A new method is described for the quantitative evaluation of the extent of in vitro laser- induced arterial injury with computer assisted image processing techniques and 3-D reconstruction of histologic sections. Using this approach, accurate measurements of ablated volume and thermally injured volume may be obtained, along with a detailed description of crater shape, symmetry (or lack thereof), and 3-D distribution of residual thermal injury. The reconstructed injury may be rotated to view from various angles, or zoomed to greater magnification. Examination of the total crater may provide insight into damage mechanisms, as well as provide a more accurate assessment of arterial injury which may have important implications on the long term healing response.

Ninety-six transmission spectra were obtained from autopsy specimens of healthy human abdominal aorta. Specimens were irradiated via a 900 micrometers fused silica fiber (contact mode) under normal saline at room temperature (21.5 +/- 1.5 degree(s)C) using an excimer laser (308 nm, 40 Hz, 115 ns, 57 mJ/mm²). The temperature increased at the fiber tip up to 66.8 +/- 8.5 degree(s)C and was monitored by a NiCrNi thermocouple. Tissue samples from untreated areas and from the thermal damage zone next to the ablation area were anayzed by microspectrophotometry (spectral range 250-800 nm, cryosections 24 micrometers , area measured 6/3 (mu) in diameter). The conclusion is, excimer laser irradiation using a high repetition rate in combination with a high output energy changes the optical properties of human vessel walls significantly.

We have recently demonstrated the efficacy of a near-infrared-Raman fiberoptic sensor for use in laser angioplasty and cardiovascular surgery. A major advantage of the Raman-based system over existing guidance techniques is its fingerprinting capability with improved specificity for detecting atherosclerotic tissues both in-vitro and in-vivo. The use of such a fiberoptic sensor will improve the safety of laser angioplasty by eliminating the current risk of vessel wall perforation. Once developed, the device also will be well suited for in-vivo monitoring and characterization of restenosis after balloon angioplasty and in-vivo study of atheroma progression and regression in animal models.

Angioscopy has proved to provide more detailed information on lesion morphology before and after interventional procedures than angiography. Therefore, to evaluate the effects of laser angioplasty, angioscopy was performed in five patients with peripheral or coronary vascular disease who underwent excimer laser angioplasty. The excimer laser was operated at 308 nm, 135 nsec, 25 Hz, and 40 - 60 mJ/mm² and was coupled into multifiber wire-guided catheters of 1.4 to 2.0 mm diameter for coronary lesions and 2.2 mm for peripheral lesions. There were three coronary (one left anterior descending, one circumflex, one right coronary artery) and two peripheral (one common iliac artery, one superficial femoral artery) lesions. Angioscopy was successfully performed before and after laser ablation without any complications in all five lesions. The characteristics of angioscopic findings after excimer laser angioplasty consisted of flaps, fractures of plaques, and abundant tissue remnants. There was no apparent thermal injury. Recanalized channels were small and irregular. These results indicate that (1) angioscopy is effective and safe for evaluation of lesion morphology after laser angioplasty, (2) laser ablation does not result in thermal injury, and (3) irregular channels after recanalization and abundant tissue remnants may explain the suboptimal results after laser angioplasty.

Magnetic resonance imaging (MRI) of atherosclerotic lipids using a stimulated-echo diffusion- weighted (STED) sequence is demonstrated. The STED sequence exploits the large difference in diffusion between lipid (primarily cholesteryl ester) and water. The optimization of the STED sequence is discussed. The results of lipid imaging are corroborated with nuclear magnetic resonance (NMR) spectroscopy. This technique is non-invasive, and therefore, it is potentially useful in following the progression of the disease in animal models and in humans.

A coupled integrating sphere system was used to measure the diffuse reflectance and transmission of rabbit aortae. Tissue absorption coefficients and scattering coefficients were calculated by a Kubelka-Munk model, and the results were compared. The absorption coefficient in (Beta) -carotene stained plaque was found to be greater than that in normal controls by fourfold at 488 nm wavelength, and by threefold at 514 nm wavelength. The scattering coefficient, however, did not change significantly between (Beta) -carotene stained and non-stained rabbit aortae.

Selective thermal coagulation of discrete portions of the myocardium is becoming an accepted method for the treatment of various supraventricular tachyarrhythmias. This paper investigates the use of conventional ultrasonography for the detection and measurement of thermally coagulated lesions in myocardial tissue. Lesions were created in necropsied canine myocardium using a side-emitting laser catheter delivering cw Nd:YAG laser energy. Following irradiation, the sites were scanned with a 20 Mhz ultrasound catheter and the maximum depth of thermal damage was measured from the ultrasonographic imagery. The surface dimensions and transmural depth of thermal damage was then measured morphometrically with a video microscopy system. Depth measured by ultrasound was found to correlate well with depth by morphometry (r equals 0.78). Both depth measured by morphometry and by ultrasound were found to correlate well with the volume of thermal damage by morphometry (r equals 0.83 and r equals 0.77 respectively). Intraventricular ultrasonography may prove useful for in-vivo detection and measurement of thermally induced lesions in the myocardium. Additionally, it may also be applied for guidance and real-time monitoring of thermal coagulation of the myocardium during various arrhythmia ablation procedures.

The initial enthusiasm related to laser angioplasty witnessed just a few years ago has waned considerably owing to the failure of thermal laser technology to meet clinical expectations. While the initial procedural success rate for the hot-tip probe was acceptable (about 79% in most series), mid- and long-term studies have shown a disappointing recurrence rate. These follow-up data have dictated a new course for the development of laser technology in the vascular system. We evaluated a new delivery system using holmium:YAG laser energy for its ability to recanalize obstructive peripheral atherosclerotic lesions in over 200 patients. The 2.5 mm Spectra Holmium laser probe delivered 2100 nm laser energy at 1000-1200 mJ/pulse at 10 Hz to achieve a maximum energy density of 4000 mJ/mm2. Maximum temperature was 85 degC. Among all lesions, 54% could not be crossed with a wire. Of these, 77% were recanalized by the probe by the probe. Average lasing time for occlusions: 44.8 seconds, and 71.6 seconds for stenoses. Residual stenosis after lasing: 68% in occlusions and 59% in stenoses. Laser success in all lesions was 76%. The Spectra Holmium probe was successful in opening occlusions but had little effect on stenoses due to the small probe size and limited laser aperture. There were no complications related to the laser, and no thermal effect was noted on direct angioscopic observation. More effective multifiber catheters are needed for greater tissue ablation.

The holmium:YAG laser, a new solid-state, infrared laser system, is being used increasingly more often for treating peripheral vascular disease. We discuss the early use of this device in coronary laser angioplasty. The holmium:YAG laser has several advantages over excimer systems and may prove to be an effective adjunctive to coronary balloon angioplasty.

Holmium laser angioplasty was performed in the atheromatous carotid artery of 10 rabbits to evaluate this mid-infrared laser as an alternative energy source for angioplasty. An additional 10 rabbits served as a control group. The laser emitted light at a wavelength of 2120 nm with pulse durations of 150 microsecond(s) . The energy density was 17.5 J/cm². Cross sections were analyzed in regard to laser specific injury 7 and 14 days following laser irradiation. Staining of (alpha) -actin was used to identify smooth muscle cells (SMC), and bromodesoxyuridine labeling was carried out to determine the extent of proliferating cells. Integrity of the lamina elastica interna fibers was disrupted in 6 of 10 animals. In all animals, loss of medial SMCs was observed 7 and 14 days after treatment. Quantification of SMCs undergoing DNA synthesis in the intima and media showed a significant increase of labelled cells following laser irradiation. This proliferative response resulted in a significant increase of intimal thickening after laser ablation.

Recently, access to the coronary arteries became available to laser angioplasty based upon a new concept which utilizes a pulsed laser source and multifiber, `over-the-wire' guided catheters. The aim of this study was to evaluate the early and long-term results and the side effects of coronary angioplasty using an excimer or a Holmium:YAG laser. Forty consecutive patients were treated with the Holmium:YAG laser (group I) and 46 consecutive patients were treated with the excimer laser (group II). The primary laser angioplasty success rate was 55% and 71.7% for group I and II, respectively. It was similar in calcified and in non-calcified lesions and in total occlusions and stenoses. Laser stand-alone therapy was obtained in 5.0% of group I patients versus 21.7% in group II patients (p < 0.05). Failures were due to the inability for the laser catheter tip to reach the lesion, to cross the obstruction, or to obtain a significant reduction in stenosis. They were more frequent in group I than in group II patients (45% versus 28.3%). Complications included acute closure in 7.5% of group I and 17.1% of group II patients and spasm in 10.0% and 13.0% of group I and group II patients, respectively. Dissection occurred more frequently in group II than in group I patients (28.3% versus 7.5%, p < 0.04). The angiographic patency rate at 6 month follow up was 33% and 29% for group I and group II patients, respectively. Multifiber, wire-guided catheters provide an easy access to the coronary arteries. Excimer laser angioplasty using large, densely packed catheters is effective but induces a high rate of dissections. Technical improvements are required to ablate more tissue to possibly reduce the restenosis rate. Further studies ar needed to elucidate the mechanism of side effects to reduce their impact on restenosis rate.

Percutaneous coronary laser angioplasty with a multifiber catheter coupled to a pulsed holmium:YAG (2.1 micrometers ) laser was performed on seven lesions in six patients who were candidates for elective coronary angioplasty. Following passage of a guidewire across the lesion the laser catheter was advanced to the lesion. The laser was used in the free running mode with 250 microsecond(s) ec pulses and delivering 50 mJ to 400 mJ per pulse at 5 Hz. Two sizes of laser catheters were used 1.6 mm and 2.0 mm in diameter. The 1.6 mm diameter catheter delivered fluences ranging from 335 mJ/mm² to 2,680 mJ/mm² and the 2.0 mm multifiber catheter delivered fluences of 219 mJ/mm² to 1,754 mJ/mm². Successful recanalization was obtained in every case. The average stenosis reduction following laser angioplasty alone was from a baseline of 96.6 +/- 3.5% to 38.6 +/- 24.1% (p < 0.01). Six of the seven lesions required adjunctive therapy with other angioplasty devices for further reduction of the stenosis to 12.9 +/- 4.9%. There were no complications specifically related to the laser angioplasty procedure. Two patients, however, did have abrupt occlusion of the treated artery following adjunctive angioplasty treatment. In this small series of patients we are encouraged by the ability of this laser angioplasty system to successfully recanalize coronary artery stenoses in a safe and effective manner. Larger numbers of patients are required to confirm these results and further investigate the clinical utility of this device.

The effects of pulsed Holmium:Yttrium Scandium Gallium Garnet (Ho:YSGG) laser energy on cadaveric human arterial tissue were compared with our current clinical laser energy source -- Neodymium:Yttrium Aluminum Garnet (Nd:YAG). Dose response, arterial recanalization in an artificial circulation model, and debris formation were assessed. Ho:YSGG was found to be more efficient at ablation than the Nd:YAG, and created a similar quantity of debris during recanalization. Ho:YSGG was also able to ablate calcified arterial occlusions which the Nd:YAG could not. However, Ho:YSGG led to more arterial perforations during the attempted recanalization of very curved vessels, most likely due to the combination of a heavily absorbed wavelength and the relative inflexibility of the 600 micrometers optical fiber used in the experiments. In spite of this shortcoming, Ho:YSGG remains an attractive source for laser angioplasty.

Pulsed laser coronary angioplasty with an excimer or a holmium-yttrium-aluminum-garnet (Ho:YAG) laser may become an alternative treatment for patients with coronary artery disease. However, little is known about its acute consequences on the normal arterial wall. This study was designed to examine the acute histologic consequences of these two pulsed lasers on the arterial wall of normal iliac arteries in rabbits. Irradiation with each laser was performed in 15 normal iliac sites on eight male New Zealand white rabbits. The excimer laser was operated at 308 nm, 25 Hz, 50 mJ/mm²/pulse, and 135 nsec/pulse and the Ho:YAG laser was operated at 2.1 micrometers , 3/5 Hz, 400 mJ/pulse, and 250 microsecond(s) ec/pulse. The excimer and Ho:YAG laser were coupled into a multifiber wire-guided catheter of 1.4 and 1.5 mm diameter, respectively. The sites irradiated with excimer or Ho:YAG laser had the same kinds of histologic features, consisting of exfoliation of the endothelium, disorganization of internal elastic lamina, localized necrosis of vascular smooth muscle cells, and fissures in the medial layer. However, the sites irradiated with excimer laser had lower grading scores than those irradiated with Ho:YAG laser (p < 0.05). Laser irradiation with excimer or Ho:YAG laser of normal arteries results in localized mechanical vascular injury.

This study was performed to assess the ablational properties of the 1.4, 1.7, and 2.0 wire- guided multiple fiber catheters coupled to an XeCl excimer laser. The samples of human post- mortem aorta were irradiated in blood at fluences of 40, 50, and 60 mJ/mm². Our results indicate: (1) An increase in the active irradiation coverage results and an increase in the ablation efficiency. (2) The ablation efficiency is not fluence-related using the 1.4 or 1.7 multiple fiber catheter but depends on fluence using the 2.0 multiple fiber catheter. (3) The depth of tissue ablated with the multiple fiber catheter depends primarily upon the proportion of the active irradiation coverage at the catheter tip. (4) The 2.0 multiple fiber catheter induces craters surrounded by a larger zone of tissue damage than that observed with the 1.4 or 1.7 multiple fiber catheter. (5) The 2.0 multiple fiber catheter should be used cautiously in laser angioplasty because of its high penetration and its possibility of arterial wall damage.

The use of the excimer laser for ablation of atherosclerotic plaque in the coronary and peripheral vasculature has been evaluated extensively in recent years. (Approximately 3,800 patients treated worldwide.) It may be possible to utilize an ultrasound image as a guide during the excimer laser procedure to determine whether additional plaque extraction should be performed. Also, as excimer laser catheters become more lesion specific and steerable it is imperative that the interventionalist is provided with a method to judge lesions other than by the `blind' guidance provided with contrast angiography. Intravascular ultrasound is a technology which could provide guidance to differentiate between normal and stenotic wall in high-grade eccentric lesions. For real-time monitoring with the excimer/ultrasound combination, we utilized a 2.2 mm peripheral excimer laser angioplasty catheter (Spectranetics Corporation) incorporating a 2.5 French intravascular ultrasound transducer within the central guidewire lumen (Boston Scientific Corporation). In this paper, we discuss our preliminary in- vivo experiments designed to illustrate ultrasound-guided excimer laser angioplasty and monitor laser ablation in stenotic porcine iliac arteries.

In this paper a novel laser angioplasty probe is presented in which the emitted beam from a multi-mode fiber is both radially reflected and simultaneously focused to form a well-defined ring of high intensity light which is concentric with the fiber axis. The intensity distribution of the probe emission will thus exhibit a maximum at a given radial distance from the fiber axis, depending on the particular geometry of the probe. As a consequence of this convergence at a particular radius, this probe has been demonstrated in vitro to act in a self-limiting manner to enlarge an existing lumen in human atherosclerotic vessel tissue using a 4W argon laser. The small diameter (1 mm) of the probe suggests the viability for in vivo angioplasty applications. A set of fiber probes having a variety of focal ring diameters ranging from 1 to 4 mm have been fabricated, tested, and analyzed. Theoretical and experimental intensity distributions are presented, and the important parameters of the probe designed for this and additional applications are discussed.

Excimer laser angioplasty was performed in 59 patients (44 males and 17 females, mean age 63 +/- 9 years, range 39 - 77) affected by peripheral vascular disease. Fifty patients had a total occlusion of the superficial femoral artery, three of the iliac artery, and one of the popliteal artery; seven patients showed a subocclusive stenosis of the superficial femoral artery. A commercial excimer laser (Technolas Max-10) was used at the Xenon-Chloride wavelength of 308 nm. The laser operated at 120 ns pulse length and at 20 Hz repetition rate. Applied energy fluence was 20 mJ/pulse. The energy was delivered through a multifiber catheter, which combines 12 (7F) or 18 (9F) fibers (260 micron diameter each), concentrically arranged. Balloon dilatation was associated in 51 patients. Successful recanalization was obtained in 59 out of 61 patients (97%). Failure to recanalize the occluded arteries occurred in two cases, and was due to dissection. Early thrombosis and reocclusion (within 48 hours) was observed in five patients. The cumulative patency rate was 56% at one year. On the basis of these results, excimer laser assisted angioplasty seems a feasible and safe procedure. However, this technique did not solve the restenosis problem. A wide application of excimer laser as a stand alone approach can be foreseen for treatment of peripheral vascular disease.

Fluorescence response of canine heart tissue is studied in an attempt to localize the conduction system atrioventricular (AV) node. Data is collected for 364 nm and 308 nm illumination via a 750 micrometers diameter fiber placed against the tissue. This is done for sample locations in the right atrium, AV ring, and right ventricle, and for a rectilinear grid of sample locations in the AV node region. Sample locations are marked via tissue ablation with a 2.1 micrometers Ho:YAG laser and removed for histological analysis. Fluorescence responses are given for 364 nm and 308 nm illumination. No evidence of distinguishable fluorescence by the AV node is seen at either wavelength.

Laser-induced fluorescence spectroscopy has been developed as a guidance system for laser angioplasty. We have investigated fluorescence spectroscopic detection of neo-intimal formation from the endoluminal surface of stent implanted arteries. Nine White Leghorn roosters had Palmaz-Schatz intra-abdominal aortic stent implantation, nine had aortic balloon angioplasty. Five roosters with stent implantation and four roosters with balloon angioplasty were on a high cholesterol diet and the remainder were on a normal diet. Roosters were sacrificed at intervals of 1, 2, 4, 8, and 12 weeks after intervention. Fluorescence emission spectra were recorded from aortic segments during excimer laser excitation at 308 nm (XeCl, 1.5 - 2.0 mJ/pulse, 5 Hertz). Spectra were then correlated with histology. Fluorescence emission intensity recorded from abdominal aortic segments with stent implantation was higher than that of adjacent segments (p < 0.002 at 440 - 460 nm). Abdominal aortic segments of roosters on normal diets with stent implantation and balloon angioplasty were similar (p equals NS). With cholesterol feeding, aortic spectra from roosters with stent implant had higher intensity at 440 - 460 nm than spectra from aortic segments with balloon angioplasty (p < 0.004). Morphometric analysis demonstrated a twofold increase in intimal thickness in stent segments from cholesterol fed roosters when compared to similar segments of roosters on normal diets (p < 0.005). Our conclusion is: (1) Fluorescence emission spectra can be used to detect native artery fluorescence in stent implant areas. (2) Neo-intimal thickening at the stet implant site can be distinguished from adjacent areas by fluorescence emission spectra. (3) Cholesterol feeding increased neo-intimal thickening.

Laser-induced fluorescence spectroscopy has been used for the detection of advanced atherosclerotic lesions. Angioplasty balloon-mediated injury was examined spectroscopically in order to assess the sensitivity of fluorescence spectroscopy for detection of early atherosclerosis. Abdominal aortic balloon angioplasty was performed via femoral artery cutdown in nine White Leghorn roosters (five normal, four atherogenic diet). Roosters were sacrificed at 1, 2, 4, 8, and 12 week intervals. Fluorescence emission spectra (n equals 114) were recorded from each aortic section (XeCl excimer laser, 308 nm, 1.5 - 2.0 mJ/pulse, 5 Hz). Changes in normalized fluorescence emission intensity were correlated with selected sections of histology. All balloon-injured segments showed intimal fibrous proliferation. For intimal thickness measuring > 70 (mu) , fluorescence emission intensity was decreased at 440 - 460 nm (p < 0.0005). Lesions complicated by thrombus also had lower fluorescence emission at 425 - 450 nm when compared to histologically normal aorta (p < 0.009). In injured segments high cholesterol diet resulted in lower recorded fluorescence emission at 440 - 460 nm (p < 0.001) associated with the increase in intimal thickness. Spectra from uninjured elastic aorta (aortic arch and thoracic aorta) had greater fluorescence intensity at 380 - 445 nm than muscular (abdominal) aorta (p < 0.01), therefore, only spectra from injured and uninjured segments of corresponding areas of the aorta were compared. The conclusion is: (1) Early intimal proliferative changes after angioplasty can be detected by fluorescence spectroscopy. (2) Spectra from elastic thoracic aorta differ significantly from the spectra of muscular abdominal aorta.

The development of laser systems suitable for vascular angioplasty is a multidisciplinary endeavor that includes development of the laser energy source, guidance modality, delivery catheter, and assessment of clinical applicability. In this paper we report on the design criteria of percutaneous coronary catheters and how these have guided development of the Spectranetics excimer laser angioplasty system. The Spectranetics CVX-300^TM excimer laser angioplasty system was designed for safe application in the cardiac catheterization laboratory while maximizing system maintenance intervals. Recent improvements in catheter design and construction have been directed at optimizing target lesion acquisition and treatment. Lesion access and alignment have been facilitated through the use of optical fiber bundles with increased flexibility. Ablation efficiency has been improved by a combination of increased active fiber area and optimization of the radial location of the fiber array compared to the original devices. Engineered stiffness profiles have been improved and lubricous coatings incorporated to optimize force transmission and tactile feedback for the clinician. Initial clinical results appear favorable. In particular, excimer laser angioplasty appears to have an advantage in the treatment of complex coronary lesions such as diffuse coronary arterial disease, total occlusions, ostial stenoses, moderately calcified lesions, and vein graft disease. In these settings, improved procedural success rates and a lowered incidence of complications have been observed compared to conventional balloon PTCA angioplasty. Examples of complex coronary lesion cases as well as a summary of the data of the initial clinical results from the multicenter trial are also presented in this paper.

The morphology and function of the cardiac chambers have been evaluated clinically using cineventriculography, computed tomography, magnetic resonance imaging, and endomyocardial biopsy. Excluding the invasive technique of biopsy where tissue is actually removed, these other non-invasive techniques reveal only indirect evidence of endocardial and subendocardial pathology and, therefore, allow the potential for misdiagnosis from insufficient data. Fiberoptic examinations, as recently demonstrated in coronary, pulmonary, and peripheral vessels, allow direct observation of pathology otherwise unobtainable. Recently, similar techniques have been applied to examine the cardiac chambers of dogs and the right heart of humans. In this study, we examine the feasibility and safety of percutaneous fiberoptic cardioscopy of the left ventricle in patients with myocarditis.

In this work we observed the result of CO₂ laser surgery used to remove hyperplastic gingiva in patients who were under cyclosporine maintenance treatment after they underwent heart transplant. The objectives were to reduce, as much as possible, bleeding, to avoid any subsequent intervention to remove stitches, and to minimize the operatory and postoperatory discomfort for the patient. Our data confirm the advantages of CO₂ laser surgery when used to remove overgrowing tissue in accessible areas.

Balloon angioplasty of coronary obstructions is limited by a 40% angiographic restenosis rate six months after the intervention. Myointimal hyperplasia is a major contributor to restenosis. In 77 normal rabbits we examined the question whether severe thermal interventional injury to the iliac artery wall would result in less myointimal hyperplasia than severe mechanical injury induced by balloon dilation. Eight weeks after percutaneous injury by electrical spark erosion, the metal laser probe, cw Nd:YAG laser energy through the sapphire contact probe, 90 degree(s)C RF heated balloon dilation, or standard balloon dilation the neointima thickness measured up to 380 micrometers . When thermally and mechanically damaged walls were compared, myointimal hyperplasia was similar. We conclude that in the normal rabbit the arterial wall healing response after any injury is neointima formation which is the vessel wall's expression of the general pattern of wound healing. It is inferred that alternative modes of injury in new recanalization techniques will lead to induced restenosis rates.

Our experience on excimer laser angioplasty in peripheral arteries is reported. During three years 34 patients were treated with improved techniques, following the evolution of the laser and of the delivery systems. Encouraging results in the laser stand alone technique allowed us to reduce the association with balloon dilatation to a limited number of cases.

To examine the process of microscopic changes during arterial thrombosis and thrombolysis a novel angiomicroscope (3 or 4 mm in diameter, magnification rate X 145) was introduced through a sheath into the right iliac artery of anesthetized dogs. A small portion of the luminal surface was mechanically damaged and processes of thrombogenesis were examined. Platelet aggregation on the damaged portion, fibrin thread growth on the exfoliated endothelium and naked subendothelial layers, trapping of red blood cells by fibrin networks, and gradual growth of mixed thrombi were observed. Following administration of prourokinase, or t-PA, dispersion of platelet aggregates and red blood cells, simulating sandstorm and gradual melting of fibrin, were also observed. The results indicate that detailed microscopic processes of thrombogenesis and thrombolysis can be observed percutaneously by angiomicroscopy.

The feasibility of a novel catheter system of percutaneous transluminal cardiomyotomy and valvulotomy was examined in anesthetized dogs. The system was composed of a guiding balloon catheter, a cardioscope, and a pair of scissors with or without guide wire at the distal tip. The system without guide wire was introduced into the left ventricle, the balloon was inflated and was pushed against the endocardial surface. After confirmation by cardioscopy, the targeted tissues were incised by the scissors. By these maneuvers, the trabeculae, papillary muscles, and chordae were incised or transected in 7, 6, and 6 of 7 dogs, respectively. The system without guide wire was advanced to the aortic root, the guide wire was introduced into the left ventricle to prevent dislocation of the catheter system, the balloon was manipulated against the aortic cusp and the cusp was successfully incised with cardioscopic guidance in all five dogs. The results indicate that percutaneous transluminal cardiomyotomy and valvulotomy can be performed with cardioscopic guidance.

To visualize small vascular luminal changes which can not be detected by conventional angioscope, a new angiomicroscopy system was developed and its feasibility was examined in anesthetized dogs and isolated human coronary artery. The system was composed of a 3 mm or 4 mm in diameter rigid angiomicroscope (magnification rate: 150 X on a 14 inch monitor), a CCD camera, and monitor television. An angiomicroscope was introduced in retrograde fashion through a sheath into the right iliac artery of anesthetized dogs, and the luminal changes were examined during infusion of saline. Details of the exfoliated endothelium and naked subendothelial layers, and the changes due to vasospasm, could be identified by the system. These changes could more easily be discriminated after staining with Evance blue, Tripan blue or Fucsin. In removed and perfused human coronary artery, small luminal changes due to atherosclerosis could also be identified. By simultaneous insertion of a metallic thread (70 (mu) in diameter) the size of the changes could be calibrated. Light microscopic examination was performed after removal and staining of the targeted portion. It was revealed that 10 (mu) or more in diameter could be discriminated. The results indicate potential use of this angiomicroscopy system for percutaneous transluminal identification of the small vascular changes which otherwise cannot be detected.

Feasibility of an Nd:YAG laser system with an automatic controller of hot-tip temperature was examined in 15 segments of the ileo-femoral artery of 13 patients. Before lasing, the temperature of the hot-tip to be attained was preset. Also, the upper limit temperature at which lasing was to be stopped was preset. A 1.8 mm hot-tip was introduced into the obstructed segments (14.7 +/- 6 cm in length) and lasing was performed. The temperature actually attained and the arterial luminal changes were monitored by monitor television and angioscopy, respectively. Complete recanalization was obtained without any complications in all segments. No thermal effects below 50 degree(s)C, coagulation at 100 degree(s)C, carbonization at 200 degree(s)C, and sticking of the hot-tip at 300 degree(s)C, could be observed by angioscopy. Rapid recanalization was obtained at 200 - 300 degree(s)C. The results indicate that the temperature-controlled laser system is feasible and tip temperature of 200 degree(s)C - 300 degree(s)C is maximal for treatment of chronic arterial obstruction.

Since December 1986, 140 laser angioplasty procedures have been carried out using a pulsed Nd:YAG laser (Lumonics Ltd. Rugby, UK). The laser produces 100 microsecond(s) ec pulses at a wavelength of 1064 nm and a repetition rate of 10 Hz. All procedures were carried out for critical ischaemia or severe claudication in patients who had complete occlusion of the superficial femoral artery (SFA). All occlusions were over 5 cm in length or previous failures of balloon angioplasty and would otherwise have proceeded to bypass surgery. The occlusion was approached percutaneously via the ipsilateral femoral artery and successful recanalization was followed by balloon dilatation. Problems with access were encountered in 18% of the procedures, about half of which were subsequently repeated with successful access. There was failure of recanalization in 26% of the cases, five due to vessel perforation. These did not result in clinical sequelae. Early occlusion (< 24 hours) occurred in nine cases, most being related to severely ischaemic limbs with very poor run-off. Three of these were salvaged with thrombolytic therapy. We have meaningful follow-up of those cases where we were successful. Forty-four patients remain patent, at a mean of 30.4 months post-procedure (range 3 - 47 months). Of the 19 patients who reoccluded, (mean 12.1 months, range 1 - 26 months), seven had bypass grafts, three underwent amputation (all three presented with rest pain), two had repeat laser procedures, and seven were treated conservatively. Thirteen percent of the patients have died, chiefly from cardiovascular disease elsewhere. Overall, continued patency has been achieved in 32% of limbs considered for laser treatment, but this rises to 60% of all initially successful procedures. In conclusion, laser angioplasty may avoid the need for vascular surgery in a significant number of patients.

Percutaneous mechanical rotational ablation with the rotablator can be used effectively as a stand alone treatment for coronary arterial lesions, including those with angiographic morphology considered unfavorable for balloon angioplasty (eccentric, at bends, bifurcating, calcified, ulcerated, completely occluded_, as well as for balloon angioplasty procedure failures. The use of single rather than multiple burrs without balloon assistance, the use of fewer passes and of the nitroglycerine infusion through the rotablator catheter have considerably shortened the time necessary to complete a rotational atherectomy. Further, the apparently infrequent occurrence of post procedure abrupt closure makes this technique attractive in the clinical management of patients with complex coronary artery lesions.

Cavitation previously has been observed in association with ultrasonic angioplasty and high- frequency rotational atherectomy. This study evaluates the production of cavitation accompanying the use of several catheter-based devices under development or in current use in the practice of interventional cardiology. Catheters were examined in an in vitro model, and cavitation was evaluated using standard ultrasound imaging equipment. Cavitation was detected with each of the devices that effects tissue ablation, but not tissue resection. Devices produced characteristic patterns of cavitation dependent on the mode of energy release of the device. The size, but not the intensity, of the cavitation effect was proportional to the energy output of the devices. The precise role of cavitation in the mechanism of tissue ablation remains uncertain.

Reports of successful use of excimer laser coronary angioplasty for complex coronary artery disease abound, yet firm indications for its use have not been defined. We attempted to treat 858 coronary stenoses in 764 consecutive patients (mean age 61 years; range 32 - 91 years; 75% men; 76% with Class III or IV angina) with excimer laser angioplasty at 308 nm. Successful treatment was achieved in 86% of patients, as indicated by <EQ 50% residual stenosis and no in-hospital complication. To define the potential indications for excimer laser angioplasty, we used relative risk analysis. This showed that certain angiographic features, such as lesions at a vessel bifurcation (odds ratio, OR equals 0.46; 95% confidence interval 0.23, 0.88; P equals 0.017;) or in a tortuous segment (OR equals 0.54; 95% CI equals 0.34, 0.88; P equals 0.041), have decreased likelihood of clinical success. On the other hand, ostial stenoses (OR equals 1.06; 95% CI equals 0.44, 2.56, P equals 0.903) and saphenous vein graft lesions (OR equals 2.17; 95% CI equals 0.98, 4.82; P equals 0.051) have acceptable success rates. Diffuse disease (> 20 mm), total occlusions and calcified lesions were treated as successfully as all other lesion types. Successful treatment with excimer laser coronary angioplasty was also achieved in almost all patients (15/16) who had a prior unsuccessful attempt at balloon angioplasty in the lesion was crossed with a guidewire yet resists either balloon catheter passage or full dilatation. Follow-up angiography was obtained in 70% of eligible patients. Angiographic restenosis, defined by > 50% stenosis, was seen in 60% of patients. Relative risk analysis showed an increased risk of restenosis when adjunctive balloon angioplasty was not used (OR equals 1.68; 95% CI equals 1.02, 2.28; P equals 0.039). Other variables known to affect the outcome of balloon angioplasty, such as lesion length or stenosis in degenerated saphenous vein bypass graft, did not influence the restenosis rates. This analysis defines the profile of risk for excimer laser angioplasty and now provides a sound basis for future, rigorous comparison of excimer laser and balloon angioplasty to balloon angioplasty for a group of lesions that appear to have acceptable success rates with excimer laser coronary angioplasty, which we have denoted the `alpha class' -- saphenous vein lesions, long lesions, ostial stenoses, lesions in calcified vessels, total occlusions, and balloon dilatation failures. Although adjunctive balloon angioplasty may be beneficial, restenosis remains a significant limitation of the procedure and will restrict the usefulness of excimer laser coronary angioplasty for may other types of lesions.

Since no one laser catheter can treat all types of disease, a new family of `lesion-specific' devices was evaluated with a holmium laser source. Three-hundred-thirty-one patients (avg. 60 years) with symptomatic coronary disease were studied. Average lesion length was 1.2 cm. A 1.4, 1.5, 1.7, or 2.0 mm, tapered-tip or non-tapered, multifiber catheter (Eclipse, Palo Alto, Calif.) was advanced over the wire while emitting 250 - 600 mj/pulse at 5 Hz. Mean percent stenosis decreased from 89% to 57% after lasing with a mean of 140 pulses. Complications were infrequent. Overall procedural success was 95%. The conclusion is that specialized laser catheters delivering holmium laser energy are capable of reducing the severity of coronary stenoses including balloon angioplasty failures and bypass graft failures. Follow up studies are in progress to assess long term efficacy.