Rotational endarterectomy in normal canine coronary arteries: preliminary report.

Endarterectomy was performed in vivo using a high speed rotating abrasive-tipped catheter device in 11 normal canine coronary arteries. The device is designed to remove atheromatous material from diseased arteries by the abrasive action of its rotating tip. It was operated percutaneously from a femoral approach using conventional angioplasty guiding equipment. The rotating device was advanced over a guide wire from just beyond the tip of the guide catheter into the distal vessel. Six arteries were harvested immediately after endarterectomy and five were left in place for 7 +/- 2.8 days; in the latter group, the animals were maintained on a regimen of aspirin, 325 mg/day. Angiography before and after treatment demonstrated vessel patency in all cases. Caliper-measured luminal diameters were not significantly changed after endarterectomy. Histologic examination of pressure-fixed vessels showed extensive intimal loss and 20 to 30% loss of the internal elastic lamina. Medial damage was superficial and never exceeded 40% of the total medial thickness. There were no vessel perforations. Results of histologic study of the myocardium supplied by the treated vessels were normal without evidence of distal embolization or infarction. It is concluded that a high speed rotating abrasive device can be safely operated percutaneously in normal coronary arteries and results in minimal vessel damage and continued patency at 7 +/- 2.8 days.

Percutaneous coronary rotational angioplasty in humans: preliminary report.

Percutaneous coronary rotational angioplasty was attempted in 12 patients. The procedure was performed with a flexible rotating shaft with an abrasive tip, varying in diameter from 1.25 to 3.5 mm, tracking along a central guide wire. Among the 12 patients (mean age 58 years), 4 had a stenosis in the left anterior descending coronary artery and 8 a stenosis in the right coronary artery. After the guide wire crossed the stenosis, the abrasive tip was slowly advanced and several passes across the stenosis were made. The residual stenosis was measured with computerized automatic quantitative coronary angiography. Success was defined as a reduction of percent stenosis by greater than 20%. If residual stenosis remained significant (greater than 50%), the procedure was completed by balloon dilation. The device could not be inserted in 2 of the 12 patients. Five of the 10 patients underwent rotational angioplasty alone, and 5 had the procedure completed by balloon dilation. The stenosis was significantly enlarged from 0.56 +/- 0.31 mm to 1.26 +/- 0.28 mm. The outline of the vessel appeared smooth and regular. There were no complications related to the procedure and all patients were free of symptoms when discharged 2 to 3 days after the procedure. Thus, coronary rotational angioplasty is a simple and safe procedure allowing marked dilation of the narrowed segment. However, long-term follow-up is required for further evaluation.

Laser scalpel for solid organ surgery.

Hemostasis remains a major technical problem in surgery of the liver and spleen. A high power neodymium-doped yttrium aluminum garnet (Nd:YAG) laser has been coupled with a fiberoptic delivery system and quartz blade designed to yield maximal hemostasis and minimal tissue injury. In a series of experiments we were unable to demonstrate a significant advantage of its use in partial hepatic lobectomy.

Rotational thrombectomy in acute canine coronary thrombosis.

We have developed a mechanical thrombolytic catheter which defibrinates a fresh intra-arterial thrombus by wrapping fibrin about its rotating shaft. Defibrination results in liquification of the thrombus and reperfusion of the thrombotically occluded vessel. In this study, we employed this catheter-based approach in dogs with coronary thrombosis to simulate possible clinical use in acute myocardial infarction. Total coronary thrombosis was generated in 11 dogs. Spontaneous reperfusion did not occur over a 30-minute control period. All vessels studied were initially totally thrombosed. After mechanical thrombolysis, there was a significant improvement in percent diameter stenosis from 100% to 28 +/- 26% (P less than 0.001). After thrombolysis, angiographically graded blood flow was normal in 9 of 11 arteries and was mildly delayed in 2 of 11. Complications included perforation of 2 vessels. We conclude that mechanical thrombolysis, with a rotating catheter, results in prompt reperfusion of the infarct vessel and significant improvement in distal blood flow. This approach, unlike angioplasty, removes the thrombus and might serve as an alternative to or supplemental form of mechanical thrombolysis.

Animal testing of endoscopic hemostasis with lasers and other devices.

A variety of animal models for testing endoscopic control of gastrointestinal hemorrhage are reviewed. Advantages and disadvantages of each are discussed. New types of mechanical devices for controllable injury are presented, and the efficacy of laser photocoagulators and other recently developed electronic devices on these new lesions is compared.

Experimental investigation of thermally scanned fabry-perot interferometry.

A thermally scanned Fabry-Perot interferometer in the flat-flat resonator configuration has been constructed. It is extremely easy to use, and, in addition, provides large values of finesse (>60), high transmission, and large usable apertures. Experimental data analyzing the characteristics of the device are presented. Use of the interferometer for the spectral analysis of several physical processes involving very high optical resolution is demonstrated.

Laser photocoagulation for gastrointestinal bleeding.

Endoscopic laser photocoagulation is one of the exciting developments in the field of gastrointestinal endoscopic therapy. However, much work needs to be done before these techniques should be allowed to proliferate into widespread use. There are few controlled randomized clinical studies evaluating any endoscopic treatment of bleeding, including argon laser and Nd:YAG laser photocoagulation. Despite this, uncontrolled clinical trials of both argon and Nd:YAG laser photocoagulation have begun. Laser photocoagulation of bleeding upper gastrointestinal lesions should be considered a procedure in an experimental stage of development, to be performed only under protocol studies at endoscopic research centres. Only after this or any other haemostatic technique has been proven effective and safe in thorough animal trials and then in controlled clinical trial should it be considered ready for general clinical use.

Distal embolization during mechanical thrombolysis: rotational thrombectomy vs. balloon angioplasty.

To determine the incidence and extent of distal embolization during percutaneous transluminal balloon angioplasty (PTA) and rotational thrombectomy (PRT), we collected, filtered, and weighed the distal effluent of acute thrombotically occluded canine arteries following mechanical thrombolysis. PRT (n = 11) and PTA (n = 10) were equally effective in recanalizing occluded vessels (91% vs. 90%) and reduced percent diameter stenosis to a similar degree (97 +/- 6% to 8 +/- 11% and 100 +/- 0% to 17 +/- 23%, respectively). Distal embolization following mechanical intervention was observed in 10 of 10 and 8 of 9 arteries recanalized with PRT and PTA, respectively. The mean weights of collected emboli were similar between the two groups (18 +/- 24 mg vs. 37 +/- 79 mg, PRT vs. PTA, P = NS), although the range of size and weight of thromboemboli was larger in the PTA group (0-206 mg vs. 2-51 mg, PRT). Angiographically defined residual thrombus was significantly less frequent in arteries recanalized with PRT as compared with PTA (10% vs. 55%, P = 0.03). In summary, PRT and PTA are equally effective in recanalizing acutely occluded canine arteries and result in similar reductions in percent diameter stenosis. Each intervention results in distal embolization of thrombi. PRT is associated with a reduced incidence of angiographically evident residual thrombus at the site of arterial injury and may avoid embolization of large fragments occasionally produced by PTA. Thus PRT may serve as a useful alternative to coronary angioplasty during acute myocardial infarction.

Lens aberration correction by holography.

The correction of lens aberrations using a hologram made with a collimated reference is discussed. Two geometries in which the theoretical third-order hologram aberrations may be avoided are demonstrated. The results of experiments which demonstrate the aberration correction using the Ronchi and DeVany tests are presented.

Ophthalmic hazards associated with laser endoscopy.

It is well documented that work with lasers poses a risk of ocular radiation damage. We specifically investigated the risk of intense backflash during laser treatment of gastrointestinal bleeding. Two well-characterized models of mucosal reflections are used to document flashback levels on several standard fiberoptic endoscopes. Both argon and neodymium-YAG laser sources are evaluated. Filter attachments that will provide adequate protection from the flashback hazard are also described.

Holocamera for 3-D micrography of the alert human eye.

A holocamera that safely records holograms of the full depth of the alert human eye with a spatial resolution of ~20 microm is described. A single-mode argon-ion laser generating 2 W at 5145 A serves as the illuminating source. Holographic exposure times of 0.3 msec are achieved by means of a fail-safe electromechanical shutter system. Integrated retinal irradiance levels are well under the American National Standards Institute safety standards. Reconstructed real images are projected directly onto the vidicon faceplate of a closedcircuit TV system, enabling convenient scanning in the x-y-z dimensions of the reconstructed eyeball. Serially reconstructed holograms of cataractous rabbit eyes and normal human eyes are presented.

Rotational atherectomy in atherosclerotic rabbit iliac arteries.

PTCA is not technically possible in many patients with symptoms of coronary artery disease. In addition, atheroma is not physically removed by PTCA, and restenosis of the treated vessel is common. We have tested a new, rotating, abrasive-tipped angioplasty device in vivo in 13 atherosclerotic rabbit iliac vessels. Atherosclerosis was generated in rabbit iliac vessels by a 2% cholesterol diet combined with balloon endothelial injury for 10 weeks. The diseased vessels were then treated with the rotational atherectomy device. Before treatment, contrast angiograms demonstrated that initial percent diameter stenosis was 81% +/- 9%. After atherectomy, there was significant improvement, with residual 38% +/- 22% narrowing (p less than 0.001). One perforation resulted from distal guidewire manipulation, and one vessel was occluded by the device. Histologic examination demonstrated loss of portions of the diseased intima in all cases. Particles were produced for analysis in vitro by operating the atherectomy device in atherosclerotic rabbit aortas perfused with saline solution. Ninety-eight percent of the particles produced by the device were less than 10 micron in diameter. We conclude that this new rotational device can remove atheromatous material from diseased arteries in rabbits. Such a device may complement other angioplasty techniques and lead to wider application of catheter-based therapeutic interventions.

Mechanical thrombolysis: a new rotational catheter approach for acute thrombi.

We tested a new rotational thrombectomy catheter in acute thrombi formed both in vitro and in vivo. The catheter consisted of a rounded platinum tip, 0.025 inch diameter by 0.08 inch long, attached to a flexible steel guidewire supported by an external sheath. In vitro, the force required to penetrate thrombus was reduced fivefold by rotation of the catheter at 4000 rpm (0.75 +/- 1.2 g rotating vs 3.9 +/- 2.1 g static; p less than .001). Fibrin was extracted selectively from the thrombus and tightly wound about the shaft (3.8 +/- 1.5 mg rotating vs 0.75 +/- 0.4 mg static; p less than .001). In vivo, subtotal or complete thrombosis of the canine femoral artery was created. Thrombectomy by catheter rotation always produced tightly wound adherent fibrin on the catheter shaft. Angiographic patency was restored in 20 of 22 (91%) arteries, totally in seven of 22 (32%) and partially (greater than 20% increase in lumen diameter) in 13 of 22 (59%). There was one arterial perforation (5%). We conclude that this new mechanical catheter device reduces the force required to penetrate thrombus. Additionally, by winding fibrin about its shaft, the catheter is able to selectively remove the fibrin matrix of thrombus. Thus both the ease of initial thrombus recanalization as well as physical removal of thrombus are promoted by this new approach. Such an approach may be relevant to the treatment of recent thrombosis in acute myocardial infarction.

High power argon laser treatment via standard endoscopes. I. A preliminary study of efficacy in control of experimental erosive bleeding.

With minimal transmission loss a high power argon laser (10 w) was coupled to a waveguide consisting of a flexible, single, coated, quartz fiber encased in a protective polyethylene tube. This waveguide can be passed down the biopsy channel of any standard fiberoptic endoscope. An aiming light improves accuracy. Safety devices were developed to protect the subject and the operator. Each of 8 heparinized mongrel dogs had three superficial erosions created endoscopically in the fundal gland mucosa by a jet of warm 0.1 N HC1. In each animal two lesions were photocoagulated with the laser and the third was left as a control. The animals were killed at 0, 4, 7, 10, and 14 days, and the erosions were examined histologically. By 14 days all lesions were covered by normal surface epithelium. Parietal and chief cells had returned to untreated erosions at 14 days but not to all lasered lesions. Only rarely did the lasered lesions penetrate through the muscularis mucosae into the submucosa. High power argon laser photocoagulation is now feasible through standard endoscopes. These data are sufficiently promising to encourage further evaluation of laser photocoagulation in a variety of animal models.

Thrombolysis by rotational thrombectomy followed by tissue plasminogen activator: evaluation by angioscopy.

Thrombus removal using percutaneous rotational thrombectomy (PRT), followed by tissue plasminogen activator (t-PA), was studied by contrast angiography and fiberoptic angioscopy in a canine femoral artery model of thrombosis. After thrombus induction and following each treatment, comparisons were made between angioscopy and angiography for the detection of thrombus and subintimal dissection. Angioscopic images were scored in a blinded fashion for lining, protruding, or occlusive thrombus (class 1,2, or 3) as well as estimated wall coverage by thrombus. Angiograms were studied for percent diameter stenosis and the presence of flaps. Following external forceps crush injury of 18 arteries, two hour occlusion, and injection of thrombin, mean angiographic stenosis was 66%, thrombus coverage by angioscopy was 81%, and mean angioscopy class was 2.5. Following PRT, stenosis decreased to 27% (p less than 0.008), thrombus coverage was reduced to 49% (p less than 0.02), and angioscopy class dropped to 2.0 (p less than 0.07). After t-PA treatment, these values were further reduced to 25% (p = NS), 26% (p less than 0.02), and 1.3 (p less than 0.008), respectively. In comparison to angiography, subintimal dissection (seen as flaps) and thrombus (lining, protruding, or occlusive) were present significantly more often by angioscopy (p less than 0.001). It is concluded that PRT results in significant thrombolysis, apparent by angiography and angioscopy. Follow-up t-PA can produce additional, incremental thrombolysis, apparent only by angioscopy. A beneficial role for t-PA following mechanical thrombolysis is suggested by this model. The superior sensitivity of angioscopy for detection of flaps and thrombus is underscored by this study.

Combined mechanical and chemical thrombolysis in an experimental animal model: evaluation by angiography and angioscopy.

In an experimental animal model of femoral artery thrombosis, contrast angiography was compared to intravascular angioscopy. Additionally, the effect of mechanical, rotational thrombectomy and the additive benefit of the administration of intravascular streptokinase were assessed by means of both procedures. After external forceps crush injury alone, contrast angiograms were generally normal (6 of 14) or showed minimal luminal irregularity (3 of 14), and 5 of 14 had 30% to 50% stenosis. With angioscopy, none appeared normal, and 14 of 14 showed thrombi layered along the wall, as well as intimal flaps, and 6 of 14 had partially occlusive thrombi (p less than 0.001 angiography vs angioscopy). After 2-hour occlusion and injection of thrombin into the injured segment, angiographic total (5 of 14), subtotal (3 of 14), or partial thrombotic occlusions (5 of 14) were created. Angioscopy showed similar results, except that total occlusions were classed as subtotal occlusions. After rotational thrombectomy, most arteries again appeared normal by contrast angiography (6 of 11) but none were angioscopically normal (p less than 0.006). Streptokinase, administered after rotational thrombectomy in seven arteries, normalized one 30% angiographic stenosis; there were no other angiographic changes. Findings with angioscopy were also unchanged. We conclude that in the diagnosis and treatment of intravascular thrombosis, angioscopy is generally more sensitive in the detection of intravascular thrombi, with the exception of total thrombotic occlusions. Angioscopy was uniquely effective in identifying subintimal flaps, which were never identified by angiography. In this model, streptokinase provided little or no additional thrombolytic benefit to mechanical thrombectomy alone.