Search PubMed⌕ Search

Biomedical subjects

K K Haase

Publications and source records attributed to K K Haase.

At least 73 records · Page 4Linked to original sources
PubMed1992

Holmium:YAG laser angioplasty. Experimental ablation of vascular tissue via flexible ring catheters.

This experimental study was designed to define the potential value of a mid-infrared holmium laser in the free running mode for angioplasty. Immediately after removal, fresh normal and diseased human cadaveric arteries were irradiated under saline with a Ho:YAG laser (wavelength 2.13 microns). The laser was pulsed at 3 Hz, 250 microseconds pulse width and fluences of 10 to 40 J/cm2. The laser beam was coupled to ring catheters with multiple low-OH quartz fibers. The tip of the delivery device was held in direct contact with the vessel surface with the laser beam oriented perpendicularly. Ablation of atherosclerotic plaque was accomplished at an ablation threshold of 10 J/cm2. The ablation rate was 2.1 to 8.3 microns/pulse. Removal of calcified plaque was only partially effective. There were marked thermal effects with vacuolizations extending up to 1505 +/- 178 microns into the adjacent tissue. Laser light at the mid-infrared wavelength of 2.13 microns is supposed to be attractive as it is readily absorbed in water and can easily be transmitted through optical fibers. However, Q-switching seems to be essential to minimize thermal side effects and to make effective ablation of calcium possible.

Angioplasty, Laser↗
PubMed1992

[Acute and long-term results of coronary Excimer laser angioplasty].

Laser and catheter technology have been considerably improved within the first 2 years of the clinical use of coronary excimer laser angioplasty. Furthermore, patient selection has changed due to increasing operator experience. We report on the acute- and long-term results achieved in 163 patients in three subgroups with different system parameters and catheter technology. In the initial series 1 (N:60) a prototype catheter with a diameter of 1.4 mm was used. In series 2 and 3, we employed improved transmission devices with 1.3, 1.5 or 1.8 mm. In series 3 the pulsewidth was increased from 60 ns to 115 ns. The target vessel was the LAD in 68%, the LCX in 10%, and the RCA in 21%. According to the AHA/ACC Lesion classification there were 13% type A, 26% type B1, 55% type B2, and 5% type C lesions. Stand-alone laser angioplasty was performed in 23/60 (38%), 24/40 (60%), and 34/64 (53%) in series 1, 2, and 3, respectively. Additional balloon angioplasty was necessary in 32, 11, and 21 interventions. Failure of laser angioplasty occurred in five patients of series 1 and 2, and nine patients of series 3. Frequently observed complications included coronary spasm in 18 to 32%, dissections in 16% to 33%, and vessel closure in 18 to 27%. Myocardial infarction occurred in three patients in the first and one patient of the second and third series. There was one in-hospital death in series 1 and 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Laser↗
PubMed1991

Usefulness of morphologic parameters in predicting the outcome of coronary excimer laser angioplasty.

The treatment of complex coronary lesions with conventional balloon angioplasty is associated with a reduced success rate and an increased incidence of complications. To evaluate the influence of lesion morphology on the outcome of coronary excimer laser angioplasty, morphologic parameters of 148 target lesions in 147 consecutive patients were determined. Morphologic analysis included target vessel, involved vessel segment, vessel diameter, minimal lumen diameter, length of the lesion, single discrete (concentric/eccentric) or complex lesions (occlusions, bifurcational, tandem or long segmental lesions), American College of Cardiology/American Heart Association Task Force classification, lesion location in curved or straight vessel segments, prestenotic vessel tortuosity and the direction of the laser approach in curved vessels with eccentric lesions. Failure of laser angioplasty occurred in 17 patients because of failed guidewire placement (n = 8), catheter placement (n = 6), or inability to pass the lesion with the laser catheter (n = 3). Successful stand-alone laser angioplasty was achieved in 68 procedures. In 63 interventions additional balloon angioplasty was necessary (n = 60) or stand-alone laser angioplasty was not successful (n = 3). The frequency of complex lesions, particularly total occlusions (p less than 0.001) and prestenotic vessel tortuosity (p = 0.002) was significantly increased in the group with failed laser attempts. Statistical analysis of the morphologic parameters in successful stand-alone laser interventions compared with combined or unsuccessful interventions revealed no significant difference. These data suggest that failure of laser angioplasty occurs because of low catheter flexibility and the need for guidewire support in treating totally occluded vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Laser↗
PubMed1991

[Laser angioplasty of coronary stenoses].

Percutaneous transluminal coronary laser angioplasty is still undergoing clinical trials. The laser systems employed are of the pulsed type - for the most part the excimer laser - which are more effective for removing calcified plaque and have a lower complication rate than continuous wave lasers. While the long-term results are comparable with those achieved with balloon dilatation, the primary success rate of laser angioplasty alone is not yet up to the standards of balloon angioplasty. Improvements may be expected through the further development of catheter systems and the introduction of new techniques with more accurate and specific ablation of arteriosclerotic plaques.

Angioplasty, Laser↗
PubMed1991

Smooth muscle cell proliferation and restenosis after stand alone coronary excimer laser angioplasty.

It has been shown that coronary excimer laser angioplasty can remove atherosclerotic intracoronary tissue. Stand alone coronary excimer laser angioplasty was successfully performed in a 53 year old white man with 90% stenosis of the left anterior descending coronary artery and exertional angina (Canadian Cardiovascular Society class III). The lesion was reduced to a 30% residual stenosis with use of a 1.2 mm and subsequently a 1.8 mm diameter laser catheter. Early follow-up angiography 24 h later revealed persistent patency and unchanged lesion diameter of the target vessel. The patient was free of symptoms during the 2 month follow-up period, but died suddenly while playing in a tennis tournament 63 days after the procedure. Postmortem histologic examination revealed 80% restenosis at the lesion site without plaque disruption or thrombosis. Specific staining of the histologic specimen for smooth muscle cells using alpha-actin revealed significant smooth muscle cell proliferation at the site of coronary excimer laser angioplasty. However, most of the vessel narrowing appeared to be due to underlying fibrotic plaque as a result of insufficient tissue ablation. This was probably related to the size of the currently available catheters, which are too small to create a large channel.

Angioplasty, Laser↗
PubMed1991

Potential use of holmium lasers for angioplasty: evaluation of a new solid-state laser for ablation of atherosclerotic plaque.

Tissue effects of the mid-IR Holmium laser (emitting at a wave-length of 2130 nm) were evaluated. This wavelength is attractive because it combines high water absorption and easy transmission through standard optical fibres. The laser was pulsed with pulse durations in the range of 100 microseconds and repetition rates between 2 and 6 Hertz. For all experiments a repetition rate of 2 Hertz was used. The laser beam was coupled into waterfree quartz fibers with core diameters of 200 and 800 microns with an efficiency of 70 and 80%, respectively. Ablation of atherosclerotic plaque has been performed at an ablation threshold of 10J/cm2 for the 800 microns and 40J/cm2 for the 200 microns fibre. Removal of calcified plaque was possible. Ablation efficiency increased in a non-linear fashion with increasing pulse energies. The ablation rate per pulse was approximately 2 mm at energy fluences of 1000J/cm2 for the 200 microns fibre and 1.25 mm at energy fluences of 70J/cm2 for the 800 microns fibre; a further increase in energy densities did not result in higher ablation rates. On macroscopic examination only very limited thermal injury was found in crater adjacent tissue structures. Crater edges were even and did not reveal signs of crater charring or debris in the crater lumen. However, the histologic specimens revealed zones of thermal damage extending 100 up to 1000 microns lateral into adjacent tissue. Thermal damage increased with increasing radiant exposures and depended on the medium used.

Angioplasty, Laser↗
PubMed1991

Effects of intracoronary nitroglycerin on lumen diameter during early follow-up angiography after coronary excimer laser atherectomy.

The incidence of coronary vasospasm during and following excimer laser atherectomy is considerable. The aim of this study was to investigate vasoconstriction of the target vessel during early follow-up angiography. In 50 patients an angiogram was performed 24 hours after intervention. Nineteen patients were treated with stand-alone laser atherectomy (group I), another 19 with laser and additional balloon angioplasty (group II) and 12 with balloon angioplasty alone (group III). Lumen diameter and percent stenosis before and after intracoronary application of 0.1 mg nitroglycerin were determined. The differences were compared between groups I, II and III, and for patients with (N = 14) and without (N = 24) vasospasm during laser atherectomy. There was a significant increase in lumen diameter, of 0.17 +/- 0.28 mm, after nitroglycerin in group I, of 0.18 +/- 0.29 mm in group II (P = 0.02) and of 0.03 +/- 0.21 mm in group III (ns). In patients with vasospasm during laser atherectomy the average increase in lumen diameter was 0.28 +/- 0.24 mm (P less than 0.01), and in patients without vasospasm 0.12 +/- 0.29 mm (P = 0.09). We conclude that one day after coronary excimer laser atherectomy intracoronary nitroglycerin significantly affects lumen diameter at the site of previous stenosis, an effect undetectable after balloon angioplasty. Thus, vasoconstriction after excimer laser ablation seems to be a common phenomenon and is prolonged in patients with vasospasm during the previous intervention.

Adult↗
PubMed1991

Morphological changes and smooth muscle cell proliferation after experimental excimer laser treatment.

BACKGROUND: Little is known about the mechanism(s) in the development of restenosis after excimer laser angioplasty. Thus, the rationale of this study was to determine the time course of intimal and medial smooth muscle cell (SMC) proliferation and histomorphological changes after experimental excimer laser treatment. METHODS AND RESULTS: Laser ablation was performed in the right carotid artery of 34 New Zealand White rabbits after development of a fibromuscular plaque by repeated weak electrical stimulations. The vessels were excised 3, 7, 14, 21, 28, and 42 days after excimer laser treatment. Staining of alpha-actin was used to identify SMCs. In five rabbits (15%), a stenosis of more than 50% of luminal area was due to intimal proliferation of SMCs, and in four other rabbits, a total occlusion was due to organized thrombi. After the initial ablation of the performed plaque (13 +/- 6 intimal SMC layers) a continuous increase of intimal wall thickness was found from 7 +/- 6 SMC layers at 7 days to 28 +/- 5 intimal SMC layers at 28 days after excimer laser ablation (p less than 0.01). After 42 days, no additional increase of intimal thickening occurred. After bromodeoxyuridine labeling, the extent of cell proliferation (percent of cells undergoing DNA synthesis) in the intima and media was determined using a monoclonal antibody against bromodeoxyuridine. Immunohistological quantification of SMC proliferation in the intima revealed a significant increase of cells undergoing DNA synthesis at 3 (p less than 0.05) and 14 (p less than 0.01) days after laser treatment. Medial proliferation of SMCs was delayed and had a significant increase 7 days (p less than 0.05) after intervention. Twenty-one days after laser treatment, SMC proliferation in the intima as well as in the media was normalized. CONCLUSIONS: The proliferative response of SMCs after experimental excimer laser treatment will occur as a dynamic process with a maximum of SMCs undergoing DNA synthesis during 14 days after laser ablation, resulting in an increase of intimal thickening within 4 weeks after laser treatment. The extent of intimal hyperplasia due to SMC proliferation after excimer laser treatment is comparable with the effect of transluminal balloon angioplasty in this experimental model.

Angioplasty, Laser↗
PubMed1991

[Transluminal excimer laser angioplasty of experimentally-induced atheromatous plaque: morphologic changes and importance of proliferation of smooth muscle cells].

To determine the time-course of morphological changes after excimer laser treatment of atherosclerotic carotid arteries, laser angioplasty was performed in 34 rabbits after production of an intimal plaque (13 +/- 6 cell layers, 30 +/- 9% stenosis) using electrical stimulations. The animals were sacrificed 3, 7, 14, 21, 28, and 42 days after laser treatment. A total or subtotal thrombotic occlusion was found in four cases. No perforation was observed, but in 10 animals histological examination evidenced a partial ablation of the medial layer with signs of local thrombus formation and local reduction of SMC in the media. In five animals a stenosis of more than 50% of luminal reduction was due to intimal proliferation of smooth muscle cells (SMC), as determined by a monoclonal antibody against alpha-actin. After the initial ablation, a continuous increase of intimal cell layers was found, from 7 +/- 6 cell layers (19 +/- 9% stenosis) at 7 days, to 28 +/- 5 cell layers (45 +/- 18% stenosis) at 28 days following excimer laser angioplasty (p less than 0.01). After 42 days no additional increase of intimal thickening occurred. Our data suggest that incidence and morphology is comparable to the proliferative response of SMC following conventional balloon angioplasty.

Angioplasty, Laser↗
PubMed1991

[Macro- and microscopic changes in the atherosclerotic arterial wall caused by high frequency current].

To investigate the effect of radiofrequency energy (600 kHz) on atherosclerotic tissue, high frequency current was applied on 160 specimens of human abdominal and iliac artery autopsies with various duration and energy density. All experiments were performed in air, saline, and blood. Application of 5 to 30 joule resulted in coagulation of the intima and the media. Time dependent a shrinking of the vessel wall did occur at energy rates above 30 joule. At higher energies vaporization was found. In blood coagulation at the catheter tip became evident at 30 joule and higher energies. Histologic cross sections showed distending of intimal layers at 25 joule, additional shrinking of medial layers at 50 joule, vacuoles at 75 joule and separation of intima layers from underlying layers at 200 joule. In vitro application of high frequency current on atherosclerotic tissue results in thermal effects only. The extent of these effects seems to be unpredictable because of the ever changing composition of the tissue, resulting in changes of energy delivery at the tip tissue interface. On calcified plaques an energy dependent contraction mainly of adjacent vessel wall could be seen. Because of the non-predictable effects and adverse side effects on adjacent normal vessel wall the method seems not to be useful for clinical application.

Aged↗
PubMed1991

[Perforation of the vascular wall after coronary excimer laser angioplasty].

A 56-year-old patient with recurrent episodes of angina pectoris at rest was admitted for left-heart catheterization. The coronary angiogram revealed two-vessel disease with a subtotal stenosis in the circumflex artery and a long 90% stenosis in the proximal part of the left anterior descending artery. On the basis of symptoms and coronary morphology laser angioplasty was performed. After a total of 99 s of energy delivery extravasation of dye occurred at the site of ablation. Due to acute vessel occlusion subsequent PTCA was performed, resulting in a satisfactory angiographic result. Extravasation of dye was terminated after PTCA and was absent at short-term follow-up angiography. No signs of pericardial effusion were detectable by two-dimensional and M-mode echocardiography. A control angiogram disclosed the identical result the day after the acute intervention, and the patient could be discharged with a normal exercise test 1 week later.

Angina Pectoris↗
PubMed1990

[Excimer laser angioplasty. I. The tissue effects of a ring catheter system on peripheral arterial vessels].

We have carried out an experimental study using a new laser catheter on 28 cadaver femoral arteries in 14 subjects and on six aortas. This ring catheter system consists of 12 circular quartz fibres with a central lumen and allows the application of energies up to 20 mJ through a 7F flexible catheter in vivo. The laser emits ultraviolet light of a wave-length of 308 nm, in pulses of 60 ns and a frequency of 2-40 Hz. The energy within a single fibre is 5 J/cm2 and exceeds the intensity required to ablate calcifications. Histologically it has been shown that, depending on the type of tissue, 1 to 2.4 microns of tissue per pulse is removed. Experimentally, rate of progress in a calcified occlusive lesion in the femoral artery, using 20 Hz and energy transmission of 20 mJ, was 3 to 5 mm per minute. Perforation of vessel wall if the catheter tip was at right angles to it depended on the degree of atherosclerosis and was between nine and 116 seconds. Marginally, there was only minimal thermal damage.

Angioplasty, Balloon↗
PubMed1990

[Excimer laser angioplasty. II: Initial clinical experience with peripheral arterial occlusive diseases].

First clinical experiences in the treatment of chronically occluded arteries with 7F-multi-fiber catheter systems transmitting pulsed laser light are presented. 16 patients (7 stadium IIb, 4 stadium III, 5 stadium IVa Fontain) underwent the procedure. 14 of 16 lesions (distance: 0.5-10 cm), most of them with visible calcification, could be recanalized successfully. After the catheter had passed lesions several times, remaining stenoses of 48% (mean value) could be reduced by balloon angioplasty. By moving the catheter with less speed than the experimentally determined speed of laser light ablation and by guiding it over a safety wire, perforation and embolization could be avoided. In one case, occlusion material was pressed into collateral vessels and in two cases groin hematomas had to be observed.

Aged↗
PubMed1990

Laser ring catheters in excimer laser angioplasty.

Percutaneous excimer laser angioplasty is dependent on a reliable and effective energy transmission through fiberoptic devices. Compared with bare fibers, ring catheters provide improved flexibility and a central channel for insertion of guide wires. Peripheral laser catheters (7-9 F) were used in 32 patients with arterial occlusive disease in the lower limbs. The technical success rate was 91%. Vessel wall dissections occurred in nine cases but caused no clinical sequelae in the preliminary follow-up period (1-6 months). The clinical application of the catheter devices proved to be safe.

Aged↗
PubMed1990

Percutaneous coronary excimer laser angioplasty in patients with stable and unstable angina pectoris. Acute results and incidence of restenosis during 6-month follow-up.

A clinical study was conducted to evaluate the efficacy and safety of percutaneous coronary excimer laser angioplasty in 60 patients with coronary artery disease. Forty-nine patients had stable exertional angina, and 11 patients had unstable angina despite medical therapy. A novel 1.4-mm diameter catheter with 20 quartz fibers of 100-microns diameter each arranged concentrically around a central lumen suitable for a 0.014-in. flexible guide wire was coupled to an excimer laser. A commercial excimer laser emitting energy at a wavelength of 308 nm with a pulse duration of 60 nsec was used. The laser was operated at 20 Hz. Mean energy transmission was 30 +/- 5 mJ/mm2. In five of the 60 patients, laser angioplasty was not attempted. In 23 patients with laser ablation alone, percent stenosis decreased from 76 +/- 14% before to 27 +/- 17% after ablation and was 34 +/- 15% at the early follow-up angiogram. In 32 patients, additional balloon angioplasty was performed because of vessel closure after laser ablation in 11 and an insufficient qualitative result in 21 patients. Of the 11 patients with unstable angina, one patient died due to vessel closure 3 hours after intervention, and two patients developed a myocardial infarction. In 22 of 47 patients with late follow-up angiography, restenosis within the 6-month follow-up period occurred. Rate of restenosis was higher in patients treated with laser ablation and balloon angioplasty (16 of 28) than in patients treated with laser ablation alone (six of 19). These results suggest that coronary excimer laser angioplasty for ablation of obstructive lesions is feasible and safe in patients with stable angina. However, development of new catheter systems is necessary for an improved success rate.

Adult↗
PubMed1990

[Percutaneous coronary excimer laser angioplasty].

Available preliminary clinical studies have shown that ablation of atherosclerotic plaques can be achieved by means of pulsed excimer laser coronary angioplasty via flexible energy transmission systems. The goal of current studies using improved catheter technology is to enhance the acute success rate since, based on initial studies, it can be assumed that only about 40 to 45% of the patients can be successfully treated. The on-going investigations were carried out primarily with three different excimer laser systems which employ a wavelength of 308 nm but differing pulse widths and transmission systems. In the first American multicenter study by Litvack and Margolis a catheter system was used with a pulse width of 180 to 220 ns. The fibers have a shaft diameter of 100 microns with a conically-thickened distal end measuring 200 microns, the ablative area encompasses 35 to 45% of the total catheter tip surface. The excimer laser used in the second American multicenter study by Sanborn and Isner has a pulse width of 120 ns. This catheter is relatively unflexible due to the 200 microns fiber diameter. The ablative catheter tip area is 25 to 30%. In Tübingen a system was used with a pulse width of 60 ns. The energy is transmitted through fibers with a diameter of 100 microns. The effective ablative area in the first series of patients was about 15%, in the second series about 25 to 30%. At present, the energy density of all three systems is comparable with at least 25 to 35 mJ/mm2. Since there is currently no means for accurate assessment, the question of whether a shorter pulse width of comparable energy density is more effective than the longer pulse width, remains an open issue. The flexibility of the systems used by Margolis and in Tübingen enable ablation not only of proximal, but also arteriosclerotic plaques located in the middle-third of vessels. The flexibility and steerability, however, are inferior to balloon catheter systems. In the study carried out by Litvack and Margolis, in which more than 600 patients have been treated, and the results from 514 patients reported, there was no patient selection in the first series. The study by Sanborn and Isner included 88 patients. Due to the relatively unflexible catheter system, only those patients were treated who had proximal stenosis of the left anterior descending or right coronary artery or marginal branches of the circumflex artery without marked tortuosity.(ABSTRACT TRUNCATED AT 400 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1990

[Experimental intracoronary Excimer laser angioplasty].

To determine the feasibility of intracoronary application of pulsed ultraviolet laser light 38 coronary arteries of 18 in situ hearts were treated with the bare fiber technique and a specially constructed catheter device. Eight hearts had no coronary artery disease, in 10 hearts coronary artery disease of one or more vessels could be documented angiographically. Total time of laser irradiation varied from 30-490 seconds. Radiation was performed until vessel wall perforation was documented. In all cases a reduction of the stenotic area was realized using the bare fiber technique. Due to a lack in the flexibility of the bare fiber only proximal lesions could be treated and the time of perforation could not be precisely predicted. Dissections were observed in six coronary arteries. The handling of the catheter device was comparable to the conventionally used balloon technique. Ablative treatment of distal vessel lesions was possible. Perforations did not occur. The histologic specimens documented smooth lumen margins not revealing thermal damage. It can be expected that the innovative catheter device will enhance the intracoronary use of pulsed laser light.

Angioplasty, Balloon, Coronary↗