Laser facilitated angioplasty and thrombolysis in acute myocardial infarction complicated by prolonged or recurrent chest pain

A reconstituted in vitro clot model for evaluating laser thrombolysis

BACKGROUND/OBJECTIVE

Laser thrombolysis is the selective removal of thrombus from occluded blood vessels using laser energy. A reconstituted clot model with reproducible optical absorption properties was developed to evaluate the effect of various laser parameters on thrombus removal rate.

STUDY DESIGN/MATERIALS AND METHODS

Reconstituted clots were made with known fibrinogen concentrations and hematocrits. Ex vivo clots were collected from ten swine. Four red gelatin phantoms were prepared. Mass removal rates and ablation efficiencies were determined using a 577 nm, 1 microsec pulsed dye laser. The ablation efficiencies of the three clot models were compared at an energy of 25 mJ and a repetition rate of 4 Hz. In addition, the reconstituted clot model was ablated as pulse energy and repetition rate were varied with average power held constant at 100 mW.

RESULTS

The mean ablation efficiency for ex vivo clots ranged from 0.4 +/- 0.1 to 3.4 +/- 0.7 microg/mJ/pulse, with significant differences between groups (ANOVA p < 0.05). Reconstituted clots of varied fibrinogen content had ablation efficiencies of 1.5 +/- 0.2 to 1.6 +/- 0.3 microg/mJ/pulse at this energy and repetition rate. Gelatin ablation efficiency was inversely proportional to protein content and ranged from 0.5 +/- 0.3 to 2.0 +/- 0.7 microg/mJ/pulse. Reconstituted clot mass removal rates (in microg/s) were clinically similar for settings ranging from 13 mJ at 8 Hz to 33 mJ at 3 Hz.

CONCLUSIONS

The reconstituted model clot is a reproducible and biologically relevant thrombolysis target. Ex vivo clot lacks reproducibility between individuals and gelatin phantoms lack clinical relevance. At a constant average power, varying laser parameters did not affect mass removal rates to a clinically significant degree.

Effectiveness of excimer laser coronary angioplasty in acute myocardial infarction or in unstable angina pectoris

This study was conducted to evaluate the feasibility, safety, and acute results of percutaneous excimer laser coronary angioplasty (ELCA) in acute coronary syndromes. Fifty-nine patients were treated with ELCA (308 nm), including 33 patients with unstable angina pectoris (UAP) (35 vessels with 39 lesions) and 26 patients with acute myocardial infarction (AMI) (26 vessels with 29 lesions). In each patient the target lesion had a complex morphology. Overall, 71% of the patients had contraindications for pharmacologic thrombolytic agents or glycoprotein IIb/IIIa receptor antagonists. All patients received adjunct balloon dilation followed by stent implantation in 88% of patients with AMI versus 76% of patients with UAP (p = NS). Quantitative angiography was performed at an independent core laboratory; 86% laser success and 100% procedural success was achieved in the AMI group versus 87% laser success and 97% procedural success in the UAP group (p = NS). In the AMI group, the minimal luminal diameter increased from 0.77 +/- 0.56 to 1.44 +/- 0.47 mm after lasing to a final 2.65 +/- 0.47 mm versus 0.77 +/- 0.38 to 1.35 +/- 0.4 mm after lasing to 2.66 +/- 0.5 mm final in the UAP group. A prelaser percent stenosis of 76 +/- 17% for the AMI group versus 70 +/- 16% for the UAP group (p = NS) was decreased after lasing to 52 +/- 16% for the AMI group versus 51 +/- 14% for the UAP group (p = NS) and to a final stenosis of 15 +/- 17% for the AMI group versus 12 +/- 15% for the UAP group (p = NS). A 96% laser-induced reduction of thrombus burden area was achieved in the AMI group versus 97% in the UAP group (p = NS). Preprocedure Thrombolysis In Myocardial Infarction flow of 1.3 +/- 0.9 in the AMI group versus 2.3 +/- 1.2 for the UAP group (p = 0.01) increased to a final flow of 3.0 +/- 0 for the AMI group versus 3.0 +/- 0 for the UAP group (p = NS). There were no deaths, cerebrovascular accident, emergency bypass surgery, acute closure, major perforation or major dissection, distal embolization, or bleeding complications in either group. One patient with AMI had localized perforation (caused by guidewire) without sequelae and 1 patient with UAP had an abnormal increase in creatine kinase levels. All 59 patients survived the laser procedure, improved clinically, and were discharged. Thus, early experience in patients with acute coronary syndromes suggest that percutaneous ELCA is feasible and safe.

Acute results, complications, and effect of lesion characteristics on outcome with the solid-state, pulsed-wave, mid-infrared laser angioplasty system: final multicenter registry report. Holmium:YAG Laser Multicenter Investigators

BACKGROUND AND OBJECTIVE

The solid-state, mid-infrared holmium:YAG laser (2.1 microm wavelength) is a relatively new percutaneous device that has recently been evaluated in a multicenter study. Because of its unique wavelength and photoacoustic effects on atherosclerotic plaques, this laser may be useful in treatment of symptomatic patients with coronary artery disease. This study sought to evaluate the safety and efficacy of mid-infrared laser angioplasty in the treatment of coronary artery lesions.

PATIENTS AND METHODS

Laser angioplasty was performed on 2,038 atherosclerotic lesions in 1,862 consecutive patients with a mean age of 61 +/- 11 years. Clinical indications included unstable angina (69%), stable angina (20%), acute infarction (6%), and positive exercise test (5%). Complex lesion morphology included eccentricity (62%), thrombus (30%), total occlusion (27%), long lesions (14%), and saphenous vein grafts (11%).

RESULTS

This laser catheter alone successfully reduced stenosis (>20%) in 87% of lesions. With adjunct balloon angioplasty, 93% procedural success was achieved. The presence of thrombus within the target lesion was a predictor of procedural success (OR = 2.0 [95% confidence interval 2.0, 4.0], P = .04). Bifurcation lesions (OR = 0.5 [95% confidence interval 0.2, 1.0], P = .05) and severe tortuosity of the treated vessel (OR = 0.4 [95% confidence interval 0.2, 0.9], P = .02) were identified as significant predictors of decreased laser success. Calcium within the lesion was associated with reduced procedural success (OR = 0.57 [95% confidence interval 0.34, 0.97], P = .03), and calcified lesions required significantly more energy pulses than noncalcified lesions (119 +/- 91 pulses vs. 101 +/- 86 pulses, respectively, P = .0002). Complications included in-hospital bypass surgery 2.5%, Q-wave myocardial infarction 1.2%, and death 0.8%. Perforation occurred in 2.2% of patients; major dissection in 5.8% of patients, and spasm in 12% of patients. No predictor of major complications was identified. Six-month angiographic restenosis was documented in 54% of patients, and clinical restenosis occurred in 34% of patients.

CONCLUSION

Mid-infrared laser has a safety profile similar to that of other debulking devices. This laser may be useful in select patients presenting with acute ischemic syndromes associated with intracoronary thrombus; however, like other coronary lasers, it is limited by the need for adjunctive balloon angioplasty and/or stenting to achieve adequate final luminal diameter. No beneficial effects on reducing 6-month restenosis rates were observed.

Enhanced laser thrombolysis with photomechanical drug delivery: an in vitro study

BACKGROUND AND OBJECTIVE

Current techniques for laser thrombolysis are limited because they can not completely clear thrombotic occlusions in arteries, typically leaving residual thrombus on the walls of the artery. The objective of this study was to investigate the possibility of using photomechanical drug delivery to enhance laser thrombolysis by delivering drugs into mural thrombus during laser thrombolysis.

STUDY DESIGN/MATERIALS AND METHODS

Three experimental protocols were performed in vitro to quantitatively compare the effectiveness of thrombolysis by 1) constant infusion of drug, 2) laser thrombolysis, and 3) photomechanical drug delivery. A fiber-optic flushing catheter delivered drug (a solution of 1 microm fluorescent microspheres) and light ( a 1 micros pulsed dye laser) into a gelatin-based thrombus model. The process of laser-thrombus interaction was visualized using flash photography and the laser-induced pressure waves were measured using an acoustic transducer.

RESULTS

Lumen sizes generated by mechanically manipulating the catheter through the thrombus were smaller than those generated by laser ablation. The microspheres could be driven several hundred microns into the mural thrombus.

CONCLUSION

Photomechanical drug delivery has potential for enhancement of laser thrombolysis. Two mechanisms seem to be involved in photomechanical drug delivery: 1) mural deposition of the drug at the ablation site and 2) increased exposure of the thrombus surface area to the drug.

Photoacoustic Fibrinolysis: Pulsed-Wave, Mid-Infrared Laser-Clot Interaction

Objectives: The purpose of this study was to determine whether a mid-infrared laser can induce selective fibrinolysis and to analyze the effect of altered fibrin structure (thin vs. thick fibers) on laser-clot interaction. Background: Mechanical disruption of thrombus can be achieved with balloon angioplasty, sonication, and thermal energy. Thrombi avidly absorb light in the mid-infrared optical spectrum due to their high water content. This phenomenon provides a potential for mid-infrared lasers as a source for selective thrombolysis. As fibrin is the essential component of clot, a study of mid-infrared laser-fibrin interaction is warranted. Methods: Clots of varying fibrin structure were lased in cuvettes with a solid-state, pulsed-wave, mid-infrared laser (2.1 micron, 500 mJ/pulse, 250 msec pulse length). Total pulse energies of 5 Joules (J), 10 J, 37.5 J, 75 J, and 112.5 J were tested. Protein content of the extruded fluid was measured by optical density absorbance at 280 nm. Th e amount of released material was studied as a function of lasing energy and clot structure. SDS-polyacrylamide gel electrophoresis was applied for analysis of protein bands in order to identify unique protein bands released by the selective effect of laser fibrinolysis. Results: A threshold for mid-infrared laser induced fibrinolysis was found; application of up to 20 J of energy did not result in dissolution. As lasing energy was increased above 37.5 J, the structure of these gels was mechanically destroyed and 12.4 +/- 6.7% (mean +/- SEM) of the original content of protein was released. Electrophoresis revealed that lased gels did not release any unique protein band. Lased, thin fibers released significantly less protein than thick fibers, indicating that they are more resistant to the effect of this wavelength of energy. Conclusions: Mid-infrared laser can induce in-vitro photoacoustic dissolution of fibrin clots. However, this wavelength laser achieves fibrinolysis by me chanical destruction of the target clot rather than by a selective effect, as induced by the pulsed-dye laser. A threshold exists for energy levels required. Thin fibrin fibers, with their high elastic modulus (i.e., gel rigidity) appear more resistant than thick fibers to the effect of lasing at this wavelength.

Laser thrombolysis using long pulse frequency-doubled Nd:YAG lasers

BACKGROUND AND OBJECTIVE

Laser thrombolysis is a means for clearing blood clots in occluded arteries. Many researchers have studied the mechanisms of clot ablation, and research clinicians have used the technique to treat myocardial infarction with a number of different laser systems. Specifically, a 1-microsec pulsed dye laser has been used clinically to remove blood clots in coronary arteries. As a comparative study, the ablation characteristics of lasers with pulse durations in the ranges of 50-150 microsec and 2-10 msec were investigated. Two frequency-doubled Nd:YAG lasers at 532 nm were used in this study. Ablation threshold and ablation efficiency of gel phantoms and thrombus using these two lasers were measured and compared with the results of the pulsed dye laser. The pulsed dye laser in this study operated at 522 nm.

STUDY DESIGN/MATERIALS AND METHODS

Gelatin samples with 150 cm(-1) absorption coefficient at 532 nm and animal clot were confined to 3-mm silicone tubes to measure ablation parameters. Additional samples with 150 cm(-1) absorption coefficient at 522 nm were prepared for use with the pulsed dye laser. A fluorescence technique and photographic bubble detection were used to determine ablation threshold. A spectrophotometric technique was used to determine ablation efficiency.

RESULTS

The ablation threshold of the gel phantoms for all three lasers was determined to be 17 +/- 2 mJ/mm(2). Ablation efficiency for the gel phantoms was 1.7 +/- 0.1 microg/mJ. Clot had an ablation efficiency of 2.9 +/- 1.0 microg/mJ.

CONCLUSIONS

Ablation threshold and efficiency are independent of laser pulse duration for 1-microsec, 50-150-microsec, and 2-10-msec pulses (P < 0.05).

Liquid jets, accelerated thrombolysis: a study for revascularization of cerebral embolism

A prior study has reported that a rapid recanalization therapy of cerebral embolism, using liquid jet impacts generated by the interaction of gas bubbles with shock waves, can potentially penetrate through thrombi in as little as a few microseconds with very efficient ablation (Kodama et al. 1997). The present study was undertaken to examine the liquid jet impact effect on fibrinolysis in a tube model of an internal carotid artery. First, the conditions for generating the maximum penetration depth of liquid jets in the tube were investigated. Gelatin was used to mimic thrombi. The shock wave was generated by detonating a silver azide pellet weighing about a few micrograms located in a balloon catheter. The collapse of the inserted gas bubbles and the subsequent liquid jet formation were recorded with high-speed photography. Second, thrombi were formed using fresh human blood from healthy volunteers. The fibrinolysis induced by the liquid jet impact with urokinase was explored. This was conducted under selected conditions based on the experiment using the gelatin. Fibrinolysis was calculated as the percentage of the weight loss of the thrombus. Fibrinolysis with urokinase alone and with a single liquid jet impact with urokinase was 1.9 +/- 3.7% (n = 16) and 20.0 +/- 9.0% (n = 35), respectively, for an incubation time of 60 min. Statistical differences were obtained between all groups (ANOVA). These results suggest that liquid jet impact thrombolysis has the potential to be a rapid and effective therapeutic modality in recanalization therapy for patients with cerebral embolism and other clinical conditions of intra-arterial thrombosis.

Holmium laser-assisted coronary angioplasty in acute ischemic syndromes

BACKGROUND AND HYPOTHESIS

Initial studies have shown holmium laser to be effective in ablation of coronary atheroma, and small studies that it may be helpful in ablation of thrombotic stenoses. Therefore, holmium laser-assisted coronary angioplasty was studied in 85 consecutive patients with acute ischemia syndromes.

METHODS

Indications for therapy were acute myocardial infarction (MI) in 7 patients (8%), post-MI ischemic in 32 patients (38%), and crescendo angina pectoris in 46 patients (54%). Coronary morphology characteristics by multivessel angioplasty prognosis group criteria were Type A in 9 (10%), Type B1 in 15 (18%), Type B2 in 44 (52%), Type C in 17 patients (20%).

RESULTS

Angiographic evidence of thrombus was seen in 37 (44%) of patients. The laser successfully crossed the total length of the coronary narrowing in 76 patients (89%). Procedure/clinical success was 92% for the total study population, 100% for patients with acute MI, 94% for post-MI ischemia patients, and 89% for patients with crescendo angina. Lesions with and without thrombus had identical procedure success rates. Major complication rate was 3.5%, (deaths 0%, Q-wave MI 0%, and emergent bypass surgery 3.5%). Six-month angiographic restenosis rate (> 50% stenosis) was 45%.

CONCLUSION

Holmium laser-assisted balloon angioplasty appears promising in the treatment of acute ischemic syndromes and thrombotic coronary lesions.

Solid-state mid-infrared laser facilitated coronary angioplasty: clinical and quantitative coronary angiographic results in 112 patients

BACKGROUND AND OBJECTIVE

Holmium:YAG is a solid-state, investigational coronary laser device. Preliminary reports indicate the clinical potential for this laser; however, its safety and efficacy in a single center experience have not yet been reported and analyzed in detail.

STUDY DESIGN, PATIENTS, AND METHODS

One hundred and twelve consecutive symptomatic patients underwent percutaneous holmium:YAG laser (2.1 micron wavelength, 250-600 mJ/pulse, 5 Hz) facilitated coronary angioplasty. Sixty-six patients (Gr 1) had 74 thrombotic lesions, and 46 patients (Gr 2) had 55 thrombus-free stenoses.

RESULTS

Overall laser success was achieved in 120 out of 129 lesions (93%), with 95% subsequent balloon angioplasty success. Laser and clinical successes among the two groups were similar. By quantitative coronary angiography, reduction in the percent diameter stenosis (mean +/- SD) was similar (79 +/- 16% to 37 +/- 14% vs. 73 +/- 16% to 37 +/- 11.5%; P = NS) in both groups. However, minimal luminal diameter improved significantly more in Gr 1 patients, (0.7 +/- 0.5 mm to 2.0 +/- 0.5 mm, vs. 0.9 +/- 0.4 mm to 1.8 +/- 0.4 mm, P = 0.03). Angiographic and clinical complications were similar in patients with thrombus and without thrombus. No death, perforation, or Q-wave infarction occurred in the catheterization laboratory in either group. In-hospital mortality occurred in two patients from cardiac causes unrelated to the laser application. Of the 98 patients who reached the 6 month anniversary, 76 (77%) remained asymptomatic. The restenosis rate among the patients who underwent repeat angiography was 50%.

CONCLUSIONS

Solid-state, mid-infrared laser can be safely and successfully applied to symptomatic patients with thrombotic and nonthrombotic lesions. Similar to other debulking devices, the effectiveness of this laser in yielding long-term patency has not been proved.

Laser-assisted coronary angioplasty in patients with severely depressed left ventricular function: quantitative coronary angiography and clinical results

Laser-assisted coronary angioplasty can be successfully applied to lesions not ideal for balloon angioplasty. Patients with severely impaired left ventricular (LV) function and complex coronary artery stenoses who call for percutaneous revascularization are considered a high risk group for balloon angioplasty. In order to determine the feasibility, safety, and acute clinical outcome of a solid state, pulsed wave, mid-infrared (2.1 micron) laser facilitated angioplasty in these patients, data from 112 patients with 129 lesions were analyzed. Patients were identified according to angiographic LV function; group I included 22 patients with left ventricular ejection fraction (LVEF) < or = 40% (mean = 25% +/- 10%) and group II included 90 patients with LVEF > or = 40% (mean = 58% +/- 8%). No difference in age, gender, diabetes, hypertension, tobacco use, history of previous coronary artery bypass surgery (CABGS) or percutaneous transluminal coronary angioplasty was registered between the two groups. Multivessel disease, previous myocardial infarction (MI), and severe angina were more prevalent among group I patients (P = 0.03). No difference was found in lesion location, complexity, length, or calcification between the two groups; although group I had more eccentric lesions. Both groups were treated with the same laser energy level followed by adjunctive balloon angioplasty. One hundred percent procedural success was obtained in group I versus 93% in group II (P = NS). By Q.C.A. (independent core lab), minimal luminol diameter increased in group I from 0.9 +/- 0.5 mm preprocedure to 2.0 +/- 0.5, as compared to 0.8 +/- 0.5 mm to 1.9 +/- 0.5 mm (P = NS) in group II. Stenosis severity improved from 69% +/- 16% preprocedure to 37% +/- 13% postprocedure in group I, as compared to improvement from 78% +/- 16% to 37% +/- 12.7% in group II (P = NS). Overall complication rate was remarkably low, with no death or perforation in either group; emergency CABGS 0% in group I and 1.1% in group II; dissections 4.5% in group I and 8.8% in group II. There was no significant difference in complication rate between the two groups. The results of this study suggest that holmium:YAG laser facilitated coronary angioplasty can be safely performed in patients with severe LV dysfunction, achieving a remarkably high procedural success and low complication rate.

Laser for optical thrombolysis and facilitation of balloon angioplasty in acute myocardial infarction following failed pharmacologic thrombolysis

This report discusses a new indication for the use of holmium:YAG laser. It includes facilitation of thrombolysis and plaque ablation in acute myocardial infarction after failure of thrombolytic agents. Further study is required to define optimal utilization and integration of this novel device for patients who fail to respond to thrombolytic agents.

Laser thrombolysis in acute myocardial infarction: results of a clinical feasibility study

Laser thrombolysis is a new, experimental, catheter based intervention aimed at selectively removing intracoronary thrombus. This first clinical study was performed to assess the feasibility and safety of laser thrombolysis, as well as its potential therapeutic place in acute myocardial infarction. Eighteen patients with acute myocardial infarction, who were either noncandidates for, or failures on, intravenous fibrinolytic therapy were included for treatment with laser thrombolysis followed by balloon angioplasty. As a result of catheter and technical failures, the laser was actually fired in only 12 patients. Improvement in TIMI flow from grade 0-1 to grade 2-3 was observed in 10 of these 12 patients after laser application. The overall results of 18 patients were: increase in TIMI grade flow from 0.33 +/- 0.49 after wire passage to 1.28 +/- 1.23 (P = 0.0051) after attempted laser application, and to 2.67 +/- 0.97 after PTCA (P = 0.0004). Two patients with previous infarctions died from left ventricular failure despite successful laser thrombolysis. One patient died during emergency bypass surgery after a failed recanalization attempt. Perforation or laser related dissection did not occur. The concept of selective laser thrombus ablation seems to be safe and feasible, but substantial improvements of the laser delivery catheters are needed. Laser thrombolysis is not an effective stand-alone therapy in acute myocardial infarction, but other possible applications warrant further research and development efforts for this potentially useful interventional tool.

High intensity, low frequency catheter-delivered ultrasound dissolution of occlusive coronary artery thrombi: an in vitro and in vivo study

OBJECTIVES

This study assessed the efficacy of a new high intensity, low frequency therapeutic coronary ultrasound catheter for thrombus dissolution in vitro and in vivo in canine coronary arteries.

BACKGROUND

Therapeutic ultrasound has been shown to dissolve thrombi in vitro and in peripheral arteries in vivo. There have been no previous studies on in vivo coronary thrombus dissolution by ultrasound.

METHODS

In vitro, we exposed 1- to 4-h old human blood clots for 3 min to pulsed-wave ultrasound. Clot dissolution under various conditions was evaluated. In vivo occlusive coronary thrombi were induced in 18 dogs.

RESULTS

In vitro irrigation alone (10 ml/min of normal saline solution) and ultrasound alone each contributed to a reduction of clot weight by 47.1 +/- 11.4 mg and 84.6 +/- 25.6 mg, respectively, after 3 min (p < 0.001). Ultrasound plus irrigation resulted in a reduction of clot weight by 216.5 +/- 31.5 mg after 3 min (p < 0.001). The magnitude of clot dissolution was considerably amplified when ultrasound energy was combined with irrigation, probably because of cavitational effects. In vivo, in three dogs mechanical passage of the unactivated probe failed to recanalize the artery, and the arteries remained thrombotically occluded. After passage of the activated ultrasound probe, angiography revealed widely patent coronary arteries in 13 of 15 dogs and partial recanalization with filling defects indicative of residual thrombus in 2 of 15 dogs. Three of 15 coronary arteries were histologically free of residual thrombi. Mural thrombi extending to < or = 10% of the vessel circumference were seen in 10 of 15 dogs. Residual thrombi > or = 50% of the vessel circumference were found in two cases. There was no histologic evidence of ultrasound-mediated vessel damage.

CONCLUSIONS

Catheter-delivered therapeutic ultrasound effectively dissolves clots in vitro and in canine coronary arteries in vivo. Thus, therapeutic catheter-delivered ultrasound has the potential to serve as an adjunct or alternative treatment for thrombus-mediated coronary ischemic syndromes or myocardial infarction.

Inhibition of platelet deposition and lysis of intracoronary thrombus during balloon angioplasty using urokinase-coated hydrogel balloons

BACKGROUND

Conventional balloon angioplasty of intracoronary thrombus is associated with a high incidence of abrupt closure, distal embolization, and no-reflow phenomenon. The purpose of this study was to assess a new technique for treating intracoronary thrombus consisting of the local delivery of urokinase directly to the angioplasty site with urokinase-coated hydrogel balloons.

METHODS AND RESULTS

We assessed local urokinase delivery using hydrogel balloons in four protocols. First, we evaluated the pharmacokinetics of urokinase delivery in vitro using 125I-labeled urokinase to measure drug loading onto hydrogel balloons, drug retention by the hydrogel polymer during blood exposure, and drug transfer from the balloon surface to the arterial wall during balloon dilatation. Second, we measured 125I-urokinase washoff from the hydrogel balloon in the intact circulation and intramural drug delivery during in vivo balloon angioplasty in 10 anesthetized New Zealand rabbits. Third, we assessed the effect of local urokinase delivery on 111In-labeled platelet deposition after balloon angioplasty in vivo in 13 porcine carotid or iliac arteries dilated with urokinase-coated balloons and compared them with contralateral control arteries dilated with saline-coated balloons. Finally, we determined the clinical efficacy of urokinase-coated balloons in 15 patients with intracoronary thrombus, including 7 who demonstrated abrupt thrombotic closure after conventional angioplasty. Between 241 and 1509 U urokinase could be loaded onto hydrogel balloons ranging in size from 2 to 8 mm. In vitro and in vivo studies demonstrated that hydrogel balloons absorbed significantly more urokinase and demonstrated less drug wash-off than nonhydrogel balloons (P < .01). Similarly, both in vitro and in vivo studies demonstrated urokinase transfer from the hydrogel to the arterial wall during balloon angioplasty, with greater intramural drug deposition with larger balloons (P < .01). Local urokinase delivery after in vivo porcine angioplasty decreased 111In-labeled platelet deposition by 47% compared with contralateral control vessels (P = .03). Use of urokinase-coated balloons in patients with intracoronary thrombus resulted in thrombus dissolution and reversal of abrupt closure in all cases, without evidence of distal embolization.

CONCLUSIONS

With the use of hydrogel-coated balloons, urokinase can be delivered locally to an angioplasty site. This technique decreases platelet deposition after in vivo balloon angioplasty and is efficacious in treating intracoronary thrombus in patients, including those with abrupt thrombotic closure.

Cardiovascular applications of laser technology

Laser technology has been evaluated for the treatment of coronary artery disease, ventricular and supraventricular arrythmias, hypertrophic cardiomyopathy, and congenital heart disease. Developments in laser angioplasty, laser thrombolysis, transmyocardial laser revascularization, photochemotherapy, laser treatment of arrhythmias and/or laser diagnostics are directed at improving upon conventional non-laser approaches, and providing new therapeutic and diagnostic options. This review will summarize the current status of the multiple applications of laser technology for cardiovascular diagnosis and therapy.

A new, safer lasing technique for laser-facilitated coronary angioplasty

In vitro studies during cold pulsed-wave laser angioplasty have demonstrated production of gas bubbles within the target tissue, creation of shock wave and formation of multi-layer dissections accompanied by an increase in the plaque and vessel wall temperature. These processes account for certain complications of coronary lasing, including acute vessel closure, dissections, spasm, and even perforation. The traditional lasing technique in which a large number of pulses is continually emitted across the lesion, may in fact contribute to the development and acceleration of the above mentioned processes. To overcome the shortcomings we have developed a new, safe lasing technique that consists of multiple trains of a small number of pulses each. Between laser sessions the laser catheter is retracted into the guiding catheter and nitroglycerin is injected intracoronary, thus providing time for dispersion of produced gas bubbles, cooling of the target artery, and adequate coronary vasodilatation. This new technique results in a significant reduction of laser associated complications.

Holmium laser coronary thrombolysis--a new treatment modality for revascularization in acute myocardial infarction: review

Thrombolytic therapy has changed the approach to management of acute myocardial infarction (AMI). Although its therapeutic benefit has been well established, only about one-third of AMI patients receive lytics. In AMI patients for whom thrombolytics fail to achieve revascularization or for whom lytics are contraindicated, percutaneous transluminal coronary balloon angioplasty (PTCA) can be utilized. However, in a clinical setting of AMI PTCA is less successful and is associated with a higher complication rate than with PTCA for angina alone. This review details a novel application of laser angioplasty; in patients with AMI complicated by continuous chest pain and ischemia, a mid-infrared (2.1 micron) solid-state, pulsed-wave Holmium:YAG coronary laser (Eclipse, Palo Alto, CA) can be utilized for coronary thrombolysis and plaque ablation. In each patient the laser was applied after failure of a thrombolytic agent or when thrombolytics were contraindicated. We have gained experience with 13 lesions, 12 in a coronary artery and 1 in a vein graft. In each case a multifiber with laser catheter (1.4, 1.5, 1.7 or 2.0 mm) was advanced over a guide wire, emitting 250-600 mj/pulse at 5 Hz, followed by adjunctive PTCA. Clinical success (defined as less than or equal to 50% residual stenosis, adequate thrombolysis, no complications [including death, CVA, CABGs, dissection, perforation]) was achieved in all patients. All patients improved clinically, survived the AMI, and were discharged. This initial clinical experience demonstrates the feasibility and safety of Holmium:YAG coronary laser angioplasty in revascularization during AMI.(ABSTRACT TRUNCATED AT 250 WORDS)