard fibrocalcific plaque. The probe then advances along the plane between the intimal plaque and the media for a variable length before perforating through the adventitia. These observations suggest that the major mechanism of thermal probe recanalization may be a mechanical process. It appears that thermal probe devices do not inherently seek the true lumen of an occluded artery and that better guidance systems need to be developed.     

A new method of laser angioplasty by contact sapphire: preliminary results. Apropos of 20 cases

We report our first 20 cases of peripheral laser angioplasty using an optic fibre with contact sapphire tip. The equipment included a teflon catheter on which was screwed a round sapphire 2.2 mm in diameter. A 600 microns optic fibre connected to a Nd-Yag laser instrument was introduced into the catheter and placed in contact with the sapphire. Twenty patients underwent recanalization of femoral or popliteal arteries occluded on a length of 5 to 45 cm. The sapphire-tipped catheter was introduced by the Seldinger technique up to the site of occlusion. The 15 watt laser emission was set at intervals of one second. Sixteen out of the 20 occluded arteries were recanalized. Among the 4 failures, 3 were due to perforation and 1 to intraparietal progression. Angioplasty was performed with laser alone in 3 cases and with laser completed by balloon catheter in 13 cases. The minimum diameter of the laser-induced channel was 2 mm and was significantly increased (3.8 mm) by complementary balloon dilatation. In the 3 patients who underwent laser angioplasty alone, no noticeable improvement in distal blood flow was demonstrated by doppler velocimetry, and reocclusion occurred either soon afterwards (n = 2) or later (n = 1). Midterm results were much better in patients who had had additional balloon dilatation: early (3rd day) or late (2 months) reocclusion took place in only 3 patients. In the remaining 10 patients, followed up for periods of 1 week to 18 months (mean: 6 months), clinical improvement and recanalization were maintained.     

Intracardiac, intravascular, two-dimensional, high-frequency ultrasound imaging of pulmonary artery and its branches in humans and animals

Intravascular ultrasound imaging is a promising new method for assessing vascular morphology. We evaluated the capability of intravascular ultrasound to quantify pulmonary artery (PA) morphology in vitro and explored the feasibility of in vivo PA imaging in animals and humans. In the in vitro study of 15 PA segments, we used a 20-MHz prototype ultrasound catheter. Intravascular ultrasound (y) provided crisp images of PA segments and demonstrated excellent correlations with anatomic measurements (x) in the estimation of luminal area (y = 0.89x + 2.95, r = 0.99, p less than 0.001), luminal diameter (n = 30, y = 0.79x + 0.96, r = 0.92, p less than 0.001), and vessel wall thickness (n = 60, y = 0.65x + 0.33, r = 0.85, p less than 0.001). We subsequently introduced the probe into the PA of 10 dogs and were able to obtain real-time, two-dimensional images of the main PA, its major branches, and farther smaller branches as far as the wedge level. To evaluate the in vivo feasibility of PA imaging in conscious humans, we used a commercially available, 20-MHz intravascular ultrasound (IVUS) catheter in 22 subjects through a femoral or jugular venous sheath at the end of standard diagnostic cardiac catheterization. In 20 subjects, we acquired dynamic, high-resolution, cross-sectional images of the proximal and distal PA. Changes in shape and decreasing luminal area could be clearly recognized as the IVUS catheter reached branching points and as it passed more distally. There were no complications.(ABSTRACT TRUNCATED AT 250 WORDS)     

Laser angioplasty of peripheral arteries after unsuccessful recanalization of the superficial femoral artery

AIM: To demonstrate the range of applying laser angioplasty after unsuccessful recanalization of the superficial femoral artery (SFA) with conventional interventional techniques. MATERIALS AND METHODS: In a prospective trial in 94 cases with occlusion of the SFA and formerly unsuccessful conventional percutaneous transluminal angioplasty, laser angioplasty for recanalization was applied. The average length of the SFA was 17.5 cm (range 4–36 cm). The recanalization attempt was made using the crossover technique in 78 patients, in eight patients with the antegrade technique and in another eight patients using the transpopliteal technique. The primary recanalization attempt was performed with Terumo wires (curved and straight) as well as different catheters (Multipurpose/Vertebralis/Cobra). the unsuccessful recanalization attempt the laser catheter was applied. RESULTS: The application of laser angioplasty demonstrated a successful recanalization of the SFA in 76/94 patients (80.9%). In 18 patients (19.1%) the recanalization was not possible even with percutaneous transluminal laser angioplasty (PTLA). The reason for the unsuccessful PTLA was in 10 cases due to obstructing calcified material, which was resistant to PTLA application. In four cases obstructing calcifications caused the laser catheter to be positioned in subintimal tissue, resulting in perforation occlusion of the SFA. In another four patients there was an aberrant anatomy of the SFA which resulted in a direct vessel injury after advancing the laser catheter. After a follow-up period of 12 months primary, primary-assisted and secondary patency rates were 50.0%, 65.8% and 73.7%, respectively. DISCUSSION: In primarily unsuccessful recanalization of the SFA, PTLA allows in After 80% of cases a successful recanalization of the SFA. The technical success rate and the patency rate support the application of PTLA. (Int J Cardiovasc 2000; 3: 153–160)     

Ultrasound guidance of laser atherectomy

Intravascular ultrasound imaging catheters and forward firing laser atherectomy systems are both being used in the coronary vascular tree of man. When used in conjunction, ultrasound imaging may reduce the probability of perforation and dissection related to laser atherectomy. A novel system is presented which combines ultrasound imaging and laser atherectomy capabilities on the same catheter. The system incorporates a holmium YAG laser directed perpendicular to the long axis of the catheter along with a co-directional ultrasound sensor. Ultrasound images are assembled by computer using the angle of the catheter tip and its linear advance associated with each ultrasound echo signal.In vivo experimental results are presented.     

A comparison of excimer laser, thermal probe, and mechanical devices for recanalizing occluded human arteries

To evaluate the mechanism of excimer laser recanalization and compare the results with those of laser-assisted thermal probe recanalization and mechanical recanalization, a total of 42 human atherosclerotic totally occluded arterial segments (2-15 cm long) were recanalized by excimer laser with a 400-800 micron quartz fiber pulsed at 20 Hz with 50 mJ/mm2 of energy (n = 21), an Argon heated thermal probe at 10-12 watts (n = 11), a guidewire directed through a 6 Fr multipurpose catheter, or an angioplasty balloon catheter (n = 10). On histologic examination, the excimer laster created a single round lumen or multiple lumens ("Swiss-cheese" like appearance) with no evidence of thermal injury at the perimeter of the lumen. The incidence of perforation in vitro was less with an excimer laser catherter (8/21 or 38%) than with the thermal prove (10/11 or 91%) (p less than 0.01). However, serial histologic cross-sectional examination showed that the pathway of the devices were essentially the same in all recanalization procedures. The pathway of the device was located outside the atheroma but proximal to the internal elastic membrane in 13 arteries with the excimer laser (62%), in 10 arteries with the thermal probe (91%), and 8 arteries with mechanical devices (80%). These results indicate that although the eximer laser could recanalize human atherosclerotic arteries without thermal injury, the fiber frequently deflected around firm atherosclerotic plaque and advanced in a dissection plane between the plaque and media. A similar course was noted for the thermal probe or during mechanical recanalization with a guidewire and catheter. To insure the safety of an excimer fiber or a thermal probe to reopen complete occlusions, better guidance systems must be developed.     

Percutaneous angioplasty of chronic obstruction of peripheral arteries by a temperature-controlled Nd:YAG laser system

The feasibility of an Nd:YAG laser system with automatic control of hot-tip probe temperature was examined in 15 segments (14.7 +/- 6 cm in length) of iliofemoral arteries from 13 patients. The hot-tip temperature to be attained and the upper limit temperature at which lasing was to be stopped were preset. A catheter with a 1.8-mm hot-tip probe was introduced into the obstructed segment and angioplasty (lasing time 5-10 sec) was performed under angioscopic guidance. Recanalization was observed in all segments without obvious complications. No thermal effects below 50 degrees C, coagulation at 100 degrees C, carbonization at 200 degrees C, or sticking of the hot-tip to the luminal surface at 300 degrees C or over, were observed by angioscopy. Rapid recanalization was obtained between 200 degrees C and 300 degrees C. The results indicate that this novel laser system is feasible and hot-tip temperature between 200 degrees C and 300 degrees C is ideal for treatment of chronic arterial obstruction in Japanese patients.     

Intravascular ultrasound cross-sectional arterial imaging before and after balloon angioplasty in vitro

A prototype ultrasound imaging catheter was evaluated in vitro using 17 human atherosclerotic artery segments before and after balloon dilatation angioplasty. The catheter was 1.2 mm in diameter and incorporated a single 20-MHz ultrasound transducer to obtain cross-sectional images of the arterial lumen. In 15 of the 17 (88%) arteries, high quality images were obtained, which demonstrated clear demarcation between the lumen and the endothelium, the atheroma plaque, the muscular media, and the adventitia. Qualitative characteristics of plaque disruption, dissection, and residual flaps were readily visible. In addition, quantitative information about cross-sectional lumen area was obtained before and after balloon dilatation. The mean cross-sectional lumen area increased from 8.7 to 15.1 mm2 (p less than 0.01) following balloon dilatation. The lumen area measured from the ultrasound images following dilatation correlated closely with the area measured from histologic sections (r = 0.88). The results from this study indicate that a small-diameter ultrasound imaging catheter can be developed that will provide high-resolution qualitative and quantitative information during peripheral and coronary angioplasty.     

Early and recent intraluminal ultrasound devices

The history of intraluminal echography dates back to the very beginning of diagnostic ultrasound. Over the years many fascinating ideas and applications of catheter tip or gastroscopic tube tip mounted transducers have been described. This chapter surveys these methods, subdividing them into a) measurements; b) Doppler and c) imaging. The survey ranges from early work of Cieszynski on the feasibility of echocardiography to more recent intra-arterial catheter tip Doppler with guidewire and balloon as described by Serruys.Examples of ultrasound catheter tip echography in combination with other techniques such as angioscopy, laser ablation and spark erosion are also described. Today practical approaches are limited to imaging only. The three major approaches for catheter tip echo imaging are described and compared. This paper concludes with the results of automatic contour analysis of the inner arterial boundaries.     

Recanalization of chronic total coronary arterial occlusions by percutaneous excimer-laser and laser-assisted angioplasty

A low primary success and high restenosis rate after recanalization of chronic total occlusions by conventional coronary angioplasty have encouraged the application of new interventional techniques like excimer-laser angioplasty. In 39 patients with a coronary occlusion for 1 to 12 months, recanalization was attempted by laser angioplasty through a multifiber-catheter coupled to a pulsed XeCl excimer laser. After successful passage of the occlusion by a standard guidewire in 27 patients (69%), the laser catheter was advanced over the central guidewire and crossed the occlusion in 25 patients (64%). In 2 patients with unsuccessful passage of the laser catheter, the subsequent attempt with a low profile balloon catheter also failed. In 19 of the 25 patients with successful laser recanalization, the residual stenosis exceeded 50% and was therefore followed by additional balloon angioplasty. The average residual stenosis after laser was 61 +/- 17% of the vessel diameter, and after balloon angioplasty 28 +/- 9% (n = 19), whereas after laser angioplasty alone it was 38 +/- 5% (n = 6). No complications associated with the laser application were observed. Angiographic control after 24 hours showed a reocclusion of 2 (8%) recanalized vessels. In this pilot study, laser angioplasty proved to be a safe and feasible method for the treatment of chronic total coronary occlusions. Because it was necessary to guide the catheter by a central wire, the primary success was limited by a successful passage of the wire of the occlusion. The rate of stand-alone laser angioplasty has to be increased by future improvements of the technique to enable a comparative evaluation of this method with conventional angioplasty.     

Percutaneous recanalization of chronic total coronary occlusions: experience with the direct argon laser assisted angioplasty system (LASTAC)

The present study reports initial experience with the argon laser LASTAC system in patients with chronic coronary artery occlusion not amenable to recanalization with conventional systems. The LASTAC system conducts focused argon laser light through an optical fiber of 200 microns which is inserted through a multiple-lumen balloon catheter. The balloon serves the purpose of coaxially positioning the optical fiber. The balloon catheter is advanced by means of a guidewire to about 2 mm proximal to the occlusive lesion. After advancing the optical fiber, in three times 10 to 20 Joules are applied. Thereafter, the optical fiber is withdrawn, the balloon deflated, the catheter system repositioned and the sequence repeated. The integrity of the system with respect to temperature increase, energy loss and contact with tissue is monitored with lens fluorescence. In 29 patients with angina pectoris and documented ischemia, 30 complete occlusions were treated. In 18 (60%), there was successful recanalization with conventional balloon dilation thereafter. The total success rate for the right coronary artery was 55%, for the circumflex artery 71% and for the left anterior descending artery 67%. With regard to complications, in one patient there was nontransmural myocardial infarction, in seven there were asymptomatic dissections, one patient required defibrillation. The value of the LASTAC system for recanalization of chronically occluded coronary arteries has not yet been fully delineated. However, the success rate of 60% in previously treatment-refractory patients as well as the fact that no perforations were incurred, is encouraging. Further assessment will require analysis of long-term results as well as comparison of other methods.     

Ultrasound guided therapeutic catheters: recent developments and clinical results

The increasing use of intravascular ultrasound technology by clinicians is providing detailed and immediate information about the results of interventions, and this is stimulating the development of new catheters that use ultrasound imaging to control therapy in real time. Cold and thermal balloon angioplasty, atherectomy, embolectomy, laser ablation and rotational recanalization are a few of the interesting capabilities now being added to ultrasound catheters. We report on the development and characteristics of some of these devices and attempt to assess their potential to precisely direct therapy.     

Immediate- and short-term outcome following recanalization of long chronic total occlusions (> 50 mm) of native coronary arteries with the Frontrunner catheter

Thirty percent of diagnostic angiograms have at least 1 chronic total occlusion (CTO). The 10-year survival of patients with a CTO is improved if they have the CTO successfully recanalized. The success of recanalization with conventional wires is 50% and the impact of new technology on recanalization is unknown. This abstract reports a single center experience with one such new device, the Lumend Frontrunner catheter in revascularization of this difficult lesion subset. A consecutive series of 18 patients with CTO's of native coronary arteries were enrolled in this single center, single operator series. The mean age of the CTO was 5.3 years. The indication for attempt at recanalization was ischemia in the territory of the CTO on SPECT imaging. Success was defined as TIMI flow restoration and < 40% residual stenosis. Primary success (defined as TIMI 3 Flow restoration and < 40% residual stenosis) was achieved in 77% of patients. At 30 days and out to 6 months, clinical TVR was 11% (2/18) in this difficult lesion subset. Conventional predictors of failure to recanalize CTOs do not appear to hold true with the use of the Frontrunner catheter. In this small series, dual cusp injections and use of the Microglide catheter appears to correlate with favorable outcomes. Fluoroscopy times and contrast use are high when attempting recanalization of CTOs with this technology.     

Percutaneous coronary mid-infra-red laser angioplasty.

A pilot study was performed to determine the safety and efficacy of coronary pulsed mid-infra-red laser angioplasty. The laser was coupled with a novel 2.0 mm multifiber catheter consisting of 37 optical fibers of 150 microns each arranged concentrically around a 0.018-inch central lumen and a soft leading tapered distal tip to maintain coaxial alignment and position plaque in front of fibers. The laser was operated at 500 millijoules/pulse, 3.5 Hz, and 250 microseconds/pulse. Twenty-three patients with stenosis or occlusion of the left anterior descending or right coronary artery were selected for laser treatment. In three patients the catheter could not be positioned against the obstruction. In the 20 remaining patients laser angioplasty increased the diameter of the lumen from 0.3 +/- 0.3 mm to 1.4 +/- 0.3 mm and reduced the stenosis from 91 +/- 8% to 57 +/- 10%. In three patients "stand-alone" laser treatment was sufficient. In 17 patients balloon dilatation further reduced the stenosis to 20 +/- 18%. In two patients who had previously undergone unsuccessful balloon angioplasty with high inflation pressure, laser angioplasty allowed subsequent successful dilatation with low inflation pressure. There were no deaths, perforations, dissections, or arrhythmias. One patient had abrupt reclosure 24 hours after the procedure. Spasm occurred in four patients, and six patients had chest sensations during laser emission. Thus mid-infra-red pulsed coronary laser angioplasty is safe and effective for recanalization of stenosed and totally occluded arteries. The efficacy may be sufficient for "stand-alone" laser treatment. The technique may improve the efficacy of balloon angioplasty in cases of unsuccessful primary dilatation.     

Initial clinical experience with a 48 by 48 element biplane transesophageal probe.

Recent technologic advances in ultrasound have resulted in the capability of transesophageal echocardiographic imaging in both transverse and longitudinal planes. Previous biplane probes suffered from inferior images because of reduced scan elements. We evaluated the utility of a prototype 48 X 48 element biplane transesophageal probe in 23 consecutive patients. Examinations were well tolerated with no side effects. In comparison to the single transverse plane, imaging with the longitudinal plane gave superior information on prosthetic valve pathology, atrial septal abnormalities, and pathoanatomy of the ascending aorta and mitral valve. Complementary information was provided by the longitudinal plane in patients with endocarditis and vegetations and in mitral protheses. Images obtained with this 48 X 48 element biplane probe along with color and spectral Doppler information were not perceptibly inferior to those obtained by single-plane probes. In conclusion, biplane transesophageal echocardiography with a 48 X 48 element probe indicates a great potential for enhanced three-dimensional understanding of cardiac pathology and diagnostic yield in specific pathologies.     

The usefulness of intravascular echography during the percutaneous dilatation of aortic coarctation]

An intravascular ultrasound study was performed in a patient, to assess the anatomy of aortic coarctation and the results obtained after percutaneous dilation with a balloon catheter. Intravascular ultrasound imaging provides important additional information, not obtainable with other diagnostic procedures, regarding aortic wall structure and thickness. After balloon dilation, aortic disruption was clearly observed, accounting, together with the stretching of the outer layers of the aortic wall, for the increase in aortic luminal area. Intravascular ultrasound permitted also the accurate assessment of the improvement obtained. Intravascular imaging was clearly superior not only to conventional angiography, but also to transesophageal echocardiography in detecting the mechanism of dilation. We conclude that ultravascular ultrasound, with the additional information that it provides, may help in the selection of patients for percutaneous dilation of the coarctation as well as contributing to the identification of the mechanism of dilation.     

"Wireless" laser recanalization of chronic total coronary occlusions

Chronic total occlusions in particular, completely obstructed aorto-ostial lesions are among the most challenging targets in interventional cardiology. Excimer laser is a debulking technology for revascularization of complex lesions. Treatment of total occlusions with laser angioplasty can be applied providing that a guidewire traverses the entire length of the occlusion prior to device activation. In many patients with total occlusions, a guidewire is unable to penetrate the target stenosis. This communication presents a new technique termed "wireless" laser recanalization. This approach entails recanalization of a total occlusion with a laser catheter without a leading guidewire.