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Angioplasty, Balloon, Coronary↗
Biomedical subjects
A Baumbach
Publications and source records attributed to A Baumbach.
Comparison of peripheral endothelial dysfunction and intimal media thickness in patients with suspected coronary artery disease.
OBJECTIVE: Flow associated dilatation (FAD%) and intimal media thickness are established markers of early atherosclerosis. This study aimed to compare the ability of the non-invasive measurements FAD% and intimal media thickness to predict coronary artery disease. METHODS: FAD% and intimal media thickness were determined using high resolution ultrasound in 122 patients with clinically suspected coronary artery disease before coronary angiography. Results are given as mean (SD). RESULTS: Patients with coronary artery disease had reduced FAD% compared with those with angiographically normal coronary vessels (3.7 (4.1) v 7.0 (3.5)%, p < 0.001), whereas intimal media thickness tended to be increased in patients with coronary artery disease (0.58 (0.35) v 0.47 (0.11)mm, p = 0.054). There was a negative correlation between FAD% and intimal media thickness (R = -0.317, p = 0.0004). Receiver operating characteristic analysis showed that FAD% < or = 4.5% predicted coronary artery disease with a sensitivity of 0.71 (95% confidence interval 0.61 to 0.80) and a specificity of 0.81 (0.58 to 0.95). In contrast, intimal media thickness showed a positive correlation with the extent of coronary artery disease (number of vessels with a lesion > or = 50%) (R = 0.324, p = 0.0003), without a clear cut off point. CONCLUSIONS: In patients with clinically suspected coronary artery disease, FAD% discriminates between the presence or absence of coronary artery disease, whereas intimal media thickness is associated more with the extent of coronary artery disease.
Adult↗
Perspectives of coronary excimer laser angioplasty: multiplexing, saline flushing, and acoustic ablation control.
BACKGROUND AND OBJECTIVE: Bubble formation, pressure wave generation, and cavitations constitute major factors influencing the outcome of clinical Excimer laser angioplasty. Thus, the rationale of this study was to determine the extent of pressure waves occurring during excimer laser ablation and to discuss possibilities that allow a less traumatic plaque removal in the coronary circulation. STUDY DESIGN/MATERIALS AND METHODS: Conventional and experimental Xenon-Chlorid-Excimer lasers emitting light at a wave-length of 308 nm and a pulse duration of 115 ns were used for testing of signals. Whereas the conventional excimer laser light source transmits light through all fibers of a 1.7 mm laser catheter simultaneously, the prototype excimer laser divides the laser beam into several areas of uniform energy fluence by scanning the beam from one section to the other using the intermission between two laser discharges. Hydrophones consisting of piezoelectric films detected the acoustic signals, which were obtained on normal arterial wall and atherosclerotic plaque. RESULTS: Multiplexing decreases maximum pressures for both normal arterial wall and calcified plaque significantly, whereas pressure rise time remains comparable. During ablation of pure blood, a linear increase of peak pressures of 1 MPa at 10 mJ/mm2 to 7.5 MPa at 50 mJ/mm2 is found. Contrast media intensifies the extent of pressure wave formation. At 20 mJ/mm2, 60% contrast media added to blood results in an increase of maximum pressures from 1.5 MPa up to 5 MPa. Dilution with saline solution is effective; however, high concentrations of > 90% are required to achieve a significant pressure wave reduction. CONCLUSION: Peak pressures of several thousand kPa occur during excimer laser ablation of contrast media, blood, calcified plaque, and normal arterial wall in a decreasing order. Multiplexing and saline flushing are capable of reducing the intensity of the generated acoustic signals during tissue ablation. It has to be taken into consideration, however, that high concentrations of saline solution are necessary to achieve a significant reduction of peak pressures.
Acoustics↗
Time course of smooth muscle cell proliferation after local drug delivery of low-molecular-weight heparin using a porous balloon catheter.
It has been reported previously that systemic application of low molecular weight heparin (LMWH) suppresses smooth muscle cell (SMC) proliferation after balloon angioplasty in experimental studies. However, the high concentration of heparin required for a beneficial effect may cause severe bleeding complications. The ideal situation to overcome the systemic side effects would be to administer LMWH locally and deep into the arterial wall, which became possible by the development of porous balloon catheters. The in vivo feasibility of local delivery of LMWH using the porous balloon has been assessed by delivering tritium-marked LMWH into rabbit carotid arteries. The efficacy of the system was investigated by using a second injury animal model. After development of an intimal plaque by electrical stimulation, 61 rabbits were treated with the porous balloon after balloon angioplasty. In 23 rabbits, local drug delivery was accomplished with a porous balloon catheter (35 holes, hole diameter 75 microns, 2.5 mm catheter diameter). LMWH was locally administered with 4 ml (solution 375 anti-Xa-units/ml) and 2 atm. To study the extent of restenosis and morphological changes, these animals were killed 3, 7, 14, 28, or 56 d after intervention. After staining (hematoxylin, van Gieson, BrdU, RAM 11, alpha-actin) procedures to quantify SMC proliferation, intimal macrophages and morphological analysis were performed. Porous balloon treatment led to an increase in intimal SMC proliferation rate in the early stage after intervention. However, during the following time period, a significant decrease of the proliferation rate as compared with the animals treated with balloon angioplasty alone could be observed, which resulted in an only moderate increase of the intimal layer after local drug delivery compared with balloon angioplasty alone.
Angioplasty, Balloon↗
Efficacy of low-molecular-weight heparin delivery with the Dispatch catheter following balloon angioplasty in the rabbit iliac artery.
Local drug delivery can be achieved with active injection systems or passive contact of a compound with the arterial wall. The Dispatch catheter allows for passive diffusion of drugs from drug compartments while preserving blood flow through the central conduit. The aim of this study was to investigate whether a reduction in neointima formation can be achieved by local delivery of a limited amount of a highly concentrated solution of the low-molecular-weight heparin Reviparin. In 16 New Zealand white rabbits, successful balloon dilatation was performed in both iliac arteries, followed by local delivery of 4 ml Reviparin (1,000 IU/ml). The arteries were harvested at 7, 28, or 56 d following the procedure. The intimal cell layers increased substantially between 7 and 28 d following balloon dilatation with or without local drug delivery. The medial cell layers showed only a little increase. Proliferation of smooth muscle cells reached an early peak after 7 d, with a significantly higher proliferation index following local delivery. The maximum amount of macrophages in the intima and media was detected after 28 d. The lumen area decreased with time and was 0.6 +/- 0.7 mm2 in the local delivery group at 56 d compared with 0.5 +/- 0.5 mm2 in the control group. In conclusion, local delivery of Reviparin with the Dispatch catheter is safe and feasible. However, the infusion of highly concentrated low-molecular-weight heparin over a short period of time did not result in a reduction of neointima formation and restenosis following balloon dilatation in the rabbit iliac artery.
Angioplasty, Balloon, Coronary↗
Local drug delivery with porous balloons in the rabbit: assessment of vascular injury for an improvement of application parameters.
OBJECTIVES: Sufficient intramural drug concentrations with the use of porous balloon catheters can be achieved with additional vascular trauma only. However, effective delivery of a potent drug even in deeper layers of the vessel wall might outweigh these traumatic side effects. Given the porous balloon catheter, the parameters of injection pressure and applied fluid volume will influence the interventional result. METHODS: We tested a 2.5-mm porous balloon (35 75-micron pores) in the right carotid artery of New Zealand rabbits and used injection pressures of 1, 2, and 5 atm and fluid volumes of 2 and 4 ml of low-molecular-weight heparin solution in combination with the different parameters (n = 5 animals/group). In 50 rabbits, an intimal fibromuscular plaque was induced by using the electrostimulation model. Balloon dilatation and then application of the porous balloon was performed in 30 animals, 10 animals were only electrostimulated, and 10 animals served as a control group with balloon dilatation only. The vessels were excised 7 d after intervention, stained, and analyzed histomorpologically. Anti-Xa assays revealed the extent of systemically escaped drug, and serial cuts allowed for exact determination of vessel wall injuries. RESULTS: Effective local drug delivery could not be achieved with an injection pressure of less than 2 atm. Specific pressure-driven effects such as jet injuries could be identified. When the pressure was high enough for disruptive drug delivery (> or = 2 atm), fluid volumes of 4 ml led to loose elastic membranes and local thickening within the media. CONCLUSIONS: Sufficient intramural drug distribution using porous balloon catheters can be achieved with low injection pressures. Different fluid volumes strongly determine the extent of additional vascular injury.
Angioplasty, Balloon, Coronary↗
Success and Procedural Outcome of Excimer Laser Coronary Angioplasty Compared to Conventional Balloon Angioplasty.
BACKGROUND: Coronary excimer laser angioplasty was suggested to be superior for treatment of lesions with complex lesion morphology. METHODS: In this study, 134 consecutive patients undergoing excimer laser angioplasty (ELCA) were compared to 203 patients treated with conventional balloon angioplasty (PTCA) in the same study period. Baseline characteristics did not differ between both groups except the distribution of target vessel (LAD: ELCA 72% vs. PTCA 50%). RESULTS: In the ELCA group, 64 of 139 lesions required adjunctive balloon angioplasty. Overall procedural success was achieved in 80% of patients treated with PTCA and in 78% of patients treated with ELCA (NS), as defined by a reduction of at least 20% of the luminal narrowing and ² 50% residual stenosis, and no in-hospital complication. Complications included acute vessel closure (ELCA: 23.7%, PTCA 6.9%; NS), myocardial infarction (ELCA: 3.6%, PTCA 1.7%; NS), emergency bypass surgery (ELCA: 0%, PTCA 0.5%; NS), and death (ELCA: 2.2%, PTCA: 0.5%; NS). No significant difference was found between the acute success rates and major complications in either A, B1, B2 and C lesions (modified ACC/AHA Task Force classification) treated with ELCA as compared to PTCA. A trend toward increased success rates were documented for ELCA of total and functional occlusion (ELCA: 86% vs. PTCA: 57%; NS) and bifurcational or ostial lesions (ELCA: 95% vs. PTCA 78%). CONCLUSIONS: Further randomized trials are needed to compare the acute success of excimer laser treatment with balloon angioplasty for these selected lesion types.
Journal Article↗
Porous balloon delivery of low molecular weight heparin in the dog coronary artery.
UNLABELLED: The aim of this experimental study was to assess the safety of local delivery of low molecular weight heparin via a porous balloon in the canine coronary artery. In 16 mongrel dogs, percutaneous transluminal coronary angioplasty was performed. In addition, eight of the dogs were given 4 ml Clivarin (1500 IU) delivered locally into the coronary artery immediately after dilatation. The animals were killed after 3 or 14 days. In the animals with local administration, the results of histopathology after 3 days showed the findings to be heterogeneous with marked disruption of the internal elastic lamina in all animals, and varying degrees of medial haemorrhage, medial necrosis, perivascular haemorrhage and signs of myocardial necrosis. Similar changes, but of lesser severity, were present in the animals treated with balloon dilatation only. After 14 days, the severity of vascular and perivascular alterations (medial haemorrhage, perivascular haemorrhage, thrombus formation) was significantly lower in the local delivery group (P < 0.05), but disruption of the internal elastic lamina, as a marker of the initial trauma, was present in all the animals. The presence of residual intracoronary thrombus was only seen in the PTCA group without local delivery. CONCLUSIONS: In this safety study, both groups showed pronounced alterations in the vessel wall 3 days following percutaneous transluminal coronary angioplasty. This changed 14 days following percutaneous transluminal coronary angioplasty when intramural injection of Clivarin resulted in a marked decrease of residual thrombus and medial as well as perivascular haemorrhage. Although the additional vessel trauma by the drug delivery technique did not result in increased complications, a careful approach with this potentially harmful procedure is essential.
Angioplasty, Balloon, Coronary↗
Double-blind comparison of the acute effects of two relevant doses of oral nicorandil on central hemodynamics, left ventricular function, and myocardial contractility.
Nicorandil is a nicotinamide derivative with potent vasodilator properties. Oral and sublingual administration of this compound in patients with coronary artery disease resulted in a predominant reduction of afterload and a small decrease in left ventricular preload. The effects of nicorandil in different doses on contractile left ventricular (LV) function, however, are not well defined. The aim of the present study was to assess the effects of nicorandil on hemodynamics, left ventricular volume and function, as well as the LV contractility index dP/dt measured by Millar-tip manometers. A total of 16 patients with coronary artery disease were included in this study. After diagnostic coronary angiography and ventriculography, the patients randomly received either 10 or 20 mg of oral nicorandil. The hemodynamic parameters, cardiac output, and LV end-diastolic and systolic pressures were determined after 15, 30, and 60 minutes, and a second angiogram was performed 60 minutes after administration. The predominant effect was a decrease in the mean aortic pressure with a concomitant decrease in the peripheral arterial resistance. Clinically relevant changes in aortic pressure, systemic vascular resistance, and rate-pressure product, however, were documented only after oral administration of 20 mg nicorandil, as opposed to minimal changes in the 10 mg group. LV volume and cardiac output were not changed significantly. LV contractility remained unchanged during the observation period. The hemodynamic profile of this compound is dose-dependent afterload reduction without a change in contractility. Because there was no concomitant increase in heart rate, calculated oxygen consumption was reduced, especially in the higher dose group.
Adult↗
Intracoronary ultrasound following excimer-laser angioplasty. An in-vitro study in human coronary arteries.
UNLABELLED: To study the ablation effects induced by excimer laser coronary angioplasty (ELCA), we examined 41 segments of nine isolated coronary arteries. An electronic intracoronary ultrasound device (ICUS: 20 MHz, 3.5F, Endosonics) was positioned coaxially within the vessel. Angioplasty was performed using a 1.7 mm ELCA catheter (Spectranetics) which was placed in the lumen and directed vertically onto the intimal surface of the vessel (fluence: 10-50 mJ.mm-2). The laser catheter was removed after each lasing cycle to allow the stepwise evaluation of the morphological effects of ELCA and to avoid reaching the adventitia. Ultrasound images were compared with the corresponding histological specimens. In all cases, the ablation site could be correctly identified by ICUS. No penetration of the adventitia was seen at histology. Ablation depth was 0.31 +/- 0.18 mm as determined by histology and 0.34 +/- 0.18 mm as determined by ultrasound; the diameter of the crater was 0.63 +/- 0.21 mm, and 0.75 +/- 0.16 mm, respectively, and wall thickness was 0.68 +/- 0.18 mm, and 0.83 +/- 0.20 mm, respectively. A statistical relationship between ultrasonic and histology measurements was only found, however, for assessment of wall thickness (r = 0.71). CONCLUSIONS: The identification of small ablation effects by ICUS was possible with great accuracy and ELCA could be performed without penetration of the adventitial layers. However, exact quantification of the crater dimensions was not possible due to limitations of the axial and lateral resolution. Thus, for the guidance of ELCA by ICUS a further improvement in the resolution capabilities of ICUS devices is mandatory.
Angioplasty, Laser↗
Prolonged proliferative response of smooth muscle cells after experimental intravascular stenting.
The purpose of this experimental in vivo study was to determine the time course of smooth muscle cell proliferation early and late after intravascular stenting compared to conventional balloon angioplasty in normal vessels. A balloon expandable 2.0 mm tantalum Strecker stent was placed in the right carotid artery of 33 male New Zealand White rabbits after they had been fed a 0.5% cholesterol diet for 28 days. In addition, balloon angioplasty was performed in 27 of the animals; 19 contralateral vessels served as controls without treatment. The vessels were excised at 7, 14, 28, 42 or 90 days after treatment. During the final 18 h before the rabbits were killed, bromodeoxyuridine (BrdU) was applied and proliferating cells were detected by using a monoclonal antibody against BrdU. In histological cross sections the proportion of cells undergoing DNA synthesis was determined. Analysis was performed separately in the intimal and medial layers. Additionally, the area adjacent to the stent wire was compared with the intermediate area. Smooth muscle cells were identified by alpha-actin staining. Intimal wall thickness increased from 23 +/- 28 microns (control group without intervention) to 323 +/- 84 microns within 42 days after stenting (P < 0.01), and to 81 +/- 82 microns at day 42 after balloon angioplasty (P < 0.05). However, between 42 and 90 days following stent implantation a significant (P < 0.05) decrease in neointimal thickness was observed (90 days: 215 +/- 15 microns).(ABSTRACT TRUNCATED AT 250 WORDS)
Angioplasty, Balloon↗
Formation of pressure waves during in vitro excimer laser irradiation in whole blood and the effect of dilution with contrast media and saline.
Pressure waves during excimer laser ablation of vascular tissue may be responsible for complications of coronary excimer laser angioplasty. In this experimental study, pressure waves were measured during excimer laser irradiation in blood and contrast media using a polyvinilidenefluoride hydrophone. At a distance of 4 mm lateral to the tip of a 1.7 mm multifiber laser catheter, excimer laser irradiation in blood resulted in a linear increase of peak pressures from 1,365 +/- 165 kPa at 30 mJ/mm2 to 2,866 +/- 404 kPa at 60 mJ/mm2. In contrast media, peak pressure increased from 3,172 +/- 573 kPa (30 mJ/mm2) to 5,763 +/- 467 kPa (60 mJ/mm2). Contrast media and saline were added to blood. At a concentration of 60% contrast in blood, a 3.4 fold increase of peak pressures was documented as compared to pure blood. Further increase of the concentration did not result in higher pressure waves. Concentrations of saline in blood of 90% and 96% reduced the peak pressures by 16% and > 50%, respectively, as compared to pure blood.
Angioplasty, Laser↗
Acute complications of excimer laser coronary angioplasty: a detailed analysis of multicenter results. Coinvestigators of the U.S. and European Percutaneous Excimer Laser Coronary Angioplasty (PELCA) Registries.
OBJECTIVES: The aim of this study was to document and analyze the incidence and consequences of complications of excimer laser coronary angioplasty. BACKGROUND: Excimer laser coronary angioplasty has been reported to be a safe and feasible alternative or adjunct to conventional balloon angioplasty, but serious and unique complications have been observed. METHODS: Data on 1,595 interventions of excimer laser coronary angioplasty in 1,521 patients were analyzed, using a merged data base from the U.S. and European Percutaneous Excimer Laser Coronary Angioplasty (PELCA) registries. RESULTS: Procedural success was achieved in 89.3% of interventions. Stand-alone laser angioplasty was performed in 17.8% of interventions. Complications included dissection (22.0%), vasospasm (6.1%), filling defects (4.8%), abrupt reclosure (6.1%), embolization (2.3%), perforation (2.4%), arrhythmia (0.7%) and aneurysm formation (0.3%). Major complications were non-Q wave myocardial infarction (2.3%), Q wave myocardial infarction (1.0%), coronary artery bypass grafting (3.1%) and death (0.7%). Logistic regression analysis revealed correlation between dissections and the use of larger catheter size (p = 0.0005), high energy per pulse levels (p = 0.0001 for native vessels), lesion length > 10 mm (p = 0.001) and presence of a side branch (p = 0.01). The incidence of perforations was higher in women (p = 0.004), in treatment of total occlusions (p = 0.02) and in the presence of a side branch (p = 0.03). Fatal complications were correlated with patients with multivessel disease (p < 0.0001), patients with acute myocardial infarction (p = 0.0009) and older patients (> 70 years old, p = 0.004). The incidence of major complications decreased after performance of 50 laser angioplasty procedures at one institution (p = 0.02). CONCLUSIONS: This analysis defines both the learning curve and the profile of complications for excimer laser angioplasty and provides insight into the selection of appropriate patients and proper performance of the procedure.
Acute Disease↗
[Peripheral pulsed laser angioplasty--4-year clinical experience].
In 134 patients, 21 iliac, 91 femoropopliteal and 22 crural arterial occlusions were treated by percutaneous laser-assisted angioplasty and in 32 patients femoropopliteal occlusions by conventional balloon angioplasty. Laser angioplasty could be performed in 126 patients following initial guide wire recanalisation using 9.7 and 4.5-F multifiber catheters, respectively. In 72 patients a 308-nm excimer laser and in 54 patients a 504-nm pulsed day laser was used. Luminal opening by laser angioplasty was obtained in 102 of 126 (81%) procedures (9 incomplete catheter passages, 15 persistent occlusions). 95% of iliac, 90% of femoropopliteal and 77% of crural recanalizations including supplemental balloon dilatations (n = 105) and stent implantations (n = 24) succeeded technically. Clinical success rates at 1 (2) years after angioplasty were 95% (89%) for iliac, 66% (63%) for femoropopliteal and 57% (50%) for crural treatments. Technical and clinical results of laser-assisted femoropopliteal recanalizations showed no significant differences in comparison to the results of conventional balloon angioplasty. The use of pulsed lasers for the treatment of peripheral arterial occlusive disease would require further technical improvements.
Adult↗
Clinical results of coronary excimer laser angioplasty: report from the European Coronary Excimer Laser Angioplasty Registry.
From January 1991 to January 1993 the clinical and angiographic data of 470 patients were included in the European Coronary Excimer Laser Angioplasty Registry. Symptoms were CCS class 3 in 23% and CCS class 4 in 14.7%; unstable angina was present in 14.7% and 6.6% of patients had acute myocardial infarction. Of 477 treated lesions, 60% were type B2, and 19% type C. The lesion was located in the LAD in 61%, in the LCX in 16%, in the RCA in 20%, in a protected left main stem in 1.3% and in a saphenous vein graft in 2.5%, respectively. Failure of laser angioplasty occurred in 56 (12%) interventions. By multivariate analysis failure was associated with the intention to treat long segmental lesions (risk ratio (RR) 3.6, confidence interval (CI) 2.9 to 4.4; P = 0.0005), segments with severe prestenotic tortuosity (RR 3.5, CI 2.4 to 4.6; P = 0.02) and total occlusions (RR 2.1; CI 1.4 to 2.8; P = 0.05). Complications included vasospasm (13.4%), dissection (14.7%), flow limiting dissection (4%), reclosure (7.8%), and perforation (1.9%). Myocardial infarction occurred in 2.1%, CABG was requested in 1.9%, and the mortality was 1.5%. Procedural success was achieved in 89%. Individual morphological criteria for a reduced procedural success were the presence of a thrombus (RR 6.4; CI 5.0 to 7.7; P = 0.007) and vessel calcification (RR 2.6; CI 1.9 to 3.2; P = 0.005). Procedural success was slightly lower in type C lesions (86%) than in type B2 (88%) type B1 (95%), and type A lesions (92%), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Angioplasty, Balloon, Coronary↗
Accumulation of macrophages in the arterial vessel wall following experimental balloon angioplasty.
Smooth muscle cell (SMC) proliferation is a key event in the development of restenosis after balloon angioplasty, and it is thought that macrophages play an important role in the complex process of activation of SMCs after vascular injury induced by balloon angioplasty. The study was designed to determine the time course of the accumulation of macrophages in the intimal layer following experimental balloon angioplasty. To determine the extent and time course of the accumulation of macrophages after experimental balloon angioplasty, an intimal atheroma was produced by repeated weak electrical stimulation of the right carotid artery of 45 male New Zealand White rabbits. Additionally, the animals received an 0.5% cholesterol diet during the 28 days of plaque development. Transluminal balloon angioplasty was subsequently performed. At 3, 7, 14, 21, 28 and 42 days after balloon treatment the vessels from at least five animals from each group were excised and analysed for the presence of macrophages using immunocytochemical techniques. In one group of five animals plaque development occurred without subsequent balloon angioplasty; the animals were killed after 21 days (sham group). SMCs were identified by immunohistological staining of alpha-actin. Intimal thickening increased after dilatation from 137 +/- 62 microns (control group without balloon treatment) to 244 +/- 47 microns in the 42 days after angioplasty (P < 0.05). The percentage of macrophages in the intimal layer displayed a significant increase (P < 0.01) at 14 days after angioplasty (9.1 +/- 4.3% vs 2.0 +/- 1.7% in the control group).(ABSTRACT TRUNCATED AT 250 WORDS)
Angioplasty, Balloon↗
Occurrence, extent, and implications of pressure waves during excimer laser ablation of normal arterial wall and atherosclerotic plaque.
Ablation of atherosclerotic plaque and normal arterial wall was performed using a Xenon-Chloride Excimer laser with a wave-length of 308 nm and a pulse duration of 115 ns. The light was transmitted via a 600 microns bare fibre and adjusted to an energy density of 3.5J/cm2. The acoustic signals generated by the laser pulse were measured with two types of hydrophones consisting of polyvinylidenefluoride with active diameters of 0.3 mm and 0.5 mm and recorded on a dual channel digital storage oscilloscope using either a 0.5 m coaxial cable or a broadband fibre-optic transmission system. Tissue was retrieved from nine cadaver human aortas and macroscopically classified as either normal or calcified atherosclerotic plaque. Histological analysis (Haematoxylin eosin, elastica van Gieson, and immunohistochemical staining) was carried out after the experiments to verify the macroscopic diagnosis and to correlate the acoustic responses with the tissue characteristics. For normal arterial wall, maximum peak pressure was 1.28 MPa +/- 0.85 MPa, rise time 163 ns +/- 43 ns, and pressure increase 8.2k Pa +/- 5.4k Pa/ns. For calcified, atheromatous segments, a maximum peak pressure of 2.02 MPa +/- 1.16 MPa, a rise time of 69.9 ns +/- 25.8 ns, and a pressure increase of 32.3 kPa +/- 21.3 kPa/ns was found. Statistical analysis showed a significant shorter rise time (P < 0.0001) and a higher pressure increase (P < 0.0001) for calcified tissue in comparison to normal arterial wall, whereas maximum pressures alone did not allow a differentiation of tissue characteristics. Several hundred kPa are generated during Excimer laser ablation.(ABSTRACT TRUNCATED AT 250 WORDS)
Acoustics↗
In vitro evaluation of ablation parameters of normal and fibrous aorta using smooth excimer laser coronary angioplasty.
A modified excimer laser energy delivery system was used to irradiate 100 segments of normal and fibrous aorta in vitro. The laser beam was scanned into 8 fiber bundles consisting of 50 fibers each resulting in a reduction of the applied pulse energy. The total repetition rate was increased to 150 Hz in order to keep the repetition rate per fiber bundle close to 20 Hz and to minimize thermal injury. The results demonstrate that effective ablation (etch rate per 8 pulses > 2.0 microns) occurred at an energy fluency of 50 mJ/mm2 in both normal and fibrous aorta. Tissue damage (carbonization, tissue separation, fissures, cracks, and vacuolization) was in a range of 100 +/- 28 to 152 +/- 30 microns for normal aorta and in a range of 57 +/- 35 to 110 +/- 39 microns for fibrous aorta. We conclude that effective ablation of normal and fibrous human aorta can be achieved by the application of smooth excimer laser coronary angioplasty. This improvement of excimer laser technology may result in a reduction of shock wave- and cavitation-induced damage leading to a reduction of tissue injury. However, this awaits further in vitro and in vivo confirmation.
Angioplasty, Laser↗