True ablation of atheromatous plaques with laser energy. A phase I safety study.

A laser system coupling pulsed dye laser to a 2-mm fiberoptic catheter with incorporated angioscope has been developed for recanalization of occluded arteries. Nine patients with superficial femoral artery occlusions of 4.5 to 49 cm in length were operated on and the recanalized artery harvested for pathologic examination. There were two arterial perforations. The ease of recanalization was determined by plaque composition. Heavily calcified and yellow fibro-fatty lesions were rapidly removed. Smooth white fibrous lesions resisted laser ablation. Direct angioscopy often disclosed discontinuous areas of occlusion that were more susceptible to recanalization. These were not seen on preoperative arteriograms. Microscopic examination of the specimens showed a central core of ablation. There was no evidence of acute damage to the vessel wall, with intact internal elastic lamina demonstrated in the recanalized segments. It appears that fibrous lesions will require a different laser for ablation; however, the delivery/angioscope systems function satisfactorily.     

Design and evaluation of a fiberoptic fluorescence guided laser recanalization system

Current angioplasty techniques for recanalization of totally occluded arteries are limited by the inability to cross the occlusion and by the risk of perforation. A fiberoptic fluorescence guided laser recanalization system was developed and evaluated in vitro for recanalization of 17 human femoral or tibial totally occluded arterial segments (length 1.9-6.8 cm, diameter 2.5-6.0 mm). A 400 or 600 micron silica fiber was coupled to a helium-cadmium laser (lambda = 325 nm) for fluorescence excitation and to a holmium: YAG laser (lambda = 2.1 micron) for tissue ablation. Fluorescence was recorded during recanalization after every other holmium laser pulse. During recanalization, each arterial segment was bent 30-90 degrees with respect to the fiber to simulate arterial tortuosity. Ablation continued with fiber advancement as long as the fluorescence confirmed that the target tissue was atherosclerotic. Arterial spectra were classified as normal or atherosclerotic by an on-line computerized fluorescence classification algorithm (sensitivity 93%, specificity 95%). Normal fluorescence necessitated redirection of the fiber greater than 30 times per segment to continue recanalization. Fifteen of 17 totally occluded arteries had multiple recanalization channels created following total energy delivery of 40-1,016 Joules per segment with no angiographic or histologic evidence of laser perforation. Two heavily calcified arterial occlusions were not recanalized due to inhibition of holmium: YAG laser ablation by the recording of normal fluorescence spectra. Therefore, this fluorescence guided laser recanalization system appears safe and effective for recanalization of totally occluded arteries and merits in vivo evaluation. However, the lower sensitivity of fluorescence detection of heavily calcified plaques may limit the efficacy (but not safety) of fluorescence guided recanalization of heavily calcified occlusions.     

Diagnosis of total internal carotid occlusions with duplex ultrasound and ultrasound contrast

It remains a significant technical challenge for duplex ultrasound to accurately differentiate between total and near total internal carotid artery (ICA) occlusions. We have evaluated the efficacy of an ultrasound contrast agent combined with improved imaging techniques in patients with suspected carotid artery occlusions. Patients identified by conventional duplex ultrasound between January and August 2003 as having a possible ICA occlusion were eligible for study. A 1 mL bolus of ultrasound contrast agent was injected into a 50 mL bag of normal saline and given intravenously at a rate of approximately 4-5 mL/minute. Ultrasound imaging and spectral Doppler analysis were done using tissue harmonic imaging for optimum contrast agent to soft tissue discrimination, or with the direct B-mode imaging of blood flow to maximize the brightness of the circulating contrast agent. Ten patients were identified, 6 men and four women with a mean age of 68.3 years. Nine suspected total ICA occlusions were unilateral and 1 was bilateral. Imaging with contrast agent confirmed occlusion of the ICA in 7 of 10 patients; 3 patients had near-total occlusion with flow detected in the distal ICA by spectral and color Doppler. All 3 of these near-total occlusions were ultimately confirmed by either conventional or magnetic resonance carotid angiography. The contrast agent was most beneficial in improving the detection of minimal flow beyond a severe stenosis and in evaluating flow dynamics in the presence of severely calcified plaque. We conclude that the use of an ultrasound contrast agent with newer duplex ultrasound imaging techniques can reliably distinguish total from near-total internal carotid artery occlusions. Future prospective studies should be able to define the efficacy of ultrasound contrast agents in improving the overall diagnostic accuracy of duplex ultrasound in technically difficult cases and in patients with complex peripheral vascular disease.     

Natural history of asymptomatic carotid plaque. Five year follow-up study

A prospective analysis of 296 carotid arteries in 293 asymptomatic patients was undertaken using real-time B-mode ultrasonography. All patients had carotid bifurcation disease and were followed for an average of 46 months. The endpoint for follow-up was a transient ischemic attack or stroke. Patients were categorized according to degree of stenosis (greater or less than 75 percent) and morphologic plaque characteristics (calcified, dense, or soft). Patients with hemodynamically significant stenosis were at greater risk of transient ischemic attack or stroke than their counterparts with less than 75 percent stenosis. However, even patients with less than 75 percent stenosis were at risk if the plaque was less organized (dense or soft). Patients with hemodynamically significant stenosis and morphologically soft plaque were at the greatest risk of transient ischemic attack or stroke. Those patients with calcified plaque and less than 75 percent stenosis had the lowest risk of transient ischemic attack or stroke. Morphologic plaque characteristics, as well as degree of stenosis, is important in determining which patients are candidates for carotid endarterectomy.     

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)     

Intravascular ultrasonic imaging: histologic and echographic correlation

The feasibility of assessing arterial wall characteristics with an intravascular 40 MHz ultrasonic imaging device was determined in vitro. Ten autopsy specimens of human arteries, with and without atherosclerosis, were studied. A close relationship was observed between the histologic section and the corresponding ultrasonic cross-section with regard to the location, maximum plaque thickness and extent of the atherosclerotic lesion along the circumference of the vessel wall. Based on echogenicity of the atherosclerotic lesion, ultrasound could distinguish four basic types of atherosclerotic plaque components: 1. hypoechoic: a reflection of lipid deposits; 2. soft echoes: reflective of fibromuscular tissue; 3. bright echoes: representative of fibrous tissue; 4. bright echoes with shadowing behind the lesion: representative of calcium deposits. It is anticipated that development of such a catheter-tip imaging system combined with recanalisation methods will be of immense benefit for the precise localisation and identification of vessel wall pathology, precise positioning of a recanalisation instrument (laser device, atherectomy catheter) and subsequent use of this recanalisation procedure and for assessing the effect of recanalisation.     

Argon laser angioplasty with a laser probe

A preliminary basic study of argon laser angioplasty with the use of a specially designed probe is presented. Arterial specimens were harvested from 10 amputated lower extremities. The studies included the evaluation of coaxial laser angioplasty in 10 partially or totally occluded arteries; the observation of the effect of perpendicularly applied laser energy on 35 thrombi, 54 soft and 10 hard atherosclerotic, and 51 normal arterial walls; the comparison of laser energy requirements for coaxial vessel lumen enlargement or recanalization vs. perpendicular penetration in 10 occluded, hard atherosclerotic arteries; and the spectrographic analysis of calcium density gradient in two specimens. The results showed that the power required for vessel lumen enlargement was 10 +/- 6 J/mm of atherosclerotic vessel (mean +/- standard deviation). The probe followed the original arterial lumen, did not perforate the vessel wall, and created a smooth, enlarged path. The power required to penetrate perpendicularly to a similar depth for thrombi, soft and hard atherosclerotic plaques, and normal arterial walls was 15 +/- 4, 30 +/- 15, 65 +/- 32, and 246 +/- 123 J/mm, respectively. In the hard calcified specimens, laser energy required for coaxial lumen enlargement or recanalization was significantly less than that for perpendicular penetration (p less than 0.05), which correlated with the calcium density map indicating an increase from inside to outside.     

Coronary laser angioplasty

With the widespread growth of percutaneous transluminal coronary angioplasty (PTC A), the realization of limitations of balloon angioplasty stimulated the development of alternative revascularization approaches such as laser angioplasty. PTCA is best suited for the treatment of discrete atherosclerotic stenoses, with lower success rates and more difficult application in patients with diffuse atherosclerotic disease or total occlusions [1–3]. Moreover, despite an initially high primary success rate, coronary angioplasty is still plagued by a restenosis rate as high as 57% [4]. The potential advantages of laser angioplasty address the limitations of PTCA. In contrast to balloon angioplasty where the plaque material is compressed or displaced, laser angioplasty ablates the plaque material [5]. This bulk removal of plaque material could improve acute procedural success rates, decrease complication rates, treat “untreatable” lesions, and decrease restenosis rates. Because laser energy can vaporize atherosclerotic plaque, there may be no requirement for a preexisting channel, and therefore laser angioplasty may have a high success rate for the treatment of coronary occlusions. In its best embodiment, laser angioplasty offers the potential for passing a fiberoptic catheter through the entire length of the coronary circulation to vaporize all atherosclerotic plaque along the arterial wall. This applicability for the treatment of diffuse atherosclerotic disease would offer treatment opportunities currently unavailable with conventional bypass surgery or angioplasty. © 1994 Wiley-Liss, Inc.     

Percutaneous recanalization of arteries: Status and prospects of laser angioplasty with modified fibre tips

Percutaneous balloon dilatation of arterial stenoses is a firmly established non-surgical treatment of ischaemic disease. The number of percutaneous transluminal coronary angioplasties performed per year in the USA approaches the number of coronary artery bypass graft operations. A great number of novel percutaneous recanalization schemes address the major problems of balloon angioplasty: failure to cross the stenosis (occlusion), failure to dilate effectively (15–20%), acute complications (5%) and re-stenosis within six months (30–40%). Laser energy can effectively evaporate atheromatous plaque, but delivery by an unmodified bare fibre creates only a small channel and carries a high risk of vessel-wall perforation in the coronary arteries. It appears impossible to maintain an axial position in small, tortuous and moving arteries with multiple side-branches. Coronary lesions are anatomically and structurally heterogeneous. Reduction of the perforation risk is being approached by four strategies: (a) optimization of the power source; (b) enhancement of laser-light absorption by plaque relative to artery wall; (c) improvement of plaque recognition; and (d) modification of the delivery system, which is discussed in detail. Recanalization of occluded femoropopliteal arteries with the 2.0-mm metal laser probe has proved to be safe and effective in more than 100 patients. The 2.2-mm rounded sapphire contact probe has been used with success in the peripheral arteries of over 30 patients. The recanalization mechanism of both probes is not yet fully understood. Closed-chest attempts at recanalization of coronary arteries by the 1.7-mm metal laser probe have been reported in 13 patients, with success in the majority. There were no complications requiring emergency surgery. The possible occurrence of embolism or spasm in three cases warrants a cautious approach to application of the metal laser probe in the coronary catheterization room. The primary benefit of laser recanalization with modified fibre tips is the possible transformation of a candidate for surgery into a candidate for balloon angioplasty. It remains to be established whether prior laser debulking of the atheroma will reduce the incidence of acute complications of balloon dilatation and will reduce restenosis in the subsequent year. In the past two years an avalanche of laser and non-laser recanalization schemes have been developed. In peripheral arteries, early results of most methods have shown an acceptably low incidence of acute perforations or other complications. The human arterial wall can take a heavy beating, both mechanically and thermally. In the next decade, catheter intervention techniques will progressively contribute to the treatment of peripheral and coronary artery disease.     

Ultrasound characteristics of recurrent carotid disease: hypothesis explaining the low incidence of symptomatic recurrence

The true incidence of recurrent disease after carotid endarterectomy (CENDX) is unknown, but noninvasive hemodynamic testing shows a paradox between the incidence of hemodynamically significant recurrent stenosis (RS) and the presence of symptomatic disease. We have shown that real-time B-mode ultrasound imaging can demonstrate the gross pathology of the arterial wall and plaque and their surface characteristics. Therefore we reviewed the clinical data and B-mode studies performed 6 months to 15 years after 276 carotid endarterectomies. Preoperative and perioperative risk factors and associated symptoms on follow-up were stored on computer. The patients were divided into three groups by the anatomy of their B-mode study. The majority of the studies were normal (203 [73.5%]), 42 (15.2%) showed mild disease, and 34 (12.3%) demonstrated significant RS. The RS group had a statistically significant increase in incidence of known lipid abnormalities (p less than 0.05), associated peripheral vascular disease, previous myocardial infarctions, and ulcerated plaque on the original carotid endarterectomy (p less than 0.01). The site of RS appeared related to the time of detection by B-mode ultrasound imaging. Internal carotid RS developed late (greater than 4 years), as did RS of the bifurcation. By contrast, stenosis at the common carotid level developed earlier. These findings suggest different pathogenic mechanisms--for the former, redevelopment of atherosclerosis; for the latter, accentuation of preexisting atherosclerosis perhaps by hemodynamic factors. Finally, in the 26 vessels with RS without occlusion, there was an 8% incidence of plaque ulcer or hemorrhage vs. a 62% incidence in 79 primary atherosclerotic plaques previously studied by both B-mode and pathologic examination. The low incidence of plaque characteristics associated with symptomatic disease may account for the low incidence of symptomatic disease associated with RS.     

Initial experience with the "Smart" laser in the treatment of atherosclerotic occlusions

A dual laser system capable of distinguishing atherosclerotic plaque from components of normal arterial wall was used to deliver laser energy to cut a channel through occluded vessels. This system was used to facilitate balloon angioplasty of short (3-17 cm) total occlusions of the superficial femoral or popliteal arteries in 17 patients. In 10 patients the occluding lesion was traversed by the laser wire and patency was effectively restored by balloon angioplasty. Satisfactory luminal patency has persisted for 2 to 12 months (mean 6 months) in 9 cases; the lesion in the tenth patient restenosed at 3 months. The laser procedure was unsuccessful in all 3 cases with occlusions over 10 cm and in 4 others. There were no clinically important complications. This experience suggests that most patients who presently require interventional treatment can be managed by standard angioplasty methods and/or require a bypass operation. The "Smart" laser is safe and effective short-term in facilitating angioplasty in some patients in whom standard angioplasty techniques are not feasible. The implications of these findings are discussed.     

Perforations in recanalization of arterial occlusions of the femoropopliteal area

Interventional recanalizations may induce wall perforations. The aim of this study was to evaluate the incidence and the management of this complication in chronic femoropoliteal occlusions. 512 cases undergoing interventional recanalization (PTA or Excimer laser-assisted angioplasty) of femoropopliteal occlusions between 5 and 32 cm in length (mean: 13.8 cm) were included. Perforations were immediately examined by angiography or colour-coded ultrasonography (7.5 MHz). Perforations were observed in 22/512 cases (4.3%). The event was coincident with guide-wire manipulations in 16/512 cases (3.1%), laser catheter advancement without wire guidance in 3/58 cases (5.2%), and balloon dilatation in 3/431 cases (0.7%), while lasering via wire guidance (n = 408) did not induce perforation. Combining treatment with prolonged balloon dilatation (success: 6/8, recurrent bleeding: 4/6), ultrasound-guided compression (UGC; success: 20/20) and regulation of anticoagulation, all active bleedings could be terminated. Due to perforation, 12/512 cases (2.3%) required repeated interventions for successful recanalization. Except hematomas of 15-320 ml volume (ultrasound measurement) and prolonged hospital stays for 24-72 h, no further clinical sequelae resulted. In conclusion, perforations occurring during recanalization of long and chronic femoropopliteal occlusions have to be considered as primary interventional failure. However, with immediate treatment including UGC, the risk of serious clinical sequelae is low.     

Laser recanalization in high risk patients

Laser recanalization was attempted in 13 patients in whom the risk of surgical therapy was increased by severe angina, infection, absent venous conduit, or recent deep venous thrombosis, and in 4 patients at high risk for limb loss due to severe infrapopliteal arterial occlusive disease. Total occlusions of the superficial femoral, tibial, or peroneal arteries were treated. Recanalization was accomplished using Argon laser power and a Spectraprobe-PLR. Two patients also required common femoral artery endarterectomy to improve inflow. Laser recanalization was successful in 9 patients (53%), and 8 (47%) had relief symptoms. None of the 4 patients with tibial and peroneal artery occlusion had successful recanalization or limb salvage. Restenosis or reocclusion developed in 4 patients during the first year after successful recanalization, but only 1 had recurrent symptoms. Limb salvage was initially achieved in 5 of 8 recanalization failures by surgical reconstruction but 3 developed graft infections requiring graft removal in 2 and amputation in 1. Thus, laser recanalization can accomplish limb salvage in selected patients whose medical or surgical risks complicate arterial bypass surgery.     

Natural history of asymptomatic carotid plaque

In April 1981, a total of 297 carotid arteries were examined prospectively. All patients were asymptomatic and were referred to the peripheral vascular laboratory at Good Samaritan Medical Center, Phoenix, for real-time B-mode ultrasonography. A measurement of luminal area stenosis was determined to be either greater or less than 75%. In addition, the ultrasound echo pattern was used to classify plaque as either calcified, dense, or soft. If, for any reason, the patient or physician felt that carotid endarterectomy should be performed, the patient was dropped from the study. In addition, the use of antiplatelet medication or anticoagulants constituted disqualification. Three groups of patients were observed for three years or until symptoms became apparent. Patients in all three groups with stenosis greater than 75% at the time of initial study were at greater risk than their peers without significant narrowing; however, even those patients with less than 75% stenosis were at greater risk if the associated plaque was less organized, ie, soft. A definite trend toward higher risk is seen in plaques of lower density. Only 10% of those patients with calcified plaque and a significantly stenotic vessel have developed symptoms. In contrast, only three patients of the original 42 with soft plaque and a tight stenosis are still being observed. This study appears to confirm that soft plaques have a greater tendency toward subintimal hemorrhage, ulceration, or primary embolization than more well-organized plaques.     

Effect of laser-heated tip angioplasty on human atherosclerotic coronary arteries

Effects of laser-heated-tip angioplasty on arteries is not fully understood. We report histology, ultrasound image properties, and vasoreactivity of human atherosclerotic coronary arteries after exposure to the laser-heated tip catheter. Segments of isolated human coronary arteries were obtained within 5-8 hours postmortem. Side branches were ligated and perfused with Krebs-Ringer solution. Coronary occlusions were recanalized during perfusion using a 1.5-mm tip heated twice with a 10 W argon laser for 10 seconds while two-dimensional 12-MHz ultrasound images were recorded. Images documented vessel recanalization and an increase in ultrasound refractile properties of vessel walls adjacent and 2-5 mm distal to the heated tip. Histologic studies showed charring along the neolumen and extensive coagulation pattern within the plaque. Vasoreactivity was assessed by measuring flow rate changes during perfusion with 100 ml of 10(-5) M serotonin followed by washout with serotonin-free solution. Recanalized arteries showed a 50% increase in magnitude of vasospasm, which was persistent for 5 hours, compared to control atherosclerotic vessels, which relaxed within 30 minutes. In conclusion, laser-heated-tip-irradiated vessels demonstrated plaque coagulation, increased ultrasound refractile properties of plaque, and increased vasospasm, which persisted for several hours.     

Effect of CO2 and blood media on laser probe temperature

Blood may limit laser ablation of arterial plaque by decreasing thermal energy transfer from metal-capped probes to arterial occlusions. Since a gas is a good insulator of heat, CO2 may be a better medium for laser recanalization. To study this possibility, a metal-capped fiber was positioned in a segment of blood-filled polyethylene tubing and activated with an argon laser. Probe temperatures were measured in blood and as the blood was displaced by flowing CO2 gas. Probe temperatures were higher at all powers studied in CO2 gas than in blood. Maximum probe temperatures averaged 518 +/- 24 degrees C after CO2 infusion versus 320 +/- 7 degrees C in blood, (P less than 0.0001). Blood aggregate formation was noted on the probe surface in blood but not in CO2 medium. Thus CO2 gas may be a preferable medium for laser recanalization, since higher probe temperatures are achieved, and the probe surface remains free of insulating blood coagulate.     

Virtual histology and color flow intravascular ultrasound in peripheral interventions

The quality and interpretation of intravascular ultrasound (IVUS) imaging has been revolutionized in recent years by two new and major advances: virtual histology and color flow IVUS. Virtual histology intravascular ultrasound (VHIVUS) is a catheter-based technology where IVUS is generated from the transducer on the catheter tip and the reflected signals from the artery wall produce a color-coded map of the arterial disease. Different histological constituents of the plaque produce different reflected signals and these are assigned different colors (dark green, fibrous; yellow/green, fibrofatty; white, calcified; red, necrotic lipid core plaque). This color-coded map assists the interventionalist in understanding more fully how the lesion will behave at the moment of treatment, whether it will resist complete stent deployment or be liable to embolization. Originally introduced for coronary interventions, VHIVUS is now being applied to peripheral situations. Because it provides a detailed and close-proximity view of plaque, its potential to improve the safety and efficacy of carotid endoluminal repair is stimulating substantial interest. Similarly, color flow IVUS provides greater understanding for the operator of blood flow, and the interface between the vessel wall and the blood stream, lumen size, and success of treatment. Color flow IVUS does not use the Doppler effect, but creates real-time images that resemble color flow Doppler ultrasound. These two technological advances in IVUS have greatly improved the ability of the endovascular specialist to understand the arterial disease they are treating and to assess the completion of treatment.     

Laser arterial disobstructive procedures in 148 lower extremities

Preoperative arteriographic findings in immediate postoperative results as well as follow-up studies of treatment with argon and YAG lasers have been evaluated in 148 lesion found in 137 patients. Preoperative arteriography revealed a solitary lesion in 42 of 148 legs (28%) examined, and a combined lesion was found in the remaining 106 legs (72%). Incapacitating intermittent claudication, rest pain, tissue loss, or a combination of these was an indication for laser arterial reconstruction. None of the argon laser-treated lesions was treated with balloon dilatation, but since March 1988 all appropriate YAG laser-treated lesions were immediately followed by laser-assisted balloon angioplasty. The lesions in 64 of 89 legs (72%) treated by argon and 42 of 59 (71%) treated by YAG were successfully recanalized. However, successful angioplasty was performed in 44 of 89 (49%) and 34 of 59 (58%) lesions, respectively. The recanalization depended on the type of lesion (tight stenosis vs occlusion) and the length of lesion (localized vs total-length occlusion). However, the success rate of recanalization was almost the same as the success rate when both laser systems were used. Argon laser treatment proved successful in 19 of 20 (95%) segmental occlusions in popliteal arteries, whereas YAG laser treatment proved successful in four of five (80%) short segmental (less than 15 cm) occlusions of superficial femoral arteries and in 16 of 23 (70%) long segmental (greater than or equal to 15 cm) occlusions of superficial femoral arteries. In 26 of 36 (72%) total-length occlusions of superficial femoral and popliteal arteries, recanalization was not possible (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Correlation of B-mode ultrasound imaging and arteriography with pathologic findings at carotid endarterectomy

Presently most noninvasive methods for assessing extracranial carotid disease have relied on hemodynamic change associated with significant stenosis. Recent evidence has suggested that both ulceration and/or plaque hemorrhage may frequently play an important role in the pathophysiology of carotid disease. To assess the ability of B-mode ultrasound to provide this anatomic information, in a prospective blinded manner we compared B-mode ultrasound and selective four-vessel arteriography to pathologic specimens obtained at the time of 89 carotid endarterectomies. The presence of ulceration, plaque characteristics (particularly hemorrhage), and luminal diameter were described for each modality. While arteriography detected only 16 of 27 ulcerations (sensitivity, 59%), B-mode ultrasound had a greater sensitivity (24/27, 89%). Both modalities had comparable specificities (arteriography, 73%; B-mode ultrasound, 87%). Moreover, B-mode ultrasound was highly sensitive for demonstrating plaque hemorrhage (27/29, 93%), as well as being quite specific (84%). Assessment of luminal reduction by B-mode ultrasound improved with technologist/interpreter experience and was significantly improved by adding real-time spectral analysis. Because of B-mode ultrasound's sensitivity for imaging ulceration and plaque hemorrhage, it offers significant advantages for the noninvasive detection of extracranial carotid disease.     

Effects of blood flow on laser probe temperature in human arteries

Laser recanalization using metal capped fibers occurs by thermal vaporization of occluding plaque. However, little is known about the effects of blood and flow on the temperature of the laser probe or the arterial wall during lasing. To study this, probe and arterial wall temperatures were measured while a metal capped fiber, activated by an argon laser, was held stationary in a stenotic human peripheral artery. Arteries were perfused with saline and blood, and flow was varied from 0 to 140 cc/min. Probe temperatures were significantly higher in blood than in saline. However, the increased probe temperature achieved in blood was not transferred to the arterial wall. Increasing flow decreased probe temperature in both media, but again arterial wall temperatures were minimally affected. Thus, the presence of blood and flow may significantly affect heat generation and heat transfer during arterial recanalization using metal capped fibers.