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The CO 2 laser has been limited in its application within the tracheobronchial tree by its lack of a fiber delivery system. Recently a new product has been marketed, Luxar's flexible CO 2 laser waveguide or Flexiguide TM , a spin-off of the presently used rigid waveguide or Microguide TM . The study was undertaken so as to delineate the properties and thus the usefulness of this new product which promised an increased ease of delivery of the CO 2 laser wavelength. We compared the flexiguide with its rigid counterpart along two parameters. Specifically, we determined the total energy necessary to endoscopically resect bovine tracheal rings with each guide and then examined the histologic crater characteristics of each guide at a given energy setting. In so doing we endeavored to see if the experience of the surgeon with the microguide could be translated to the use of the flexiguide. We found the flexiguide to require a greater total energy than the microguide in the continuous wave (cw) and chopped pulse (cp) operational modes p < 0.01. There was, however, no demonstrated difference in required energy in the superpulse (sp) operational mode. Preliminary histologic evidence when measuring such indices as crater depth, crater width, and shoulder width thermal damage seem to suggest that the flexiguide is less efficient at tissue ablation than its rigid counterpart at the same given energy. It also appears to cause a greater degree of associated thermal injury.

A pulsed spiking and nonspiking Cr; thulium (Tm):YAG flash lamp pumped laser operating at 1.96 and 2.01 μm was investigated in vitro in the clinically relevant power range for its basic laser-tissue interaction with soft, cartilaginous, and bone tissues. Some explanations of the differences and possible medical applications are discussed.

We describe the TULIP procedure, a new system to relieve bladder outlet obstruction caused by benign prostatic hyperplasia. This device is composed of a real-time 7.5 MHz ultrasound transducer coupled to a Nd:YAG laser with a 1.064 μ m wavelength that fires through an intact intraprostatic balloon. A series of feasibility studies in 21 canine prostate glands was performed with a follow-up time to 3 months. Results indicate that the Nd:YAG laser in the 20 to 40 W range at a pull rate of approximately 1 mm. per second is an effective means of removing substantial amounts of canine benign prostatic hyperplasia. Transurethral ultrasonography was a reliable means of identifying essential landmarks and of controlling the laser. Prostatectomy by laser coagulation necrosis resulted in no bleeding or postoperative obstruction. Intraoperative irrigation fluids were not required, eliminating systemic volume related problems.

The MagellanTM coronary laser atherectomy system is described. It uses high- resolution ultrasound imaging and electromagnetic sensing to provide real-time guidance and control of laser therapy in the coronary arteries. The system consists of a flexible catheter, an electromagnetic navigation antenna, a sensor signal processor and a computer for image processing and display. The small, flexible catheter combines an ultrasound transducer and laser delivery optics, aimed at the artery wall, and an electromagnetic receiving sensor. An extra-corporeal electromagnetic transmit antenna, in combination with catheter sensors, locates the position of the ultrasound and laser beams in the artery. Navigation and ultrasound data are processed electronically to produce real-time, transverse, and axial cross-section images of the artery wall at selected locations. By exploiting the ability of ultrasound to image beneath the surface of artery walls, it is possible to identify candidate treatment sites and perform safe radial laser debulking of atherosclerotic plaque with reduced danger of perforation. The utility of the system in plaque identification and ablation is demonstrated with imaging and experimental results.

A coronary laser atherectomy system combining laser delivery and ultrasonic imaging capability is described. The system is being developed by Intra-Sonix, Inc. to treat severe stenoses. The imaging system provides the clinician with the guidance needed to remove substantial plaque without perforation. The ultrasound transducers and laser optics are mounted in a small (less than 4 F), flexible catheter, that is deliverable over a standard guidewire (0.016 inch). The laser and ultrasound beams are directed at the artery wall to permit debulking of lesions and ultrasonic depth profiling of the tissue structure throughout the thickness of the artery. This allows the physician to determine the level of therapy to be applied and to monitor the plaque removal as the therapy progresses. The precise location of the ultrasound and laser beams in the artery is determined by a navigation system. Navigation data are processed electronically in conjunction with ultrasound data to produce real-time cross-sectional and longitudinal images of the artery wall at selected locations, which are updated as the catheter progresses through the vessel lumen. Results of in vitro tests on human atherosclerotic arteries and early in vivo experiments in a canine-human xenograft model showing image construction and radial laser delivery are discussed.

During the implementation of an NIH sponsored contract program titled “Assessment of Ultrasonic B-Scan Imaging for Detection and Quantification of Atherosclerotic Lesions in Human Carotid Arteries”, 289 endarterectomy specimens became available for pathologic examination at five participating centers (Miami Heart Institute, Bowman Gray School of Medicine, New England Deaconess Medical Center, Jefferson Medical College, and University of Rochester Medical Center). These specimens were fixed in 10% neutral buffered formalin, decalcified, and cross-sectioned at 3 mm intervals. An overlay template was used to measure lumen diameters and near and far wall thickness in four planes.

Short-term survival of cardiac allografts has increased markedly because of surveillance by protocol endomyocardial biopsies and improvements in immunosuppression, which have largely prevented graft loss from acute rejection. Currently, 85% of allograft recipients survive for 1 year, and 70% can expect to survive 5 years. 1 Despite this progress, chronic cardiac allograft arteriopathy (also known as chronic rejection, graft vascular disease, or accelerated atherosclerosis) remains a substantial and intractable obstacle to long-term survival, accounting for 21% to 30% of deaths. 2,3 The other major complications relate to the immunosuppression treatment itself (malignancy, infections). See also p 1169. Although graft atherosclerotic disease shares certain aspects with native coronary atherosclerosis, including dysfunctional endothelium with subsequent endothelial—inflammatory cell interaction, there are significant differences in the morphology, distribution, and most certainly pathogenesis. 4 The introduction of intravascular ultrasound has also shown that the process is much more prevalent and occurs earlier than had been

Between January 1973 and January 1989, 241 patients with Barrett's esophagus were treated at the Lahey Clinic Medical Center, Burlington, Mass. Of these patients, 65 presented with adenocarcinoma in Barrett's esophagus for a prevalence rate of 27%. Of 176 patients followed up for a total of 497 patient-years, adenocarcinoma developed in five patients for an incidence of one per 99 patient-years. The development of adenocarcinoma during endoscopic surveillance 1, 2, 2, 4, and 10 years after the initial diagnosis of Barrett's esophagus emphasizes the importance of long-term endoscopic and histologic surveillance. All five patients had severe dysplasia before adenocarcinoma developed. Yearly endoscopic follow-up examination is recommended for all patients with Barrett's esophagus unless mild dysplastic changes are found, in which case surveillance should be increased. Patients with severe dysplasia who are otherwise acceptable candidates for operation should be advised to have esophageal resection. ( Arch Intern Med . 1991;151:2212-2216)

Endoscopic sinus surgery using a holmium: yttrium aluminum garnet pulsed solid-state laser oscillating at 2.1 μm with fiberoptic delivery was performed in the laboratory, and the results were compared with those of conventional endoscopic sinus surgery. Three beagle dogs, six human cadaver heads, and one calf head were used in the in vivo and in vitro studies to evaluate the bone ablation, tissue coagulation, and hemostatic properties of the holmium: yttrium aluminum garnet laser. Modified endoscopic telescopes for sinus surgery, a newly developed handpiece for fiberoptic delivery, and other surgical instruments were used

A 3-methyl substituted radioiodinated long chain fatty acid analogue was evaluated as an agent for the noninvasive detection of altered fatty acid uptake in reperfused, postischemic myocardium. This iodinated fatty acid analogue, 15-(para-iodophenyl)-3-methyl pentadecanoic acid, was given intravenously at 3 hours of reperfusion following 15 minutes (Group 1, n = 5 dogs) or 60 minutes (Group 2, n = 5 dogs) of left anterior descending coronary artery occlusion. Myocardial blood flow (MBF) was measured during occlusion and reperfusion with radiolabeled microspheres administered via the left atrium. Paired ultrasonic subendocardial crystals were placed in the ischemic perfusion bed to assess regional left ventricular systolic function at baseline, during ischemia and reperfusion. Electron microscopic analysis and staining with triphenyltetrazolium chloride (TTC) was performed. Groups 1 and 2 dogs had similar (p = NS) myocardial blood flows during occlusion. TTC positive 1 g endocardial segments from Group 1 (n = 98) and Group 2 (n = 71) had 37% greater fatty acid analogue activity (0.26 +/- 0.04 vs. 0.19 +/- 0.09 percent injected dose per gram; p less than 0.05) compared with TTC negative segments from Group 2 dogs (n = 37). When fatty acid analogue activity was related to near simultaneous reperfusion blood flow, this ratio was 27% greater (p less than 0.05) in TTC positive segments (0.38 +/- 0.1) compared with TTC negative (0.30 +/- 0.16) segments, and 9% greater than normal (0.35 +/- 0.09; p less than 0.05). While ischemic regions from both Groups 1 and 2 dogs became similarly dyskinetic during occlusion (systolic shortening, -11 +/- 6 vs. -11 +/- 2%; p = NS), TTC negative segments remained akinetic (= 1 +/- 7%) at 3 hours of reperfusion while TTC positive zones had recovered partial systolic function (8 +/- 22%). Electron microscopy confirmed the presence of reversible ultrastructural changes in TTC positive regions. A 60-minute occlusion, 3-hour reperfusion model adapted for in vivo single photon emission computed tomography showed a similar excess of 123I fatty acid activity over flow when compared to perfusion (as measured with 201Tl) in the ischemic border zone of 4/4 canine myocardial infarcts. We conclude that the accumulation of this non-beta-oxidized fatty acid analogue noninvasively identifies zones of discordance between fatty acid and flow distribution that are characteristic of ischemically "stunned" but viable myocardium.

The area-length method is widely used in the determination of left ventricular volume. Although previous studies have reported that this technique overestimates true volume (TV), it is unknown whether this overestimation is the same at different volumes. In the present study, with the use of 10 postmortem human hearts, left ventricular volumes were determined by contrast x-ray biplane cine ventriculography (LVA), biplane radionuclide (LVR), and absolute-counts (LVC) technetium scans, and the results were correlated with TV. LVA correlated well with TV (r = 0.98). LVR correlated well with TV (r = 0.97), and LVR also correlated well with LVA (r = 0.96). Both area-length techniques (LVA and LVR) resulted in overestimation of TV with an upward shift of the regression line of 30.4ml +/- 3.8 (SEM) for LVA and 28.5 +/- 4.4 for LVR. The percentage of overestimation error was significantly greater at smaller left ventricular volumes (error = 33% at TV = 30ml and 10% at TV = 100ml, p less than 0.001). LVC correlated well with TV (r = 0.99), TVA, and LVR but underestimated TV. Thus left ventricular volumes can be reliably obtained from LVR and LVA by means of the area-length method and from LVC. When the area-length method is utilized, the percentage of error in the determination of left ventricular volume is proportional to 1/TV.

To determine how administration of a hyperosmotic agent alters regional nuclear magnetic resonance (NMR) relaxation parameters and imaging characteristics in ischemic-reperfused myocardium, 7 dogs were infused with mannitol for 15 minutes before and after the release of a 3 hour left anterior descending coronary artery (LAD) occlusion. Nine control animals received normal saline during the 3 hour occlusion and 1 hour reperfusion periods. Normal posterior left ventricular (LV) wall and the ischemic anterior LV wall (risk area) myocardium was sampled for calculation of segmental microsphere myocardial blood flow, % tissue water content, NMR relaxation times (T1, T2) and myocyte ultrastructure using electron microscopy. Mean infarct T1 values were 14% greater than normal segments in saline-treated controls, but only 5% greater after mannitol. The difference in tissue water content between infarcted and normal segments was 4% in saline-treated (83 vs. 79%) compared to 2% in mannitol-treated dogs (79 vs. 77%). T1, T2 and % water content of control infarct segments were greater than treated infarcts (p less than 0.01). T1 and T2 rose as occlusion flow fell below 0.5 ml/min/g in control hearts but did not rise until flows were reduced to 0.1 ml/min/g in mannitol-treated hearts. Areas of increased signal in T1 and T2 NMR images correlated well with histochemical infarct volume (r = 0.98, SEE = 1.1 cc) in mannitol-treated dogs, but infarct borders were qualitatively less well-defined than in controls. We concluded that mannitol (1) diminishes tissue edema and reduces NMR relaxation parameters (T1, T2) in infarcted myocardium; and (2) attenuates the rise in T1 and T2 and ultrastructural myocyte injury in ischemic-reperfused myocardium.

Right ventricular (RV) volumes determined by echocardiography were compared with those measured using established angiographic formulas. RV cast displacement volumes were first correlated with data derived from radiographic images of the casts corresponding to standard anglographic RV views. Four established anglographic formulas (Ferlinz, Boak, Fisher and Thilenius) correlated well with cast volume, with the corrected prism method of Fisher showing a best fit (r = 0.98, y = 1.1 + 0.9x, standard error of the estimate = 3.6). Cast volumes calculated using our echocardiographic formula were then examined relative to the volumes derived from radiographic images of the RV casts. Volumes Calculated using the corrected area-length Thilenius formula correlated best with those obtained using our derived 2-dimensional echocardiographic formula (r = 0.96, y = 4.6 + 1.0x, standard error of the estimate = 6.8). These data confirm that volume calculated using the suggested optimal echocardiographic formula correlates well with volume obtained using derived angiographic data. Accordingly, confirmation In humans by the use of angiography is a rational step.

Objective: Cotransplantation of a donor kidney along with a heart allograft can induce tolerance to both organs and prevent cardiac allograft vasculopathy in miniature swine. To determine whether the tolerogenic effect of donor kidney cotransplantation was due to an effect specific to the kidney graft or to an increase in donor antigen load, we compared heart-kidney recipients with recipients receiving two class I disparate hearts or with recipients receiving donor peripheral mononuclear cells at the time of isolated heart transplantation. Methods: Recipients of major histocompatibility complex class I disparate allografts received 12 days of cyclosporine (INN: ciclosporin; 10-13 mg/kg administered intravenously on days 0-11). Group 1 animals received a heart alone (n = 5). Group 2 animals received heart and kidney allografts (n = 4). Group 3 animals received two major histocompatibility complex–matched heart allografts (n = 4). Two double-heart recipients were thymectomized 21 days before transplantation. Group 4 animals received a heart allograft and an infusion of high-dose donor peripheral blood leukocytes (2.5 × 10 9 cells/kg, n=2). Results: Vasculopathy developed in group 1 recipients and the allografts were rejected within 55 days. Group 2 recipients accepted their heart and kidney allografts indefinitely without vasculopathy. Euthymic recipients from group 3 accepted their hearts long-term (>190 and >197 days), but vascular lesions developed. In thymectomized recipients from group 3, the hearts were rejected in 63 and 96 days with severe vasculopathy. Group 4 recipients demonstrated transient macrochimerism but their hearts were rejected within 47 and 63 days. Conclusions: The beneficial effects of donor kidney cotransplantation on cardiac allograft survival and prevention of cardiac allograft vasculopathy are likely to involve both an increase in donor antigen load and an effect specific to the kidney allograft. (J Thorac Cardiovasc Surg 2000;119:709-19)

ObjectivesThe aim of this study was to evaluate the feasibility and the ability of intravascular optical coherence tomography (OCT) to visualize the components of coronary plaques in living patients.BackgroundDisruption of a vulnerable coronary plaque with subsequent thrombosis is currently recognized as the primary mechanism for acute myocardial infarction. Although such plaques are considered to have a thin fibrous cap overlying a lipid pool, imaging modalities in current clinical practice do not have sufficient resolution to identify thin (

Ultrasonic images of cadaver arteries are presented in this paper. The images were produced from within the arteries by a pulsed transducer capable of being mounted on a 0.8 mm catheter equipped with both a guide wire and a laser delivery system. The image data were acquired, processed, and displayed by a computer based real-time system. Example images show some of the display formats which are available for elucidating the internal structure of arteries with this imaging modality. Transverse and radial sections of the artery are shown in both A-Scan and B-Scan modes. Derived thickness images are also presented. In each mode the internal artery structure, including plaque areas, is clearly apparent. Histologic sections are shown beside ultrasonic data to verify the utility of these images.

The clinician interested in using the CO2 laser endoscopically in the tracheobronchial tree presently has limited options due to problems in fiberoptic transmission. Three delivery systems have been used in a laboratory setting in a canine model: a CO2 laser coupler with a specially modified rigid bronchoscope (Cooper LaserSonics), a metallic waveguide (Laakmann Electro-Optics) and a polycrystalline fiber (Cooper LaserSonics). The most efficient laser delivery system for clinical application occurred with the wave-guide requiring 32 joules to create a standard 5 mm2 lesion, as compared to 54 and 184 joules for the coupler and fiber respectively. Limited bend radius with both the fiber and the waveguide limited clinical usefullness even through rigid bronchoscopes. In addition, only 60% power transmission was possible with the waveguide (bend radius of 6 cm). This loss of power was not associated with the fiber use. Waveguide and fiber transmission of the CO2 laser have the advantages of open bronchoscope systems with excellent telescopic optics. Unfortunately, due to the awkward, semi-flexible nature of the current waveguide and fiber deliver systems flexible bronchoscopes can not be utilized and the clinician is still obliged to use the laser coupler for most clinical applications.

The effects of pulsed holmium-YSGG laser energy (2.1 μm) on arterial tissue were studied in vitro and in vivo. Delivered through silica optical fibers, the laser ablated calcified and noncalcified tissue in air and saline in a noncontact mode. Early in vivo healing studies in normal canine carotid arteries showed minimal chronic sequelae at 3 weeks.

We have described a spectrum of pancreatic surgery after cardiopulmonary bypass. At one end is a subclinical lesion which was manifested only by elevations in serum isoamylase levels (27 percent of patients) and increased ribonuclease levels (13 percent of patients) in asymptomatic patients followed after cardiac surgery. At the other end is a severe and often lethal necrotizing pancreatitis. Acute necrotizing pancreatitis was found at autopsy in 25 percent of 138 patients who died after cardiac surgery, and it correlated strongly with low output, acute tubular necrosis, and infarction of the liver, spleen, or bowel. It was the principal cause of death in 4 percent of these patients. In addition, 24 percent of 38 nonsurgical patients who died from cardiac failure and hypoperfusion had acute pancreatitis at autopsy, whereas acute pancreatitis was not observed in 55 nonsurgical patients who died without a significant period of low output. Acute pancreatitis was recognized postoperatively in 12 patients (0.2 percent). Three had mild pancreatitis, and all responded well to conservative therapy. In nine patients, fulminant necrotizing pancreatitis developed. Their courses were characterized by significant early postoperative hemodynamic compromise, abdominal distention, ileus, fever, and episodes of late vascular instability associated with hypocalcemia. The diagnosis of pancreatitis was usually missed because of the absence of pain, tenderness and hyperamylasemia. The diagnosis was confirmed at laparotomy in eight patients and at autopsy in one. The only two survivors among the nine with severe cases had aggressive mobilization, debridement, and wide drainage of the necrotic pancreas. We suggest that a mild subclinical injury to the pancreas may occur as a consequence of cardiopulmonary bypass and may progress to severe ischemic necrosis if hypoperfusion follows in the postoperative period, the presentation of necrotizing pancreatitis may be atypical in the cardiac surgical patient and should be considered if nonspecific abdominal symptoms are present, and aggressive debridement and drainage may be the optimal treatment for aggressive forms of this disease.

Hepatotoxicity secondary to the administration of thiabendazole has been rare since this drug was produced in 1964. In 14 of 15 patients reported previously in the literature, severe intrahepatic cholestasis resolved within seven months of the onset of illness. A recent report documented the progression to cirrhosis in a 15th patient. We report the second case of a patient with intrahepatic cholestasis that developed after treatment with thiabendazole and progressed to severe micronodular cirrhosis.